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Hi all, new guy here. I will take this opportunity to introduce myself and my car.

 

About me

My name is Mario, I live in Cedar Rapids, IA. I'm in my low 30s (for those who care), I like to work on cars, but I don't have a whole lot of detailed experience, however I'm very willing to learn. In early April igot the car (I wasn't necessarily looking for one, it found me). I've knew about 2X0Z for a while (my father in-law has two of 240Z sitting in his backyard rusting away :( ) but when this deal came I could not refuse.

 

About the car

1978 280Z, 59,XXX miles when I got it. Original, survival (I have all the original paper work including signed contract from the dealer and window sticker). Never saw snow, rarely  any rain. Previous owner had it for over 25 years and drove it maybe a 1000 miles a year. Always garaged. Few things he did to car: lower suspension with Tokico springs and adjustable shocks, big brake kit upfront, SS brake lines,cold air intake, newer spark plug wires, 2.5" exhaust form MSA, including down pipe and all the way to turbo muffler. Other than that all was stock, including all the engine gaskets! 

 

What I did when I got the car

Replaced the fluids: engine oil and filter, rear diff, MT oil, coolant. replaced the spark plugs with with the stock NGK ones, replaced fuel filter, distributor cap and the rotor, replaced battery cables, installed new 16x8, 0 ofset XXR513 black/silver wheels that came with the purchase.

 

The issue

I have hard time starting the car after it sits for a while (for example a day at work). The car did not have this issue when I first got it, but slowly it developed it. One point to mention is that it started BEFORE I did any part replacement under the hood. Here is the link to a youtube video of wha the car does. Sometimes it is more sever, sometimes it is less sever:

One additional point to mention is that the RPMs are typically low for "cool start". I would expect the RPMs to sit around 900-1000 when the engine is warming up and slowly come down to 700-800 rpms. It's as if the engine does not recognize the "cool start" and perhaps does not go into fuel enrichment period.The starting issue is there regardless of the outside temperature. It could be 85 or 60 degrees, still acts the same. Based on what I noticed this morning when I sarted the engine I'm thinking it has something to do with the air delivery. Right after I started the car (RPMs were hovering around 700) I went in and unplugged the vac hose between intake manifold and fuel pressure regulator. As soon as I unplugged it at the FPR and left it opened (therefore providing more air to the system), the engine reved up to around 800-900rpm. When I plugged the vac hose with my finger engine would drop rpms. After few minutes of running, this drop and rise of rpms was much lesser, if any at all.

 

Here is what I did for troubleshooting so far

I do have EFI bible and the Service Manual and  I actually have performed quite a bit troubleshooting in the cold start department: replaced water temp sensor as well as water temp sensor connector, cleaned thermotime switch and replaced its electrical connector. I performed continuity/resistance/voltage tests as described in Service Manual at the ECU for water temp sensor, themotime switch, Cold Start Valve, and Auxiliary Air Recirculating valve. All checked out OK, unless I misinterpreted the results. I pulled out CSV, cleaned it externally and cleaned its electrical connector. I pulled the AAR valve and made sure that the internal flap was moving freely. I took out Air Flow Meter and made sure the flap was moving freely. I wiped it inside. Having AFM out gave me inside look at the throttle body, so I sprayed some electrical connector cleaner and wiped it clean (there was actually quite a bit black gunk that came out)...the starting problem persists.The fuel pressure is not maintained in my system. I installed inline fuel pressure gauge right after the fuel filter. The pressure drops to 0 after few hours of car being off. However, before I crank the car I prime the fuel pump by turning ignition to ON/OFF position 4-5 times, until I see that pressure gauge reads around 31 psi. Even then I still get the problem. ...I started to run out of ideas.

 

​What else can it be? One of the comments in my youtube video says it could be a vapor lock. If so, what could cause this vapor lock?

 

Beside this starting issue I believe car drives well (I say believe, because I have never driven a Z so I don't have a benchmark to compare to). It feels like it pulls all the way through the RPM range. The only other thing I have noticed is that when I drive it harder I get slight afterfire when up shifting 1-->2 and 2-->3 gear.

 

Help...

