Fuel pump / relay issues. 280Z

[Thewondrous]

Thanks in advance for reading this, and hopefully you can help.

 

I've got a 78 280Z that has its fair share of problems like all Zs, but this is one i cant seem to find the answers for anywhere. Checked all the forums here, atlantic Z club, the efi bible, the FSM etc. So the problem goes as follows..

 

For about 3 months now my z will have this nasty habit of dropping the RPMs to 500 while idling. I used to pump the gas pedal or just hold it at a steady 3 or 4000 RPM and it would eventually right itself and go back to idling and driving proper. I thought that it was clogs in the fuel lines and if i just kept pressure on the fuel lines they would bust loose and everything would be fine, but i guess i was wrong about that.

This past Sunday i was driving and it dropped to 500 RPMs again, but this time, no matter what i did, it would not right itself. It sounds almost as if only half of the engine is firing while the other half sits there.

So i drained the tank, cleaned the pump, new fuel filter, cleaned the lines (and i found a lot of black powder gunk, a LOT of it) put everything back together thinking, "That should do it!" But it did not.

 

In short: I can start my car if i give it gas but it will not stay running. And while it's "running" it only has half the RPMs it should. when i turn the key to the ON position the fuel pump will turn on for a split second and then turn off.

 

 

My dad and I think that the problem is the fuel pump relay not sending power to the pump.

 

I'll try to be as helpful as i can to anyone who wants to help.

[JayBee280]

well i had a similar problem i drive 78 280z.

 

Before i get on to what i did. Check your spark plugs. you should run copper plugs in that car. I put platinum spark plugs in my car hoping for the best....then got the worst 3000 miles later. They looked like they were 20,000 miles old. The copper plugs run much better. I went to autozone hoping to get some more platinum plugs until the guy told me copper plugs were recommended.

 

well anyway

First thing that happened to me was my car would run like crap it would idle below 700 rpm then shut off. on the fuel pump itself there is a filter screen....well heres the link http://www.atlanticz.ca/zclub/techtips/fuelpump/index.html. basically i removed the whole screen because it was gunk all in it...after that it ran and idle smooth like new.

 

um and the relay issue...i had the same problem mine would flicker on and off sometimes cutting my car off. So what i did was cut the wires that ran to the relay. found a 12v positive power source. ran the positive to the switch grounded the negative wire and now i have a fuel pump on and off switch. my came with and on and off switch for something i dont know what for. But you can find switches and lowes or hardware store and they also have relays there that people use in homes. im not sure if it would work but i figure if you buy a relay with the right amperage/voltage whatever and run the wires you need you can probably replace the relays in the car i havent tried it yet. Just ran the switch it works perfectly. umm well if you dont get anything i just said than ask im more than welcome to help where i can.

[Daeron]

http://forums.hybridz.org/showthread.php?t=135748&highlight=efi+bible+step

[Thewondrous]

Daeron: I know i know the EFI Bible is holy and all that, but honestly it did not help me.

 

JayBee: The fuel pump seems to be working fine once he hit it with a hammer a couple times. The switch thing is a good idea, i've got some for my wipers, the Z motor crapped out, so now i have high speed civic wipers. much better, even with the one speed

 

Took out the plugs and they were all black and wet, cleaned em up, redid the connections with the injevtors, ecu, relays and blew out the fuel rail on top.

 

Now all 5 cylinders are firing, yes five. The frontmost injector crapped out on me. I have no idea how if stopped working completely, or how it running again, or why during that process one of my injectors died. We did the old screwdriver to ear to injector trick and all other five click along great, but you can barely hear the first one at all. Just about to replace it with one we picked up from autozone for $42.

 

I was worried about replacing all injectors at the same time. Partly because getting the fuel rail off is a *****, and second just because one has already gone bad... and i dont want to risk 5 more

Edited February 28, 2010 by Thewondrous

[Daeron]

My car was running with a switch on the fuel pump for a long time, too.

