Hard starting

Have a 1990 laredo 148xxx. Last six months has had hard starting issue. It will keep cranking and ill have to pump the accelerator to get it stated. It also is not idle great intermittently sometime in at the first notch or or higher. Ive replace the tps, sync sensor, crank sensor, new plugs wires. Any ideas..

Search for Cruisers renix refresh posts. Make a list and start checking them off as you complete them. You will soon have the Renix gremlins resolved.

I had chased this problem on my '93 XJ 4.0L for weeks and I solved it only last month.

At first I was under the impression that it was "normal" for Cherokee engines to require
several revolutions during startup for the ECM to pick up a signal from the CPS in order
to roar to life. Changing the CPS, dist cap & rotor, spark plugs did not make any
improvement and so I figured that was the way these cars are made to behave and
so I lived with it for a few years.

Then 2 months ago the car startup became worse. It took much, much longer to
crank and fire up, and it would often cough and spit for a few seconds afterwards.

There were no codes and my OBD1 scanner showed everything was within specs.
I tested all of the sensors OK (or so I thought, more below) and I also replaced the
CPS, MAT, and coolant temp sensors with a factory units just to be sure. No change.

By chance, late one night, I ran into some online info about testing the MAP sensor using
a vacuum pump and an ohmmeter. See link, below

http://troubleshootmyvehicle.com/jeep/4.0L/how-to-test-the-map-sensor-1

As before, the MAP sensor tested OK while at rest - but as soon as I applied vacuum
the resistance became way out of spec from those given on the website.

I put in a new MAP sensor (by Delphi, from NAPA) and the change was like day & night.

Now my car fires up in 1-2 revolutions from a dead cold start and purrs like a kitten.

88trailcrawler said:

Search for Cruisers renix refresh posts. Make a list and start checking them off as you complete them. You will soon have the Renix gremlins resolved.

Click to expand...

Begin with numbers 1, 3 and 4.


http://www.cherokeeforum.com/f51/cruiser54s-mostly-renix-tips-153657/

Sounds like a bad, leaking fuel pressure regulator, FPR. It is on the front of the fuel rail, and has a vacuum hose on it. Pull the vacuum hose and if there is even an odor of gasoline, the FPR is leaking gas into the intake, bypassing the injectors and flooding the engine.

RENIX XJs have to "spin up" to start. Manuals state that the signal from the speed sensor--the crank position sensor--won't be strong enough to get the ECM to trigger spark UNTIL the engine is cranking at 300 RPM or higher.

That said, Cruiser54 and other have shown that adjusting the crank position sensor's relationship--moving it closer to the flywheel/flexplate--can boost the signal and lessen the RPM speed required.

So, try modding your crank sensor, MAKE SURE THAT YOUR BATTERY AND CABLES are top notch, and consider having your starter rebuilt at a local rebuilder. A strong battery with a high CCA rating, along with large well-constructed cables, and a healthy starter will go a long way to shortening your cranking time.

Also, check your fuel system for correct pressure and volume, as well as its "bleed off" time. You can "prime" your fuel system by cycling the key from OFF to ON a few times before cranking.