Fuel Pump Putting out to Much Pressure

[nick.falconer]

Hi,

I have been having issues with getting my engine running properly. I have been trying to go through and check everything I can. I have installed a new fuel pump and flange. When I first put it in I only used one of each gasket and didn't check the pressure as I didn't have a gauge. I have now checked that and it was putting out 6 psi. The carb I am using is a 34 PICT 3 and as I understand it I need to be around the 3 psi mark. I had some gaskets for shimming the pump up but after putting all of these in the pressure only dropped to 5 psi. Adding the shims spaced the pump up around 1mm.

I also measured the height at which the rod sticks out with no gaskets and at it's highest point it is only 4mm out. I read elsewhere that it should be approximately 5mm, so with my shims in there it is only 3mm out. Why would the pressure still be so high?

Do I just have to get a regulater like this instead of shimming?

Also I haven't been able to get the motor idling below 1700 RPM. After some reading I assume that there might be something blocking the idle jet. Also there is no vacuum being produced from the advance port, only the retard port which I have blocked off as it will be used with a SVDA. Where should I be checking for blockages? I'll be pulling it apart later this week.

Regards,

Nick

[modok]

Return the fuel pump, get your money back! Buy a different brand.

[nick.falconer]

This is the one I got, but it was bought back in 2012 and with me being in New Zealand it would probably cost more to ship it back than to just buy a new one.

[kreemoweet]

The VW specs for fuel pumps used with the 34 PICT-3 is 3-5 psi, so you should be OK. You should seek a more authoritative source for your
information needs, and nothing can beat the Bentley official service manual for that. In that manual you will also find
carb adjustment procedures which will likely point out where your carb troubles lie. The fuel pump rod you have
seems to be for an "alternator-style" fuel pump and should be 100 mm long. If it is not, they are readily available.
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[nick.falconer]

I might leave the pump for now then. This is what I tried to follow when I set up the carb. I have removed the carb from the car and noticed that the hole in the throttle butterfly has been soldered closed. I understand that this is to allow it to work better with an 009 distributor. Could this be the cause of no vacuum from the advance port. I have checked that it is clear by blowing through it.

Also the idle jet is 65 and the main is 145. This sounds very high from what I have read. Do you think that reducing these to a smaller size would help my idle problems? If so what size?

Thanks,

Nick

[kreemoweet]

Under what circumstances are you determining that there is "no vacuum"? If your carb is correctly set up, there will be no vacuum at the advance
port (the one on the left side of the carb, yes?) at idle, because the throttle butterfly will be completely closed. Immediately upon operating the throttle,
the vacuum will be the same as manifold vacuum, which can be considerable.

Your main jet is grotesquely large. Normal size for that jet is 125 - 130. Most 34 PICT-3's had a 55 pilot jet (I assume what you mean by "idle jet").

The closed hole in the throttle plate is a proven technique to make a recalcitrant PICT carb behave itself, and not just with 009 distributors. I have plugged
the hole in my throttle plate, use an SVDA dist., and it's the best thing I ever did - dramatic improvement in tuneability and driveability. It seems the
PICT carbs are absurdly sensitive to even the tiniest, virtually undetectable, vacuum leaks, and many of them were designed to run with an idle spark timing of 5 deg ATDC and do badly at a traditional 7.5 deg BTDC timing. The plugged butterfly hole seems to compensate. Soldering it is neater, and will allow
you to fine tune the size of the hole, but a pop rivet is much easier, and if it doesn't help, is easily undone. A plugged throttle plate hole will not affect
the vacuum at the advance port.
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[nick.falconer]

I am getting no vacuum at all throttle positions. I thought it was blocked. I removed the carb from the engine and I can blow through the advance port and feel air coming out the bottom and through a hole by the throttle plate. Maybe something was stuck in there and I've blown it out now. I'll try it back on the engine and see what happens.

I have a couple of other carbs at home so I'll see if I can find some smaller jets to try.

[kreemoweet]

The advance vac route includes a short channel in the base of the carb, so it might have been blocked if you used
some kind of goop on the base gasket.
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[Erik G]

back to the original question. Stack gaskets, or grind down the rod. You shouldnt have to do either, but the replacement BS fuel pumps have too stong of a spring. There is a thread in the bus forums about taking apart the rebuildable kind, and using your original spring to get it down to 3psi