Re: Fuel pump problems - continued

[DeWitt Harrison <de@aztek-eng.com>]

At 11:07 PM 11/22/97 -0500, Steve Manning wrote:

>>Dead or missing pump silencer thingy?
>
>Exchanged w/another car; no change.

Sounds good.

>>Dead/missing fuel pressure accumulator?
>
>If you mean the one screwed onto the fuel pump, a new one came w/each fuel
>pump.  If there is another, where is it?  Or is what is in the fuel pump
>just the check valve?

On the 5kt cars, there is a fuel pressure accumulator mounted near the fuel
tank, in the fuel line plumbing accessible from under the car.  It's kind of
like the hydraulic accumulator (bomb) in function in that it keeps the fuel
lines pressurized after the engine is turned off (for maybe 30 minutes if the
injectors don't leak too badly and the check valve is good). It's much smaller
though and it's real purpose is to aid in hot restart by preventing vapor lock,
etc. I am speculating that it also works as a pressure pulse damper. The
bomb is known to help quiet the hydraulic pump as a secondary function. 

>>Non-standard pump mount, i.e. mount not made of soft rubber isolation stuff?
>
>Looked normal to me; fit correctly in in-tank mount (after figuring out you
>can put it in 180 degrees wrong).

Off the wall, I know, but best to keep an open mind when dealing with an
off the wall problem.

Maybe it would a good idea to go over the business of contamination from
the tank coating again. Assume that this junk ended up somewhere bad
during the course of the repair history. where would it go? There is the
screen on the fuel pump. I imagine you've looked there (recently?).  There
is a TSB that recommends removing this screen because the coating will
presumably continue to disintegrate. I don't recall whether you did this or not.
If not, it could be covered again. But if it has been removed, where would
the junk go now? To the main fuel filter up front? The check valve assembly?
I don't know, but until you are sure the tank has stopped shedding, keep this
kind of thing in mind.

>>System pressure too low (regulator shooting too much fuel back to tank making
>>pump work too hard.)?

If someone knows whether the fuel pump is loudest when working against
high back pressure (pluged line) or low back pressure (leaking/bypassed line)
it would provide a helpful clue.

>Is this the thingy attached to the metering head?

Could be. I think that's were mine is although some engines have a stand alone
system pressure regulator - not to be confused with our friend the control
pressure regulator on the side of the block nor with the fuel mixture frequency
valve mounted to the air flow meter housing. Follow the incoming fuel line
to the big fuel filter near the metering head. Whatever follows the filter
should
be it. There will be a fuel return line from this regulator back to the tank.
System fuel pressure is easily checked by any CIS fluent garage. Have you
had any fuel starvation symptoms? Misfire under load? Unusually high
engine temps under load?

>Thanks for the suggestions.....I appreciate any help.........SLM

You're welcome and good luck. This sounds like a son-of-a-gun. 

DeWitt Harrison    de@aztek-eng.com
Boulder, CO
88 5kcstq