cosmo11

when i start the cherokee it will crank 10 to 15 times before it starts everytime i start it , what could it be, i got a fresh tune up cap,wires, plugs, on it

tjwalker

Always post the year/engine when you start a thread. A common problem is a failing check valve. Here is more....
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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.

freegdr

one thing you forgot if its 87 to 90 its a renix thing

cosmo11

Sorry guys it is a 89 cherokee lerado, 4.0 auto

tjwalker

freegdr, you got me! That's why I asked for a year/engine. Here is my standard cut and paste RENIX schpeeel for a long crank time.
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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 that, performing basic tune-ups on a regular basis is important, (plugs, wires, cap, rotor, fuel filter)

The above suggestions are things that will help optimize start times on a Renix engine.

freegdr

when i did the 703 upgrade it seems to start a little quicker about 3 to 5 turns def better throttle response and idle

cosmo11

thanks guys i'll do so checking into what you've said, don't know alot about the 4.0 and the various vaccum lines things of that nature, thanks again

freegdr

87 thru 90 are a lot different than the others

cosmo11

lol i don't know if thats good or bad, she runs good for 230000

XJDC

Im not %100 on the 89s but if it has an inline fuel filter, replace it, and if its in the tank it could be a fuel filter/check valve in one. Its right on top of the tank so you don't have to tear into it, but the fuel filter is a cheap way, because it is technically a one way valve. Not necessarily the strongest one way but it may help and its really easy to do.