ok after my jeep sits over night in the cold ohio weather it won't start right up in the morning. It takes a while like its not getting fuel and then when it does start it will die. After a few of these cycles it will start and run then all day it will start up fine. I have noticed that I cannot hear the fuel pump until I crank it a few times. When is the pump supposed to kick in is it when you turn the key or is it when the starter kicks over or what. I just am wondering what the problem could be. I have a 94 firebird that after it sits it will lose fuel pressure but all you have to do is goose the fuel pump a bit to build pressure back up. The jeep however the pump doesnt kick on every key turn. also the guy i bought it from told me the pump was new thanks for any help

 

What is the year/engine? Always include that information. Here is some basic information that may be helpful, depending on your vintage. By design, when you turn the key to the ON position, you should hear the fuel pump energize and run for approximately 2 seconds.
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The check valve is part of the fuel pump assembly on 95.5-2001 vintage 4.0 XJs. When the check valve starts to fail, it reduces fuel pressure to a point where an extended crank is needed to start the engine. It is a very common failure. I experienced it on my 99 at around 75K.

A good (and simple) way to troubleshoot this problem is called “the poor mans prime”

1. Turn key to ON position (do not crank the engine!)
2. The fuel pump will energize and run for a couple of seconds
3. Turn key to OFF position
4. Repeat above a two more times
5. NOW crank the engine over

If the engine starts quickly and cleanly after performing this procedure, you may have the check valve issue. If it starts and runs poorly for a few seconds, it could also be a leaky fuel injector resulting in the bleed down and the stumble upon startup is the engine clearing the excess fuel that has leaked into the cylinder because of the faulty injector.

Also be aware that a bad battery can give you this symptom. Sounds strange but it definitely does happen. Have battery load tested if you have any questions; your XJ does NOT like low available battery voltage. Be sure battery connections and posts are CLEAN.

Some troubleshooting tips for extended crank times:

Hook up fuel pressure gauge on the schrader valve on the fuel rail

Start engine and bring to normal operating temperature.

Observe test gauge. Normal operating pressure should be 49.2 psi (plus or minus 5 psi)

Shut engine off.

Pressure should not fall below 30 psi for five minutes.

If pressure falls below 30 psi, it must be determined if a fuel injector, the check valve within the
fuel pump module, or a fuel tube/line is leaking. An adaptor tool/hose included with the fuel pressure gauge can help you with this. Consult gauge manual for more information on this but here is basically how it works:

*Turn the engine off and immediately clamp the fuel line at the adaptor hose. Watch the pressure gauge and see how long it takes to lose pressure.

*If the pressure remains at 49 psi for an extended period of time then the problem is in the tank - possibly the check valve. If the pressure falls below 49 psi fairly rapidly then the problem is probably a leaky fuel injector.

You can limp a check valve problem along indefinitely if you wish as it doesn't mean the fuel pump itself is going bad. Normally, the check valve is replaced as an entire assembly as you have to drop the gas tank to access the assembly. Fuel pump assembly consists of fuel pump, regulator, check valve, filter. If you do replace the fuel pump assembly, purchase a high quality OEM style unit. Some cheap aftermarket assemblies don’t hold up and fail prematurely. I specifically seek out Bosch fuel pumps as they are the best in the business. Stay away from Airtex, as IMHO, they have a bigtime reliability problem.

 

sorry it is a 94 high output 4.0 and like i said the guy told me the fuel pump was new aswell as the whole sending unit

 

Can't rule out the fuel pump assembly because he said it was new. New(er) stuff fails way more than you think. Especially if it was an Airtex assembly that was installed. Not my favorite brand.

 

yea thats true especially because he is full of crap but what you are saying is the pump should kick on every key cycle i figured it should but you never know and its a 92 not a 94 not sure why i put that lol. and the check valve is on an issue on the 95 and newer so you are thinking more along the lines of the pump itself then i know for sure its not kicking on every key cycle it seems to only kick on after the motor tries to fire

 

ok i know this is an old post but still havein same problem only its gotten worse i have changed the pump and sending unit and the relay but here is what is happening the pump wont kick on when I turn the key the pump doesnt prime then maybe after a hundred key cycles the pump will prime but it takes a few cycles to fully prime then the jeep will start and die a few times and eventually run then as lond as it doesnt sit for more than a few hour it will start and run fine used to be only after it sat for a few days or it was a super cold morning now its every morning and at the end of the day at work so it has gotten much worse