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JFairman JFairman is offline
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Join Date: Jul 2006
Location: S. Florida
Posts: 7,267
I'm guessing you have a black cast iron euro fuel head on there because you mentioned it is a '78 and not the aluminum lambda fuel head from a 1986 or later USA car.

My car is an '87 and I've used the stock USA fuel head, 2 different CIS flowtech modified USA fuel heads, and a stock black euro fuel head. I have the CIS opressure gauge and checked all of them while they were installed on the car.

The aluminum lambda heads system pressure runs in the high 90's to 100psi and the black euro fuel head system pressure I had ran in the high 80's similar to yours. I thought that was low at first but then learned thats in the normal range for a euro fuel head so I don't think your fuel system pressure is too low.. but maybe it is.

The euro head is a little different than a 1986 on USA aluminum lambda head. It has a stiff stainless steel metering diaphram and no lambda system with frequency valve like a USA fuel head, and normal system fuel pressure is in the high 80's for them.

The USA head has a more flexable metering diaphram in between the upper and lower diferential pressure chambers and a lambda system returning fuel to the tank from the lower chamber for emission lean AFR control and system pressure is around 10 psi higher for them.
Pelican sell parts for the fuel head system fuel pressure regulator you're calling a poppet valve but I think yours is OK. The orings on it look good and it's clean. They don't all have 3 shims under the spring, some have one thick one or 2 or 3 thinner shims stacked together if that got the static sytem fuel pressure set correctly 33 years ago.
Pelican Parts - Product Information: 928-110-920-01-M14

Your fuel head may need cleaning and rebuilding inside. Those euro fuel heads rust in the bottom of the lower differential pressure chambers if water gets in there and that can clog things up in the thin fuel passage ways and metering orifices and fine mesh fuel screens inside. The rubber o rings around the control plunger steel cylinder can also disintegrate over time and clog fuel flow.

Some fuel additives can accelerate the 30+ year old orings breaking down. It can also loosen up old accumulated dirt or varnish and let it move some where else where it will cause fuel flow problems.

You can do an injector flow test into 6 seperate plastic small water bottles with and with out injectors on the ends of the lines to get an idea whats going on there.
Alot of things can cause problems in an old mechanical injection system like CIS.

Last edited by JFairman; 09-13-2011 at 07:20 AM..
Old 09-13-2011, 07:11 AM
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