Originally Posted by tjwalker

You have a Renix XJ (87-90) By design, the engine is not going to fire until the computer (ECU) gets a signal from the crankshaft position sensor and measures that signal to indicate that 300 rpms while cranking has been met/exceeded.

Somewhat extended crank times should be considered a “characteristic” of your engine, rather than a problem.

You can upgrade the battery and battery cables--at least 4 ga., 2 ga. better--and buy a high-torque starter.

Be sure that all grounds are good. Remove them and freshen them. You cannot tell if the grounds are electrically good by looking at them! Renix vehicles are very sensitive to ground issues.

Other than good basic tune-ups on a regular basis which should always be reviewed, (plugs, wires, cap, rotor, fuel filter) the above suggestions are things that will help optimize start times on a Renix engine.

Originally Posted by ceonaigh

My 2001 Cherokee does exactly what you're talking about. My question is how do you splice in a new check valve (aftermarket) into the lines? I certainly don't wanna buy a new fuel assembly, because my friend changed his once and it took longer than I care to spend on it.

Originally Posted by tjwalker

I'd pass on the check valve. I have heard that it is not compatible with the fuel pump system on yours.

Either live with it (prime it by turning the key to the on position, then off, then repeat, then start) or replace the fuel pump assembly.

Originally Posted by BotakBeng

If it is just not holding pressure, wouldn't a replacement of the pressure regulator work or do we need a whole pump replacement?

Originally Posted by tjwalker

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.

Originally Posted by tjwalker

Been a while since I tore one apart, but I believe the "primary" fuel pressure check valve is inside of the regulator, but I believe there is a "secondary" check valve at the outlet of the pump itself.

Yes, you can install individual parts on the 4.0 fuel pump assembly, and some have had success with this.

But because oftentimes when one component fails, others aren't that far behind, I always recommend replacing the entire fuel pump assembly when you have the gas tank down. That gives you a fresh pump/regulator/checkvalve/filter. I don't like doing things twice!

Another tip for anyone that has to replace their fuel pump assembly. Do NOT buy an Airtex. They are available at many parts stores as a low cost option, but don't let price lead you astray. Airtex fuel pump reliability is very poor IMHO, and because of personal experience, I will not recommend them or install them in anything I work on. I specifically search out Bosch. They are the best in the business when it comes to fuel pumps. Yes, Bosch are more expensive, but you really get what you pay for here, so don't cheap out. It will cost you more in the long run if you try to save money with a cheap assembly.

Originally Posted by Saudade

Wrong forum. Try https://www.cherokeeforum.com/f5/

Good luck.

Originally Posted by Jeroen

I have a small problem with my '98 Jeep, 4.0L.

Since a couple of weeks, when cold, it will only start on the second try.

It cranks well but won't fire up even if I keep cranking it for 10 seconds. Second try it'll fire up immediately. Even if I crank it for 2-3 seconds, stop and the try again it'll fire up immediately, but not the first time.

Battery is fine, replaced plugs, leads, distributor cap and rotor a while ago.
Once it's running it idles well and it runs fine, with reasonable MPG.

Any thoughts?

Jeroen