78 280Z - Finally got it driving - High Idle, will occasionally die (but restart), sound like it has a misfire

[NocturnalEmber]

7 minutes ago, Patcon said:

The rubber insulators are square pads of rubber glued to the top of the tank to prevent it rubbing against the car body.

If you used 2 gallons in just testing then the car is running really rich. Running better with vacuum leaks, which leans the mixture would make sense.

EFI is not my forte. Maybe someone can chime in and tell you what areas need Inspection to see what the PO messed with to make it run with all those leaks. Also the connections at the thermostat housing are important.  If they get reversed it will be really rich. An AFR gauge would still be really useful

 

I replaced the temp sensor with a new one, verified with the FSM that the connections were hooked up right, for 78 its Black to green on the main efi harness.

I don't think the previous owner really..messed with anything. This car from what I can gather, sat inside a garage for probably decades. The clutch master cylinder fluid had turned to a fine powder. I've never seen brake fluid dry out.  I had to replace the entire clutch hydraulic system minus the hardlines, and the same with the front brakes just so it would run and stop. Fuses were oxidized so bad current wasn't passing through because of the increased resistance.

Not that any of that directly relates to why I'm getting fuel pressure issues all of a sudden, but the car sat for awhile. I could be wrong on this but I don't think it was really tampered with much. Both hoses I replaced (PCV and the one on the valve cover) were so brittle they had gaping holes from dry rot/heat.

 

The brand new plugs I put on it when I got it were black with soot, so whatever it is is causing an extreme rich condition, but now I've got the fuel pressure issue to contend with. I'll try filling up the gas can again and removing the feed/return lines and using the gas can as a portable fuel source today and see if the fuel pressure changes. If not, then I'll move onto the pump.  Even though its been replaced already, and I've had an inline fram filter on it since day one (that isn't dirty), Possibly the pump is bad, who knows. 

 

Ideally I'll have more results by the end of today.  I think I might just adjust the valves while I'm at it, the FSM did have that listed in the troubleshooting steps, and I could stand to re seal the cam cover anyway, who knows if that gasket is suspect or not. Hose kit also came today, so all of the vacuum hoses are getting changed out. Maybe if I'm lucky I'll be able to accomplish all of this today.

Will report back with results. As always, if anyone has anything to add, it is sincerely appreciated!

[Zed Head]

6 hours ago, NocturnalEmber said:

15 hours ago, NocturnalEmber said:

After I put the gas in, I started the car, and fuel pressure shot up to exactly where it should be (high 20's, low 30's.) I pulled the nipple off the FPR and I want to say it even read around 36 when I did that.I

 

6 hours ago, NocturnalEmber said:

I'll try filling up the gas can again and removing the feed/return lines and using the gas can as a portable fuel source today and see if the fuel pressure changes. If not, then I'll move onto the pump.  Even though its been replaced already, and I've had an inline fram filter on it since day one (that isn't dirty), Possibly the pump is bad, who knows. 

 

You might be getting distracted with all of the different things you're looking at.  You said that you were getting 36 psi.  That is the correct pressure.  Looks like your fuel supply and control system is working right and you were just running out of gas.  If you're getting ~36 psi with the vaccum hose removed from the FPR, or engine off, and it drops to about 28 - 32 psi with the engine running then the FPR and pump are working fine.  Move on to other things.

I'd measure resistance on the water temperature sensor circuit at the ECU connector.  The 1980 EFI book is the best resource for doing that type of work.  Go to the electrical section.

 

Edited March 6 by Zed Head
+ like

[NocturnalEmber]

3 hours ago, Zed Head said:

You might be getting distracted with all of the different things you're looking at.  You said that you were getting 36 psi.  That is the correct pressure.  Looks like your fuel supply and control system is working right and you were just running out of gas.  If you're getting ~36 psi with the vaccum hose removed from the FPR, or engine off, and it drops to about 28 - 32 psi with the engine running then the FPR and pump are working fine.  Move on to other things.

I'd measure resistance on the water temperature sensor circuit at the ECU connector.  The 1980 EFI book is the best resource for doing that type of work.  Go to the electrical section.

 

I was getting the correct PSI a few months ago when I was troubleshooting the hard start/no rev situation. 

Not that its related (just for a timeline point of view) but back in October ish when I had that fifteen page thread going, I swapped in a used distributor because mine had a chipped tooth on the reluctor wheel and that got the engine in a slightly better state.

After I got the brakes and clutch done last week I finally pulled it into the garage instead of having it backed in, so I started running the engine again, did the test drives, and that is what made me I notice the low fuel pressure issue.

