Crank - No Start

[kshelby99]

About a week ago I got in my 90 Cherokee 4.0L in the morning and started her up. Slow start and all lights were VERY dim. Kind of odd. About two blocks down the road all the dash and headlights brightened to normal. Stopped at a convenience store for a soft drink. When I went back out and tried to start the Jeep to leave it would crank, but not start. Normal crank now. I did not hear the fuel pump hum when I turned the ignition on, so assumed it was the pump. Replaced it this weekend and same problem. No hum from the pump, normal crank, but no start.

I checked for fuel pressure at the rail with the new pump and when cranking I get 39 psi while cranking. Checked voltage at the wiring harness going to the pump and I show about 7 volts with ignition on and drops to between 5.5 and 6 volts while cranking (assuming I check it correctly). Pulled a plug wire (cylinder 3 I think) and held it to the head while my wife cranked the engine and I did not feel any spark.

Any ideas? I'm a shadetree mechanic, not hardcore.

Thanks.

[MN12racer]

I had the same problem not only on my 89' but on two of my buddies as well. First take a stathoscope, or a screw driver and see if the fuel injectors are firing. If not then you have no ignition or fuel, and I would say your crank position sensor is faulty.

[tanno]

Try the simple things first, why don't ya.
Corroded battery terminals will give the same symtoms. Check the volage from + batt post and - batt post (not the terminals, but the post themselves). Then check the voltage at the batt terminals.....is there a difference? Most of the time that's where the issue is. Don't make a monster out of it.

The Crank Position Sensor doesn't go out as often as people would think. Check the connection from it to the harness...that's where the problem is most of the time on these 4.0L's. But I'm not so inclined to think that this is it. The CPS does not affect headlights and fuel pump. It only affects the timing as it is the TDC sensor for the computer. The Camshaft Position Sensor is the other one that directly affects timing, as it is the Machine Cycle sensor for the computer. The MAP sensor affects timing also, but not at idle.

If the Crank PS was intermittant, dead, or bad connection, the computer would not know where Top Dead Center is so it could fire.....hence Misfiring or a no start would occur. If the Camshaft PS was intermittant, dead, or bad connection, the computer would not know if the #1 cylinder was on compression stroke or exhaust stroke, hence it will not run, or start at all.

This guy had a power fluxuation before the no start, so I would start with the battery connections then move to the alternator. One must first find out why the voltage was dropping first before trying to find a dead sensor that was not causing the drop in the first place.

Let me know what you find.

[kshelby99]

Thanks for the suggestions guys. Gives me a place to start. As far as battery is concerned - terminals are in great shape. Had a new battery installed not long ago. Right before this I replaced both cables because I did have one corroded cable.

I'm leaning towards altenator, because I keep coming up with "dead" batteries about every 18 - 20 months. Had it tested on the vehicle at two different auto stores. Both said it was within specs, but not really putting out the voltage it could. Also, one of them noticed a higher than normal drain when the engine is off. Seems like he said anything over .2 amps was high (mine was .5).

I tested the battery at the terminals and it was showing around 12.37 (If I remember correctly). Would a bad altenator really prevent a start?

Anyway, cold and rain here, so I will check on these tomorrow.

[kshelby99]

Weather finally clearing today, so I will start tonight on re-checking voltage, etc.

Saw another thread on here that had a link to a site regarding cleaning the neutral safety switch. Any thoughts? Could this be the problem?

[tanno]

The neutral safety switch will prevent a start, but will not drain the batt.

12.37 volts should start. Does it crank and sound like it's moving fast enough to start? Or does it sound really sluggish?

I did have to replace my starter once because it was killing the battery overnight for three days in a row....on the third day, it was so sluggish that jumper cables didn't help in trying to start. I tried a different battery but only killed that one. Replaced the starter and the damn thing starts up with a vengence with the old battery and now all voltages are fine again.

If it seems to be spinning fast enought to start, then unplug the Crank PS and plug back in...insure that it's pluged in good. If it starts right up, then you have the same issue that still plagues many of Jeep owners.

I can help more and a little faster if you instant message me on MSN Messenger...use my email address: [email protected]

[kshelby99]

Thanks tanno. Crank is fast enough. Had to replace my starter about 6 - 8 weeks ago. Slow crank that killed my battery. Then compression problems became amplified. My engine has 220,000+ on it and is just wearing out, but my crank is surprisingly strong. In fact, strongest since I go the new starter in. I'll update you this weekend as I dive in. I'll check connections to all major sensors one at a time and see if I can get it started. Then start replacing.

[tanno]

My 88 has 230,000 on it and still is my daily driver. I only have one issue with it now is a valve guide leaking....this requires the head to be pulled off. I choose not to do that unless I'm ready to rebuild it or I'm left with no choice.

This issue only leaves me with oil being blown into the air box....well, I re-routed the vent hose to blow into a 1 qt bottle and then that is vented back into the air box....I just pour the bottle back into the motor when it's at least 1/2 full. I blows the most oil when about 35mph or higher and under load (like climbing a hill or passing traffic). If I'm trying to hold 80mph, it's floored all the time....the most oil blown and will dump 3/4 of a quart in 50 miles.

Anyway, it's under control.

[kshelby99]

tanno, I feel your pain with the blowby. Never thought of routing into a bottle first. I'll have to give that some thought.