Edited by Marios280Z

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What I did when I got the car

Replaced the fluids: engine oil and filter, rear diff, MT oil, coolant. replaced the spark plugs with with the stock NGK ones, replaced fuel filter, distributor cap and the rotor, replaced battery cables, installed new 16x8, 0 ofset XXR513 black/silver wheels that came with the purchase.

 

The issue

I have hard time starting the car after it sits for a while (for example a day at work). The car did not have this issue when I first got it, but slowly it developed it. One point to mention is that it started BEFORE I did any part replacement under the hood. 

 

One additional point to mention is that the RPMs are typically low for "cool start". I would expect the RPMs to sit around 900-1000 when the engine is warming up and slowly come down to 700-800 rpms.

 

Right after I started the car (RPMs were hovering around 700) I went in and unplugged the vac hose between intake manifold and fuel pressure regulator. As soon as I unplugged it at the FPR and left it opened (therefore providing more air to the system), the engine reved up to around 800-900rpm. When I plugged the vac hose with my finger engine would drop rpms. After few minutes of running, this drop and rise of rpms was much lesser, if any at all.

 

The pressure drops to 0 after few hours of car being off. However, before I crank the car I prime the fuel pump by turning ignition to ON/OFF position 4-5 times, until I see that pressure gauge reads around 31 psi.

 

 The only other thing I have noticed is that when I drive it harder I get slight afterfire when up shifting 1-->2 and 2-->3 gear.

 

Help...

In the video the RPM went to 1000 after it started and it didn't sound too bad.  Doesn't fit your description.  It does sound like you might have a starter problem though.  It seems to be letting go before the engine starts.  Oddly, a 1978 parts car that I had would do the same thing.  You had to keep trying until it would catch.

 

The RPM increase with a small vacuum leak is normal.  

 

Your fuel pressure readings seem low but it's not clear what you're doing.  I don't know why the pump would get power just from turning the key ON/OFF.  The pump shouldn't run unless you hit Start, or the engine is actually running.

 

Get the engine running, and take the hose off of the FPR again.  Then read the fuel pressure.  That will tell you about your fuel pump and FRP.  Or take off the small wire from the starter solenoid and turn the key to Start.  That will run the pump, but not the starter.

 

One last thing - you said that you confirmed that the AAR flap was moving freely but you didn't say that it was open when cold, and closed when the engine is warmed up.  If it doesn't move, then there's no idle speed increase when cold.  Basically, it's not doing anything.  You can apply 12 volts directly to the two pins if you want to verify it's closing.  It only takes about a minute.

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In the video the RPM went to 1000 after it started and it didn't sound too bad.  Doesn't fit your description.  It does sound like you might have a starter problem though.  It seems to be letting go before the engine starts.  Oddly, a 1978 parts car that I had would do the same thing.  You had to keep trying until it would catch.

 

ZedHed, you are right, in that video the RPM went to 1000. That's becuase I had my idle screw artificaly set to high so thtat during the start engin would run at higher RPM. That in turn casued increased RPM during idle once the engine warmed up. I have another vidoe over here that shows lower RPM:

 

 

That's interesting theory about the starter. I don't have a problem starting it at any other times. Perhaps I just let go before the engine catches because I feel like I'm dragging the starter.

 

Regarding fuel pressure. When I unplug the vacume hose, the pressure goes up to around 38-39 psi. I have found on one of the forums few people saying that 31/32 with the vac hose ON and 38-39 without the vac hose at idle is normal. Service manula talks about 36psi...

Every time I turn key to ON, the fuel pressure increased by around 8-10psi, that's why I do it few times to get up to around 32. I have unplugged the starter and turn the ignition key to start, at which point I could actually hear the pump running.

 

What I did with AAR is I removed it and put in in the fridge for few minutes. When I pulled it out the flap was 3/4 way open. Not sure if it will ever fully open from what I saw in a AAR fix DIY found on atlanticzcar website. I have not warmed it up to see if it would actually close the flap.  I can try and do that.

 

Any other suggestions?

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ZedHed, you are right, in that video the RPM went to 1000. That's becuase I had my idle screw artificaly set to high so thtat during the start engin would run at higher RPM. That in turn casued increased RPM during idle once the engine warmed up. I have another vidoe over here that shows lower RPM:

 

What I did with AAR is I removed it and put in in the fridge for few minutes. When I pulled it out the flap was 3/4 way open. Not sure if it will ever fully open from what I saw in a AAR fix DIY found on atlanticzcar website. I have not warmed it up to see if it would actually close the flap.  I can try and do that.

 

Any other suggestions?

IF we redefine your issue from "difficulty starting" to "low idle after starting" or "high idle after short warmup" then the problem is most likely the AAR.  IT's supposed to be almost completely open at normal cold engine temperatures, like anywhere from 30 - 90 degrees F, then close slowly as it warms up.  It actually has an electric heater inside to make sure it closes within a short amount of time.

 

I would pull the hose from the AAR and see where it's at engine cold.  If it's closed already, you have a problem.  They can be adjusted.  Maybe someone messed with yours already.

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Numbered my edits

 

3.  Actually, I'm not sure what will happen with that setup.  Looks like the AAR is directly to air.  You'll get a lot of unfiltered air if it's open, might get the high RPM.  Or you'll get nothing if it's closed.  The loop on the throttle body to the big hose probably has no affect.

 

2.  Moved to front!~ - BUT.  Your picture shows that you completely bypassed the throttle blade.  The engine might go to sky-high RPM right away.  Don't start it like that.

 

 

1.  Aacck...

 

The AAR can't be bypassed without having the idle speed problems.  All cars, even carb'ed cars, have devices to increase idle speed for a minute or two until the combustion chambers get warm enough to work right.

 

Your idle speed with the bypass can either be set to have a very low idle RPM that needs throttle pedal action to stay running, or it can be set with a good cold idle that gets too high after it warms up.

 

If nothing changes though, you'll know the AAR wasn't working.

Edited by Zed Head

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Did that hose nipple on the big hose have a plug on it or was it open to air?  It should be plugged, I believe.

 

Anyway, I think that your problem is a simple one, don't do anything crazy like adjust the AFM or change timing or what you showed in that picture.

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I looked in the FSM and see what you did in your picture and where your hose ends are.  Sorry, I couldn't tell what you were doing.  My mistake.  Haven't looked at AAR connections for a while.

 

 

All that "bypass" will do is confirm that your AAR was never opening or closing,  Not moving at all.  All you've done is open the passage permanently.  You'll be stuck with an idle that's too low, then gets right, or just right then gets too high.  Best to fix the AAR.

 

Sorry for the mess of posts.

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I'm not sure where your concern is coming from Zed Head. Right now it is isolated (air wise) from the engine. When the AAR is operating correctly during inital start up and is wide open, than it acts exactly like the hose I connected. The one end of the hose is connected before the throttle body to pick up the air, just like the AAR assembly does. Then istead of flowing through the assembly: the rubber hose--->metal pipe--->again to a short rubber hose---> to AAR valve---> to another short rubber hose--->to the emettal niple---> into the intake manifold PASSED the throttle body, I simply connected the two points prior to throttle body and passed the throttle body with just a continues hose. I was NOT going to drive it this way. I was going to ONLY start in the mornig to see how it would go. There is no signal to the ECU from the AAR at all, as you know.It's a dumb air passage with heating element to close it when things get warm.

"2.  Moved to front!~ - BUT.  Your picture shows that you completely bypassed the throttle blade.  The engine might go to sky-high RPM right away.  Don't start it like that." That's exactly what the AAR does, it bypasses the throttle blade. From the EFI Bible:

"You know that idle speed can be raised by simply bypassing throttle plate. During warm up, we do exactly that by using an air valve, called an Auxillary Air Regulator.(...)When the engine is cold the valve is open;so when the engine starts, ari can bypass the throttle plate and go through the valve."

 

I'm not sure what you mean by: "Did that hose nipple on the big hose have a plug on it or was it open to air?  It should be plugged, I believe."

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Ha, you must have posted your last message as I was writing my response :) No biggy.  I will let you know tomorrow if bypassing AAR helped to start the engine right up.

 

Does anybody have any other idea what may be happening here? looks like we have a lot of audience Zed Hed,but nobody is pitching in ;)

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It's early.  

 

I would put more in to your description of "difficult starting".  Do you mean that you have to try two times?  Or that it idles poorly for 1/2 second?  The sputters, before it dies?  Because really, it seems to start pretty quickly.  How does it start when it's warmed up?  Is this only a cold start problem?  The more details on the actual problem, the better.

 

 

If you want to mimic what the AAR would do, open the idle screw up so that when it starts the RPM sit at 1200 RPM, engine cold.  You can do this in one shot, the engine won't heat up that fast.  Start it, adjust the idle screw, turn it off, restart.  See if it starts the way it used to.  If it starts fine, but the idle never drops, then it's not a starting issue, it's an AAR issue.

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It's early.  

 

I would put more in to your description of "difficult starting".  Do you mean that you have to try two times?  Or that it idles poorly for 1/2 second?  The sputters, before it dies?  Because really, it seems to start pretty quickly.  How does it start when it's warmed up?  Is this only a cold start problem?  The more details on the actual problem, the better.

Yes, the fact that I have to try 2,3, sometimes 4 times before the engine catches, the fact that it sputters before it dies, and the low idle on start up.  I will take a video of how it starts when it is warm (with a touch of a key). I'm also concerned that if I don't get to the bottom of this I will have a heck of a time starting it when the temps start dropping to 40s and 30s (note,  I will not be driving it in the winter). Also, one time I have started it cold (with the typical trouble, so it took me couple of tries), and about 2-3 seconds after it finly started I turned it off. Then attempted to start it again and the enging started right up...Not sure if it was just a fluke or what. Next time I encounter the difficulty I will repeat this test to see if it will start right up or not.

 

Another point  I should mentioneis the CSV test I performed. I pulled the CSV out of the intake manifold and put it in the jar. I had my wife crank the engine (when cold). There was no drop of fuel coming out of the CSV. Granted, it was about 85 degrees outside, so I don't know how valid the test was. I think the FSM talks about the upper temp limit for the thermotime switch being 70 degrees. At that point I also checked the wire continuity between the CSV connector and the thermotime switch and it was OK. On the other hand I  had peopl tell me that they have entirly removed the CSV from their Z cars and never had problems starting even in cooler temps.

 

You have a good point with that idle screw. But for tomorrow morning I will try with the AAR bypass.

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Is the new fuel filter's arrow pointing toward the engine?  If it was starting right up before you did the things you mentioned it has to be something simple.  Are the thermo time plug and the coolant sensor plugs reversed at the thermostat housing or possibly the bullet connections?  Just guessing this morning, you seem to know what you are doing so I apologize for sounding pretentious.  :)

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Is the new fuel filter's arrow pointing toward the engine?  If it was starting right up before you did the things you mentioned it has to be something simple.  Are the thermo time plug and the coolant sensor plugs reversed at the thermostat housing or possibly the bullet connections?  Just guessing this morning, you seem to know what you are doing so I apologize for sounding pretentious.  :)

 No offense taken at all. I have thought about switching the thermotime switch and water temp sensor connectors. I believe they are OK a the bullet connector. They are color coded at that point, but  I will double check that with continuity check. The starting issue began before I did almost any work under the hood, however I cannot recall is it started before or after install of new fuel filter. When I installed it I paid attention to the IN/OUT marking on it, but I will go back and double  check my work.

 

This morning (car sitting outside over night, the temps were around 60 degrees this AM) I recorded a video of a start up with the AAR bypass, as I mentioned in the previous post. As expected with the extra injection of air the RPMs went up almost to 2000rpm. I then immediately turn the engine off and attempted to start it again (in the past when I did that once the car fired right up). Unfortunately this time the trouble was still there. This test proved that the AAR is NOT the root cause of the issue, however it also proved that my AAR may not be operating 100% correctly since I get low idle RPM when engine is not warm - I'm guessing that AAR is not opening all the way.BTW, I have removed the AAR bypass before I drove to work. Here is the video:

 

 

Let's get to the bottom of this guys...

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However, before I crank the car I prime the fuel pump by turning ignition to ON/OFF position 4-5 times, until I see that pressure gauge reads around 31 psi. Even then I still get the problem. ...I started to run out of ideas.

 

 

That last video was informative.  Did you "prime" the fuel system like you describe above or just try it with zero fuel pressure?  That would make a difference.

 

You're getting closer.  Working on these EFI systems is best done by being rigorous, detailed, and repeatable.  For example, my question about fuel pressure.  Can't tell if the latest video is different from the other ones.