 

The only time yesterday I got the  PSI to go back to "normal" was after I put the gas in it and started it up. It held within normal FSM ranges for *maybe* a minute or so of it running. After that it just slowly began to fall and settled around the 12-14 PSI its been since this problem started.

 

That was the only time the fuel pressure was correct when I was testing yesterday, after I had put the gas in. 

Right at startup and for *maybe* one minute while running. Pressure continuously fell after that period of time down to the 12-14 psi I mentioned. 

 

Should I still move on or check the fuel system further @Zed Head ?

The fact that it held correct pressure for such a short period of time has me thinking that I should check the supply side of the fuel system, but that being said, I will default to the expert opinions here and move onto the resistance check of the water temp circuit if you believe that is the best course of action. (Actually I'm going to check it anyway, I just want to know if its safe to "rule out the fuel supply side of things (ex, tank & pump.)

 

Edit Edit: Downloaded the 80 EFI bible. Are you referring to the water temp sensor checks on page 79 ?

 

Edited March 6 by NocturnalEmber

[Yarb]

First test IMO should be to isolate the tank as suggested earlier by disconnecting supply and return lines. Supply line to pump 3/8. Return line 5/16. Drop them in a 5 gallon can. Start the engine. One variable eliminated.

[NocturnalEmber]

Just now, Yarb said:

First test IMO should be to isolate the tank as suggested earlier by disconnecting supply and return lines. Supply line to pump 3/8. Return line 5/16. Drop them in a 5 gallon can. Start the engine. One variable eliminated.

I suppose I will test it shortly and report back. For such a simple test it could provide valuable data, or eliminate a variable as you say.

[Yarb]

The steps I’m recommending worked for me personally. I was in the same boat. Car sitting for a very very long time.

[Yarb]

Have you replaced the fuel pump? If so tell us about what you installed.

[NocturnalEmber]

55 minutes ago, Yarb said:

Have you replaced the fuel pump? If so tell us about what you installed.

 

In regards to the fuel system (all of these were done when I got the car a few months ago):

Pump is new, (aftermaket unit.)

All soft fuel lines are new.

New engine bay fuel filter

New injectors and seals (x6)

Fram clear filter coming off tank feed line (that is clean.)

Edited March 6 by NocturnalEmber

[Zed Head]

Yarb's suggestion is good.  You could make it easier and leave the return line alone though and let the gas flow in to the tank, if you just want to test the pump and tank.  If it was mine, I'd disconnect the inlet hose from the tank and stick it in to a can of fuel back by the pump and tank.  Measure pressure once.  You'll know.  Super easy.

Your symptoms kind of sound like the "crud in the tank" problem.  The crud floats around in the tank and gets sucked on to the inlet pipe sock, clogging it.  Then when the pump turns off it floats free.

Break your problems in to pieces.

And yes, page 79.  The higher the resistance the more fuel the ECU adds.  Corrosion on the connections can cause excess resistance.

[NocturnalEmber]

Okay, so a potential major update -

@Yarb @Zed Head, like you suggested, I took the feed line off the tank, and stuck it down into my two gallon gas can that was basically at capacity. Left the return line going to the factory tank.

Started the car up, fuel pressure was spot on, car sounded great. I didn't try to rev it, but it was a noticable difference from its shaking/misfiring, etc.

However, after about a minute or so, the pump had sucked up so much fuel from my two gallon gas can (and started puking gas out the feed line in the cars gas tank while it was at it) my fuel pressure again dropped into the teens and it died.

 

So I attempted the test later tonight, refilled my two gallon gas can, but this time I blocked off my feed line on the cars gas tank to keep fuel from spilling everywhere.

 

Same result, initial startup, fuel pressure was great, in the 30's, but as the two gallon can started to run out, the fuel pressure dropped and I shut the engine off by the time it had gotten to 8~ psi.

Fuel pressure at initial startup:

 

 

Fuel pressure after the car had been running for a minute or two (enough to suck the can low enough where the feed hose wasn't likely getting as much gas, causing the fuel pressure to drop (my best guess.)

 

Does this point to the tank being clogged, or the pump itself? I'm kind of at a loss.

Edited March 8 by NocturnalEmber

[Yarb]

As I suggested, place both supply and return lines in your 2 gallon tank. You won’t run out of gas until the engine has burned the 2 gallons.

[NocturnalEmber]

4 minutes ago, Yarb said:

As I suggested, place both supply and return lines in your 2 gallon tank. You won’t run out of gas until the engine has burned the 2 gallons.

I'm still in the garage, so I'll try that right now, gonna drain some gas back into the two gallon can.