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crazy fuel pump prob 82 brat


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13 replies to this topic

#1 tacotim

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Posted 21 September 2003 - 01:28 AM

I was about to drive across the nevada desert to get back home to utah when my 82' brat petered out just as i left the driveway and wouldn't start back up. After trying a few other things, we took a voltmeter to the fuel pump wire, it read 0.2 volts. Then we ran a wire straight from the battery to the fuel pump and heard it pumping, with the wire still conncted we started the brat, and it ran no prob. Then we took off our wire, and it didn't die, ran it around the block, no problems. Shut it off, let it sit 3 hours, started right back up, so all seems well, but we never really "fixed" anything, so I'm worried about trying to cross the Desert!! any suggestions?

My grandpa thought maybe something along the lines of the auto choke trying to shut off the fuel, or some other mechanism doing so??

Thanks, Tim I

#2 bushbasher

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Posted 21 September 2003 - 01:43 AM

I thought a choke restricts the air, not the fuel. My only guess since it's not computer controlled it would have to be a bad connection, in whatever switches the pump on/off, or ground etc

#3 GLCraig

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Posted 21 September 2003 - 04:50 AM

The fuel pump is controlled by the fuel pump control unit (sometimes refered to as the revsensor) It's located on the driver side kick pannel and one of the screw for the hood release bracke goes through it.

#4 camosuba

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Posted 21 September 2003 - 06:28 AM

is this a carbed car? i had a problem with my electric pump once and it was getting lazy and stopped midway between strokes/contacts and the car stopped gave it a tap and away it went for several weeks before it stopped again I pulled it apart and cleaned all the contacts and gave the plunger a lube and it s been going ever since. hope this helps :D

#5 tacotim

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Posted 21 September 2003 - 10:29 AM

Well, we measured the voltage at several places along the wire before the pump and all were reading very low until we "jump started" the fuel pump. what about this fuel control pump thing, how can i tell if that's the problem?

Thanks, Tim

#6 tacotim

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Posted 21 September 2003 - 10:32 AM

we also determined that it was the blue and red wire that had the problem, not the black wire with orange bands. But am interested to learn more about the fpcu, could that be cutting the voltage to the fuel pump?

Thanks, Tim Irwin

#7 Cougar

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Posted 21 September 2003 - 10:58 AM

I think there is a relay in the control circuit. My hunch is, the relay may be intermitant or, there is a loose connection to the pump from the control circuit that caused this to happen.

I would purchase a service manual for your car so you will have a reference to go too when things like this happen. It can save you a lot of money in the long run.

#8 tacotim

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Posted 21 September 2003 - 03:05 PM

yeah, I actually have a service manual, but like a bonehead, I left it in my garage (in Utah) not in my car, and I'm in southern CA. So I've been having my poor wife look things up in the manual, and then faxing pages to us. Bless her heart. But I'll be checking out the FPCU today. Any more tips are very welcome, thanks for the help so far!

-Tim

#9 Sweet82

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Posted 22 September 2003 - 10:40 AM

TacoTim,

My 82 Hatch had an intermittant fuel pump problem too. It would just leave me stranded and then it would fix itself. I took it to Nate Wade Subaru and they attached a light bulb to test/diagnose the fuel pump system and were able to determine that I had an intermittant short.

Replaced the pump and never had a problem since.

I have a Trooper that ate SIX fuel pumps in TEN months! (Dealer paid for most of them) They finally figured out that the wires were corroded and causing a low volatage to the pump causing it to burn out. Are your wires corroded?


Good luck,
Glenn
82 Hatch, transforming.....:temper:
01 Forester, Jealous.........:madder:

#10 ShawnW

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Posted 22 September 2003 - 11:12 AM

The above comment about the vehicle not having a computer is possible but not 100%.

An 82 Brat can have an ECU/Computer. If you have an oxygen sensor you have an ECU. Its bolted to the bottom of the steering column in the area above your shinbones/knees when you are sitting in the brat. 1bbl carter weber carb models had the ECU. I have an ECU from one in my basement.

I think check/clean all ground wires is a great suggestion that was noted above. Its also a 20+ year old component so if you can find a good price on one-replacement wouldn't hurt.

#11 tacotim

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Posted 22 September 2003 - 12:03 PM

well, the FPCU seems to be doing it's job, when we start we can feel the relay click. The brat has run but died 3 times over the weekend, finally took it to a mechanic this morning and he reckons it needs a new fuel pump. I sure hope he's right, but I have my doubts. We have traced the wires, and near as we can tell, they seem to be in good shape, as well as all the connectors and grounds we could find. I sure appreciate all the suggestions and help, man this board is amazing! very glad I found it.

Thanks again, Tim Irwin

#12 Cougar

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Posted 22 September 2003 - 01:31 PM

Just because you hear and feel the relay click, it doesn't mean it's good. You have to check the contacts across the relay when it is energized to be sure you are making good contact to the switched leads. This is where most relays fail due to burned contacts inside the relay you can't see, but you can measure them.

You can use a voltmeter to measure the switched leads. When the relay is engaged, the meter should show zero volts (a shorted condition) between the two switched leads. If you show a voltage then there is a resistance between the leads causing the voltage drop and you need to replace the relay. You will need to catch this when the problem is happening to prove out the relay because relay contacts can be intermitant just like the problem you are having. You could just try replacing or swapping it to see if that will stop the problem. It is much cheaper and easier to replace the relay than the pump. I would want to prove it is the pump first before replacing it if this were my car. Pumps are a common problem also though.

#13 tacotim

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Posted 22 September 2003 - 05:20 PM

turns out it there was a short within the fuel pump, the mechanic showed us. They had it pulled out and hooked up to 12v, and it ran fine, but if you bumped it or shook it, it would stop, bump it again and it would start, so put in a new pump and problem solved (hopefully) I still have to drive it across nevada and half of Utah. Thanks for all the suggestions

-TIm

#14 Cougar

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Posted 22 September 2003 - 07:08 PM

Glad to hear the problem is solved Tim. It sounds like you got it alright. It's great when you can prove the problem part. You should be fine for some time now on this area of the car.

Thanks for the feedback on this.

"Drive On"




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