[JEEPINWI]

I have a 2000 XJ sport 4.0L automatic tranny with 110k on the clock. The engine has never started on the first try. I always turn the key to on and wait for the fuel pump to prime. I can crank the engine forever on the first try, but it won't start. Normally I will crank for about 3 seconds, release key for about 2 seconds, then crank again. Battery is good. Engine always idles good and never sputters when driving. I've cleaned the throttle body and replaced the TPS with a good spare that I had laying around.

I've attached a fuel pressure guage to the fuel rail. When first turning the key to ON for the pump to prime, pressure builds to about 25 psi but within 10 seconds drops back to zero. When I turn the key to START, pressure build with every crank. Once running pressure stays steady at 54 psi. Apparently the fuel pump is working fine, correct? Once I shut off the engine, pressure will drop back to zero within 30 seconds. I've heard there is a check valve in the pump. Can I test this somehow? What else can I check to fix the problem?

[That1guy]

Yes there is a check valve in the pump that can go bad a release the pressure.

[CJ7-Tim]

You have the symptoms of a failed fuel pressure check valve on the 1997 to 2001 fuel system. The valve holds the pressure in the fuel line and fuel rail when the motor is off. It should hold pressure for weeks at a time. The valve is located on the fuel pump and is not repairable or replaceable.

There are a couple of ways to fix this: 1) Ignore it, turn the key to ON ( just before start ) and then back to off, then try to start. This helps build pressure in the line. 2) Try cranking to start as many times as needed. 3) Install some sort of aftermarket check valve in the fuel line just outside the gas tank. 4) Spend big bucks on a new fuel pump. Be sure to get a good one, the cheapies fail altogether in 6 to 18 months.

You can do the key on and off trick forever, it cause no harm to the system and is really cheap and easy.

[mfinkler]

Mine is doing the same thing. Mine always started fine until last weekend. My fuel pump went out. I purchased a whole sending unit which had a new pump and pressure regulator on it from the dealer. After the install it cranked up fine. I also replaced the filter at the same time. The next day it cranked for about 10 seconds before firing up and has done that all week if it sits for more than 10-15 minutes. You think I got a new pump with a bad check valve in it? I don't have a pressure tester so I'm not sure about the numbers. It fires right up if you only let it sit a few minutes. Isn't all that cranking bad on the starter/battery?

[That1guy]

Its not good for the starter. You probally got a bad pump. I think you ca rent fuel gauges cheapy. Get one and see if the pressure drops when shut off. Sounds like its leaking slowly.