A wiring problem was noticed and fixed. Other wiring problems are ruled out. The fuel pump prime wire at the + battery line was followed to the computer & is in good health. As far as I can see, the computer or the fuseable link is the culprit. Are there any other reasons a fuel pump won't prime? Pump comes on as I'm attempting to start the car and for a few seconds after. Don't want to spend $85 for a computer without other advice.

Thanks,
Brandon

 

Before you condemn what is probably a good ECM, check for voltage at the 'A1' terminal right at the ECM. The signal will only be present for two seconds when the ignition is first turned on. After that, you must turn off the ignition for twenty seconds before the pump relay will cycle again. Only if there is no voltage directly at the card edge should you consider replacing the ECM. If there is voltage for two seconds, you still have a wiring or other hardware issue, like a relay or connector.

 

What's the best way to tell if there's voltage? In other words...what tool is needed?

Brandon

 

If you don't already have access to one, a medium-priced digital multimeter would be a good investment. You can get a really cheap one for $20-30, or a decent quality one for about $59 (like a John Fluke 70-series).

 

Any other reasons a pump won't prime?

 

My car primes slow as hell. It only starts up right away if I have ran it in the last like 2-3 hours or I prime it twice. If I dont do that it just turns over till the system primes itself. (about 5 cranks) not bad really. but I would like it to start up with just a flick of the key.

 

Any other reasons it won't prime? Oil pressure switch maybe?

Brandon

 

The auxilliary oil pressure switch is there as a redundant system to supply power to the fuel pump. It operates in addition to and parallel to the relay circuit (see schematic). Failure of the oil pressure switch will not necessarily prevent the fuel pump from operating, unless it has shorted to ground and is shunting all power to the pump.

I'm not clear on where you are mesuring power in the circuit, but there is a 20A fuse protecting the fuel pump and ECM power circuits, located in a holder under the hood.



Taking this whole situation backward a step, exactly what car/engine/fuel system do you have? A CFI 305?

 

I wish a 305! Running an Iron Duke in an 84 Camaro.

Brandon

BTW, pump will come on as I'm starting the car and will stay on for about 2 seconds after trying to start it. Pump just won't prime before hand.

 

The pump shoudl operate for two seconds after turning on the ignition. Although, to prevent overuse, the pump will not "prime" the system in this manner again until the ignition has been turned off for at least 20 seconds. However, the pump will operate immediately when the ECM detects distributor reference pulses (from cranking) or at any time that the auxilliary oil pressure switch closes.

 

I take it the oil pressure switch and the distributor are fine....from your comments above. Either a wiring problem or faulty ECM may be the culprit.

Brandon

 

Certainly seems like all is pointing to the relay (as mentioned before)!

 

Ok! But.....tried the old relay and the new one. Guess what.....nothing! Still think it's the relay? Maybe a wire problem.

Brandon

 

Watch the MIL lamp when you first turn on the ignition. Do not crank the starter, just turn on the ignition. What does the light do?

 

Not sure what a MIL lamp is .

Brandon

 

Got the same problem on my 90 TA, pump won't prime. We see no voltage on the scanner when I turn on the ignition. After maybe 10 seconds of cranking, we get a solid 14 volts and the TA starts. Taking the meter to it tomorrow..

 

I need to get a scanner and meter for it! Unfortunately....there's not enough juice in the battery for 10 seconds of solid cranking. Have to jump off another vehicle just to get 4 or 5 cranks.

Brandon

 

Think I found the culprit! I noticed this toggle switch on the dash. Knew it was there...nothing happened when the toggle was swtiched. Didn't figure it was connected to anything. Anyway....it's connected directly to the fuel pump relay. It's definitely a wire issue.

Brandon

 

It sounds like that switch was an attempt at a fuel cutoff device for either theft prevention or safety. It certainly isn't a factory switch.

 

Some safety device ! The switch was mounted in plain view on the dash. A big is in order for me. Knew that thing was there, just didn't think it went to anything.

BTW....do you connect a fp cutoff switch to the relay?

