ThE_CaPtaIn

My fuel pump performs great but if I let my jeep sit for more than about 2 hours it will hard start. Due to the fuel draining outta the fuel line into the tank and the pump having to reprime it. So my question is the check valve that is suppose to hold the fuel in the line built into the pump or is it something separate I can replace?

DFlintstone

I'm looking at the same problem. I hear it's in the pump, and that's that. Was told there is an in-line valve for BMW's....I might check rockauto.com. D.

grantman18

I was having this problem as well, and I can't install the in-line check valve because I have a 2000, and late model XJ's don't have the same return line. I ran techron fuel system cleaner and it seems to have fixed the problem. I'm guessing that there was some gunk or sediment in the check valve that was preventing it from seating properly. It was a hell of a lot easier than replacing the pump or regulator.

ThE_CaPtaIn

So u just ran some pour in the tank fuel cleaner and it fixed Ur problem? I have no issue replacing the fuel pump. I just wanted to make sure that it was the culprit b4 I did. But I will try thAt first.

grantman18

Ya that seems to have fixed it, and it was cheap and quick so I firgured it was worth a shot. You can also just turn the truck "on" and then wait about 5 seconds before starting it. That gives the fuel pump enough time to prime the fuel line.

ThE_CaPtaIn

Yeah that's what I'm doin. Now but I would just like to get it fixed.... I'll try the additive and if don't work I'll swap the pump.

tjwalker

The BMW checkvalve will not work with 97 and newer. Don't even try it.

Here is more on the checkvalve; it is a common failure.
----------------------------------------------------

The check valve is located on top of the gas tank and 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.