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  #1  
Old 12-02-2003, 10:02 AM
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PEH Quote Opportunity

In our last cold snap, Marlene the Wonder Wagon decided that she would be cantankerous about starting; troubleshooting revealed that the No1 GP had died.

So, on the way home yesterday, I stopped at the local excuse for a foreign car parts house to buy a (one) replacement GP.

The counterman looked askance when I asked for a (one) plug for a 300TD Mercedes. And, when he brought it out, queried me again, "Only one?"

"Right," I replied, "you don't change all the light bulbs in your house if only one burns out. Do you?"

Thanks again PEH!

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  #2  
Old 12-02-2003, 10:13 AM
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  #3  
Old 12-02-2003, 10:24 AM
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I'm not sure I agree with this one - It's quite a bit easier to change a light bulb than a glow plug. I would assume you don't actually BUY a light bulb until one fails - I mean why buy something you don't need RIGHT NOW.....

You may also want to buy a champion or a monarch glow plug - they are quite a bit less expensive than a beru or a bosch plug. Of course they last about 20% as long and they have a nasty habit of coming apart in the prechamber.....

Most of the glow plug failures I've dealt with over the years have been not been hard failures. My glow plug performance seems to degrade over a couple of year period - cold starts take a couple of compression cycles as opposed to first or second compression stroke with fresh glow plugs.

I'd rather pay the $50 every 4 years and change them out -based upon the number of post on this board about cold starting problems think many people would benefit from this approach.

Of course PEH will flame me for this post (and yes I do change fuel filters every 30K) but my cars start every time in any weather with no help from a block heater.

Tim
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  #4  
Old 12-02-2003, 11:02 AM
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Quote:
Originally posted by TimFreeh
...my cars start every time in any weather with no help from a block heater.

Tim
Now, mine does too...and it only cost me $13.25. However, I may have a different viewpoint if Nos 2-5 fail anytime in the next few weeks.
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Last edited by R Leo; 12-02-2003 at 11:11 AM.
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  #5  
Old 12-02-2003, 11:16 AM
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Tim,

My 300SDs seem to start on the first compression stroke even with very old GP, especially the '80 with 250,000+ miles. Its almost like it starts by itself. As long as I wait long enough for the GP to glow sufficiently, I don't even hear the starter. I think I replaced one or 2 GP in the 13 years I've had it. Had I replaced the GP every few years like you do over that period of time, I would be out $100s of dollars. How about sending me your old "usless" GP. I will make good use of them. I'll pay the postage.

Have you ever connected the new and used GP across the battery and observed the glow to see if you could tell any difference between new and old?

As fuel filters go, I replace than as required. There is absolutely no correlation between number of miles to when a filter needs to be replaced. It ONLY depends on the cleanliness of the fuel put in the tank. I got a load of dirty fuel in CO once and I replaced the filters 3 times in the next 1000 or so miles because they kept plugging up from the contaminated fuel. I didn't pass that fuel station on the way home or I would have gone and raised Hell.

R Leo,

I would have bought 2 as I always carry a spare GP just as I always keep a spare light bulb. GP are not like spark plugs (SP) that can degrade engine perfomance if they are not up to par. Once the engine is started, except for some in newer engines that keep the GP on a short time after the engine starts for emission reasons, the GP have no effect on the running of the engine. Once the engine is running you could take out the GP, plug the holes and the engine would hum right along. Can't do that with spark plugs.

I might excuse the counter guy because he might not know the difference between a SP and a GP and usually SP are sold as a complete set, one for each cylinder or 2 per cylinder for some later model MB gasoline engines. Actually when I used to run gasoline engines, I only replaced SP on an as required basis. I always carried spares. I also serviced my SP by cleaning, filing and gapping them frequently, maybe every 5000 miles. That PITA job is long gone now that I run Diesels. The only SP I use now are in small, one cylinder gasoline engines.

Thanks for the compliment. I thought your comment was going to be about another GP reply I made yesterday.

P E H
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  #6  
Old 12-02-2003, 11:26 AM
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Good advice

After having this one fail and experiencing the difficulty of getting her running at 35°F I agree, carrying an extra GP is a good idea!! I can only imagine what would (or wouldn't ;-) happen trying to start up with a bad plug in sub-freezing temps.
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Old 12-02-2003, 03:44 PM
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PEH

Yes I have directly wired old and new glowplugs to see how they perform. New plugs glow red hot in a matter of seconds while older plugs take 10-15 seconds to begin to glow. The new plugs ALWAYS glow much brighter after 4-5 seconds than the old plugs glow after 10-15 seconds. Glow plugs have a service life and their performance will degrade with time and use - in your post you mention having to wait a "sufficient" amount of time for the plugs to heat up to produce an instant start - how long do you wait? Do you think your 13 year old plugs would perform as well as my 1 year old plugs in marginal starting conditions? (like maybe a -5F start at 1am from an airport parking lot where the car had been sitting for two weeks.....) Would you be interested in figuring out which plug was bad and then swapping in your spare plug from the trunk if your first start attempt failed? My $50 every four years seems like a pretty good deal.

I do have 3 or 4 old glowplugs in my parts box that I would be happy to send to you - email me your address and I'll send them on the way. I can also send you some used 30K mile fuel filters - should be plenty of life left in them.

Tim
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  #8  
Old 12-02-2003, 05:58 PM
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I was told to test GP's with an ammeter. If the GP pulls the specified amps then its okay, if its low, replace. When I got my MB it had two dead plugs in it and started hard below 40*. I checked the GP's for continuity and found the 2 dead GP's and replaced them. The other plugs I checked with an ammeter to see how many amps they pull and they all pulled 7-8 amps, AFAIK.... My experience with other diesels has been most GP's pull 7-8 amps. Unfortuately I didn't' have the presence of mind to test the new MB plugs..... I have had GP's in other diesels pass the continuity test but fail to pull enough amps to glow well/quickly. When they fail like this they do exactly what TimFreeh describes, a long dim glow cycle. So just replacing a GP because its old doesn't make sense. As long as a GP pulls some healthy amps it should be fine. The only reason I can see to replace them all is if a new GP design, like the new PTC plugs available for some vehicles, become available. I'm also cheap like PEH..... RT
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  #9  
Old 12-02-2003, 08:28 PM
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RWThomas,

I take exception to you calling me cheap. Cheap implies poor quality.

I'm not cheap, I'm thrifty! Or frugal, as some people call it. LOL.

I agree with you theory that as long as a GP draws enough current, it is OK and that a current draw test is a better test than a resistance test for overall GP performance. But the resistance test will spot GP that are open or have a high resistance which will solve the problem most of the time.


P E H


Last edited by P.E.Haiges; 12-02-2003 at 08:41 PM.
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