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Old 08-01-2001, 11:45 PM
mattklionsky mattklionsky is offline
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'95 Windstar fuel pump circuit electrical problem

I've never met an electrical problem I can't solve - until now, so advice is desparately needed. Here's the situation:

I have a '95 Windstar with a 3.8L engine. It won't start, but the starter turns it over just fine. There's good spark - but no fuel pressure.

First I checked the fuse and the relay in the relay box next to the battery. Both were OK. Then I checked voltage (with key 'on') at the inertia switch infeed: 12 V, as expected. And, I I tested the interia switch too; it was OK. Next I opened the connector where the leads to the fuel pump connect to the leads to ground and to the inertia switch. The ground wire gave zero resistance back to the battery, so it is good. And, with the inertia switch connected, I get 12 V (with key 'on) at the pink+black wire. So, I assumed I had a bad fuel pump.

I removed the tank and got the pump out, but it bench tested OK (that is, it runs fine whenever connected directly to 12V power). So, I tested the wires between the pump and the end of the pump harness leads. They test OK (zero resistance) also. That is, none of my testing found any indication of a problem.

But, since it is such a pain to take out the tank and I have 110K on the car, I replaced the pump anyway (along with the undercar fuel filter and the in-tank filter) and put everything back together only to find I still had precisely the original problem. So I also replaced both the relay in the relay box (next to the battery) and the other fuel pump relay in the expensive PCM power relay (an enclosed multi-relay box) next to the radiator. Neither of these replacements had any impact on the problem.

Further testing with ammeter, voltmeter, and ohmmeter indicates that when there is any appreciable load on the fuel pump circuit, no power gets through (i.e., some relay doesn't work?), but when there is no load, the same circuitry manages to deliver 12V consistently. This is made more baffling by the fact that I have checked the internal resistance of both the old and new fuel pumps. The original pump has a 2 ohm resistance, while the new pump has a 30 ohm resistance across its terminals.

Can it be possible that even a 2 ohm resistance is enough to keep one of the relays from working properly? Is a fuel pump supposed to have as little as 2 ohm resistance (or as much as 30 ohm, like the new pump?) Is there any way that the PCM itself (rather than the PCM power relay, which is a separate module) could play a role in this problem? Does anyone have any ideas or advice about what I can test or replace next to try to solve this problem? I'm already on my second event of removing the gas tank, and that's enough!

Greatful for any ideas anyone of you might have,

Matt Klionsky
klionsky@megsinet.net
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Old 08-02-2001, 05:50 AM
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'95 Windstar fuel pump circuit electrical problem

Matt two suggestions 1- move to the Windstar forum, you may get better help there.(This one stops at 79) 2- Put 5 gal. of gas in the car and try to start it. My 97 Taurus just ran out of gas, (was running when I shut it off) and 1 gal would not do the trick. I put 6 gal in and it fired right up. :-)

John

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Old 08-02-2001, 10:09 AM
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'95 Windstar fuel pump circuit electrical problem

"Further testing with ammeter, voltmeter, and ohmmeter indicates that when there is any appreciable load on the fuel pump circuit, no power gets through (i.e., some relay doesn't work?), but when there is no load, the same circuitry manages to deliver 12V consistently. This is made more baffling by the fact that I have checked the internal resistance of both the old and new fuel pumps. The original pump has a 2 ohm resistance, while the new pump has a 30 ohm resistance across its terminals."


Seen this before the meter will show 12volts but when you put on a load you get nil. This is usually caused by a high resistance in the circuit, corroded connectors or wiring.
Try running 12 volts direct to the pump, that will show if the pump is good or not. 30 ohms seems kind of high for a pump motor.

Sparky

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Old 08-02-2001, 10:17 PM
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'95 Windstar fuel pump circuit electrical problem

On the negative battery cable there are two smaller wires that run several inches to a connecter and then on to ground check the connection ( pull it apart and check for problems). It is the computer ground and will cause some very stange problems.


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Old 08-02-2001, 11:00 PM
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'95 Windstar fuel pump circuit electrical problem

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Old 08-02-2001, 11:00 PM
 
 
 
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95, 97, 99, check, connector, ford, fuel, gas, inertia, intank, motor, ohms, pump, relay, resistance, shut, switch, windstar

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