Weird problem, possible fuel pump?

[galloguy05]

Ok so here is my problem. A few days ago I parked my car in the garage to do suspension work. After gettig the front done I wanted to take it for a drive to feel how the ride was. But to my suprise the car will not start. I go through the steps to figure out what is wrong and discover that I am not getting fuel. So I go into the back and tap on the fuel pump and then the car starts! So it runs fine after that for a while ad then I let the car sit overnight. Go to start the car the next morning and nothing again. Fiddle with the wires on the fuel pump and tap the pump again with a wrench and it starts. It ha ran fine since then (allbeit at idle since it was in the garage.).

 

So today I go to drive it again and it starts and I pull it out of the driveway and park it on the road. I go to take off and after a few feet the car dies and will not start again. So my question is, is this a bad fuel pump or a bad relay or bad wiring?

 

Thanks in advance.

[roger.svoboda]

if you tap the pump and it runs what do you think? you didn't hit the relay. wiring check with a vom.

[galloguy05]

I went to start the ca. And it started but immediately died. Then afterword it just turned over with no fire. I was also thinking that maybe it could be a bad afm? Since I know that the afm controls the pump power. I will install the new fuel pump later and see ifthat fixes anything. I just didn't want to spend the money ifthatbwasnt the problem but I went ahead an bit te bulle and got one anyways, that way I figure if it still doesn't work then atleast I know it Isnt the pump.

[NewZed]

I went to start the ca. And it started but immediately died. Then afterword it just turned over with no fire. I was also thinking that maybe it could be a bad afm? Since I know that the afm controls the pump power. I will install the new fuel pump later and see ifthat fixes anything. I just didn't want to spend the money ifthatbwasnt the problem but I went ahead an bit te bulle and got one anyways, that way I figure if it still doesn't work then atleast I know it Isnt the pump.

 

What car and engine are you working with?

 

AFMs control fuel pump power only in certain years. Your pump-tapping solution suggests that is not the problem though. Plus the fact that it turns over but doesn't fire now.

 

When you hit Start, the fuel pump cutoff is bypassed, whether it is AFM or oil pressure controlled. If it was the AFM switch it would start, run for a few seconds, then die.

[galloguy05]

75 280z running everything stock as far as the engine and fuel management. When unsaid it doesn't fire I meant that it doesn't start. I have spark at the coil and at each plug and the timing is correct.

 

I can't say that the tapping on the fuel pump is what solved the problem. I took off the main fuel line into the fuel rail and there is no fuel coming out at all.

[galloguy05]

NewZed- You were correct. It was not the fuel pump. I took it out to replace it with the new one that I got and i noticed that one of the power wires was barely hanging on there. So tapping the pump and messing with the wires fixed the wires temporarily until they shifted again and would not allow current to get to the pump. I put new connectors on the ends of the wires and hooked them up to the pump and it works perfectly fine.

 

Thanks everyone!

[galloguy05]

So I ended up replacing the wire connections to the fuel pump and it was still doing te same thing. I traced the positive power wire back all the way under the car (the previous owner ran a seperate wire not in the harness). And it was spliced into some wire in a relay up under the dash. So I got rid of all that and ran a direct power wire to a switch in the cabin with an inline fuse and re-ran it to the pump and it worked awesome. Is this bad to do though? I can run the wire into an accessory wire if that would be better so that way it comes on like the radio does. I figure this way it's somewhat of an anti theft device as well though ad I am happy with it. Took the car out for a spin with the new front shocks and the car feels like a completley different car and can't believe it is 35 years old!

Edited June 9, 2010 by galloguy05

[19762802+2]

So I ended up replacing the wire connections to the fuel pump and it was still doing te same thing. I traced the positive power wire back all the way under the car (the previous owner ran a seperate wire not in the harness). And it was spliced into some wire in a relay up under the dash. So I got rid of all that and ran a direct power wire to a switch in the cabin with an online fuse and re-ran it to the pump and it worked awesome. Is this bad to do though? I can run the wire into an accessory wire if that would be better so that way it comes on like the radio does. I figure this way it's somewhat of an anti theft device as well though ad I am happy with it. Took the car out for a spin with the new front shocks and the car feels like a completley different car and can't believe it is 35 years old!

 

You might want to add in a fuel cutoff switch, I think you can get them at Blackdragonauto. It will be nice to have in an accident if your knocked unconscious or forget about the pump, it will shut it off in an accident.

[galloguy05]

You make a very good point. I will look in my black dragon catalog when I get home.