1989 XJ START UP ISSUE HELP!

HEY jeep experts! I'm in need of help...new to jeeps and this forum I bought an 89 xj 4wd 4.0 I have done a lot to in since but I still have the start up issue !! Okay so when I crank the car is does it for about 3-4 seconds before starting sometimes it stumbles like it wants to start but also doesn't its very frustrating. ive changed the fuel pump, filter, distribution cap and rotor it runs fine and idels good but its just the start up that's a hassle for me. Please if anyone hads any ideas as to what can cause this I would more than appreciate the help . Thanks

Sounds like your idle air sensor, if you look on the top of the engine, there should be a brass plug on the drivers side near the brake booster with two wires coming out of it. It is on the intake manifold, not the block!!!! (the one on your block is the temperature sender)

Pull it out, spray it out with seafoam, brake cleaner, degreaser, and do your best to clean it, it should look like a little cage with a wire dealy inside it. you shouldn't poke at the stuff inside, as it's somewhat delicate, I usually just use brake cleaner, and compressed air to clean it out.

1. Finish the tuneup with new Champion copper plugs, quality plug wires

2. Clean your throttle body and idle air control. They get carboned up over time and miles

3. More on a slow start with RENIX below.
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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!

If your only problem is 3-4 second crank time before it starts, that is normal for Renix 87-90 Jeeps. 2-3 seconds, is the best I have ever seen on a Renix jeep.

Ecomike said:

If your only problem is 3-4 second crank time before it starts, that is normal for Renix 87-90 Jeeps. 2-3 seconds, is the best I have ever seen on a Renix jeep.

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Mine starts as soon as the starter engages and thumps like metronome at idle. It only took me 2 1/2 years to get it that way.:wow: And to tell you the truth I can't remember exactly what I did.:wave:

IMO most likely to be air in the fuel rail, try the old trick of turning the key to the run position (not start) a couple of times to make sure the fuel rail gets primed and purged well and then try a start.

Check your high voltage spark. It should be sharp and blue and able to jump a 1/4" to 3/8 " gap to ground. Many reasons for weak spark.

Old gas can also cause long starts.

You must be the only one on the planet with an instant start Renix!

Ecomike said:

You must be the only one on the planet with an instant start Renix!

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Sometimes accidents are good, I don't exactly what I did, but it works.LOL

Thanks a lot I appreciate the help, I got me the maf sensor cleaner and carburetor cleaner to clean the throttle body. I'll give that a shot I know its a mess in there...my main concern was that when I start it the car rumbles a bit kinda like its having a hard time sucking in air usually when I start it it cranks then u can hear the air intake once then start up. Now its like crank crank stumble stumble crank crank stumble then start. I figured if I let off the crank and start it again it starts up and so it did. Hmmmm

Check the vacuum tube from the MAP sensor to the throttle body, and see if is loose or leaking near the throttle body.

Be careful of getting carb cleaner, or any solvent on the TPS, it will screw it up. Even getting it wet can screw it up.
I learned the hard way to take the TB off, remove the TPS and IAC then scrub it out on the workbench. I use Liquid Wrench 2 and a toothbrush to clean it, then rinse it off with brake cleaner. Carb cleaner may attack some stuff, it is sometimes pretty strong.
Also pick up a new TB basket before you start, the old TB to intake gasket gets hard as a rock and can separate when you take the TB off. I coat the new gasket with a thin layer of anti seize or copper paste.
There is an idle air bypass passage in the TB, the adjuster is behind a slug (anti tamper) cover. You can remove the adjustment screw, (count the turns) and clean the passage out. Most come full closed from the factory some are slightly open from the factory, but eventually close up with trash. My guess is that the idle air bypass is a fine adjustment at the factory for emissions, it almost has to interact with the IAC on some level.