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Guest Message by DevFuse

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Fuel Pump Help for 85 GL SW

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4 replies to this topic

#1 Guest_Great85GL_*

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Posted 22 July 2003 - 09:14 PM

Need help with understanding the fuel pump system on my 85 GL station wagon (carburated).

It left me stranded for the first time ever, would crank but not start.

I suspect fuel flow problems, I started by checking voltage at the fuel pump with the ignition on. Voltage was zero.

As usual, my Haynes manual was worthless, but it implied the car had a "fuel pump controller" and possibly a fuel pump relay.

Can anyone give me the basics of how the fuel pump works on this car? And when I should be seeing voltages? And where the electronics are located?


#2 Guest_tomrhere_*

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Posted 23 July 2003 - 03:58 AM

Skip has the upper hand on this topic, but I'll give out what I know. There is a fuel pump contrl unit, (FPCU), relay if you prefer. It's located above and behind the fuse panel, on the sidewall, has a 6 place connector. They do go bad, and I'm not sure there is a replacement, other than from a parts vehicle. As for voltages, you should have battery voltage at pump when you first turn the key to the "on" position, for a couple of seconds. Then after engine starts, voltage will be present again. The unit is more or less a safety item, and will shut down the pump if the engine stops, for whatever reason, with the key "on". You can test the pump by using some wire ran from battery, back to the pump, just to see if it wasn't the pump itself that died. The Blue with Red stripe wire is the positive, and the Black with White stripe is the negative. I did a work around wiring job on my '82 BRAT, because of a faulty FPCU. I can put that up here if you find that you pump does actually work by running the test wires. Would do it now, but I have to be heading out the door for work in a couple minutes. Will check back after work.......Tom

#3 Guest_Great85GL_*

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Posted 23 July 2003 - 06:21 PM

Thanks for the scoop. What you said corresponds with my Haynes manual, but when I looked in your prescribed location, all I found was a flat plastic box with about 14 connectors. Inside was a printed circuit board with several chips and a capacitor or two, but no relay.

I DID notice that the box (and two additional ground wires) was only loosely attached. The screws, which also hold the hood release handle, were stripped.

I've fixed the ground problem and am charging the battery now, to retest, with fingers crossed.

Pls let me know if you think I've stumbled on the wrong box. Thanks for the advice!!

#4 Guest_tomrhere_*

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Posted 23 July 2003 - 08:31 PM

Thinking you had the wrong box. Both of the ones on my BRATs are Black and about the size of a deck of cards. One, six place connector, on the lower face of the box. Should be right above the piece of kick-panel trim. Here's the work around wiring I did on my '82. Not sure the wiring color code will be the same, but it will get you headed in the right direction. Got my digital multi-meter out and started checking out wire runs. I found a Pink six place connector under the hood near the battery, that had the Blue w/ Red wire for the fuel pump in it. Right next to it in the connector, was a Black w/ White wire, that is key "on" powered. Used the Black wire to power the coil of a relay. Ran a fused wire from the + battery to one of the switching terminals, then over to the Blue wire for the pump from the other switching terminal. Didn't do it at first, ( but have now, Thank you Skip), I got a pressure switch on the oil pump, that closes when it sees pressure. Wired the - side of the relay coil to this switch. Now pump turns off when oil pressure goes to zip, thus restoring the safety factor. Hope this helps you out. Post back with what ever you fid, or do........Tom

#5 Guest_Great85GL_*

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Posted 27 July 2003 - 09:47 AM

Thanks Tom, I don't think I'll need the workaround. I think my grounding problem was it, I'm up & running now. Pretty clever though, using the oil pressure switch.

Of course, things never happen the easy way--I went to start the car after charging, and the battery was still dead--I guess this incident finally finished it -- but I got 7 years out of a 5-year battery!

But I tested the pump as you suggested and it worked. I was surprised at the noise it made, kind of a glugging sound, I guess I was expecting a whine sort of like a winshield washer pump. I jumpstarted the car, and it started up fine.

Regarding the box, I suspect it must be some sort of solid state version of the pump relay you have in your brats. It did have the red/blue wire leading out of it, and was in the same place as you described. There's a picture in my haynes manual of the box as you decribed it, it definitely wasn't mine.

The only other explanation could be that the box had nothing to do with it, and it was the other ground wire that was loose in addition to the box, or it was a battery problem all the time. I doubt this, since on the day it died it had enough juice to crank the engine during several hours of troubleshooting. I think it was the recharger that fried it.

Thanks for the assistance,

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