EFI Datsun Z - only runs with throttle slightly pressed

[siteunseen]

My egr tube came loose and after years the exhaust gasses rotted a hole in my intake manifold about the size of a golf ball. Chased that problem until I put a handheld mirror under there and saw the huge vacuum leak. Replaced the intake and deleted the egr which is way more than just pullung that stuff off. There's some vacuum lines and thermal vacuum switches you have to deal with too. 

I'm with Zed Head on the reverse tuning you're going to have to do but you're here where everybody likes to solve issues. The forum has been needing a good puzzle too.

You are a pleasant and thankful guy so it'll get back to running soon. We like pictures that show what you're talking about so the more the better even though the car's in one place and you travel. Do a photo dump when you're back with the car. Zed Head will figure it out. 

 

 

[milligan21]

8 hours ago, siteunseen said:

8 hours ago, siteunseen said:

My egr tube came loose and after years the exhaust gasses rotted a hole in my intake manifold about the size of a golf ball. Chased that problem until I put a handheld mirror under there and saw the huge vacuum leak. Replaced the intake and deleted the egr which is way more than just pullung that stuff off. There's some vacuum lines and thermal vacuum switches you have to deal with too. 

I'm with Zed Head on the reverse tuning you're going to have to do but you're here where everybody likes to solve issues. The forum has been needing a good puzzle too.

You are a pleasant and thankful guy so it'll get back to running soon. We like pictures that show what you're talking about so the more the better even though the car's in one place and you travel. Do a photo dump when you're back with the car. Zed Head will figure it out. 

 

 

 

Oh I know there is more than just blocking it off but... for a temp fix its blocked off until I get it running right 😉 I was thinking of deleting some stuff later and adding a new fuel rail because all those windy pipes is just asking for trouble. But then.. I am unsure about doing that either and maybe leaving it as stock as possible 

"You are a pleasant and thankful guy so it'll get back to running soon." << for now hahah Its frustrating but I enjoy frustration at times until I am going around in circles then I get a bit flustered haha. I will for sure do a photo dump but I also seen rotted out intakes which now I am thinking I will just pull the whole intake and fuel lines off and check ABSOLUTELY EVERYTHING and make sure that its good to go 😄 or at least go for a while 😄 

 

 

14 hours ago, Zed Head said:

36 psi while running is not right.

The EGR can leak internally, within the ports on the intake manifold itself.  Even with the a plate on the top.  You'd have to block the bottom hole too to be certain.

You said that you tested the TPS (actually TVS).  Did you test at the ECU connector?  Best to do all tests at the ECU connector as described in the 1980 EFI Book I linked above.

Did the fuel canister on the front have a pump that gave proper pressure at the rail?  Not really clear how things were when it ran for you.  Might be that the PO "tuned" the system around a bunch of wrongness and you'll have to undo all of that wrongness.  

Well ... it was trying to run on 40psi until I adjusted the pressure regulator ( yes i replaced that with a newer adjustable one ) and once I reduced the PSI to 36 I was able to ( light bulb moment maybe ) run it with throttle pressed a little. So... thinking out loud here... maybe if I reduce it to 30 or below I might not have to have the throttle pressed? It could be a case of too much pressure for the injectors to handle ? hmm

Regards the TPS / TVS ( as in the manual ) I prefer to call it TPS hahha ... did I test it at the ECU... Yes ( had to think there ) but yes and it was fine when I had the pedal pushed and not pushed I had continuity etc.  Sorry, I should have written the results down for all the tests when I done them but I didn't think I would be in this situation. The forum is a step above the EFI bible.... the 74th Bible if you will  😄

The fuel canister at the front had the pump that is now on the back ( the Bosch 044 pump - reminds me to order a check valve ) I would say that the PO was tinkering with it no doubts then gave up and left it lie in a shed in Germany for 10 odd years 😕 Anyways, I think ( again I wasn't in the country when it arrived ) that the pump was connected directly and a canister at the front. My dad got to drive it up and down the garden - I have yet to drive it 😕 So, that is how it was running. 

 

Just to add.. I added new fuel and brake lines and done the Fuse / Fusible links upgrade  ( again from the Atlantic Z site)

 

THANKS again for the input guys 🙂 gets me thinking out of the box 

[Zed Head]

9 hours ago, milligan21 said:

the pump was connected directly and a canister at the front. My dad got to drive it up and down the garden - I have yet to drive it

The great thing about the early EFI systems is that they are very primitive and the service manual has an in-depth explanation of what each component's function is.  Since it ran before and was even drivable then it seems like something that you did afterward caused a problem.

Might help to go back and discuss why you made the changes that you did.  Did it stop running right after you fixed the fuel tank or did you do some other things also?  Maybe you should undo some things and start over.  Put the old FPR back on, etc.

There might be hoses to the intake manifold and throttle body that you moved or left disconnected.  For example, the auxiliary air regulator (AAR) is in the vicinity of the fuel rail and has hoses and an electrical connection.  If it is not right you could have starting and running problems.

Also, all air must pass through the AFM.  No intake leaks at all.  The only planned intake leak is the one through the charcoal emissions canister.  Not even sure that a German 280Z would have a charcoal emissions canister.

[milligan21]

On 1/28/2023 at 8:51 PM, Zed Head said:

The great thing about the early EFI systems is that they are very primitive and the service manual has an in-depth explanation of what each component's function is.  Since it ran before and was even drivable then it seems like something that you did afterward caused a problem.

 

Well yes maybe I done something but ...as it stands now it kind of goes but not as it should. 

I will have to examine for leaks or a busted manifold and other things

It has a charcoal canister. It's a Nissan Fairlady from Japan so it's a 2.0litre right hand drive with efi. 

