Fuel Pump gets no power

[zewald]

19-20 is great guys, remember, i said i have a truck. haha. i get 16 on average. any savings helps.

I've tried depressing the flap of the AFM, but nothing happens. actually, i have the fuel line disconnected from the intake manifold, because i just want to see if the pump will fill the line and make it overflow (into an empty coke bottle) does that have anything to do with it? will it not pump if the manifold isn't registering fuel or air movement?

Zed, yes, i've done that, and thanks for all the info. the pump doesn't run. i'm getting very discouraged.

BTW, at O'reilley auto, the combined relay is around $140 but at nissan genuine parts, it's only about $80 at least that's what my research has found: just a quick fyi. I've checked the relay and it clicks just fine, how would a faulty fuel tank sensor effect anything? i think mine might be faulty.

[Zed Head]

The EFI fusible link is a green wire with a connector on each end, that is in-line from a tap off of the positive terminal of the battery, in the engine bay. Check it for power on the output side, it's hard to tell if they're bad.

It looks like the coil and ignition module are on a separate circuit so maybe the car will run on starter fluid with the EFI fusible link blown.

Back to what cozye suggested. Page EF-4 in the FSM shows that the injectors, the fuel pump and the air regulator all get power from the EFI/Fuel pump combo relay. I would turn the key to On and see if I had power to the injectors, then open the flap, key still On, and see if I had power to the air regulator plug (the air regulator has a heater inside that turns on when the engine is running), I think that pump might be on the same circuit (according to the big wiring diagram). If you don't have power on the output side of the relay (injectors, air regulator and pump wire), but do have power in, then maybe the relay is bad. If you stare at the diagram long enough you can figure out how to jump it to get power to the fuel pump wire, just for a test (I did it to install a cutoff and priming switch for my pump).

Page EF-54 has the procedure for checking the combo relay. Not too difficult if you can reverse things in your head to figure out what pins you're looking at. You can at least check all of the pins on the connector for power to see if you have input power to the relay.

If you browse through the Engine Fuel section of the FSM you might get some more ideas.

Edited March 9, 2011 by Zed Head

[tlorber]

Have you tried hooking 12v directly to the pump? Just to see if it will push fuel through?

My car is a '73 which doesn't have all the cut-offs but it sounds like the later Z's have a series of sensors that tell whether the motor is running. If you can jumper around these to provide a "yes" condition to all, and then one by one remove the jumpers you may be able to eliminate the problem.

Where in North Hills are you located? I spend a fair amount of time in Van Nuys.

[zewald]

right next to CSUN. off the 405

[zewald]

you guys, and girls of course, thanks fast woman, have been great, thank you. i think friday is the next day i'll have enough time to do anything, so i'll let you know how it goes.

Edited March 9, 2011 by zewald

[FastWoman]

You're welcome! Tlorber has a good point. I've read on this list where someone had a steel fuel line clogged with crud. It's not a common problem, but it could certainly happen.

[zewald]

ya, checked that too, i sent compressed air through the whole line.

[FastWoman]

Or maybe crud from the tank could have clogged or jammed your fuel pump?

Check your fuel pump for electrical conductivity. If you don't have any (infinite resistance), then that's your problem. Then try jumpering some power directly to it to see if it runs.

[zewald]

ok, so after checking every circuit that runs through the control unit, it looks like everything but the air flow regulator circuit is good. also, i took the fuel pump relay off and tested continuity (based on the FSM) and that seems to be shot. I was under the assumption that it was functioning regularly because when i turned the ignition to "start" it clicked once. apparently it should click repeatedly? i'll see if i can get a mechanic friend of mine to get me a good deal on one, and keep you guys posted.

also, at pick a part i found a throttle valve switch and a motorized antenna, i'm happy about that.

hope the relay and air flow regulator fix my problem. thanks for all the ideas guys.

on a side note, when i turn the car ON, my catalyzer lamp comes on, should that happen? i'm actually still confused on what that actually indicates.

[FastWoman]

I don't remember the way the '75 is wired. It was long ago that I owned one. My '78 has two relays in that circuit. One is the fuel pump control relay, which shuts down the fuel pump if the engine dies. It's a rather complicated relay that could only be replaced with an OEM part. The other is the actual fuel pump relay (which is controlled by the fuel pump control relay). It's a very simple relay that could be replaced with a Bosch-style SPST relay, available at any auto parts store for maybe $5. (You'd have to change connectors.) I'm hoping it's the simpler type that's giving you headaches.

[zewald]

Alright, after installing the new throttle valve switch, replacing the contacts on the cold start valve and the air flow regulator, and fixing some broken wires...

IT WORKS!!!

you guys have been great, and honestly, even with help from my step dad (who used to work as a mechanic) i would not have been able to figure it out. Thank you SOO much.

the car is running, and after about 10 seconds of holding my breath, waiting for it to start clanking and shaking and blow up, it didn't. the engine sounds great. i think that's about it on this thread for me. i'll probably transfer over to the "what i did today" forum. hope to see you there

thanks again

[knarfrabot]

Could any of you guys point me to the direction of the fuel pump relay and the starter relay for a '78 280z, I have the same issue with the pump not getting power. thanks in advance!