4drgl

should I see?

The car is a 1980 928 4.5 ltr automatic. I am hooking up the pressure gauge now.

Thankyou!

RicerSchnitzzle

75 psi (5 bar) before the distro. Control pressure from the WUR will vary. Where are you hooking up to measure?

James Bailey

What are you trying to FIX ? USA or Euro car ? reason for the test ?

4drgl

It's a us spec car. Reason for test is that the motor runs... yes but only for about 5 minutes or so then pump seems to get hot loses pressure and shuts down.

Also while motor is running it stumbles all through the rpm band and to get it over 2k rpm is impossible.

Now back to the first statement the car starts immediately on first try after a cold start let it sit a couple hours or overnight and the pump cools down... However, once started and you let the motor idle until it shuts down, it will not restart... but what I discovered is that if you jumper the fuel pump (throught the ce panel) and let it run long enough jumpered with the ignition off, the pump winds up and eventually pressurizes the lines high enough to get the motor started again... but it won't idle very well or for long maybe a minute max once the pump is warm. I think the pump is weak, and not pressurizing the system high enough. I have tested the voltage at the pump and I am getting battery voltage. 12.5 vdc. With or without the relay.

I didn't have the proper fitting to connect my pressure gauge to the end of the passenger fuel rail so I will find the proper fitting and go after it again in the morning.

What is WUR??

Can I connect the gauge to the end of the rail to test pressure or should I hook it up somewhere inline before the rail??

James Bailey

WUR is for a CIS injection car, not what you have. The end of the fuel rail is a start BUT the pressure regulators at the rear of the rails BYPASS the excess pressure so it MIGHT read low due to a bad return valve but not very likely they seldom fail.

jpitman2

Were 1980 4.5 already on L-jet? Do you have hard steel 3/16" OD pipes to the injectors - NO= L-jet, Yes=CIS/K-jet, very different systems, with different diagnosis.
If the pump struggles to get enough pressure to run, sounds like a restriction in the line from pump to engine. If it overpressures after a short time, sounds like a bad prpessure regulator, or a blocked return line . Check for exhaust going black and sooty as it warms - going rich , too much fuel; if exhaust stays clear, and hot, going lean, lack of fuel.
Please confirm.

jp 83 Euro S AT 52k, CIS

4drgl

Ok, I have rubber lines leading from the fuel rails to the injectors. I'm pretty sure its not cis injected. I have 80's vw's as dailys and the setup is not even close to the same... From what I've read it's afc injection.

As for the exhaust... The engine finally ran more than 5 minutes today. It pulled the same stunt as usual but stalled after 20-25 minutes. The exhaust is not sooty and rich it is warm and clean no grayish smoke indicating rich condition.

I have been unsuccessful at hooking up the pressure gauge.... anybody know if I need a special one??

jpitman2

Any idea when the fuel filter was last changed? If NO, change it now, and see if behaviour changes. If its not going rich, it can only be going lean to kill it, UNLESS something unrelated to fuel is getting hot and failing?
jp