Intermittent Starting Problem

Formula233 · **Joined:** Thu May 26, 2016 4:54 pm **Posts:** 26

Hey Folks,

A week ago jeep would crank but not start. Turned out be a blown fuel pump fuse; replaced, fired up, everything OK.

Couple times after it took more cranking than normal, but still started.

Then one day, same thing, crank and crank but no start, not even a grumble. This time it is not that fuse, or any other fuse. Bled the fuel system, no air. Swapped relays around. After frogging around for an hour, it did start, but seemingly not because of anything I did.

Ran fine for a few more days, then today, once again it won't start. Bled fuel, checked fuses/relays. Cracked the first lines to the first two injectors, there is fuel there.

Any ideas? Haven't scanned for codes yet. One possible pattern, it seems like this happens when the jeep was running a few hours before or less. Haven't had this problem starting from dead cold in the morning. But maybe just coincidence.

I have not done all the usual mods on this CRD but I do run it with the MAF unplugged. Had new rockers and valves and a total clean out a couple years ago. It's at about 200k.

Billybob · **Posted:** Sat Aug 03, 2019 2:20 pm

What year is your CRD?

Starting well when cold but not firing at all when hot is often either the crank or cam sensor...they can fail when hot.

You need to pull codes to try pin this down a bit more. :wink:

WWDiesel · **Posted:** Sat Aug 03, 2019 2:49 pm

Have you replaced the crank sensor? They are usually suspect. :?:

TKB4 · **Posted:** Sat Aug 03, 2019 3:51 pm

I vote for crank sensor. Less likely the cam sensor. If no code or no CEL would start with crank sensor otherwise follow whatever code suggests. I however also wonder what caused the fuse to blow even though not blown now this could still indicate another root cause such as grounding out a damaged wire but hey its about time to replace the crank sensor anyway or you could take it off and test it cold and hot for resistance but if I went to trouble of taking it off I would replace anyway and keep old one in glove box for a spare in case on a trip and cannot get one.

Formula233 · **Joined:** Thu May 26, 2016 4:54 pm **Posts:** 26

Thanks folks,

After I started this thread, once again it eventually fired up for no apparent reason. Problem has not yet recurred, despite starting in all conditions. Still need to get to the bottom of it.

I've been thinking about fuel issues, since this seemingly all started with a blown fuel pump fuse. Bought a new fuel filter, reasoning that maybe a clogged filter could have caused the pump to overload the fuse. But no real way to know if that was the problem until it never happens again.

Wouldn't the crank or cam sensor failing cause it to shut down instantly? Have seen threads about these sensors but didn't seem like they could cause an intermittent problem... Will order one anyway though.

Have not yet located my code reader.

TKB4 · **Posted:** Mon Aug 05, 2019 9:39 pm

Yes at least the crank sensor will cause either intermittent no start or complete shutdown at cruise. Typically will start when cold then when heats up won't start back until it cools off a while. Recently my son and I were going about 30 miles in his and it just quit at highway speed we checked out things and found nothing then it started back went about 5 miles and did same thing time after time. we had my wife standing by to come get us with car hauler if we couldn't make it but we made it home after about 6 stops but lucky it only took a few minutes to restart. Ordered crank sensor and no more problem. BTW got it on amazon sold by chrysler and it was delivered much quicker than quoted. That one has gone up about $20 in last 2 months I believe ID parts or sasquatch is more economical now. Her is link for the amazon one
https://www.amazon.com/gp/product/B013W ... UTF8&psc=1

Once removed you can test crank sensor resistance then heat it up and resistance will change dramatically if bad.

I would think the cam sensor would not be as repeatedly dependent on temp but who knows with any given episode.

Formula233 · **Joined:** Thu May 26, 2016 4:54 pm **Posts:** 26

Interesting, ok will order a crank position sensor. And my understanding is that when it fails it does not throw a code, right?

Found my reader, plugged in and got the following codes: P0102, P1261, P1265

Looks like the first is the MAF Sensor (unplugged) and the other two are glow plug related? Would any of these cause the no-start condition I'm experiencing?

Billybob · **Posted:** Wed Aug 07, 2019 2:16 pm

Formula233 wrote:

Interesting, ok will order a crank position sensor. And my understanding is that when it fails it does not throw a code, right?

Found my reader, plugged in and got the following codes: P0102, P1261, P1265

Looks like the first is the MAF Sensor (unplugged) and the other two are glow plug related? Would any of these cause the no-start condition I'm experiencing?

I doubt those codes would cause a no-start condition.

If in extremely code weather the glow plug codes could be relevant but you guys are in a heatwave at the moment right?

The crank sensor it seems can sometimes throw a code and at other times not...from what I have read on the various Jeep sites. Definitely all sites are agreed the both cam and crank sensors can fail when engine is hot and then work again when engine has cooled down! :wink:

Formula233 · **Joined:** Thu May 26, 2016 4:54 pm **Posts:** 26

Still waiting on the crank sensor. Problem recurred today for the first time in a while, this time after sitting 2 days. So, no pattern.

