[cm961]

Hi guys,

This is the 3.3L, 1992. Sometime during my long head gasket replacement, my fuel system stopped holding pressure. The leak appears to be in the return line above or inside the tank. All the lines are new (rubber and metal) for the complete system. Fuel pressure regulator and vacuum lines are new. The pressure relief/rollover valve is not connected to the charcoal canister (broke the valve connector though the valve is still good, it just vents to atmosphere for now). I figure the leak must be right on top of the tank, or something wrong internally. If I cap off the return line just before the rubber hose to the tank, the system holds pressure. I'm just wondering what could possibly be wrong before having to drop the tank again (tank and everything except fuel pump is new).

Thanks,
Pete

 

[fjb37]

Do you have a fuel pressure gage to connect to the schrader valve in the front fuel manifold line? Just my $0.02.

FredB

 

[cm961]

Yup, fuel pressure at the rail is fine but drops to zero immediately when engine is shut off.

 

[fjb37]

When I had that problem with my 94 3.3L it was the pressure regulator in the fuel manifold. New one cured the problem. If you block the return line and the pressure holds then the regulator is the first suspect. If you turn the key to the run position and the pump runs for a second or two your system pressure should go to over 50 psi. With the engine running the pressure should be around 48 psi and if you remove the vacuum line from the regulator it should increase to over 50. If the pressure drops when the engine is turned off the regulator is suspect. Just my $0.02.

FredB

 

[cm961]

Thanks, I'm suspecting the fuel pressure regulator as well, which is funny because it is new. Perhaps wrong part. It does seem a little different than the old. This would be a great relief. I still have the old one which was fine. I thought it was a hard swap so I replaced it with everything else I was doing, but I've since realized it's very accessible. Will keep all posted. It would be a great relief to not have to drop the tank.

 

[AJ_Schreiber]

there is a check valve (one way valve) in your fuel pump that can go bad causing this issue

 

[cm961]

I took out the fuel pressure regulator only to discover the smaller of the two seal gaskets was torn. It turns out it was totally my fault for not following the FSM procedure. You have to install the o-rings into the fuel rail first, then push in the fuel pressure regulator. I had them on the unit and pushed it in and one tore. I'll likely have to order a new FPR just to fix this since I already spent $15 on a mixer pack of fuel safe o-rings and none of them fit. Right now I've got the broken o-ring in there which slowly leaks so it turns over for awhile before starting if it's sitting for more than a few minutes.

Thanks guys, greatly appreciate the help and so glad I won't have to drop the tank.
Pete

 

[Bob Lincoln]

Service manuals also say to put a drop of engine oil on fuel system O-rings before installing, to prevent ripping.