1989 Jeep Yj cranks but no spark.

phnguyen7 · 06-10-2012, 02:03 PM

Hi guys. I was wondering if you guys can help me out. The jeep was running great and all of a sudden it stopped running.

1989 Jeep YJ 4.2 Auto
Howell TBI

I've changed the ICM twice. Original one tested bad and the second one tested bad. Not sure if it was just bad or my ignition shorted it out.

I've changed out the coil, spark plugs and the distributor. I'm going to change the cap rotor and wires next.

As of right now I've tested for spark and no spark.

I tried to hook up a direct ground to the ICM and still didnt get spark while cranking but when I let go of the ignition it would spark and then cut out.

I checked my fuel injection and as of right now I am not getting fuel but I think it has something to do with my ignition. If i unplug the negative on the coil the pump will go off and the fuel will come out of the injectors.

Ive check all the wires and all the wires look fine. Now i am stumped and not sure what to do next. Thanks in advance for your help!

EABiker · 06-10-2012, 02:15 PM

The crank position sensor is the weak link in the ignition system; it's cheap, replace it first.

phnguyen7 · 06-10-2012, 02:56 PM

Quote:

Originally Posted by EABiker

The crank position sensor is the weak link in the ignition system; it's cheap, replace it first.

do we have a crank position sensor in the 89 yj? I thought that was only in the fuel injection models. If we do have one where would I be able to find it? I looked on the transmission housing and was not able to find it.

phnguyen7 · 06-10-2012, 06:14 PM

I tested the coil with a test light and the positive side lights up bright and the negative side also lights up bright when i ground it to the battery. When I tested it on my buddy's jeep, same model and year the positive lights up bright and the negative lights up but is dim.

Old4X · 06-10-2012, 07:21 PM

Please correct me if I am wrong, but isn't the Howell based on the 4.3 Chevy TB system from the early 90s?

phnguyen7 · 06-10-2012, 07:44 PM

Quote:

Originally Posted by Old4X

Please correct me if I am wrong, but isn't the Howell based on the 4.3 Chevy TB system from the early 90s?

I believe so. I know the kit is parts from the chevy. They sell the kit for the yjs and was already on the jeep when i got it.

Old4X · 06-10-2012, 07:51 PM

Have you attached a high pressure fuel pressure gauge to the schrader valve on the back of the TB? If so, what was the pressure reading when you piut the key in "run"?

phnguyen7 · 06-10-2012, 08:05 PM

Quote:

Originally Posted by Old4X

Have you attached a high pressure fuel pressure gauge to the schrader valve on the back of the TB? If so, what was the pressure reading when you piut the key in "run"?

I have not tested the pressure of the tb. I dont think there is anything wrong with the tb unit. When the key is turn to the on position the fuel pump turns on but fuel is not coming out of the injectors. I think its because whatever triggers the injectors is what triggers the ignition to spark. Since what ever triggers the spark is not working the injectors dont know when to work. Im guess something that has to do with the pulse in the negative wire that connects to the coil since when i unplug it and tap on the coil it will trigger it to go off.

Old4X · 06-10-2012, 08:12 PM

On that system, the distributor (actually the pickup coil in the distributor) is what tells the computer to fire the injectors.

But, first make sure you are getting fuel. A quick check is to pour about 1 ounce of gas down the TB (put air cleaner back on) and see if the engine fires. If no fire, it is ignition related.

I have had 2 of those systems just up and quit on me. Both times installing a rebuilt distributor fixed the problem, but you say you already installed a new distributor.

A charged coil will always fire when you pull the ground from the system, don't get too hung up on that right now.

Old4X · 06-10-2012, 08:50 PM

Just checked, you do not have a GM distributor, but are still using the Jeep(ford duraspark) unit and the OEM ICM..

Make sure your black wire (in 3 wire harness on side of distributor) is a good, solid ground, if not, splice in a dedicated ground to this wire.

Also, if you bought a new ICM, and it tests bad, return it to where you bought it for one that checks good.

phnguyen7 · 06-10-2012, 08:59 PM

Quote:

Originally Posted by Old4X

On that system, the distributor (actually the pickup coil in the distributor) is what tells the computer to fire the injectors.

But, first make sure you are getting fuel. A quick check is to pour about 1 ounce of gas down the TB (put air cleaner back on) and see if the engine fires. If no fire, it is ignition related.

I have had 2 of those systems just up and quit on me. Both times installing a rebuilt distributor fixed the problem, but you say you already installed a new distributor.

A charged coil will always fire when you pull the ground from the system, don't get too hung up on that right now.

I sprayed starting fluid down the tb and cranked it and nothing. Yeah the ignition is the ford one and the bad icm i have already traded for another. This system is already nutter bypassed.

The last time when i grounded the black wire to the engine itself and the negative on the battery, I cranked it and still didnt get spark but i did get spark right when i let go and it putted and died.

Old4X · 06-10-2012, 09:06 PM

Is your "service engine soon" light working? When you put key in run, is it lit up?

Does it stay lit up when you are cranking it?

phnguyen7 · 06-10-2012, 09:12 PM

yea the light turns on and stays on when i crank. Should i keep the dedicated ground on the black wire on the distributor? I just dont want to short anything out. I think it might have shorted out the other icm that i got.

phnguyen7 · 06-10-2012, 09:17 PM

Quote:

Originally Posted by Old4X

Just checked, you do not have a GM distributor, but are still using the Jeep(ford duraspark) unit and the OEM ICM..

Make sure your black wire (in 3 wire harness on side of distributor) is a good, solid ground, if not, splice in a dedicated ground to this wire.

Also, if you bought a new ICM, and it tests bad, return it to where you bought it for one that checks good.

when i did my dedicated ground i did it on the icm wires. does it matter or should i do the dedicated ground on the distributor wires?

Old4X · 06-10-2012, 09:22 PM

The black wire grounds the ICM via the distributor body and the distributor hold down clamp-to the block. You will not hurt anything adding an additional ground to this wire.

Your SES light indicates you are getting proper power to the ECM, that is good.

Now check the 2 wire harness going to the ICM. The red wire should have 12V in the (ignition switch) on position, and the white wire should have 12V while cranking. It is possible you blew the fuse that feeds this circuit (or have a bad ignition switch) Have you checked the fuses under the dash? Also, the Howell conversion has additional fuses on the firewall near the 2 relays associated with the fuel pump.