Should I still suspect that crank sensor?

TKB4 · **Posted:** Sun Aug 11, 2019 2:19 pm

yes I would. There could also be bad ground or connections . It is possible to check the resistance of the crank position sensor when it is malfunctioning without removing this by checking continuity and resistance to the ECM I believe but I am not good with schematics perhaps someone could help with that . I believe the resistance at the sensor wire should be about 850 ohms and rise some as it heats up but certainly if its an open circuit or several thousand ohms it is the culprit. Here is a video which at least partially addresses it.
https://www.youtube.com/watch?v=77KXvZzRxRU

WWDiesel · **Posted:** Sun Aug 11, 2019 2:43 pm

Formula233 wrote:

Still waiting on the crank sensor. Problem recurred today for the first time in a while, this time after sitting 2 days. So, no pattern.

Should I still suspect that crank sensor?

At least once you replace it, you have ruled out that part.

What year is yours?
06's have a history of wiring harness chafing right behind the OEM fuel filter head & bracket.
If your's is an 06, you might want to take a look this location.
Another identified wiring harness chafing area is is right behind the alternator bracket. Some have found a shorted wire in this area.

With the problem coming and going with no pattern, it could also be a bad connection on one of the ECM pins. Some have had this problem.
You have to remove the ECM and disconnect it large wiring harness connector and inspect the pins/connections closely on the ECM.
If you see any that are discolored or look different from the rest, I would suspect and clean it with some real fine emery cloth.

These vehicles also have a history of some grounds going bad and coming and going.
One is right behind the left front headlamp assembly right under the Power Distribution Panel that is in front of the battery.
The ground is a bolt on top of the fender. See picture below:
Another one is under the rubber seal on the firewall on the cowl vent. See picture below.

Formula233 · **Joined:** Thu May 26, 2016 4:54 pm **Posts:** 26

Think I'm giving up on replacing the crankshaft position sensor for now.

Thought I would share here that the bolt that holds that on appears to be, of all things, a T30 Torx cap screw. That would have been extremely useful for me to know, as you cannot see it from underneath and I munged it all up with a 5mm allen key before I came at it from the top (removing the coolant tank) and realized what it was, or at least used to be. No way to get hold of it now and it is thoroughly seized in there.

Is this unusual? I'm surprised no one mentioned this odd fastener, and the replacement part listed on IDparts looks like a regular 10mm bolt.

WWDiesel · **Posted:** Thu Aug 15, 2019 4:56 pm

Formula233 wrote:

Think I'm giving up on replacing the crankshaft position sensor for now.
Thought I would share here that the bolt that holds that on appears to be, of all things, a T30 Torx cap screw. That would have been extremely useful for me to know, as you cannot see it from underneath and I munged it all up with a 5mm allen key before I came at it from the top (removing the coolant tank) and realized what it was, or at least used to be. No way to get hold of it now and it is thoroughly seized in there.
Is this unusual? I'm surprised no one mentioned this odd fastener, and the replacement part listed on IDparts looks like a regular 10mm bolt.

The reason no one mentioned it; normally it is a 6mm metric "Allen Head" bolt as pictured below!
Someone must have replaced it with a Torx head bolt? :shock:

You can see clearly in this picture the head of the bolt holding the CPS.

[/url]

Formula233 · **Joined:** Thu May 26, 2016 4:54 pm **Posts:** 26

Well, its hard to see, it may just be that I beat it up so bad it looks like torx. But are you sure it is supposed to be 6mm, not 5mm? Still cant get a 6 in there.

TKB4 · **Posted:** Thu Aug 15, 2019 8:18 pm

if its original it is an allen screw I thought it was a 7mm but it could well be a 6mm I used allen bits that fit on ratchet to get mine out . You might try some pn blaster etc. and a pair of small vice grips if you can get that on it or even needle nose vise grips. If you move the exhaust downpipe out of the way you should be able to get to it.

iakj11 · **Posted:** Thu Aug 15, 2019 9:09 pm

A trick for removing a beat up Allen head bolt actually employs a torx socket. Tap a torx socket that is slightly larger than the rounded out Allen hole firmly into the bolt head with a hammer. This can get you just enough purchase to loosen the bolt with a ratchet. You'll want to replace the bolt with a new one upon reinstalling the sensor. Good luck!

WWDiesel · **Posted:** Thu Aug 15, 2019 10:34 pm

Formula233 wrote:

Well, its hard to see, it may just be that I beat it up so bad it looks like torx. But are you sure it is supposed to be 6mm, not 5mm? Still cant get a 6 in there.

I was referring to the bolt itself, it is a 6 x 1.0 mm bolt, the wrench to remove it may well indeed be a 5mm allen wrench?

TKB4 · **Posted:** Sun Aug 18, 2019 10:20 pm

I checked the size on the salvage jeep I have been working on either a 3/16th inch or a 5mm allen wrench fit mine but I am sure its meant to be metric so 5mm allen wrench and its same size that fits the intake pin holes caps

Intermittent Starting Problem

Who is online