 

Another thing to look at is the TVS (aka TPS).  It's the switch on the throttle body that tells the ECU the engine is at idle, so it can add a little fuel.  And are you starting with your foot off the gas pedal or are you pressing it?  These engines start best with no pressure on the pedal.  When the AAR is working correctly.

 

Also, the fact that you can run the fuel pump with the key alone (which you never explained, above) could indicate a wring issue.  Maybe your ACC circuit is enabled at Start and the voltage drop is weakening the spark.  Could be that the ballast resistor is incorrectly wired, with Start passing through the resistor.  Weak spark plus lean mixture = hard starting.

 

Lots of little things to look at, but any one or combination could be a contributor.  You didn't get the quick fix so it's time to open up the Engine Fuel chapter and start testing components.  Make a list of what's not right and post it (like the fuel pressure issue and the way power is supplied) and somebody might see something.

 

Here's a sample of what you'll find in the FSM.

post-19298-0-72185500-1438878183_thumb.p

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I've thought that maybe your throttle plate is crudded up around the bottom and not letting any air pass by like it should, it affects idle.    

 

It may not help your current problem but cleaning all the electrical connections is always helpful.  You already know about atlanticz's tech tips so look at this, http://atlanticz.ca/zclub/techtips/electricalconnections/index.html

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That last video was informative.  Did you "prime" the fuel system like you describe above or just try it with zero fuel pressure?  That would make a difference.

 

Yes, I did prime the fuel pump like I described above.

 

Another thing to look at is the TVS (aka TPS).  It's the switch on the throttle body that tells the ECU the engine is at idle, so it can add a little fuel.  And are you starting with your foot off the gas pedal or are you pressing it?  These engines start best with no pressure on the pedal.  When the AAR is working correctly.

I have though about TPS, but have not look into it.I was a bit "scared" to remove it since EFI bible talks about some very specific way of reconnecting the switch, and I did not want to mess it up. I leave my foot off the until (only sometimes) the very end when I see that engine is sputtering and is almost there to catch it, then I give it gentle tap.Sometimes it works, others it doesn't. 

 

Also, the fact that you can run the fuel pump with the key alone (which you never explained, above) could indicate a wring issue.  Maybe your ACC circuit is enabled at Start and the voltage drop is weakening the spark.  Could be that the ballast resistor is incorrectly wired, with Start passing through the resistor.  Weak spark plus lean mixture = hard starting.

Not sure what kind of explanation you are looking for. As i stated above: "Every time I turn key to ON, the fuel pressure increased by around 8-10psi, that's why I do it few times to get up to around 32. I have unplugged the starter and turn the ignition key to start, at which point I could actually hear the pump running." the fuel pump does not really run "run" with the ignition key in ON position. It looks more like it's getting energized just for a split of a second. I can definitely tell when pump is running when I disconnect the positive terminal from the starter and turn ignition key to start. As soon as I let go of the key I no longer hear the pump. As far as I know, and I can confirm with previous owner who never had this starting problem, the wiring on this car is all original and was not messed with, so I have hard time believing the ballast resistor is wired wrong. Dirty?-maybe. However, if the spark was week due to corroded/dirty wiring, I would most likely notice driveability issues other than just starting.

I've performed several tests form FSM in the cold start department and have not found anything incorrect. There is definitely more tests to run, like the TPS. I've looked at that graph form FMS to try and get some clues on what may be causing the issue.

 

 

I've thought that maybe your throttle plate is crudded up around the bottom and not letting any air pass by like it should, it affects idle.    

 

It may not help your current problem but cleaning all the electrical connections is always helpful.  You already know about atlanticz's tech tips so look at this, http://atlanticz.ca/zclub/techtips/electricalconnections/index.html

When I pulled out the AFM the other day  I got access to throttle plate. I used electrical connector cleaner and sprayed and wiped it inside. Got a lot of black grime out of there. I did that one evening and interestingly enough next morning the car started with a touch of a key! I was excited like a 5 year old in a candy store. later that afternoon when I was leaving work that car started nicely again- that was like Christmas in August. Unfortunately the next morning the problem came back as well as the following afternoon.  In all the cases I primed the fuel pump as described above (I do try to stay consistent with the way I do/test things and try to varied only one variable at a time). I also did NOT change/adjust anything between the day the car started and the next day when it did not. Later today when I come back from work I will post a video of the car starting correctly, just as a reference to what it is capable of. I will perform all electrical connections/grounds clean up as described in the atlanticzcar post. I have done some of it (battery positive cable terminal replacement, thermotime switch and water temp sensor connector replacement, as well as AAR and  CSV connector clean up.)

