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Old 12-22-2003, 04:48 AM
Posts: n/a
Not again...


Same symptoms are back again after 2 days of driving.

All the fuel pressure regulators installed so far have been from the wreckers on an exchange basis.

I hope it's not the fuel distributor which was already replaced.

I checked the FD by bleeding each line to the injectors (with the engine running) and all 4 lines had fuel.Also, each time I cracked open a line, the engine idled a little rougher.So obviously, the fuel distributor is firing on all 4 lines.

Took the FD out and found that none of the vents (on top where the lines to the fuel injectors are connected) were blocked.

In my previous FD diagnosed as faulty by a techie, one of the vents from the FD were blocked.

My only guess at this moment is the FPRs that I got from the wreckers (btw they're all dirty) are already faulty (1 was venting fuel) or going bad (1 lasted 2 days).

Summary of FPRs used :

1 was venting fuel.
1 made the car run ok (after readjusting mixture) for 2 days before old symptoms came back.
1 did not solve the problem; neither was it venting fuel.

My question is could a fuel pressure regulator be faulty and not vent fuel?Would this result in too high fuel pressure (which I think is the case here) and cause my symptoms - black smoke, bad fuel mpg, a slight adjustment in mixture either way results in too lean or too rich (due to stuck high system fuel pressure?).

I have seen a confirmed case of a faulty FPR coz it was spitting fuel out of the vent hose with the engine running.

Does a stuck diaphragm mean that the FPR is faulty but does not vent fuel?After all, if the diaphragm is stuck, how can it push the fuel out of the vent hose (this is my reasoning)?

As always, all techies are screaming "fuel distributor" wihtout even wanting to diagnose further.

I would think that FDs go a long way.Also, having seen my previous FD with one vent blocked and the "new" used one after cracking the lines open with the engine running, I would deduce that the "new" used one is OK.

Or am I wrong?

I would assume that if I had a bad FD, swapping out the FPR would make no difference to the problem and yet, I had managed to get the car running for 2 days earlier before the symptoms came back again.

On one hand, I think that it's not likely that all the FPRs that I have used are faulty, but they're all from the wreckers so I'm unsure.

When I swapped the old FD out, I also swapped out my FPR with a used one from the same wreckers at the advice of one of my tech friends even though we did not test it.It was not venting fuel but had a little fuel in the side where the vent hose is attached to.The FD/FPR swap was done 2 months ago.

Fuel pump, fuel filter and accumulator checked out ok but none of the symptoms point to these stuff anyway.

Sensors have been checked and tested as per MB CD specs, running the car with the EHA disconnected so the electrics are eliminated from the equation anyway.

I hope anyone out there has more specific info (I thought I had) on fuel pressure regulators and how they specifically fail.

Thanks in advance.
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