codykrr

ok so I know I read about this somewhere on here(unless Im loosing my mind) But I cannot find the info again.

My 01 cherokee sport(4.0) always takes two cranks to start. I remember reading somewhere on here how to test the "check valve" or maybe it was the fuel pressure regulator..or something.

it was like turn the key on, then off, then on then off again then if it starts normal thats what it is...

I been searching for the last 20 min and havent found the info again....

I was just curious if someone could point me in the right direction! lol maybe towards a write up or the original thread I read about it.

CCKen

There's hundreds of threads with the same problem.

You had it right; turning the key to RUN several times to prime the fuel rail.

The fix is to change the fuel pump module assembly.

Use a Bosch or Carter pump module, not and Airtex, if you make up your mind to change the module.

codykrr

yeah I have read some of the issues. but there was a particular thread regarding the pressure regulator, and or a check valve of sorts...

I do need to change the fuel pump assembly as my sending unit isnt working properly.

PocketsEmpty

Yep, I'm having the exact same issues with my 98. I'll probably order a Carter. It's a little lower on the fix list though since it's not a show stopper.

Here's a tip for searching the forums: use Google.

codykrr

Lol, I found that out earlier^

Good, plus whatever it is, the cherokeeforum. I found it BTW. it was in the "project hippo thread"

PocketsEmpty

That thread is incredible, that guy did a full write up on every single mod he did in it I think, lol

codykrr

^ yes it is! amazing walkthrough's and pictures!

Shame he sold it!!! I was like WTF at the end of the thread! All that work, just to sell....

tjwalker

The check valves (there are two of them; one on the fuel pressure regulator and another on the fuel pump) 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 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 one is on 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 unit; 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.

naverillsn001

Okay, I have the same problem and I've read this whole thread (and several related ones) and am fuzzy on....

I have a 96 xj 4.0 auto rwd. Is that a "you can add an external check valve" model or a "if you add an external check valve your xj blows up" model?

Is the check valve always a component of the pump; i.e., if I change the pump have I automatically changed the check valve? Can't find "check valve" as an independent part.