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Glow Plug Question
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=16019		 Page 1 of 1
Author:  Drewd [ Sat Dec 30, 2006 1:17 am ]
Post subject:  Glow Plug Question
I've had 2 occurences in the past week of hard starting. Today, it took 3 attempts for my Jeep to fire up. Each time I cranked, the engine ran roughly -like it was running on 2 or 3 cylinders for a couple of seconds before it died.

Question: Will a bad glow plug trigger a CEL?

No, my fuel did not gel in the 15 deg weather and this isn't a fuel quality related issue. We have two diesels in our household and fuel from the same place. The other diesel had no problem starting.
Author:  no-blue-screen [ Sat Dec 30, 2006 7:04 am ]
Post subject: 
Sounds like a glow plug problem. These are text book symptoms of failed glow plug(s).
Author:  Drewd [ Sat Dec 30, 2006 10:24 am ]
Post subject: 
The question still remains, will a bad glow plug trigger a check engine light???
Author:  Goglio704 [ Sat Dec 30, 2006 10:40 am ]
Post subject: 
I believe it will. I don't have my service manual right now, but I'm pretty sure the glow plugs are monitored for correct current draw by the ECU. Others have posted glow plug failures that were accompanied by the CEL. As to your problem, have you tried purging the air from the fuel filter with the manual pump and bleeder screw?
Author:  RFCRD [ Sat Dec 30, 2006 11:22 am ]
Post subject:  Re: Glow Plug Question
Drewd wrote:
I've had 2 occurences in the past week of hard starting. Today, it took 3 attempts for my Jeep to fire up. Each time I cranked, the engine ran roughly -like it was running on 2 or 3 cylinders for a couple of seconds before it died.

Question: Will a bad glow plug trigger a CEL?

No, my fuel did not gel in the 15 deg weather and this isn't a fuel quality related issue. We have two diesels in our household and fuel from the same place. The other diesel had no problem starting.

It would be typical for a bad GP to throw a CEL. What you describe sounds more like a fuel system leak (sucking air) causing a mild loss in fuel prime while parked. If you intend to search for a leak, remember that this type of leak rarely appears as a wet/leaky area. This problem can be very evasive and often fixed without actually finding the leak by systematically checking/tightening hose connections.
Author:  no-blue-screen [ Sat Dec 30, 2006 1:47 pm ]
Post subject: 
Drewd wrote:
The question still remains, will a bad glow plug trigger a check engine light???


Yes, it should. Just to be sure, follow the procedure below:

Credit goes to Ranger1 for posting this.:

Check your glow plug resistance with the motor off. The connector block is on the engine block, on the drivers side, midway of the engine. When the connector is separated, the pins leading to all 4 glow plugs is easily reachable with an ohmeter. If they measure outside of .5 to 1.5 ohms, they may be bad. If they are, you should have a CEL or a code set soon.

P.S. use the search function, it will help you find relevant information
Author:  Drewd [ Sat Dec 30, 2006 10:03 pm ]
Post subject: 
I'm pretty sure it is the POS Optima Battery. The glow plugs check out ok. I replaced my fuel filter this afternoon as a precaution before a 1800 mile road trip next week. Any suggestions as to what kind of "real" battery to put in this thing? The Optima, I believe, is rated for 700CCAs.

PS Removing the two 13mm bolts that retain the fuel pump bracket is the easiest and quickest way to replace the fuel filter. It took me less than 15 minutes to remove and replace the fuel filter. I used a vacuum pump to bleed the system in conjunction with the little pump dealie on the filter assembly. With an assist from my battery charger/jumper, it fired up on the first attempt.
Author:  RFCRD [ Sat Dec 30, 2006 10:48 pm ]
Post subject: 
Drewd wrote:
I'm pretty sure it is the POS Optima Battery. The glow plugs check out ok. I replaced my fuel filter this afternoon as a precaution before a 1800 mile road trip next week. Any suggestions as to what kind of "real" battery to put in this thing? The Optima, I believe, is rated for 700CCAs.

Just wondering what make you sure it's the Optima battery? One charactoristic of most electronic diesels is the ECM will disable the starter if battery voltage is under @ 11v. So, if you have a dead cell or it's just a little drained from leaving the lights on, you will turn the key and get nothing from the starter (won't even get the classic click-click-click sounds). The glow plugs run on 7 volts. Would personally try load testing the battery first but can tell from experience that if the engine is cranking, it's probably not a defective battery.
Author:  Joe Romas [ Sat Dec 30, 2006 10:54 pm ]
Post subject: 
Drewd wrote:
I'm pretty sure it is the POS Optima Battery. The glow plugs check out ok. I replaced my fuel filter this afternoon as a precaution before a 1800 mile road trip next week. Any suggestions as to what kind of "real" battery to put in this thing? The Optima, I believe, is rated for 700CCAs.


On another group I belong to there was a thread on batteries both coach and starting and your right about the optima battery. It has a better then normal deep discharge ability but not as high of a total current draw. It's a compromise battery in that respect:!: It's supposed to be very shock resistant but what good is that if it won't start :shock:
Author:  no-blue-screen [ Sun Dec 31, 2006 3:47 am ]
Post subject: 
RFCRD wrote:
Drewd wrote:
I'm pretty sure it is the POS Optima Battery. The glow plugs check out ok. I replaced my fuel filter this afternoon as a precaution before a 1800 mile road trip next week. Any suggestions as to what kind of "real" battery to put in this thing? The Optima, I believe, is rated for 700CCAs.

Just wondering what make you sure it's the Optima battery? One charactoristic of most electronic diesels is the ECM will disable the starter if battery voltage is under @ 11v. So, if you have a dead cell or it's just a little drained from leaving the lights on, you will turn the key and get nothing from the starter (won't even get the classic click-click-click sounds). The glow plugs run on 7 volts. Would personally try load testing the battery first but can tell from experience that if the engine is cranking, it's probably not a defective battery.


Joe, I agree that it doesn't sound like the battery. He also said in his original post that the vehicle was running rough for a short time which is normally an indication of incomplete combustion caused by failing glow plug(s).

At this point I think we need more information.

1) Does the vehicle eventaully start and stay running?

2) Have you tried plugging in the block heater to see if it starts okay when warm?

If your glow plugs are the problem, then the vehicle should run okay once it is warmed up. With a Diesel, it usually takes at least 10k miles before the rings begin seating and the compression comes up. Even then, depending on how cold it is, the vehicle may not start at all. An engine with decent compression will usually start with a failed glow plug down to a certain temp (not sure what that is, but would guess it is above freezing).

If you can't get the vehicle started, you aren't going to see a CEL. So if that is the case and you can't get the vehicle started at all, then you need to get a scanner and scan the computer for codes.

It could also very likely be a fueling issue, but we need a little more info to be able to help you from here.
Author:  RTStabler51 [ Sun Dec 31, 2006 4:14 am ]
Post subject: 
A bad GP WILL throw a CEL. I had 3 out of 4 of my GPs replaced...all during warm spring/summer months too.
Author:  Drewd [ Mon Jan 01, 2007 12:20 am ]
Post subject: 
How do I know its the battery? Easy, it acted up again and before I made another attempt, I attached a battery charger to the battery and set the switch to start assist which provides additional 200 amps to the battery. Guess what, it fired right up. I suspect the Optima battery isn't cranking fast enough for all 4 cylinders to "light".
Author:  no-blue-screen [ Mon Jan 01, 2007 12:25 am ]
Post subject: 
So it doesn't do it all the time?
Author:  RFCRD [ Mon Jan 01, 2007 12:45 am ]
Post subject: 
Drewd wrote:
How do I know its the battery? Easy, it acted up again and before I made another attempt, I attached a battery charger to the battery and set the switch to start assist which provides additional 200 amps to the battery. Guess what, it fired right up. I suspect the Optima battery isn't cranking fast enough for all 4 cylinders to "light".

Which take you back to problem #1, you are probably getting air in your fuel causing a partial loss in pump prime. True, the faster you can get the engine to crank, the faster the pump will turn, the faster you can overcome the loss in fuel prime and develop sufficient pressure to work the injectors. I'm not trying to defend an Optima vs any other type of battery. If you don't find & fix the leak, eventually you will reach a point where you can crank all day long and it won't catch.
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