Fuel pressure help

I've exhausted my own ability to solve this problem... I have a 3.0 Euro SC motor, with Euro fuel distributor and pump. The motor runs great until it comes up to normal operating temp. Fuel pressue initially is 1 bar, then goes to 3bar once the car is warm. As soon as the car gets warm, it runs too rich. I bought a new fuel regulator, but it didnt help. Any ideas? Do Euro motors require different fuel pressures than their US counterparts?

When I set the mixture in my car, the engine is at normal operating temperature. Therefore, it has little chance to run rich at that temp.

The mechanism that changes your mixture depending upon temperature is the Warm Up Regulator, AKA the Control Pressure Regulator. This controls the pressure that goes the the TOP CENTER fuel line on your fuel distributor. When cold, pressure onto the TOP of the plunger in the fuel distributor is reduced, allowing the plunger to move further up into the distributor (from the bottom) for a richer mixture. As the car warms up, this pressure increases, preventing the plunger from going so deep and leaning the mixture. If this pressure to the top of the fuel distributor, from the Warm Up Regulator which sits over the #2 cylinder head, rises according to spec, then this (choke) mechanism should be working. What happens when you set your mixture while the engine is hot?

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'83 SC

jmcjunkin -- When you say "fuel pressure" do you mean "control" pressure as measured between the WUR and the fuel distributor? 3 bars sounds a little low for warm control pressure. Check the vaccum lines to the WUR, specifically the lower vaccum line. At idle, disconnecting the lower vaccum line should result in about a 10 psi drop in control pressure. If you don't see that drop, then you're operating in "full throttle enrichment" mode all the time.

What year is your car?

Also, Superman is right. Mixture should be set with the engine warm, but your control pressure needs to be within spec also.

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Bill Krause
'79 911SC Euro

Thanks for the help. The car is 71 911t, with a 1981 Euro SC motor. The car doesn't have vacuum lines. The WUR is brand new.

If I set the mixture while the car is hot, the sensor plate is adjusted so high that the injectors are injecting all the time (e..g just with key in and turned). If I put slight pressure on the plate (pushing back against the downward pressure), the car runs fine. In all cases, it runs perfectly until it reaches operating temp.

Thanks for the help. The car is 71 911t, with a 1981 Euro SC motor. The car doesn't have vacuum lines. The WUR is brand new.

If I set the mixture while the car is hot, the sensor plate is adjusted so high that the injectors are injecting all the time (e..g just with key in and turned). If I put slight pressure on the plate (pushing back against the downward pressure), the car runs fine. In all cases, it runs perfectly until it reaches operating temp.

One more thing... I did mean "control" pressure.

I feel that this is a "pressure differential" problem, and need somehow to reconcile the interaction of the WUR and other components.

How are you adjusting your mixture? What procedure are you following? Adjusting your
mixture won't change the position of your sensor plate. Sounds to me like you are adjusting the zero position instead.

Have you inspected your sensor plate for zero position, and alignment. Something sounds very out of whack. When I checked mine, it was covered with an oily sludge from oil overflow.

Does an 1981 SC Euro have the lambda circuit?
Are you sure you have the correct WUR? I thought for sure it would have two vacuum lines for full throttle enrichment.

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Bill Krause
'79 911SC Euro


[This message has been edited by wckrause (edited 11-20-2000).]