Okay, Saturday I got out Chilton's (I know, not the best, but it's what I have) and started checking sensors. I'm not that much of a mechanic or electrician, but I think I was checking these things right. Seemed like everything I checked had no voltage.

I decided to start at the beginning. Checked for spark and had none. Checked resistance on the ignition control module - it was within specs. I do not have HEI, but Chilton's said to check voltage on the HEI at the BAT terminal and one of the points in the distributor cap. Should have 12 volts with the ignition on. I checked for 12 volts from the BAT terminal on my starter relay (I assume it was the starter relay - it was a metal box with a 12v line going from my batter. has tabs with wires to the solenoid, field, ground, etc.), anway, I checked voltage between the BAT terminal on the relay and a distributor cap point. with key off I got 12 volts, but with key on or engine cranking I had nothing. Chilton's indicated on HEI that this would mean checking continuity back to the ignition switch. Would it be the same for mine? Since I did not get voltage at the harness for my MAP and TPS would it mean my ECU is fried? Do these tidbits give anyone any clues or did I waste my Saturday?

[Dale Aeppli]

Originally Posted by kshelby99

tanno, I feel your pain with the blowby. Never thought of routing into a bottle first. I'll have to give that some thought.

Okay, Saturday I got out Chilton's (I know, not the best, but it's what I have) and started checking sensors. I'm not that much of a mechanic or electrician, but I think I was checking these things right. Seemed like everything I checked had no voltage.

I decided to start at the beginning. Checked for spark and had none. Checked resistance on the ignition control module - it was within specs. I do not have HEI, but Chilton's said to check voltage on the HEI at the BAT terminal and one of the points in the distributor cap. Should have 12 volts with the ignition on. I checked for 12 volts from the BAT terminal on my starter relay (I assume it was the starter relay - it was a metal box with a 12v line going from my batter. has tabs with wires to the solenoid, field, ground, etc.), anway, I checked voltage between the BAT terminal on the relay and a distributor cap point. with key off I got 12 volts, but with key on or engine cranking I had nothing. Chilton's indicated on HEI that this would mean checking continuity back to the ignition switch. Would it be the same for mine? Since I did not get voltage at the harness for my MAP and TPS would it mean my ECU is fried? Do these tidbits give anyone any clues or did I waste my Saturday?

DID YOU TRY UNPLUGING AND REPLUGGING THE CRANKSHAFT SENSOR TRY THIS AND EMAIL ME MAYBE WE CAN FIGURE THIS OUT DALE [email protected]

[kshelby99]

The crank position sensor connecting harness is a mystery to me. I have looked all over my engine and can't find the harness (on top anyway). I think I am going to have to crawl under and trace it backwards. I'll give it a try tonight or tomorrow and let you know.

[kshelby99]

Originally Posted by kshelby99

The crank position sensor connecting harness is a mystery to me. I have looked all over my engine and can't find the harness (on top anyway). I think I am going to have to crawl under and trace it backwards. I'll give it a try tonight or tomorrow and let you know.

Just a quick thought - were you referring to camshaft sensor? Mine is coated in sludge from a leaking seal. Oddly enough when I wiped it down I thought I could detect where the plastic wrap on one of the wires on the harness had been "rubbed" through to copper. Very small area and I am not sure which wire off hand. Obviously a short to repair, but I would not expect it to prevent spark. Perhaps if it touched the engine block it could have blown the camshaft sensor? Any way to test the sensor without removal?

I'll try the disconnect and reconnect on both sensor harnesses and look up the details on camshaft sensor testing.

[Dale Aeppli]

Originally Posted by kshelby99

Just a quick thought - were you referring to camshaft sensor? Mine is coated in sludge from a leaking seal. Oddly enough when I wiped it down I thought I could detect where the plastic wrap on one of the wires on the harness had been "rubbed" through to copper. Very small area and I am not sure which wire off hand. Obviously a short to repair, but I would not expect it to prevent spark. Perhaps if it touched the engine block it could have blown the camshaft sensor? Any way to test the sensor without removal?

I'll try the disconnect and reconnect on both sensor harnesses and look up the details on camshaft sensor testing.

HI, ITS POSSIBLE THAT THE WIRE ON THE CAMSHAFT SENSOR COULD SHORT OUT YOUR CAM. SENSOR. IF YOU EMAIL AT [email protected] I'LL SEND A PICTURE OF WHERE CRANKSHAFT SENSOR IS LOCATED. ALSO I CAN SEND CAM. SENSOR TEST DALE

[tanno]

Crankshaft position sensor connection point is VERY near the #6 injector. It's also near the Manifold Temp sensor plug.

I'm not sure if the camshaft sensor can really be 'blown'. But most anything electrical can be shorted. Repair the bare wire and hope it's good. Because replacing it requires pulling the distributor out and apart. (I've done this before)

[kshelby99]

Hey all, thanks for the great replys. I was speaking to a mechanic friend at church last night and he said that if the tach does not register any rpm's while the engine is being cranked it is the crank position sensor. First I have heard of this little tidbit so thought I would pass it along in case it helps anyone else out. Anyway, I spent Saturday testing other components that are easier to get to. I guess I have to bite the bullet and replace the CPS. I'll let you know the results.