we are working on a 98 jeep cherokee 4.0l mt w air came in no fuel pressure put a pump in, now has 40 psi but will not start checked spark /injector pulse vantage pro the ckp sensor seams ok ,replaced it any way and nothing ./put new spark plugs in and now it will start at wot only, starts and just dies / i heard suffering builds character but this really is got me! any ideas
-
-
Check the tps if it starts at wot. The pcm should shut the injector pulse off at wot while cranking. Maybe the tps voltage is not correct and the pcm is shutting off the injector pulse with throttle closed.
EarlComment
-
checked tps sensor is good, changed it with a known good one and nothing ,also cleaned out the iac and, i do have injector pulse with throttle closed, also if i let the jeep sit for a day it will fire and just die without wot . spark is not blue but we have another jeep and same colorComment
-
Check the cam sensor in the distributor. Its main function is injector timing, not ignition. Driven by a worm gear in the middle of the cam it also drives the oil pump. An oil pump failure can lead to the cam sensor causing a no start.At WOT the PCM gives it all the fuel it can allowing it to start. JTEC (Jeep Truck Engine Controller) does not have a clear flood like most PCMs.Comment
-
I have checked the cam and crank sensor with my solus and it is seeing them and they are in syn. also when i wot the jeep the injector pules once then stops this is when the jeep starts up and runs for a second .also thanks for the help.Comment
-
Are you sure you are getting enough volume of fuel. Perhapes one of the lines got pinched or you just have a bad pump. Does that year have a fuel filter? That is around the time they started doing away with them. Check it. If it is pluged you could get PSI but not enough fuel.Comment
-
It's a Jeep Thing
Some things I have seen , Plugged exhaust , Remove 1/1 02 and see if it runs as that gives the exhaust some place to go if the exhaust is too plugged , Also VTSS ( Vehicle theft alarm ) has been activated and or the PCM ( JTEC ) for some reason thinks it is supposed to have an alarm it will start and stall as it shuts down the injectors if no run signal is seen from the VTSS, Will need a new PCM in that case if the Jeep was never equipped with VTSS, MAP sensors have done this to me too , Unplug the electrical from the MAP sensor and see if it runs in default settings ( With no MAP the PCM will run in a guess type mode ) I would also disconnect the fuel pump electrical and see if I could run it on carb spray down the throttle body ( Be careful at that idea ) If it dose run on spray down the throttle body you're in the area of not enough fuel as maybe injector drivers have gone or low volume .......
Manic Mechanic
Comment
-
I was wondering if the jeep was sitting for a while? you said it came in with no fuel pressure!!! I Had a jeep with sounds like same problem. it was customers second car so it sat for a year, he new it needed a fuel pump it had no fuel pressure, so we put one in it still did not run, I had everything spark, fuel it had a new pump, compression I did a compression test, So I unbolted the fuel rail with the injectors and cranked over the motor! no fuel came out of the injectors, they were pluged solid! put new injectors in and then the jeep ran. just a thought they may be pluged or blocked enough that it wont idle but when you hold it wot it is trying to force fuel through and it gets a little through but not a full flow, I know it is hard to tell cause you have everything you need but cause the injector is inside the intake manifold you can not see if it is spraying a good pattern. Just a thought let us know what you find.JOENASHComment
Comment