Sometimes turns but doesn't start

1990 XJ inline 6 automatic 291k miles :O (engine was rebuilt and odo not reset so I'm not sure how many miles are actually on it.)
This doesn't ALWAYS happen, but it's happened a few times inconsitantly with no warning in the past couple weeks. It just turns and doesn't start, and then I'll wait about 5-10 minutes and it'll start up fine but act a little funny for a few minutes clicking, missing, talks back, doesn't come home at curfew etc.

I replaced the CPS not 8 months ago (which was a pain in my arse) so I 1. hope its not. 2. don't know why it would be since its relatively new.

Anyone else have this problem?

It could be as simple as low voltage from the battery. Does it crank real good or is it a little slow? Do you have a meter to check battery voltage?

Next thing to check would be the spark plugs.

Basics first for starting issues.

1. Fresh tuneup hardware. Includes plugs, wires, cap, rotor, air and fuel filter
2. Clean battery terminals and posts. Load testing of the battery is never a bad idea

Question for you. When this happens, does it happen to a cold engine only, a hot engine only, or both? Answering this question can be helpful in the troubleshooting process. Sometimes an engine stumble upon startup (after the vehicle has sat for a while) can be related to a leaky fuel injector(s). Raw fuel leaks into the cylinder(s) and upon startup, it runs rough for a short period of time until the excess fuel is burned off.

You know what. I had a problem last week where my posi battery cable was being a jerk and I had to wiggle it around to get power at all. I probably need to replace it.
I'll definitely try that, thanks a lot!

Your RENIX Jeep has numerous grounds throughout the engine bay, under the dash, behind the taillights, etc. It sounds like you need to make an afternoon project of finding ALL of the grounds on your Jeep, disconnect them, scrub the wire end and body connection with baking soda and water and a small wire brush. They need to be completely clean of all rust, grease, corossion, etc. Make them SHINY!! Include the bolt or screw that fastens them. Also, clean battery terminals as well. Inspect ALL of the battery cables and ground wires for broken insulation or other defects, replace as neccessary. It is O.K. to replace with larger wire, but NOT smaller. Finnally, have your battery tested at a reputable shop or parts store. Stay awy from the stores with pimple faced kids or ditzy chicks behind the counter.

By doing this throuogh inspection and cleaning of your RENIX electrical system, your CPU and the rest of the Jeep will be much happier. Also, this will make future diagnostics quicker and easier.

Matt

It sounds like it could be the same problem that I had. (Bendix would not engage)
1st- I would check and clean the battery connection
2nd- I would climb underneath and look for any corrosion, damaged wires, loose wires, anything that looks out of the ordinary.
3rd- grab your starter make sure that it is secure and has not come loose.
4th- if you are getting proper voltage at the solanoid and the bendix gear still does not engage then your silanoid is bad and you will need a new starter.

Good luck, it is a real easy fix.

birchlakeXJ said:

Basics first for starting issues.

1. Fresh tuneup hardware. Includes plugs, wires, cap, rotor, air and fuel filter
2. Clean battery terminals and posts. Load testing of the battery is never a bad idea

Question for you. When this happens, does it happen to a cold engine only, a hot engine only, or both? Answering this question can be helpful in the troubleshooting process. Sometimes an engine stumble upon startup (after the vehicle has sat for a while) can be related to a leaky fuel injector(s). Raw fuel leaks into the cylinder(s) and upon startup, it runs rough for a short period of time until the excess fuel is burned off.

Click to expand...

So far what's been happening is i'll drive for a while and stop and it'll sit for about 15minutes-hour and it starts fine for a few times then finally i'll leave it for 15 minutes-hour and it won't start.
Then i'll wait for about 5-10 minutes and it'll start right up and act a little funny for a few minutes.

Orodreth said:

You know what. I had a problem last week where my posi battery cable was being a jerk and I had to wiggle it around to get power at all. I probably need to replace it.

Click to expand...

ummmmmm...this is what you need to concentrate on first. Cables/connections are critical.

Yeah, pull the cables, clean both ends and then check their resistance with an ohm meter--should be near ZERO.

There are CRITICAL grounds at the dipstick--that's right, some dipstick engineer put the critical grounds on the dipstick, go figure. Hit the ground strap at the rear of the head to the firewall--on the Renix XJ that is the one and only OEM ground for the unibody, another great engineering feat! If you still have the braided strap replace it with a 4 ga cable. All grounds should be cleaned, stripped to bare metal, treated with an anti-corrosion material, and then attached tightly.

I had the exact same problem and it was a bad silonoid on the starter. It was doing it on and off for a little over a week.

joe_peters said:

There are CRITICAL grounds at the dipstick--that's right, some dipstick engineer put the critical grounds on the dipstick, go figure. Hit the ground strap at the rear of the head to the firewall--on the Renix XJ that is the one and only OEM ground for the unibody, another great engineering feat! If you still have the braided strap replace it with a 4 ga cable. All grounds should be cleaned, stripped to bare metal, treated with an anti-corrosion material, and then attached tightly.

Click to expand...

Seems like a great upgrade would be to add a ground directly from the negative battery post to the body. It would take less than a foot of wire and would not be subjected to any engine mount flexing. Most cars are that way from the factory.