homestd

90 xj losing fuel pressure almost immediately after shutting off. I'm told there is a check valve for the fuel pump. My question is: Is the check valve integrated in the pump itself? Will this cause problems other than longer crank times?

Saudade

Yes, the check valve is part of the fuel pump assembly. Have you checked the fuel pressure using a gauge?

You can try turning on the Key to RUN (don't crank), listen for the fuel pump whine. When it stops, turn the key off, then try to start. That will build fuel pressure before you attempt to start.

You could have a leaky injector or leaky pressure regulator that could cause the quick drop when you shot down. If you're certain it's the check valve, you can get inline check valve and splice it into the fuel line.

homestd

Got my gauge on Mon. FP at the rail is 31, 39 w/ PR vacuum line pulled. I tried letting the pump run first thing, no change. Wouldn't an injector cause a more gradual drop? Thanks for the check valve insertion suggestion, what should I should use?

EuroJeep

interesting. WHERE would you put the check valve. I bought this one but hesitate about the best place.

cruiser54

Does it start up nicely when it does start? Original injectors?

There is a test that determines whether it's the injectors leaking or not. I don't have it at my fingertips right now. Those fingers are helping me grasp my first cup of coffee.

homestd

Cruiser, Yes it starts & runs fine, about a count of 10 - 12 to start. Original injectors AFAIK.

lawsoncl

Pinching off the supply and then return lines, and seeing if the pressure still drops on key-off? (Don't pinch the return line first...)

homestd

Is the return line the one in the back with a quick disconnect?