Diagnosing a Fuel Pump Issue

[Dusty_Duster]

My new Walbro 255 l/hr fuel pump finally arrived, so I'm going to install it on Saturday. Before I drop the tank, though, I'm going to double check that voltage is applied to the pump when the key is first turned to the "RUN" position.

To do this, I simply disconnect the plug at the pump, put my voltmeter across the two terminals of the plug, and have a second person turn the key to "RUN," correct? There should be 12.5 Volts or so for about 2-3 seconds?

Also, if I DON'T get the voltage, what could cause that problem other than broken wires? (Relays, etc)

Thanks for the help in advance. This site rocks. :rockon:

[off the map]

Its about 1 second. The relay is by the battery(if you are working on minivan).
What vehicle?

[Dusty_Duster]

Its about 1 second. The relay is by the battery(if you are working on minivan).
What vehicle?

It's a '93 Duster, but the wiring is basically a '90 Dodge Shadow.

So the relay is the only thing other than the wiring that could cause the fuel pump not to come on?

[JDAWG]

no, hep not owrking, distributor not working (timing belt broke, skipped teeth, etc.), i think that car has a asd as well as a fuel pump relay, could be alot of things

[off the map]

It's a '93 Duster, but the wiring is basically a '90 Dodge Shadow.

90 turbo harness, is the ECU from that car?
is it tuned? stock? socketed?
I have heard that the fuel pump sometimes will not operate if a different ECU is used-(diff from what it rolled off the lot in 1990 with)-problem could be somewhere in your harnness too....

[Dusty_Duster]

90 turbo harness, is the ECU from that car?
is it tuned? stock? socketed?
I have heard that the fuel pump sometimes will not operate if a different ECU is used-(diff from what it rolled off the lot in 1990 with)-problem could be somewhere in your harnness too....

It is a stock 1990 ECU. The problem occurred all of a sudden. I went to start the car one afternoon, and the fuel pump would not come on.

I tried jumpering from the + terminal of the battery to the + side of the coil, and the pump still did not come on, though there was a spark when I touched the jumper to the + side of the coil.

[HoverFish]

If there was a spark when you touched the coil, I'd look at the ASD.

[Dusty_Duster]

If there was a spark when you touched the coil, I'd look at the ASD.

Really? Thanks! I'll check that first.

Is Autoshutdown Relay the correct term to ask for at the autoparts counter, or is there some other term I should use? (For instance, we call it the AIS, but most other vehicles use the term IAC, or Idle Air Control.)

[JDAWG]

auto shut down relay

[BIGBRUDDA]

Careful there Dusty!:nod:
Check the plug connection, ground, and thru-plate terminals. I've had "hair pullin/burst inta flames":eek: problems from those.
The triangular rubber plug is a known trouble maker.:mad: The terminals inside corrode, run the current up and melt the insulators. Both at the plug, and inside the tank. Test for a GOOD ground at the plug, and or run an auxialury ground wire.:thumb:

[Dusty_Duster]

Careful there Dusty!:nod:
Check the plug connection, ground, and thru-plate terminals. I've had "hair pullin/burst inta flames":eek: problems from those.
The triangular rubber plug is a known trouble maker.:mad: The terminals inside corrode, run the current up and melt the insulators. Both at the plug, and inside the tank. Test for a GOOD ground at the plug, and or run an auxialury ground wire.:thumb:

Thanks for the tips!

I'm going to check for voltage at the fuel pump plug first. If there is no voltage, I'm going to check the resistance between the ground terminal and the chassis. If that resistance is fine, I'll try swapping out the ASD and fuel pump relays.

Of course, if I get voltage, I guess I'll have to install that new pump after all. :(

[JDAWG]

jump power right from the batt to the pump and see if it turns on

[Dusty_Duster]

It turned out to be a bad ground--behind the dash! WTF?! Any way to run a "redundant" ground wire to try to keep this crap from happening again?

[BIGBRUDDA]

Said it in my quote.Auxialary ground at tank plug to frame cross member. 12" of wire and a #10 SM screw.