 

HI......I have problem to with my fuel pump. i have a 87 iroc-z, tpi v8 305. when i turn the ignition key to the on position the fuel pump makes that noise singnaling that its collecting fuel or whatever it does. then i turn the key to start the car. now all of a sudden the fuel pump stays on with that noise it makes like its not getting fuel or its stuck! can it be a relay is bad or wiring? the funny thing is it might be the wiring cause when i shift into a gear. the fuel pump kicks on again......yeh it sounds really silly but yeh thats what happens also! the fuel pump is stuck and my injectors arent getting any fuel or little fuel. you can here the injectors clicking rapidly cause there is little fuel or no fuel goin threw and my car wants to die out! basicly fuel in my car has been a probby for a long time. right now i have new fuel injectors, oem fuel lines, and then im getting a new holley fuel pump made for my camaro. so what do you think i should check out for the problem. if anyone can help that would be cool. thanks

ps. just for the record the shifter i have is a b&m
shifter and maybe the wiring is messed up causing the
fuel pump to come on?

pss. where can i get the official owners shop manual
for my camaro? book or cd type?:hail:

 

WSD,

Your fuel pump isn't "stuck".

The fuel pump operational cycle is as such:

The fuel pump relay controls 12VDC power to the in-tank fuel pump. When the relay is enrgized, the pump should be running, providing fuel pressure and flow to the injector(s).

The fuel pump relay is energized for two seconds by the ECM when the ignition is turned on. This fuel pump "prime" cycle will not repeat unless the ignition has been turned off for at least twenty seconds, then turned back on.

The fuel pump relay will be energized by the ECM whenever the ECM detects distributor reference pulses from the HEI module (meaning the engine is turning).

The fuel pump will be energized directly, bypassing the relay, whenever the engine oiling system has a pressure of 4-7 PSIG or higher. This redundant system provides fuel pump operation in case the relay or its circuit fails for any reason. This is also the reason that you will sometimes hear the pump running after the ignition is shut off, and until the oil pressure has been relieved.

The engine will not run unless the fuel pump is running. The pump is not there to simply "prime" the system than shut off. Additionally, the injectors should make a clicking sound whenever they are operating. The rate that the injectors operate is controlled by the ECM and is based on engine speed, not whether there is adequate fuel or not. The ECM will fire each injector on a TBI220 or each bank of injectors on a TPI system twice every engine cycle (once every engine revolution). Therefore, the higher the engine RPM, the faster the rate of injector operation. The ECM controls the amount of fuel delivered not by controlling when the injectors are operated, but for how long (duration) the injectors are operated.

It sounds like your engine is operating normally to me.

 

I wouldn't connect it to the relay, since the auxilliray oil pressure switch will still operate the pump whenever there is oil pressure from cranking or running. You'd have to interrupt the circuit to the fuel pump itself to be effective.

 

ok......thanks guys but just one more thing. its just that before this happened the car was running fine and the fuel pump did its priming as you guys call it and thats it. but when it keeps priming..and doesnt shut off the car is acting like it wants to die. but ill check out some of the wiring and relay. thanks again.

i bow to the thirdgen. camaro's and the tech help :hail:

 

im having a simular problem. i tried what vader suggested in the first reply of this thread. im not sure where he ment to try this test so i used the plug under above my right knee beside the steering column. i dont have any power in any of the outputs and some have .5 and some have 12v when the key is on. but i did not see power in the top right hole as mentioned by vader. did i even try the right hole? thanks guys

 

You should be testing for pump voltage at the pump relay itself (under the hood on most cars).

 

Finally replaced the relay on mine and it fixxed the problem. I hear the pump prime and it starts right up after 2+ hours of sitting. Advanced claimed it was a dealer part.
Napa has them Part #AR279.

 

oh.....i just wanted to say thanks guys for the help......my fuel pump was getting gummed up with particles in the tank so i just replaced the fuel pump and put in a new tank. i checked the the fuse under the hood and its good but the wiring is still a problem because say the car is off i turn on the lights the fuel pump goes on for a split second, if i turn on the fog lights the fuel pump kicks on again, very strange.....if i put the car in neutral or drive when the car is off the pump kicks on again for a second, still very strange and get this if i turn my hazards on or flick my signals when the car is off the pump kicks on again for a split second, very very strange, and very retarded too and to let you guys know the key was turned on the on position as i did all of this. and also for the record im not the original owner of the car...so i dont know if things were wired wrong or wires being spliced into wires i mean who knows. but other than that the car is excellent. so if any of you know what i should trace in the wiring let me know cause its really annoying. i took out an alarm thinkin this original owner might of messed suttin up and plus i didnt want it so i uninstalled it to see if this could be the cause but nope. thanks again for the help.

ps. i need to know how do i put my pic of my car on this site cause i tried before and the file size is to big how do i get it to fit in the right file size! no one hasnt answered me that ? yet and i would like to know. :hail: :hail: :hail: