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Author Topic: Fuel pump problems  (Read 1835 times)
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« on: December 07, 2008, 09:58:13 PM »

From: Iain  (Original Message)   Sent: 10/04/2008 22:06
Thoughts please on the following:
Last year I replaced the mechanical fuel pump on my 1981 Coupe 2000 with an electric 'Huco' version as I'd been having problems with fuel starvation.  All seemed well, no more cutting out and running smoothly although I did notice that if the car was left unused for a while it was difficult to start and the fuel consumption seemed pretty awful.   The reasons for which became apparent when the sump came off this week and around 3 gallons of fuel/oil poured out.  It seems that the pump has been continuously sending fuel into the carb after the car's switched off.  The pump is not running when this happens so presumably a vacum is causing this, there is an audible sound of pressure release when the fuel cap is unscrewed. 
Any ideas? I don't want to have to keep diconnecting the fuel line every time I park the car!

From: hutch6610   Sent: 11/04/2008 00:21
The only way you are going to get a sump full of fuel is because the mechanical pump has a perforated diaphragm and fuel is leaking into the block via where it actually bolts to the block.
This probably happened before you went over to electric or you are feeding the mechanical pump with the new electric item.
Possible also a third party poured the offending fuel into you engine (just covering all possibilities!)

The audible hiss you get from the filler is normal - fuel tank has a pressure valve to stop all that lovely EXPENSIVE juice from escaping into the atmosphere.
It does allow excess pressure to vent though.

If your pump ran continuously when you switched it off -
1) You would hear it.
2) Your car would have ended up in a "lake" of fuel overflowing from the carburettor, so i am afraid i doubt that amount would get past the rings without you noticing until now.
3) No way would this turn over due to the fuel in the cylinders causing a serious hydraulic lock.

I doubt all that fuel/oil did any good to your oil pump and bearings.
Where have you taken power to run the pump?

From: Omicron   Sent: 16/04/2008 22:52
What pressure rating is the electric fuel pump working at?      do you have a fuel pressure regulator?

From: A1-6HPE   Sent: 20/04/2008 12:56
Hello Iain,
After you told me about the Huco pump I got one and it has run on my Trevi for over 2 years very happily. I by-passed the mechanical pump. As Hutch66 says, petrol in the sump is usually because a mechanical fuel pump diaphragm has split.
Is the idle cut-off solenoid stuck open? Unscrew that and check that the plunger is free to move and therefore shutting off when the ignition is off. A slow trickle could find its way in to the sump via a cylinder and the manifold would have a residue in it which would make starting difficult (mixture too rich).

Best regards, Leo

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