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Fuel pressure diagnosis

I'm trying to resolve what I believe is a fuel pressure problem with my '88 240. The car will barely idle and has no power. I replaced the in-tank pump (was definitely bad) and the fuel filter. Main fuel pump is working, and passes the volume test (1L @ 30 seconds).

When I pinch off the return line from the pressure regulator, car runs fine. This suggested to me that the regulator was a dud (not holding pressure). I replaced the regulator - problem still there, but everything is fine with the return line pinched off.

I checked the current draw on my main pump. 3.5 Amps without the return line pinched, 8 Amps with the return line pinched.

Any ideas... perhaps my replacement regulator was a dud too?

Thanks, Andrew

Reply to
Andrew Ebbern
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From a point at sea, to the circles of your mind, this is Andrew Ebbern:

What type of fuel system do you have?

Different countries got different fuel systems at different times, and without knowing what system you have, or where you are posting from, you may not be able to make much sense of the replies you get.

Reply to
Stewart Hargrav

It is an LH 2.2 system... 1988 240DL, Canadian .

Thanks, Andrew

Reply to
Andrew Ebbern

Sounds like bad pressure still. When you did the volume test, did you do it right at the pump? If you do the test it should be after the pressure regulator. If the line is clogged (eg filter) the volume may be good at the pump output, but not good at the engine, where it counts.

Reply to
Mike F

Mike - I tested the volume output right at the return line from the regulator. Operated the main pump by jumpering the appropriate terminal at the pump relay, collected 1L with 30 secs operation.

At the suggestion of someone on brickboard, I checked operation with the AMM disconnected. Engine started and ran fairly well in the "limp home" mode, without the return line being pinched.

So now I'm thinking that perhaps all I did by pinching the return line was raise the pressure well beyond normal (e.g. regulator was okay) and this offset a problem with the AMM (or its electrical connection). Will do some testing on the AMM later today.

Andrew

Reply to
Andrew Ebbern

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