Cruiser..couldn't the pump relay be an issue? Rob, there is no harm in swapping the 2nd and 4th relays just to see.

 

A bottle of Techron in the tank can do wonders. If it's starting up the injectors are working at least well enough to run the engine. Perhaps not well, but at least run.
I'm betting on ignition switch. Did you find a multimeter yet?

 

Maybe. Let's figure out why it won't stay running first. Get your meter yet?

 

all right what am I checking

 

Did you try swapping the relays? Here's a diagram, Some are for the 2.5, but the 4.0 is there>>
http://www.scribd.com/doc/11033020/Jeep-Cherokee-1989

 

yes i did that did not work

 

OK, Cruiser or someone probably knows better. (which positions in the pump relay socket). I think he has a diagram. The ign switch energizes both a yellow and an orange when it's on. It's really tough up there under the dash, but possible. (It is sort of above the petals, on top of the steering column)

At your coil there are 4 wires. The third one from the front, a yellow, should turn on, and stay hot with the ign on. Booger is, although you need that, I think it's the orange you might have a problem with.

(don't confuse that one with the 4th yellow,(5v from the ECU)

If you want, check that yellow, (for about battery voltage), and I'll look into where to get at that orange..

 

OK, without taking more tome on the diagram then I want to spend right now, at the pump relay socket second from the front, the rearmost socket needs to be energized when the key is on. (in photo)

The one nearest the engine should always be hot. (that's the actual power that the relay shoots directly across to the works)(the pin across from the one I asked you to check is grounded by the ECU, to tell the relay to do that)

 

ok got home for work and tied to start the jeep it started right up ran for 15 20 mins thin died and starts and dies starts and dies i have change the relays still does the same so i ran a hot wire to the fuel pump it ran all the time and the same thing happens starts and dies so what else can i check

 

Common culprit, I just did mine a few months ago:　


Renix CPSs have to put out a strong enough signal to the ECU so that it Renix CPS Testing and Adjustingwill provide spark.
Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue as the CPS will test good when in fact it is bad.
The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark.
Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected.
You should get a reading of .5 AC volts.
If you are down in the .35 AC volts range or lower on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!! That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer.
Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off.
A little trick for increasing the output of your CPS is to drill out it’s mounting holes with the first drill bit that just won’t fit through the original holes. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.
　
Revised 11-29-2011

 

I suggest the CPS test partly because it only takes a minute. It's nice to have that out of the way since they get weak and cause any sort of mischief. The three wire plug has only two wires. They go down toward the bell-housing back by the rear of the manifolds, on the drivers side.

Does sound like possibly fuel. Having a gauge to the schrader valve on the rail when it's dieing would be Ideal . Right when it dies you can push in the little deal there, (like a tire valve), and see if fuel spurts out into a rag. Of course you want to be careful there, gas at 30 40 lbs around an engine is clearly a hazard.

 

my new 89 cherokee had this same problem and i spent a fortune replacing all kinds of things includingthe ecu, and it turns out it all boiled down to a plugged up exhaust system, replaced it from the joint back and it runs like a champ now, just a thought

 

That's why this is a good test to do:



CRUISER’S VACUUM TEST FOR EXHAUST RESTRICTION
Your vacuum gauge should come with an instruction booklet outlining the procedure. Hook the vacuum gauge up to a source on the intake manifold. Start the engine and note the vacuum reading. Usually 17 to 21 inches of vacuum. Throttle the engine up to 2,000 to 2,500 RPM for 20 seconds or so and the vacuum reading should stabilize to the same reading you got at idle. Let the throttle snap shut. The vacuum reading should shoot up about 5 inches of vacuum higher for a second and then come quickly down to the original reading. If the vacuum reading stays high and comes down slowly with jerky needle movements, you have an exhaust restriction.

 

I went ahead and put that in the Renix stuff in my Signature below..V..

 

Good. I've gotta get my butt in gear and do some more write-ups so we can start a comprehensive thread on CF.