 

Thanks for your help guys, and please keep throwing ideas at me.

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Here is an exampe of how she starts up when she plays nice. This was caround 3 hours after I came back from wark. Engine wasn't hot, but it wasn't cold eithere, around 110 degrees according to the engine temp gage in tha car. I did prime the pump as before since the pressure was showing 0psi.

 

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There could be an issue in the afm. I can't remember exactly for the 78 but the 75 has a connection for one of the pins that kills the fuel pump when the vain isn't actuated. Does it look like the cover for the afm had been removed?

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There could be an issue in the afm. I can't remember exactly for the 78 but the 75 has a connection for one of the pins that kills the fuel pump when the vain isn't actuated. Does it look like the cover for the afm had been removed?

 Are you thinking that the the fuel pressure drop may be caused by that possibly faulty connection in AFM? Or you're  thinking that it may be causing hard start issue? 

Answering your question, yes, the AFM has been opened few years back by the previous owner and adjusted according to some procedure. I can find the paper work he gave me for it and let you know what the source of the procedure was. Keep in mind that he has never had this starting issue. From what he told me he was trying to adjust rich/lean fuel mixture.

I have not had a chance to do any more testing and or ground connection cleaning last night so nothing to report.

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I'm think it might be causing the fuel pump to cut off intermittently during start up causing a hard start issue but like I said I can't remember when they switched over from the fuel pump cut off being controlled by the afm to being controlled by the oil pressure.

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I'm 99.9% sure the '78s had the switch in the oil pressure sending unit.  He may have the wrong year oil sender or the wire could be loose or corroded.

 

From MSA;

 

small178001.jpg Oil Pressure Sender, 70-2/77 240Z-260Z-280Z
Code:17-8001
Price: $47.30
Quantity in Basket: none

  small178003a.jpg Oil Pressure Sender, 3/77-84 280Z-280ZX-300ZX
Code:17-8003
Price: $59.95
Qua

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My oil sender looks like the one for 3/77-84 280Z. I do have that two prong connector, unlike the earlier Zs that have that single nipple. I have read somewhere (it might have been the EFI bible or some other forum post) that  I could trigger the fuel pump by setting ignition key to ON and moving the AFM flap passed the resting point. Is that not the case for my car because I have the trigger inside the oil pressure sender?

 

I have noticed in the past that the connector on my oil sender unit is oily, as if the sender itself was slightly leaking the oil through the connector portion of the sender (white plastic and the prongs). 

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Here's the 1978 fuel pump control scheme.  BUT, back to my other point, this scheme does not provide power to the pump by turning the key On/Off as described earlier.  In a correct system you should not be able to "prime" the fuel system with the key.  

 

So you're studying something that has already been shown to be modified somehow.  OR, your oil pressure switch is bad, but this would just give power via two methods, one when the switch is open, and one when the switch is closed.  Neither scenario cuts power to the pump.  The Start circuit bypasses the control scheme anyway.

 

I see FSM avoidance.  It's not as bad as it seems, it's actually very educational and a good read.

post-19298-0-21154200-1438977485_thumb.p

post-19298-0-31225200-1438977698_thumb.p

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It would be handy to add your cars build info to your signiture or at least year and model. I had to go back to the first post to find it again.

Your car is a 78 so it should have the two prong sender unit unless someonechanged the efi system to the later type.

I think they changed somewhere in August 77. I know that is different to what MSA is quoting, but and I know two around my build date have the single prong unit and we (mine and the other two) are all 2 to 4 months after the March 77 change over MSA is quoting.

I believe Datsun didnt have a fixed change over method. They seem to use bins as they come. If a bin of old parts came along a month later they would be installed. I have seen a very early N47 head with a spray bar and I have heard of someone else with one. They are not modified combi spay bar internal drilled setups. They only have they spray bar and N42 cam.

Back to your problem. You could also be having problems with the fuel pump relay. It could be failing when the voltage is low during stating. You could wire a test lamp to the fuel pump wires to see what is happening.

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