Help! Odd fuel pump reading

[Achilles]

I put a fuel pressure gauge on the schraeder valve today and when I turn the key to the "on" position the needle shoots up to about 43-45 lbs, shakes erratically and imediately drops to 20 PSI.

Does this sound like a bad diaphram in the regulator? I thought it could also be a stuck injector, but there not very old. How would I check to see if I have a stuck injector?

 

[Hib Halverson]

I put a fuel pressure gauge on the schraeder valve today and when I turn the key to the "on" position the needle shoots up to about 43-45 lbs, shakes erratically and imediately drops to 20 PSI.

Does this sound like a bad diaphram in the regulator? I thought it could also be a stuck injector, but there not very old. How would I check to see if I have a stuck injector?

The rise to 43-45 psi then the erratic shake as the pump shuts off is normal. The immediate drop to 20 psi is decidedly abnormal.

The service manual's fuel pressure tests will show you have to determine if it's injectors or other problem with the fuel system causing that, but I'm going to guess that it's not the fuel pressure regulator.

 

[Achilles]

Thanks Hib,

Do you know how to test the injectors?

 

[Hib Halverson]

Thanks Hib,

Do you know how to test the injectors?

Well, you didn't say what year the car was so I'll refer you to the FSM for the model year in question. Look in the engine controls section covering fuel pressure testing.

 

[Achilles]

Its an 86 with aftermarket injectors and I don't have a service manual:W