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No fuel pump activation at key-on


keller
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I was going to pull my 'beater' high mileage '89 out of the garage for some pics so I could get it registered for collector insurance. Well...it would not start. I quickly determined that the pump was never doing the 'prime' sequence at ignition on. I did a few cranks, and it did not run either. Probably not enough cranking to generate enough to run the oil pressure high enough to trigger the backup circuit. (I believe it has one, right? My '87 turbo Regal does. Haven't scanned my manual yet...)

I did check the fuses that I presumed were relevant. All were fine. I also grabbed a relay (sadly, not a skirted/sealed type) and that made no difference. The manual indicated there is a test/prime connector underhood, but I could not find it and I was tired of freezing in my garage. Sooo...

- Do these cars really have such a test/prime fuel pump connector, and if so where is it? My info indicated somewhere near the fusebox underhood.

- Other than the FP fuse and/or relay, anything else I should check before I get ready to buy a pump and drop the tank shortly?

Only have a few decent weather days this week. Hope this won't be a big PITA. Already want to sell this one. May start grumble about parting it again...

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I'll have to check the schematics. On the other GM cars I've used these connectors on I've always had to apply +12V to get the solenoid to activate and the pump to run.

Thanks for the lead on the location. I'll poke around tomorrow.

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It really has two purposes:

1) apply 12v to put power on the pump

2) meter to see if you get voltage to the pump on key-on

Since the relay is used only to initially prime on key on, if no voltage for 2 seconds when key is turned on then replace the relay.

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Just verified that the original relay 'clicks' when tripped by a 12V supply out of the car. Didn't check the other side of the circuit, but at least that is a good sign for the relay. GM still carry these?

I'll try to test the circuit in the car. Still could be the pump.

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I've verified that the BWD R3074Z (non-sealed relay) I have functions as well with a power supply. Actuates, at least. I picked up a Bosch (69222) pump and strainer, as well as a Purolator filter. I've read the horror stories about no-name pumps, but I I feel that the Bosch was a solid choice, immediately available, and actually reasonably priced. Plus, I'd like to get this done before the weather gets evil again.

In case it really isn't the pump, where is the electrical connection for the pump hanger? Under the car? Want to test things before I drop the tank.

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With everything off, from the prime lead to ground should just be a few ohms: the pump motor. If it shows an open then there is either a wiring problem or the pump is bad.

In that case the hardest thing about the job is draining the tank, it is much easier to drop a Reatta tank than a Fiero's.

However, if you need to replace the pump, use only an AC-Delco and replace the sock also. I would flush the tank while out as well, it is not something you want to do often.

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It appears you have ignored good advice offered by two other members but I will also try to help.

Here is what you need to check:

(See photo below)

<span style="font-weight: bold">Does the pump run when 12 volts is applied to the test connector [C] or to the fuel pump relay terminal [4]?</span>

-If the answer is NO:

The problem is with the pump or wiring going to it. No need to test farther until the pump runs with 12 volts applied to terminal [4].

-If the answer is YES:

Test terminal [1] for 12 volts to ground.

<span style="font-weight: bold">Does terminal [1] have 12 volts when the key is turned to RUN?</span>

-If the answer is NO:

Check the 15 amp fuse #8 and replace if needed.

-If the answer is YES:

Test terminal [2] for a good ground. Repair if needed.

Report back here with the results of your testing.

post-52331-143138037229_thumb.jpg

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<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Ronnie</div><div class="ubbcode-body">It appears you have ignored good advice offered by two other members but I will also try to help.</div></div>

Would those be both the one that told me to ground the test connector <span style="font-style: italic">and</span> the one that told me to hit it with V+? wink.gif Going to have to side with Mr. Padgett on this one.

Since this car hasn't moved any further than the driveway in a year or so, I somewhat doubt that there are any wiring anomalies that have crept up. No mice in the garage that I'm aware of.

While I'm well aware of offshore Walbro pump clones in other applications and other horrid cheap fuel pumps, are there any specific bad experiences with the Bosch?

I'll report back tomorrow.

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As expected:

- Pump does not run

- Does not run with 12V applied to terminal either (green terminal, grey wire)

- Testing resistance on the running car shows low resistance and applying 12V to the 'test' terminal makes pump run, as I would expect. Testing resistance on troubled car shows very high resistance (and its increasing until eventually showing infinite), plus applying 12V does nothing. Switching relays between cars changes nothing.

- Tried to check fuse for giggles. "#8" appears to be a 3A and not for the FP/INJ circuit. All 15A fuses do not appear to be related by description. Regardless, all 15A are fine.

I suppose the harness near the pump should be examined as a final exercise before the tank comes down. But so far it looks like the pump. A few quick questions:

- What is the fuse in this circuit labeled?

- What is its location in the panel?

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Click here to see where the fuse panel is located. There is a hidden fuse panel next to the one that is accessible on the passenger side of the console. The panel layout lists the fuse as #7 and the illustration in my post above lists it as #8. One has to be wrong.

However you can test to see if the fuse is good at the fuel pump relay terminal [1] as I recommended before.

I agree that the fuel pump or the wiring to it is likely the problem.

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Very high resitance could be bad wiring or a bad pump. I'd suggest checking again at the pump once tank is dropped but before removal.

BTW I *always* replace the rubber O-ring (and usually the metal ring also - they usually come with a new doughnut) and sock whenever opening a tank.

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