Help!! Crank but no spark!!

88 4L ran fine when I parked it two weeks ago now it cranks but no spark. Should I be looking at the coil? Starter relay? Any thoughts would be appreciated.

Thanks

CPS CPS CPS! try replacing ur cps it is the sensor that is on top of the bell housing! about 40 bucks and 20 min of ur time!

stoney

Absolutely... Sounds like the infamous CPS strikes again. When you take out the two bolts that hold the CPS on the Bell housing MAKE SURE you don't drop one into it like I did. Made a 10 minute job a 4 hour job.

Hawaiian Style said:

Absolutely... Sounds like the infamous CPS strikes again. When you take out the two bolts that hold the CPS on the Bell housing MAKE SURE you don't drop one into it like I did. Made a 10 minute job a 4 hour job.

Click to expand...

The CPS should have a plastic dust cap around it that should prevent this. If it doesn't now, the new one should come with a new cap. If you snap the cap onto the bellhousing first, it will not only help prevent bolt fall-in but also help hold the cps in place while you fumble in the dark trying to stick the bolts into the holes.

And if you really need the Jeep to get going temporarily, try just disconnecting and reconnecting the cps. It may or may not fire up but it's worth a try. Good luck.

I didn't have one and didn't get one with the new CPS. Did you get yours at the dealer? Mine was a Advance Discount Autoparts cheapo.

CPS test

Burnsie:
The CPS is easily tested on the vehicle. disconnect the CPS connector at the harness (located just below the MAP sensor near the middle of the engine by the firewall) Connect an ohm meter between the leads. Cold, you should read app 250 ohms. Anything in that ballpark indicates a good sensor.

If that reads ok, e mail me, I'll give you the next step.
Michael

Thanks guys for the input! The new CPS is on it's way and I will hopefully have it in later today or tomorrow. I appreciate all the help!!

Warning!!

Why would you want to replace an electrical part so critical to the starting of your vehicle with, what you admitted, a cheapo?? Have found 'discount' auto stores replacement parts seriously lacking in quality and fit. This has included mechanical parts as well as especially critical electrical parts. I'd do the dealer for anything so essential!!!! Being left stranded is certanly no fun and would want to do what is possible to keep that from happening!!

Also, having read so often about reconnecting that sensor then the vehicle starts, tells me the whole problem might be in the connector itself. Maybe all it needs is attention to that part. Could possibly just eliminate the connector totally or to install a new better one.

If the CPS does not fix it.....pull the coil out of the coil holder and clean the 2 contacts that supply power the coil from the coil holder.

Or...you may want to check this anyway, last time mine did not start this was the problem.

Rev

Here is a post I have put up a few times to describe my cps fix:

"If on a crank but no start the unplug and replug of the cps wire harness connector gets you going you may just have a wire harness connector going bad and may not need to replace the cps sensor. Here is how to test: hook volt meter to both wires from cps sensor w. harness unplugged. Set the range on meter to less than one volt. Crank engine and if cps generates .5 to .8 or more volts it is ok and your connectors need tightening or replacing. I got my parts for a couple of $ at pepboy but advanceauto.com also has them. They were made my Dorman under the Motormite Conductite tech grad name # 85303, 85304 and 85305. There are about 5 pieces in each box. You can also get a small tool set that helps on the install number 85360. I fixed my 89 this way a couple of months ago when I got tired of unplugging and replugging the connector every few weeks. My cps was only 1 yr old so the engine side harness connector part was worn out. I replaced both the female and male side internals of the connectors and it not only starts every time but the idle was also improved. Greg"

Good Luck. Greg

Re: CPS test

michael-esq said:

Connect an ohm meter between the leads. Cold, you should read app 250 ohms. Anything in that ballpark indicates a good sensor.
Michael

Click to expand...

Well sort of. The sensors fail do to heat cycling. Basically they expand/contract and over time the coil of wire inside goes open circuit but it may only do it at a certain temp (this is why sometimes dumping a ice chest on the CPS might get you going again for a little while). The manual suggests checking it when it's hot. But otherwise it is a good test if it is being tested at the same time you are getting no spark.

Also the CPS or wiring connections are the most common problem. For 87-88 models it could be in the C101 connector. The factory has had bulletins for a direct overlay harness for the CPS also.

I did just help a friend with this problem and it turned out to be his ECM which is not a common failure.

Hey, that heat cycle theory would explain why my XJ would start up sometimes and not others... It seemed to act up in the morning or after it had been driven. Thanks for the enlightenment!

Crank. I've heard of this drug.

Spark, is this a new one??? Where do you get it? :smoker: