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No Start, only sparks on cylinders 1 & 4 HELP PLEASE!

Dolby Gray

NAXJA Forum User
Location
Texas
I'm ready to pull my hair out and need some help. I've been a professional mechanic for 30 years, but I'm having issues diagnosing my own jeep. I have a 91 Jeep Cherokee 4.0L 5 speed 4x4. I just rebuilt engine and installed it with new injectors, ignition coil, cap, rotor, plugs, wires, crank sensor, battery, and battery cables. I have verified the distributor is indexed with cylinder #1 on compression. I've got 40 pounds of fuel pressure. The engine wants to start but then just spins over. I've tried 2 different engine computers, 2 different cam sensors, 3 different crank sensors and 3 different ignition coils, but it still won't start and run. I've checked for spark and it consistently on sparks on cylinders 1 & 4 but not on any other. The only other thing I've noticed is that the ASD relay is cycling on and off while cranking. Any thoughts or ideas would be greatly appreciated. Sorry for the long post just trying to include all relevant information.
 
Tested each plug and wire on the #1 distributor cap terminal all are fine, but still only have spark at cylinders 1&4.
 
The problem is that I only get a spark only cylinders 1 & 4. I tested all the wires and plugs on the number 1 post of the distributor cap to verify they were all functioning.

I have also checked the wiring from the computer to fuel injectors, crank sensor, coil and cam sensor for continuity and all read no resistance and have no corrosion at the terminals.

I am still unsure why the ASD RELAY is cycling on and off while cranking. I have also exchanged it with a known working unit, which had no effect.
 
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Did you use your old flex plate (tone ring) or did the engine come with one?
 
Every time I've run into this it has been distributor indexing. Retard it one tooth and try it. If it doesn't work, advance it 2 teeth from there.
 
Ditto on the flex plate. You may have gotten the wrong one.
 
I reused the flywheel after having it resurfaced. I checked the flywheel to make sure all the slots in the tone ring were clean. I had heard of another guy that had gotten a magnet accidently lodged in one of the slots. I have double, triple and quadruple checked the distributor indexing to make sure that the rotor is lined up with #1 distributor post on the cap while the crank timing mark is at 0 degrees and #1 cylinder is on the compression stroke. I verified that cylinder 1 was on compression by observing the valves through the sparkplug hole. I haven't tried advancing or retarding the distributor. I'm beginning to wonder if there might be a problem with the Engine Control Module, but I even tried another ECM that I had on hand, but yielded the same results. Cylinder 1&4 are the only ones that have spark, and I kind of doubt the distributor would cause the ASD relay to cycle on and off while cranking.
 
Try swapping out the fuel pump relay with a known
good one. Since the ignition and fuel pump are both on the
ASD circuit, the FP relay might be affecting the ignition.

If no joy with that, I'd focus on the CPS circuit. The ASD
relay is cycling because it sees a run/no-run signal from
the ECM and that signal is generated by the CPS.
 
Just A WAG (wild arsed guess) as I've never set mine up wrong, either accidentally or on purpose, so I don't really know what will happen. A lot of the diagrams show the number one pole on the distributor at the six O'clock position (while standing on the passengers side of the motor lloking towards the drivers side), which is a bit misleading.

When the no.1 piston is at TDC at the end of the compression stroke, the rotor should be pointing in the direction shown (five o'clock position when standing on the passenger side looking towards the driver's side).

Picture here, http://www.angelfire.com/my/fan/dist_index.html

Camshaft Position Sensor
The camshaft position sensor is located in distributor. This
Hall Effect type sensor works in conjunction with engine speed signal
of crankshaft position sensor providing PCM with inputs necessary to
establish and maintain proper fuel injector firing order.
When leading edge of pulse ring enters the sync signal
generator on the camshaft position sensor, the resulting change in the
magnetic field causes a 5-volt reference signal to be induced. On 4-
cylinder engines, this indicates to the PCM that piston No. 4 will be
the next piston at Top Dead Center (TDC). On 6-cylinder engine, it
indicates that piston No. 3 will be at TDC.
When trailing edge of pulse ring leaves the sync signal
generator on the camshaft position sensor, the resulting collapse of
the magnetic field causes reference signal to drop to zero volts. On
4-cylinder engines, this indicates that piston No. 1 will be the next
piston at TDC. On 6-cylinder engine, it indicates that piston No. 4
will be at TDC.

