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Another "Not Starting thread"

RLR_69_XJ

NAXJA Forum User
Location
Oregon
OK, I have read through a ton of posts and am at a loss. I have an 88 XJ with the 4.0 and I was driving home from work and it did this little stutter, like it ran out of fuel, then it just dyed. I got towed home by a friend then started looking around here to see what it might be. This is what I have done so far, in no particular order.
1: Checked for spark, it has spark. I replaced the cap and rotor just for the heck of it.
2: Checked the Crank Positioning Sensor, it reads 199 Ohms at the plug on the firewall. As I understand it that is within specs.
3: When I crank the engine, I can smell fuel and I get good pressure from the little valve on the fuel rail. And I can hear the fuel pump kick on. I am going to replace the fuel filter just to make sure.
4: I sprayed starting fluid into the intake just to see if it would attempt to fire but it did not help at all. I would think that would have got it going for at least a second?
5: I checked the compression, and one of the the cylinders only reads 60 lbs. Is that my issue? All the others read 115-125. I would think it would at least run, just not very well.
Let me know what you guys think.
Thanks in advance.
 
60 lbs should not keep you from starting, but is definately not good.

If you are getting spark, did you smell the tail pipe for gas fumes?

If there are fumes, you could simply have a flooded engine. A camshaft position sensor can cause the same problem but it normally does not surface while the engine is running, but after you shut it off and then try to start again.
 
You have spark, so the CPS is fine. Is it a good hot blue spark or weak and yellow?

Spark, compression, and fuel should do it... I agree with Tom that it could be flooded. Try pulling the spark plugs, disabling the fuel pump, and turning it over a few times to clear the cylinders then put it back together and try again.
 
The spark looks “large” but it’s not that blue looking. It’s more of a yellow color. I get a blue looking spark from the coil but it’s not that bright at the plug. That’s why I replaced the cap and rotor just in case.
Where is the camshaft position sensor located?
Would it get flooded while driving?
One other thing, there is a white ceramic resistor (I believe) with orange wires going into it on the driver’s side fender wall. How do I test that? I have read that might be a problem.
Thanks for the help so far.
 
The resistor you can test easily - you remove it and connect the two wires directly together. If the vehicle works fine again, you forget about it... though it'll start and run for a few seconds even with a bad resistor.

camshaft position sensor is in the distributor.

Wouldn't get flooded while driving, but it would get flooded trying to start it unsuccessfully multiple times.

Based on the sound of it, I'd guess maybe you need new plugs or new wires? Blue spark at the coil but not at the plugs sounds like an indication of that to me.
 
As said, pull the plugs and see if they are wet--an indication that the synch sensor (stator) a.k.a. CPS/CMP a.k.a. camshaft position sensor in the distributor is sending a signal to the ECU/PCM to fire the injector pulse. An alternative is a $3 NOID light to check for the firing pulse.

Agree that poor spark to the plugs, after new cap and rotor, would indicate poor plug wires.

Bypassing the fuel pump ballast resistor is a good idea.

If the engine is flooded then you can try and start it: engine off, press the accelerator to the floor and hold it there, try and start the engine while continuing to hold the accelerator firmly to the floor.
 
I just thought of one other thing.
I was having this weird electrical problem for a month or so before it stopped running. I thought it just needed a new alternator so I put one in and it helped but did not fix the problem. What it would do is the voltage would drop real low when ever I would run the heat or turned the lights on. I can’t figure out what is causing this.
I have no idea if they are related but I just thought I would throw that out there.
 
Could have a marginal coil. Try testing it for primary/secondary resistances. Need to rule it out. And testing of the cam sensor also makes sense.
 
I just thought of one other thing.
I was having this weird electrical problem for a month or so before it stopped running. I thought it just needed a new alternator so I put one in and it helped but did not fix the problem. What it would do is the voltage would drop real low when ever I would run the heat or turned the lights on. I can’t figure out what is causing this.
I have no idea if they are related but I just thought I would throw that out there.

Well, the XJs instrument panel voltage meter is at the end of the draw, so loads show up as lower voltage when the actual voltage at the battery is usually higher.

You have a RENIX--grounds to a RENIX are like wine and cheese to a Frenchman--essential components of life itself.

On the RENIX there is one and only one OEM unibody ground. Rear of head to firewall, driver's side. It is OEM a self-destructing braided strap. Replace it with a 4 ga cable. Make sure both mounting surfaces are clean, down to bare metal. Treat the metal with an anti-corrosion product--any hardware/paint store. Make sure the connections are TIGHT. Also, CRITICAL grounds to the dipstick tube (WTF?!?). Yep, they put some of the most critical grounds possible on the dipstick tube--ICM/ECU are two of them. Make sure those grounds are also taken down to bare metal, anti-corrosion, and damn tight.

Check your static (engine off) battery voltage. Test with a voltmeter at the battery terminals. Should be about 12.5 volts. Start engine and check again. Should be about 13.6~14.5 volts after starting, and will drop a towards the lower 13.6 after running a bit.

Poor grounds, bad/weak battery, poor battery cables can all lead to some weird electrical issues.

Post back and let us know what you find.

Please bookmark and read this article: http://www.olypen.com/craigh/charge.htm

You will not regret doing any of the recommend upgrades.
 
Will a weak spark always lead to a no-start condition?

No, not always. So much depends on other issues--fuel quality, fuel formulation, fuel atomization, compression, cranking power, and other things. However, a weaker spark can aggravate other marginal conditions leading to a no start condition.
 
Thanks for all the help so far, I am going to try and work on it this weekend and see what I can come up with. I have not had a chance to look yet, but where is the ground on the dip stick?
 
Mine wasn't starting either - After doing much troubleshooting (similar to yours), I sprayed some starting fluid in the intake and it cranked up and started running. It's started up on subsequent attempts as well.
 
Try jump starting the rig. The Renix computer has a down side. If the battery is low, even though the engine cranks over, the ECU will not function correctly. That is a downside of having the large diameter battery cables. It allows the starter to spin well even when the ECU won't function.
 
I wouldn't do one more thing until I did what Joe suggests about the grounds. They are super critical and the cause of many problems on our Jeeps, especially Renix. I suspect Joe went to the same school of hard knocks that I did at the dealership level and that's why we both suggest the ground refreshing. I saw all the problems they caused and also saw all the problems that were solved by maintaining them. I am now in the habit of also adding a ground cable from the dipstick tube over to an 8mm stud below the passenger side shock. We're working with a rather poor design at best and we need to make sure it's working at least as good as it was new. And heck, they had problems with the grounds when new!!!!
 
Could have a marginal coil. Try testing it for primary/secondary resistances. Need to rule it out. And testing of the cam sensor also makes sense.

How do I test that?
OK, I just went through and replaced the fuel filter, replaced all the “small” power wires with 4ga wires per the link that was provided, cleaned and took a steel wire wheel to all the grounds and added an extra ground wire. I also pulled the spark plugs, disabled the fuel pump and then cranked it for about 6 seconds, then I let it air dry for about an hour before I put the plugs back in. I also bypassed the resistor on the drivers side fender wall by connecting a wire from one to the other.
She still won’t start.
I cant jump start her because it is an automatic.
I am going to get a NOID light and see if I am get fuel through the injector not just to it.

1: I need to check the camshaft position sensor, how do I do that?
2: Also, if the injectors are not working where do I start looking?
 
Coil:

coil%20test%20primary%20windings.jpg


coil%20test%20sec%20windings.jpg


Camshaft Position Sensor:
http://www.lunghd.com/Tech_Articles/Engine/Cam_Position_Sensor_and_Sync_Pulse_Stator.htm
 
Sorry to be a downer on all this, but you are wasting your time if you have 60PSI on one cylinder. Rebuild or get a JY motor that has 150 on all 6 cylinders. No real point in getting this one running.
 
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