1989 Cherokee 4.0 renix. Since its been cold my jeep takes forever to crank before it starts, I have surging idle too. lately its really been a hassle to start the damn thing because it keeps cranking but no spark. after a while I guess fuel reaches the injectors and it fires up. Is this a bad fuel pump?

 

oh and it still starts up just fine if the jeep is warm or weather is warmer than like 35 degrees outside. Also every time I run the fuel pump before cranking it runs so I have no clue as to what the problem could be.

 

Without a spark, fuel or not doesn't matter. First check and see if you have 12V at the coil and check the fuel pressure with a gauge.

 

Sounds like you have spark, but extended crank time BEFORE it starts?

1. You may be experiencing fuel pressure drop as the vehicle sits. The "poor mans prime" detailed below, is a good test. Sounds like when you try this, it starts quickly?

A. Turn key to ON position (do not crank the engine!)
B. The fuel pump will energize and run for about 2 seconds. Be sure to wait until it stops running.
C. Turn key to OFF position
D. Repeat above steps 1-3 two more times
E. NOW crank the engine over

If the engine starts quickly and cleanly after performing this procedure, you may have a fuel pump check valve issue. If check valve fails, your fuel pressure can drop quickly and it takes extended cranking to build it back up to a pressure that will start the engine. 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. Further troubleshooting can be performed to isolate the root cause.

2. Be sure all tuneup hardware is FRESH. The importance of this cannot be overstated. Fresh Champion copper plugs gapped to .035, quality plug wires, distributor cap, rotor and fuel filter.

 

What TJ describes above (was it you TJ, that actually came up with this term, IIRC?), is something I've learned about and been doing for months on a frequent basis when tired of long crank times. Keep in mind your Renix will usually take a bit longer than the younger XJ's, but the "pmp" does no harm and you can keep doing it until you're tired and decide to fix the problem...

 

Thanks Roler; ha! I'd love to take credit for "poor mans prime", but actually I stole that term from somebody else. I have disseminated the information enough though that people do credit me for it. What the hey.

Agreed. If you have a failing check valve, you can perform the poor mans prime (once or twice) before actually cranking the engine over to provide a quick start. And also agreed that a failing check valve does NOT mean that your fuel pump itself is going to fail; all it means is that one small component on the very end of the fuel pump is failing. So if you want to resolve it, then you would have to replace the fuel pump assembly. But otherwise, poor mans prime and carry on!

Here is more information on why RENIX engines may take a bit longer to start.
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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.

Your CPS can be a bit weak, too. Unplug it and probe the two wires with your meter set on AC volts. You should get .5 as a reading. Anything down around .35 will cause long crank times and possible intermittent no-starts.

Other than that, performing basic tune-ups on a regular basis is important, (plugs, wires, cap, rotor, fuel filter) The importance of fresh secondary ignition (tune up parts) cannot be overstated.

Good luck!

 

You need to see which is not present at time of issue Spark or Fuel .