so for starters I have a 1990 Cherokee 4.0 with 180.000 miles.
so about a month ago it rained for 3 days and the jeep would not start, this had happened before but ones it dried out after 3-4 days it would start back up, this time it didn't.
so for the past month every time I get some time I have been checking things out
So what I have checked so fare is, Tps getting 210ohms, map sensor 5v output when cold (I have also checked the vacuum lines to the map) , throttle position sensor starts at .86v and slowly rises to 5v when moving the throttle, pickup coil tested good, I have good spark on all the cylinders, I have fuel on the rail, I can hear fuel pump running, I have cleaned the IAC, have swapped plugs.
And still All I can manage to get is a spit and sputter, ones and a while I can get it to fire up for about 20 seconds. Its getting lots of gas, had gas coming out of the exhaust.
odd question but I did hear some talk on here about this, could it be the battery ? I normally get about 4 mins of cranking out of it before it starts to die. I have jumped it from another truck to to help it out.
I had a similar issue where my '89 Cherokee Laredo which would idle fine but sputter when trying to accelerate. It turned out that one of the hoses on the fuel pump had slipped down the metal pipe and was just about ready to come off. The fuel was leaking back into the tank.
I don't understand ohming a TPS as it should be checked for voltage. and, A TPS will not cause a no-start.
CPS, on the other hand can cause a crank-no start. Here's how to properly test a CPS:
Renix CPS Testing and Adjusting
Renix CPSs have to put out a strong enough signal to the ECU so that it will 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 the upper mounting hole, or slot it so the CPS bracket rests on the bell housing when pushed down. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.
Originally Posted by chris87xj
If you own a Renix Jeep, you'll want to check this out. >
An index to over 25 write-ups can be found in Post #1.
Jeep misses on acceleration and stalls occasionally
Before you do anything pull the cap and check rotor shaft for excessive play. I changed fuel filter, plugs, cap, rotor, and crankshaft position sensor just to find out I had a bad distributor 50 dollars at O'Reilly and it took about 15 minutes to change. Live and learn.
How old is your tuneup hardware? Never underestimate the importance of fresh tuneup hardware. The fact that you have more symptoms when it is wet could be due to a distributor cap, etc. Be sure you have fresh plugs, plug wires, cap, rotor, fuel filter. Basics first; always.
Be sure you have a strong, BLUE, snapping spark. Yellow/orange/white indicates a weak spark which may not be strong enough to start the engine. Spark quality is important. A weak spark is usually caused by a failing ignition coil. Testing your crank sensor with cruiser54's procedure is never a bad idea and very easy with the RENIX engine.
Always have a fresh fully charged battery when you are trying to start an engine that is symptomatic. A marginal battery only muddies the water and can create a condition where you don't have enough available battery voltage to actually start the engine and then you end up with a flooded engine and that makes it even more difficult to figure out.
If all of the above checks out, verify proper fuel delivery. For a 90, you need 31 psi to start the engine. Must be verified with a gauge which can be rented from many parts stores; call around.
99 Cherokee, 4.0 AW4, NP242
Past Jeeps: 49 Willys, 81 Scrambler, 88 Comanche Without "data", all you have is an opinion!