 

Then I had an electrical fire, and here I am six years later with no Z-car. The fire wasn't related to the fuel pump wiring (at least, not directly.. it seems to have been related to the original fuel pump/ignition lockout circuit but I haven't ripped it all the way apart yet.

 

You are obviously getting ample fuel to your spark plugs; possibly far too much. Is the TPS functioning properly?

 

The fuel pump relay will not keep the fuel pump on after letting go of the switch if the engine is not running. At the very least, get the relay out of the car and visually inspect it; if that really is the culprit then go ahead and bypass it with your own wiring, but understand you are bypassing a factory safety cutoff.

 

It has been a while since I read the EFI bible through, cover to cover, myself, but I know it has thorough diagnostic procedures for all the components, and I know it explains the theory of how they all work together well enough, and outlines troubleshooting methods (flowcharts etc) thoroughly enough that just letting you know you are running rich ought to help point you towards finding your problem. Make sure your spark coming out of the plug is good and blue, (unless there is any chance the timing is off; then you'd need to check that.) but if thats okay then your problem lies in the EFI. Check the AFM signal, and the TPS signal, each at the component and then once more with the multimeter back at the ECU plug (testing through the whole wire harness.) Sometimes a component works fine, but the harness is to blame, and the ECU gets bad data. GIGO, Garbage In, Garbage Out.

 

 

Sorry I missed your first paragraph; I skim these posts sometimes and just post the link just as above. I figured I may as well try to give you a hand by way of apology.. but without more concrete data you are quite frankly stabbing blind. The Bible has pretty well all diagnostic bases covered. The first time I read it through it was about 80% Greek to me, but like the thread i linked to says.. re-read. After about five or six times (with a few time gaps in between) all of a sudden I was diagnosing peoples problems from my keyboard.. and this is without an EFI Z to play with!! (I didn't get my hands on the Bible while I still had my car on the road.) Eventually the cold, crisp, simple logic of the system will work its way into your head and you will speak its language. Believe it or not, it is a matter of dumbing your brain down to L-Jet's level to understand how he works.

[Tony D]

Seriously, if the 'EFI Bible didn't help at all' then you're missing the obvious. A case of not seeing the forest because of all the trees in the way!

 

Think about what you said: "The fuel pump worked fine after we hit it with a hammer a couple of times."

 

Why on earth would you blame a power relay for a physical blockage jamming up the fuel pump?

 

Sorry if I missed it, but you stated (or not) that the power is being interrupted to the pump, this is why you suspect the relay? Is this it, or just a grasp?

 

What controls the relay (EFI BIBLE) --- the AFM switch contacts in some cases. If the bypass has been dorked with, and there is not sufficient AFM Flapper angle, the contacts may be intermittently opening when a plug misfires (yes, the RPMs can be affected enough to do that!) and that will shut the power off to your pump.

 

Revving the engine to 3-4000 rpms likely cleaned off plugs which were wet-fouling due to incorrect bypass setting of the AFM (EFI BIBLE) and then when you returned the engine to idle all was well again. (see how this stuff works together--incorrect bypass/flapper angle/fuel pump operation/idle speed/misfires due to bypass screw bing set rich...)

 

Perhaps only turning up the idle speed screw on the TB will move the rpms to 850-900 and see if it continues to happen.

 

But at this point, after taking a hammer to the EFI pump to 'get it working again' perhaps, plain and simply, the thing is crudded up or worn out to a point where it's in need of a replacment.

 

But "EFI BIBLE USELESS"? Only because the trees were in the way! Only because the trees were in the way!

 

All my post above is a direct result of drawing lines of reason between circuit functions and component functions as described within the EFI Bible. This stuff isn't rocket science, don't try to make it that hard. And in the same vein, not everything is solved with a hammer---it may have a symptom revealed, but it wasn't FIXED!

Edited March 1, 2010 by Tony D