I really don't know what will happen if you plug number one into the number five pole on the distributor on the initial setup. But it will clock the cam position sensor wrong and is likely to send conflicting info to the PCM. Just a possibility that should be looked at closely.

It is also easy to mistake the top of the exhaust stroke for the top of the compression stroke. The main reason I don't use my finger and use a compression gauge when trying to find TDC. It can build a little pressure on the exhaust stroke and you may mistake it for compression.

You may have to pull off the valve cover and verify TDC. Compression stroke on number one, timing marks aligned with the last turn to the right facing the motor (don't back up or if you have to back way up and then try again). *Both of the number one valves closed, rockers a high as they go, you can usually wiggle both a rockers a little, they will be loose enough to have a bit of sideways play.* It's possible (I have to guess) to have the timing chain clocked wrong and this may be causing sensor to PCM conflicts. No telling how the PCM is going to react to really wrong sensor inputs, I doubt the engineers programmed for every possible failure mode..

The only time I've ever seen an ASD relay chatter it was a bad connection, at a splice in the harness. Mine was at/near the dealer installed anti theft module. My issue was on the power into the actuator coil inside the ASD relay and not on the ground side of the actuator coil going to the PCM or the PCM (because of faulty sensor inputs) pulsing the ground). But it is unlikely I've seen every possible permutation that would cause the ASD relay to chatter.

Just some ideas. When I get really stuck I back up and start over from the beginning and recheck my initial setup and the first thing to do is verify TDC. Don't skip any steps and assume anything, motor basics 101.

My hunch is you have a conflict between the Cam position sensor and the crank position sensor. Or maybe something simple like the CPS isn't reading the tone ring for whatever reason.

I'm old as dirt and my memory fails somewhat. But I seem to remember one guy going nuts because he used the wrong bolts for the CPS. I don't remember exactly what the issue was, he maybe used accidentally magnetized bolts or whatever. But a new set of OEM CPS bolts cured his issues. A long shot but if all else fails, something to try.
 
I reused the flywheel after having it resurfaced. I checked the flywheel to make sure all the slots in the tone ring were clean. I had heard of another guy that had gotten a magnet accidently lodged in one of the slots. I have double, triple and quadruple checked the distributor indexing to make sure that the rotor is lined up with #1 distributor post on the cap while the crank timing mark is at 0 degrees and #1 cylinder is on the compression stroke. I verified that cylinder 1 was on compression by observing the valves through the sparkplug hole. I haven't tried advancing or retarding the distributor. I'm beginning to wonder if there might be a problem with the Engine Control Module, but I even tried another ECM that I had on hand, but yielded the same results. Cylinder 1&4 are the only ones that have spark, and I kind of doubt the distributor would cause the ASD relay to cycle on and off while cranking.

Actually, the trailing edge of the rotor should be aligned with #1 post, not dead on. See pic ('99 distributor). Shown is the position of the rotor when the timing marks on the crankshaft damper and the timing chain cover are aligned at zero.

With the rotor centered on #1 post, the timing is off scale advanced.

RotorPosition_0DegonTimingMarks.jpg


You may want to consider the camshaft position sensor. The CPS tells the PCM which group of two cylinders are at TDC but the Cam Sensor tells the PCM exactly which cylinder is in position for triggering the coil to fire the plug and which fuel injector to actuate.
 
Just wanted to follow up on this post. First of all thanks for all the great ideas, I really appreciate the help. So a quick run down on what happened and the solution:

Ignition spark on cylinders 1 & 4 only.

