mason.canner

Whats up everyone, my XJ takes to cycles to start and then runs great. Ive read the it could be the check valve and checked my fuel line after letting the jeep sit for 30min. I had no pressure. So can someone send me a link to a check valve that I can install? -Thank You

jordan96xj

Greetings. You will need to provide more detailed information regarding the year your vehicle. The answer to this question can vary depending on those details.

On my 96, the check valve is part of the fuel pump assembly. I just installed a new one last weekend. Prior to the new assembly having been installed, my system would not hold pressure very long either, and would result in a slightly delayed startup (2-3 extra cranks) when the vehicle had sat for more than 30 minutes or so. On warm starts (gas stations, etc) it would start up in 1 crank. But I never did experience the symptoms where it would require very long crank times to start, nor did priming the pump multiple times with the ignition key make any difference. So I don't know if that is just a 96-ism (might be because the 96 fuel pump and assembly is unique to the 96 model year - for example the 96 has no return line to the fuel pump).

mason.canner

It is a 2000 Cherokee Sport

cruiser54

Try this for verification. Key On, then off. On again, then off. Then turn to Start.

You can also have injectors that leak down when sitting for a while causing the same issue.

tjwalker

Adding a check valve will not work on your 2000, where the fuel system has no return line.

Some have had success with using the check valve on earlier models (95 and earlier where you have a fuel pressure regulator under the hood and a return line), but I would not try it on anything newer than 96.5 which was the year of change for the fuel systems. Doing this has actually been linked to starting a fire on a couple of later model XJs. Search the NAXJA XJ forum for information on this check valve where there are a few specific threads on this mod.

There are a couple of different check valves on the fuel pump assembly so I always replace the entire fuel pump assembly, as when one component on that assembly is failing, other components are not far behind. I'm not fond of doing things twice.

Other than that, you can try performing the "poor mans prime" in post #4 which Cruiser54 posted. Doing that can sometimes restore enough fuel pressure for the engine to start cleanly. Just because a check valve is failing does not mean that the pump itself is failing.

As this is a very common issue on the XJ, here is my "cut and paste" reply to give you yet more information. Good luck and keep us updated!
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The check valves (there are two of them; the primary one is on the fuel pressure regulator and a secondary one can be found on the fuel pump itself) are part of the fuel pump assembly on 95.5-2001 vintage 4.0 XJs. When a check valve starts to fail, it can reduce fuel pressure to a point where an extended cranking time 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) first step in helping you 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 about 2 seconds. Be sure to wait until it stops running.
3. Turn key to OFF position
4. Repeat above steps 1-3 two more times
5. NOW crank the engine over

If the engine starts quickly and cleanly after performing this procedure, you may have a check valve issue. If it starts and runs poorly for a few seconds, it could also be a leaky fuel injector resulting in the fuel pressure leaking down and the subsequent 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 starting symptoms as well. Have your battery load tested (any parts store will do this for free) if you have any doubt; your XJ does NOT like low available battery voltage. Be sure battery connections and posts are CLEAN.

Some troubleshooting tips for extended crank times. You will need a fuel pressure gauge. Many parts stores will rent you this tool inexpensively.

*Hook up fuel pressure gauge on the schrader valve on the fuel rail under the hood

*Start engine and bring to normal operating temperature.

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

*Shut engine off.

*Observe pressure on gauge. Pressure should not fall below 30 psi for five minutes.

If pressure falls below 30 psi, it must be determined if a fuel injector, a check valve within the

fuel pump assembly, or a fuel tube/line is leaking. An adaptor tool/hose normally included with the fuel pressure gauge can help you with this. Consult the manual that comes with the fuel pressure gauge and the Factory Service Manual for your year XJ for more information on this exact procedure, 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 – most likely a check valve. If the pressure falls below 49 psi fairly rapidly then the problem is probably a leaky fuel injector.

**Note. Where check valve is suspect, a quick loss of fuel pressure is often the fuel pressure regulator check valve and a slow loss of pressure is often the fuel pump check valve. But keep in mind that either or both check valves can be to blame.

You can limp a check valve problem along indefinitely if you like, as it doesn't mean the fuel pump itself is going to fail. Perform the “poor mans prime” before cranking to speed up your starts. However, if you have a check valve issue and want to resolve it, it is recommended that you replace the entire fuel pump assembly for two reasons. First, you have to drop the gas tank to access the assembly. Secondly, with two check valves, replacing just the fuel pressure regulator where one of the check valve resides may or may not resolve your problem; remember there are two check valves; the other check valve is part of the fuel pump.

The fuel pump assembly consists of fuel pump, fuel pressure regulator, fuel gauge sending unit, fuel gauge float, pickup filter and pigtail wiring harness. If you do replace the fuel pump assembly, purchase a high quality assembly. Know this….you do get what you pay for here. Some cheap aftermarket assemblies have been known to fail prematurely. I personally prefer Bosch fuel pumps as they manufacture the best fuel pump assemblies for the XJ. Carter is my second choice. Airtex is my least favorite choice and I will not recommend or install them. A Google search will show you why.