sboulton36

i have a 94 cherokee xj sport 4.0L.

what it's doing now: after sitting for a while (like over night) when i turn the key it will start for only about a second and then die almost instantly and then it just cranks without starting no matter how many times i try.

what it was doing: as i was driving it sputtered like it was running out of gas but wouldn't completely die at first then it would die and i would be able to start it right back up and then it just died and i couldn't get it running for a week, i then unplugged the crankshaft position sensor (which was only 2 months old) plugged it back in then it worked for about 400 miles before sputtering and eventually dieing.
i took the CPS back and got a new one and it didn't change a thing.

the fuel pressures at 40. and im getting spark at the spark plugs.

things i've replaced in the last 3 months: flue pump (and filter), ignition coil, distributor cap, crank shaft position sensor (twice), and the computer.

any thoughts?

RTorrez1

Where did you get the CPS from? Aftermarket ones are garbage.

Roler

As Robert states, the CPS you have in there might still be an issue.
It might be worth checking for codes, since it might reveal any other issue (like Cam shaft sensor, code P0340

sboulton36

Ok I'll try and check the codes tonight, what does the cam shaft sensor do?

sboulton36

If the cam shaft sensor was bad could it be giving me these problems?

Roler

Camshaft and crankshaft position sensors, give the ECU info on....well, the camshaft and crankshaft position. That info is used for timing issues.
Faulty sensors like that will either give faulty or no information, and therefore interfere with how the ECU is managing the way the engine starts/runs. I'm sure there is a more scientific way to explain this, but this will hopefully make some sence.

Just keep in mind: to start or run you need 1)fuel 2) spark 3) combustion 4) good synchronised action of all this. No start conditions therefore can ususally be tackled by systemcatical approach to identified the cause.

PDEM87

Roler, you mean "3) compression " ,don't you? Syncronized fuel+spark+compression=combustion

PDEM87

Lets say that you turn the key and start cranking the motor. Pistons 1 and 6 approach top dead center(TDC) at the same time. One is on compression stroke and the other is on exhaust stroke. The only way the computor knows which cylinder needs the fuel and which needs the spark is determined by the cam position sensor. Hope this helps.

sboulton36

So I'm pretty sure I don't have a cam shaft sensor but I have a "pick-up coil"which does the same thing, it's inside the distributer any know how to take a party the distributer?

Roler

Yes, apologies. Nightshift.

PDEM87

sboulton, the sensor in the base of my 87 renix distributor is titled SYNC sensor. It does the same job as a later CAM sensor. Regardless , you should be able to test yours with a multimeter.

PDEM87

Please leave your distributor in place. You don't want to pull it if you don't have to. You may have to do some research on how to test your 94. My 87 sends an intermittent 5 volt signal to the ecm .

sboulton36

where exactly can i test that at? i'm not sure how to test it? i'm familiar enough with a multimeter but i'm not familiar with this unit

PDEM87

This may work for your 94 also http://www.lunghd.com/Tech_Articles/...lse_Stator.htm

PDEM87

According to the chilton, Your distributor pick-up coil has a three wire connector. The middle wire should be ground. One end wire should be constant 5 volt supply(while cranking) and the other would be the signal wire to the computor. Set the meter on dc voltage and back probe the center(black lead) and either end to find out which is which. If the non-constant signal wire is not consistantly switching, you've found a culprit.An anolog meter may be easier to watch the signal.