Items checked & or replaced

Distributor alignment - dead on
#1 TDC on compression - again perfect
Fuel pressure - 38 psi - within specs
Plug wires - new - tested - all tested good
Spark plugs - new - checked gap and tested - all good here
Ignition rotor - new - looks good to me, no damage
Distributor cap - new - looks fine to me but tried another new one - no luck
CPS - used - no change
CPS - used - nothing
CPS - new - no luck
Ignition coil - used - same result
Ignition coil - new- nada
Distributor - used - not a chance
PCM - used - no soap

By now I'm ready to pull my hair out, consulted forum for ideas, couldn't find much other than to replace the CPS. So I posted this thread. Went back and double checked everything and then checked it again. Still no luck. Checked flywheel notches, all clean, and verified that it only fits on one way.

Cleaned all engine and body grounds - no dice
Checked engine wiring harness for continuity from the PCM to each component, WHAT A PAIN! All tested good with good clean connections.
Checked all fuses and circuit breakers - All test good
Checked ignition switch - found a burnt connector and wiring - replaced
Ignition switch and replaced damaged wiring - still no luck

I used to work for a Dodge dealership 15 years ago, and remembered that the PCM looks for a signal from the CPS and fires the coil and fuel injectors for a revolution or two while it looks for a signal from the Camshaft position sensor and if it doesn't find one then it cycles the ASD (Auto Shut Down) relay untilit gets a signal from the CAM sensor. So out of desperation I got a new Distributor, $10 more than the CAM sensor alone and a whole lot easier to install. Hit the key and it fired right up, PRAISE THE LORD!

So the take away from all this is - Just because the part worked when you took it apart, doesn't mean it will still work when you put it back together, and no spark is usually the CPS, but it can also be the CAM sensor, especially if it's only sparking on a few cylinders and cycling the ASD relay.

Thanks again for all the help, Dolby.

P.S. After all the headaches over this issue, I decided to name the Jeep "SKULL CRAMP"
 
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Just wanted to follow up on this post. First of all thanks for all the great ideas, I really appreciate the help. So a quick run down on what happened and the solution:

Ignition spark on cylinders 1 & 4 only.

Items checked & or replaced

Distributor alignment - dead on
#1 TDC on compression - again perfect
Fuel pressure - 38 psi - within specs
Plug wires - new - tested - all tested good
Spark plugs - new - checked gap and tested - all good here
Ignition rotor - new - looks good to me, no damage
Distributor cap - new - looks fine to me but tried another new one - no luck
CPS - used - no change
CPS - used - nothing
CPS - new - no luck
Ignition coil - used - same result
Ignition coil - new- nada
Distributor - used - not a chance
PCM - used - no soap

By now I'm ready to pull my hair out, consulted forum for ideas, couldn't find much other than to replace the CPS. So I posted this thread. Went back and double checked everything and then checked it again. Still no luck. Checked flywheel notches, all clean, and verified that it only fits on one way.

Cleaned all engine and body grounds - no dice
Checked engine wiring harness for continuity from the PCM to each component, WHAT A PAIN! All tested good with good clean connections.
Checked all fuses and circuit breakers - All test good
Checked ignition switch - found a burnt connector and wiring - replaced
Ignition switch and replaced damaged wiring - still no luck

I used to work for a Dodge dealership 15 years ago, and remembered that the PCM looks for a signal from the CPS and fires the coil and fuel injectors for a revolution or two while it looks for a signal from the Camshaft position sensor and if it doesn't find one then it cycles the ASD (Auto Shut Down) relay untilit gets a signal from the CAM sensor. So out of desperation I got a new Distributor, $10 more than the CAM sensor alone and a whole lot easier to install. Hit the key and it fired right up, PRAISE THE LORD!

So the take away from all this is - Just because the part worked when you took it apart, doesn't mean it will still work when you put it back together, and no spark is usually the CPS, but it can also be the CAM sensor, especially if it's only sparking on a few cylinders and cycling the ASD relay.

Thanks again for all the help, Dolby.

P.S. After all the headaches over this issue, I decided to name the Jeep "SKULL CRAMP"

Do I get a cookie? Ref. post #14.

LOL
 
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