Can't wait to get back to it. The feedback on what it might be is a great help 🙂

all the photos I have of the engine bay right now ...kinda pointless 

[siteunseen]

There's no fuel filter. The pcv hoses look messed up to me. There's a lot of stuff not terminated it looks like? What's up with the injectors. Looks like a fuel line to each one. Fairlady 2.0 is very different than my Datsun 2.8. 

[milligan21]

10 minutes ago, siteunseen said:

There's no fuel filter. The pcv hoses look messed up to me. There's a lot of stuff not terminated it looks like? What's up with the injectors. Looks like a fuel line to each one. Fairlady 2.0 is very different than my Datsun 2.8. 

Oh ... didn't even see that. In the other photo there is a fuel filter 🙂 old photos is all I have for now. I think the 2.0 and 2.8 are more or less the same just minus 0.8 😛 probably minus a lot more these days hahah 

I will get updated photos 😉

[siteunseen]

17 minutes ago, milligan21 said:

Oh ... didn't even see that. In the other photo there is a fuel filter 🙂 old photos is all I have for now. I think the 2.0 and 2.8 are more or less the same just minus 0.8 😛 probably minus a lot more these days hahah 

I will get updated photos 😉

And I must apologize. Your car is different, duh, from what I'm used to seeing. Caught me off guard.

Anyway 6 of 1, half a dozen of the other. It will be fun learning the differences in our cars.

Old dog here but I enjoy new info.

[Zed Head]

Can't tell much from the pictures.  It's the same basic EFI system that the USA 280Z's use.  You can even see the EGR valve in one of the pictures.

The key is probably somewhere in whatever was changed from when his dad was driving it to now.  Something that got disconnected or bumped or moved intentionally.

[milligan21]

Hey again 🙂 I am back to Ireland now and had a day of sanding parts then took some photos of the engine bay 😄Also while I was away I got someone to do a new paint job .. happy out .. now i can reassemble yayy! 

But.. yes its still not running as it should. 

What I tried today:

• turned down the pressure regulator 25psi > done nothing different
• turned up the pressure on the fuel 40psi > no different. 
• watched the afm opening while i had my foot semi down on the throttle ( could be opening too far? to be investigated )
• found TDC on the piston > which on the distributor cap pointed the rotor to spark lead #1 as it should be > checked the harmonic balancer ( it was at 20 - not sure if this is right or not? have to get a timing light tomorrow but if the car needs to be warmed up then i cant check the timing?  )
• still only runs with my foot a little down on the pedal and will only do so when the TVS is disconnected and wired like in the photo for some bizarre reason. Still no revs and usually cuts out if i push the pedal too much. 
•  

So thats where I am at.. if you are lookin at the photos and think.. my God what a mess.. yes.. YES it is. But it will be done after  I get the engine running in-situ I will pull the engine out & tidy the engine bay and maybeeeee put a manual box on it. 

   Also the FPR is routed that way cause its handy 😄 and yes its the right way ( in and out lines )

I have got a new filter which I will try get on tomorrow but cant see that making any difference?

Thanks again guys and I am happy to be back at it 😄I included a shiny white car now and not the grey and white as before haha  Also yes I know the EGR pipe isnt connected ( its blocked off for now as the pipe was broken and was so hard to see actually )

 

 

 

[Racer X]

2 hours ago, milligan21 said:

Hey again 🙂 I am back to Ireland now and had a day of sanding parts then took some photos of the engine bay 😄Also while I was away I got someone to do a new paint job .. happy out .. now i can reassemble yayy! 

But.. yes its still not running as it should. 

What I tried today:

• turned down the pressure regulator 25psi > done nothing different
• turned up the pressure on the fuel 40psi > no different. 
• watched the afm opening while i had my foot semi down on the throttle ( could be opening too far? to be investigated )
• found TDC on the piston > which on the distributor cap pointed the rotor to spark lead #1 as it should be > checked the harmonic balancer ( it was at 20 - not sure if this is right or not? have to get a timing light tomorrow but if the car needs to be warmed up then i cant check the timing?  )
• still only runs with my foot a little down on the pedal and will only do so when the TVS is disconnected and wired like in the photo for some bizarre reason. Still no revs and usually cuts out if i push the pedal too much. 
•  

So thats where I am at.. if you are lookin at the photos and think.. my God what a mess.. yes.. YES it is. But it will be done after  I get the engine running in-situ I will pull the engine out & tidy the engine bay and maybeeeee put a manual box on it. 

   Also the FPR is routed that way cause its handy 😄 and yes its the right way ( in and out lines )

I have got a new filter which I will try get on tomorrow but cant see that making any difference?

Thanks again guys and I am happy to be back at it 😄I included a shiny white car now and not the grey and white as before haha  Also yes I know the EGR pipe isnt connected ( its blocked off for now as the pipe was broken and was so hard to see actually )

 

 

 

Don't these have an idle air bypass circuit?

Edited March 5, 2023 by Racer X

[milligan21]

2 minutes ago, Racer X said:

Don't these have an idle air bypass circuit?

Ehhhh not sure what that is 😄 The bypass screw on the AFM? or the other one on top of the manifold? 

[Racer X]

1 minute ago, milligan21 said:

Ehhhh not sure what that is 😄 The bypass screw on the AFM? or the other one on top of the manifold? 

Sorry, I'm not knowledgeable enough about this particular EFI, but usually the throttle butterfly remains closed at idle (including starting unless one depresses the accelerator slightly while cranking to start, which shouldn't be done with EFI systems), so some provision must be in place to allow sufficient air to enter the engine for starting. The GM throttle body fuel injection systems used in the early days of electronic fuel injection well into the 1990's all used an idle air bypass to provide startup and idle air for engine air/fuel management.