# Hot Fuel Pump



## tyrediron (Jul 27, 2011)

Hi; 

Keith here, a newbie to the forums. 
Our 82 VW Rabbit Convertible was a no-start. 

Fuel pump wasn't working at all. 
I banged the pump a bit, and ran a jumper wire to the positive terminal, and jumped it on and off a lot, and it finally started pumping, but not enough to start the car. I used the pump to drain the fuel tank (put a hose on the downstream end of the fuel filter, into a fuel can), but the pump got VERY HOT; started to melt the foam insulation around the pump. 

I've installed a new fuel pump, new fuel pump relay, new pipe fuel pump to accumulator, new pipe fuel filter to fuel distributor. 

I drained and flushed the tank, and put 5 gals of fresh gas in. 

Car will now start and run for a second or two, and then again the same, and then finally will start and idle rough for a minute or two (can't get over 1500 rpm), and then the (new) fuel pump starts to hum/buzz, and gets hot. Engine stops, when I try to restart, the fuel pump buzzes. 

When I first turn the key on (when car has been sitting and fuel pump has cooled off), I hear the fuel pump kick in for a second or so. I also hear some click click clicking at the fuel distributor or fuel filter (pressure valve sending fuel back to tank???). 

I did not replace the fuel filter (yet, I will order one today). 

I will try to plumb in a pressure gauge to the downstream end of the fuel filter. Not sure if I have anything that reads 75 psi. 

Could the accumulator be plugged/blocked, causing the pump to work too hard and overheat? 

Any ideas? 
Thanks.


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## ps2375 (Aug 13, 2003)

Check the wiring from the fuse panel to pump. Make sure the the wire has the same resistance as some new wire of a similar length. If the old wire has too much resistance it'll cause a voltage drop at the pump and will cause it to draw more amperage and that can cause excessive heat at the pump. 

If this is a CIS-Lambda motor, the buzzing at the fuel dist is normal, as that is the frequency valve. 

And before you get too involved, do you have a Bently Manual for this car, I would highly recommend it for diagnosing this fuel system issue.


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## tyrediron (Jul 27, 2011)

ps2375 
Thanks for the help. 

I've disconnected the wires at the fuel pump. 
I've jumped new wires directly from the battery posts to the fuel pump. 
Same result. Engine will run after a few tries; runs rough, will not rev above 1500. 

Fuel pump humms at first, sounds normal, then starts to get hot and after a few minutes gets quite hot to the touch and starts to buzz loudly, very loudly; I can hear it from the drivers seat, with engine running. Seems to get so hot it vaporizes the gas. Engine then stops. (I then disconnect pos wire from battery). 

Fuel pump is a Bosch 69430. 

I have a Bentley (and some Haynes and a Chilton). 
I read a lot last night, will do more tonight. 

I don't have a pressure gauge that will do the job, I'll try to source one. 

Thanks, Keith


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## Glegor (Mar 31, 2008)

sounds like a fuel pressure issue.. ore a regulator issue.. 

hot pump is because it is working too hard to get power..


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## tyrediron (Jul 27, 2011)

Still no (good) luck with the hot fuel pump issue. 
I left it alone for a couple of days, and have done a little more playing this morning. 

I plumbed a line back onto the downstream end of the fuel filter, and hot wired the fuel pump; lots and lots of volume coming from the filter. Hard to guess how much pressure, but when I try to block the end of the line with my finger, I sure can spray gas a long distance. 
I'll try to get a gauge to check pressure at the downstream end of the filter. 

I don't think that there's an issue from the filter on back; seems like a problem under the hood. 

Hmmm; ran good when parked. Then pump wasn't working. I've replaced the pump (and some lines). Still having a problem. 

I'll read up on the fuel distributor. 

Any other suggestions? 

Thanks; Keith


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## Glegor (Mar 31, 2008)

i would say its a bad ground.. 

the pumps shouldnt get hot.. period. 

they are working too hard..


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## tyrediron (Jul 27, 2011)

Glegor thanks for the hints. 
But it does not seem to be an electrical issue. 
I've connected the new fuel pump (pos and ground) directly to the battery. 
Engine will only idle, won't rev over 1500; and the pump gets hot after a minute or two. 

Seems like a blockage. 

It may be in the fuel distributor??? 
Maybe the pressure relief valve??? 

Next I'll use the pump to move 5 gal of gas from the tank, through the accumulator, through the filter, and then through a hose into a gas can. I'll see if the pump heats up. 

I'll also check the return line. 

Crossing my fingers. 

Thanks; Keith


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## Glegor (Mar 31, 2008)

the pump should not get hot, period.. 

theres only 2 ways it can get hot. 

1.) dirty power 

2.) not flowing enough fuel/building too much pressure. 

the engine not revving over 1500 revs, that seems like a fuel pressure issue to me.. not enough pressure.


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## tyrediron (Jul 27, 2011)

*Problem solved*

Problem solved. My error.

When I originally replaced the fuel pipe joining the fuel filter to the fuel distributor, I must have mixed up the bolts (through the banjos).
I didn't notice that the downstream bolt (to the distributor) had a one-way valve hidden inside it )sneaky German engineers!!). I had it in the out end of the fuel filter, and was blocking the fuel flow.
Bolts are now in their correct locations. Starts and runs well now.
Thanks for the help.


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