Crank - No Start

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.

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.

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.

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.

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?

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]

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.

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.

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?

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]

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.

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.

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

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)

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.

Try the plug to it first. Unplug it and plug it back in. If it starts then, the sensor is good. Mine was replaced only to have the same problem about a week later.

Okay - quick update. My crank sensor and wires from the harness to the sensor were in pretty bad shape. Replaced it - looks like it needed it anyway - but still no spark. Grrr!

Pulling the ECU and going to see if the local Jeep dealer will test it for me.

They should be able to if Napa, Autozone, Checker, Advanced Auto, PepBoys, etc. can.

Try these before spending the funds on a diagnostics test.


To do a complete test of the CKP circuit, you'll need a scan tool. But you can do a quick test of the CKP with an ohmmeter.

Near the rear of the right cylinder head, disconnect CPS wiring harness connector from main wiring harness.

/---^--\
| A B C |
\-------/

Place an ohmmeter across terminals B and C of the CPS connector. The meter reading should be open (infinite resistance). Replace sensor if resistance is indicated.



*** NOTE: For this test, an analog (non-digital) voltmeter is needed. Do not remove the distributor connector from the distributor. To perform a complete test of the Camshaft Position Sensor and its circuitry, refer to the DRB II diagnostic tester. Also see the appropriate Diagnostic Charts.

To test the sensor only, refer to the following:

Using small paper clips, insert them into the backside of the distributor wire harness connector to make contact with the terminals. Be sure that the connector is not damaged when inserting the paper clips. Attach voltmeter leads to these paper clips.

1. Connect the positive (+) voltmeter lead into the sensor output wire. This is done at the distributor wire harness connector.
2. Connect the negative (-) voltmeter lead into the ground wire.
3. Set the voltmeter to the 15 Volt DC scale.
4. Remove distributor cap from distributor (two screws). Rotate (crank) the engine until the distributor rotor is pointed towards the rear of vehicle. The movable pulse ring should now be within the sensor pickup.
5. Turn ignition key to ON position. Voltmeter should read approximately 5.0 volts.
6. If voltage is not present, check the voltmeter leads for a good connection.
7. If voltage is still not present, check for voltage at the supply wire.
8. If voltage is not present at supply wire, check for voltage at pin 7 of Powertrain Control Module (PCM) 60 pin connector. Leave the PCM connector connected for this test.
9. If voltage is still not present, perform vehicle test using the DRB II diagnostic scan tool.
10. If voltage is present at pin 7, but not at the supply wire:

a. Check continuity between the supply wire. This is checked between the distributor connector and pin 7 at the PCM. If continuity is not present, repair the harness as necessary.
b. Check for continuity between the Camshaft Position Sensor output wire and pin 44 at the PCM. If continuity is not present, repair the harness as necessary.
c. Check for continuity between the ground circuit wire at the distributor connector and ground. If continuity is not present, repair the harness as necessary.

11. While observing the voltmeter, crank the engine with ignition switch. The voltmeter needle should fluctuate between 0 and 5 volts while the engine is cranking. This verifies that the camshaft position sensor in the distributor is operating properly and a sync pulse signal is being generated.

If sync pulse signal is not present, replacement of the Camshaft Position Sensor is necessary.

I hope this clears it up for ya. Let me know.

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.


Try checking voltage back at fuel pump where wiring goes into tank and pump. Where did you check for voltage and got t volts and 6 when cranking? dale [email protected] :licka:

Dale,

My pump has a wiring harness at the rear of the vehicle by the tire. I check voltage at the harness, not the pump. The 7 volts was what was at the harness connector (so I assume 7 volts feeding the pump).

Dale,

My pump has a wiring harness at the rear of the vehicle by the tire. I check voltage at the harness, not the pump. The 7 volts was what was at the harness connector (so I assume 7 volts feeding the pump).

SOUNDS FUNNY THAT THERE ISN'T 12 VOLTS THERE THATS WHY THERE A RELAY SO IT GETS FULL VOLTAGE, DID YOU CHECK THE WIRING TO SEE IF THERE WAS A CHANCE IT MAYBE CUT OR FRAYED. HAD ONE FOUND SCREW HAD CUT INTO HARNESS HOLDIN IT IN PLACE.
DALE [email protected]
Did you try unplugging and plugging the crankshaft sensor,still sounds like crank sensor

Crank sensor replaced - still no spark. I'll recheck the harness on the pump for voltage. I swapped relays on my fender (4 of them with 3 the same - I assummed one was fuel pump relay) but no help.

tanno - thanks for the info. I'll try checking the sensors again with VOM.

Part of the problem is that I am not reading voltage on ANY of my sensors. I am thinking ECU is shorted out. If so, would it prevent voltage to all sensors for a check with VOM? I can still check resistance but not voltage.

Crank sensor replaced - still no spark. I'll recheck the harness on the pump for voltage. I swapped relays on my fender (4 of them with 3 the same - I assummed one was fuel pump relay) but no help.

tanno - thanks for the info. I'll try checking the sensors again with VOM.

Part of the problem is that I am not reading voltage on ANY of my sensors. I am thinking ECU is shorted out. If so, would it prevent voltage to all sensors for a check with VOM? I can still check resistance but not voltage.


Check the 4 th. relay its the b+ latch relay it should have 12 volts. also check the fusuable links under relays. pull on each fuseable link if it stretchs its blown. When you turn the key on can you hear the fuel pump relay click dale

If the ECM / PCM is bad anything can or won't happen. It's a computer and you really can't tell what went bad in it if anything. All you can do is eliminate everything else being the issue. It is not unheardof to have the ECM / PCM to go bad even because of age. Electronics are not infalable just like everything else on the vehicle.

Try spraying some starting fluid in the throttle body and see if it starts...if it does, it's fuel related. Then you can ignore ignition and sensor troubleshooting. If it does not even try to start with starter fluid, then it's determined that it's an electrical issue.

I think they only original Electronic stuff still in my Jeep is the ECM and the Knock sensor. Everything else I have replace at one time or another.