78 280Z Funky Fuel (EFI) Problems

[The_Wondrous]

I purchased my Z around late June of last year with the car running fine, well except for a oil leak. For the longest time I had no clue where the oil leak was coming from, until one day we found that it had been leaking out of the oil pressure sender. I've never heard of that happening before but a new oil pressure sender certainly did fix the leak. Now this is where the problem started... For a few days the Z drove perfectly, then tragedy struck in the form of, from what I can tell, a faulty fuel pump relay.

The car will start right up about 95% of the time and drive just fine. After a minute or so though the RPMs take a dive and the car sputters and stays under 1000 RPM before either stalling out, or if I'm lucky, revving back up to normal. My dad and I think that it's the relay cutting out and the fuel pump shutting off and not sending fuel to the engine. And all things I've researched online, (The manuals arn't helpful at all for this problem) point towards the relay being the culprit. BUT, I read somewhere that the relays are somehow connected to the oil pressure sender...

My delima is as such... Is it the Fuel Pump Relays causing my fuel pump to cut out, or could it have something to do with the installation of the new oil Pressure sender?

(I had no part in the installation of the new pressure sender, so I can't answer many questions about that.) Oh, The fuel pump has been tested and it's in 100% working order. If anyone can shed some light on this I'd be very grateful. It's been almost a week since I've dared to drive my car for fear of stalling out and having someone slam into me.

Thanks,

Charlie O

[Neumeier]

Hi Charlie,

I would recommend buying a pressure gauge to test the pressure in the fuel line. You can purchase one at an auto parts store, which probably has fittings and hoses. Or, you can buy one from a company like McMaster Carr. I have one from them. It is an Ashcroft gauge (0-60 psi). The number on the dial is 593-06 (maybe this is a part #). I believe that you should have between 30 and 36 psi (depending upon whether or not the pressure regulator is connected to vacuum). It is 30 with it connected.

Checking the pressure (after the fuel filter) is a sure-fire way to know if it is a fuel delivery problem. Your problem might even be as simple as a fuel filter.

I really doubt that it has anything to do with your oil pressure sensor. Its not part of the fuel injection circuit.

Good luck!

John

[sblake01]

I've had a bad connection at the temperature sensor on my 810 and a bad temperature sensor on my 280Z cause that same problem. Not saying that that's your problem but it's easy to check. Pull the connector from the temp. sensor and clean the terminals on both the sensor and the connector and see if the problem goes away. If it doesn't, run a resistance check as per the FSM on the temp. sensor. If it's good you can rule it out and if it's bad you've solved the problem.

[The_Wondrous]

Fuel pump relays both bench test "good". Fuel pump bench tests good. However, once installed, pump runs about 0.5 to 1 second after ign switch is moved to 'run' position then shuts off. It took several 'hits' to prime the new fuel filter and the FI rails.

I'm thinkin'... How might the airflow meter impact voltage going to fuel pump via the relays? Could the AFM possibly be the culprit in shutting off the fuel pump?

AFM cover has been off before or so says the silicone sealant 'round the perimeter of the sealing surface. Not nasty in there, really but there could be some corrosion hiding 'round electrical contacts...

This is Charlie O's daddyO secretly postin' on the 'puter who don' know nuttin bout the workin's of an AFM... Yet! With questions of those who BTDT...

[m4xwellmurd3r]

it wouldn't. in a 78, the AFM has no part in the control of the fuel pump. you must have a loose connection somewhere in the wires, maybe from your oil pressure sender or a ground wire something.

[The_Wondrous]

I think it is a loose connection. This car appears to have a lot of them. Disconnected and reconnected all fuel relays and the ignition relay and the Z decided to idle well. I didn't have a chance to drive it because the interior and tail lights went out.

If anyone knows if those are on the same connection and where that is, (Or where they are separately if they are indeed separate.) it'd be nice to know and not have to dig through the wiring diagram with no guarantee of finding it.

:classic:

[The_Wondrous]

I've had a bad connection at the temperature sensor on my 810 and a bad temperature sensor on my 280Z cause that same problem. Not saying that that's your problem but it's easy to check. Pull the connector from the temp. sensor and clean the terminals on both the sensor and the connector and see if the problem goes away. If it doesn't, run a resistance check as per the FSM on the temp. sensor. If it's good you can rule it out and if it's bad you've solved the problem.

The temperature sensor connector on my Z is a bit worn, so we were hesitant to say the least about messing with it in the cold, and as for the FSM resistance check... Well, at the moment I don't have the $80 to spend on the FSM. You wouldn't happen to be able to give me the values of what they should be could you?

[m4xwellmurd3r]

the fuel injection bible has the numbers it should be. ummm lemme find it.

http://www.atlanticz.ca/zclub/techtips/efisystem/280zfuelinjectionbook.pdf

there's the link. it has the resistance measurements for the water temp sensor iirc.

[sblake01]

You wouldn't happen to be able to give me the values of what they should be could you?

Here's an old thread with the page that shows th test procedure. It's from a 76 FSM but the values are the same as a 78.

http://www.classiczcars.com/forums/showthread.php?p=220706&highlight=temp+sensor#post220706

[TBK1]

Might want to check the condition AND Tighness off all 4 fusable links , they can cause a similiar problem

[ktm]

www.carfiche.com They may have an FSM for your model year. If not, grab one that is closest in year. If it is showing N/A, just wait an hour and try again (as indicated on the web page).

[EdMo]

Just wanted to say thanks for your posting, because I am having a similar problem. My problem seems to be more of getting to much gas and choking itself.... but your post answers give me a few more things to try. Thus far, I have replaced fuel pump, fuel filter all injectors and sensors are new and even replaced the temp sensors of the fuel injection and water temp. I did not change the connectors that plug in but did try and clean, but still do not have a complete resolution. I was thinking of working on the AFM, but before so may try a few other things, like fule pressure regulator and fuseable links...I'll post later if I have any good results after this weekend. My plan is to work on it some...