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Thread: Diesel Glow Plug System

  1. #1
    Join Date
    Dec 2001
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    Having recently returned from a Westy roadtrip to the American Southwest, and experiencing a bit of trouble along the way, I thought other diesel Westy-owners might benefit from my lessons learned the hard way.

    One morning a few days into our trip the van absolutely would not start on her own. The engine spun with its usual gusto, the battery did not seem depleted, clouds of stinky fumes emanated from the tailpipe, but she simply refused to fire. A test light on the glow-plug bus bar confirmed the plugs were getting power, so I turned my attention to the fuel system; at 8200' elevation, I presumed there was an altitude-related mixture problem. The gray exhaust clouds which appeared while spinning the engine told me it was getting plenty of fuel, perhaps too much, but was unable to ignite it. Nonetheless, we eventually pushed the van out of our campsite, got it rolling down the loop road, and popped the clutch. EUREKA! She fired right up and was very well-mannered the rest of the day, even when we stopped for lunch or fuel, always firing-up easily with the starter.
    Unfortunately, this scenario was repeated for the rest of our 2-week vacation through southern Colorado and Utah, requiring a roll- or push-start first thing nearly every morning.

    The most frustrating part, upon returning home and troubleshooting the problem, was discovering that our vacation troubles were caused by my own clumsy thumbs and cramped quarters in the glow-system wiring box, inside of which resides the glow-system fuse, relay, and a veritable rat's nest of wires which is barely accommodated by the tight confines of the box. Several months previous, while checking this fuse -- an odd, UNinsulated metal strip -- I had evidently mashed several wires against it when I snapped the cover back on. The heat of this fuse, combined with several thousand miles of vibration, had apparently burned and chaffed through the insulation of one of these wires. And as luck would have it, this particular wire was the signal lead from the starter, which tells the glow-system relay to continue sending power to the glow plugs whenever the starter is used. This effectively created a closed feedback loop which kept the glow plugs glowing constantly, or at least intermittently, until they finally burned-out. Hence the trouble with cold starts, but easy warm starts.

    Replacing the glow plugs solved the starting problem, but a test light revealed that upon start-up the plugs were staying on a full 3 minutes instead of the normal 30 seconds. Evidently the short circuit had fried a portion of the glow-system relay; replacement of the relay solved that problem too.

    Lessons learned:
    • Like a light bulb, just because power is getting TO the glow plugs doesn't necessarily mean power is getting THROUGH them, i.e. makin' 'em glow. My initial test at the glow plug bus bar indicated the plugs were indeed getting power, but they're worthless when burned-out.
    • Don't bark up the wrong tree. My suspicions of the fuel system blinded me to the true problem with the glow plugs, even despite clues to the contrary.
    • I was surprised to learn that even with dead glow plugs, a diesel can be pop-started. At temperatures above 40F, get a good rolling start and pop the clutch in first or second gear. Repeat daily as necessary.
    • Carry spares. Because I'd replaced the glow plugs only 10,000 miles previously, I trusted I wouldn't need spares, and I never even considered the glow-system relay. I've now added these to my onboard collection of spares, as well as the usual tools and Bentley manual.
    • Keep your wits about you -- attitude is everything. Don't let an overwrought travel partner distract you from your troubleshooting, nor allow the inconvenience of a daily push-start to dampen your enjoyment of a once-in-a-lifetime vacation. Figure out what you can, fix or replace what you must, and get on with your life.

    Besides the venerable Bentley manual and its wiring diagrams, I also found an excellent online resource pertaining to the VW diesel: http://4crawler.cruiserpages.com/Die...ks/index.shtml.
    Created by Roger Brown, the site is mostly dedicated to the VW diesel pickup, but there's lots of info which applies equally to our diesel Vanagons. The page I found most valuable in understanding and troubleshooting the glow system was "Stupid Glow Plug Tricks".

    Now that I've confessed to you the low points of our trip, please see my posting under VACATIONS & DESTINATIONS > AMERICAN SW for the highlights.

    I have also compiled a travelogue of the abovementioned trip, "Southwest by Westy", which can now be viewed at, www.vanthology.com/1Layout/Journeys/southwest1.html.
    And for more photos of our American Southwest trip, click on the "Gallery" link.

    [This message was edited by A. Cooper on December 23, 2002 at 10:20 AM.]

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  3. #2
    Join Date
    May 2000
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    Heres' some added glow-plug observations I've accumulated over the years.

    I have a Ford diesel tractor. The glowplugs take 1-2 MINUTES to reach operating temp. Obviously Ford (Japan) didn't think a quick-start plug was necessary. But . . . the amount of juice they consume is significant. This helps battery sales. But it's also taught me that a HOT diesel doesn't necessarily need the glowplugs to restart, a typical scenario with the tractor. Probably why Coop's bus ran good the rest of each day.

    The Admiral's MBenz oil-burner has quick-start glow plugs. As she's now in the 170K mile range, a couple have burned out. When one does, the engine is a little harder to start and runs rough to begin with. The reasoning is that besides the one bad cylinder, the glowplug system on her car keeps going for a little while after the car starts until the system stabilizes. Thus the one cylinder still isn't firing correctly and you sound like a threshing machine for the first couple miles. Bosch obviously likes to make things as difficult as possible so the glowplugs use a different size socket (12mm) that is too tall for a standard socket while not leaving enough room in the engine compartment for a deep-well. Plus there's usually some obstruction, sending you off to Snap-On to trade your first-born for one of those half-depth universal flex-sockets. That same lack of working room makes you choose between ¼" drive that will break before removing the stubborn old plug, or the still-too-big 3/8" drive. One can always remove the intake manifold, whose directions are longer than the dead-sea scrolls and start something like "remove right rear taillight."

    My mom has one of the new Jetta TDI's. Love it!. The glowplugs are so quick that it took me until the first winter to locate the dash indicator light. It'd be off before I could get the bifocals aimed in that direction. The salesman -- not that I consider him anything close to gospel -- said the glowplugs will start when you unlock rather than waiting until you turn the ignition to on. That sounds a little Orwellian to me, but is an interesting theory. I know that even on a cold day, if I'm watching where the indicator light is, it's never on for more than 1-2 seconds. Of course our "cold" is anything below 32°F -- those up in International Falls MN might consider that mid-summer temps.

    The other thing I learned from the MBenz is that Bosch apparently has an infinite number of varieties of glowplugs, they supercede them every time they change underwear, they don't necessarily look like their predecessor and none are compatible with each other. In the MBenz case, that leave you at the mercy of the dealer who has the secret code of supercession in the CD/computer parts system none of us can afford.

    Cummins, on the other hand, uses an air pre-heat system, at least on the B5.9 in my Redneck Pickemup. I presume that has two major cost advantages. First it's cheaper to produce one intake heat source than 6 in-the-head glow-plugs, and two, it creates a steady source of service department income since there are still an unconvinced number in the target market (Rednecks) who think you should always squirt in a shot of ether in lieu of any engine maintenance. This, of course, means you have small fires, explosions and related entertainment on a cold morning. In Cummins defense, it is mentioned somewhere in the 150 page manual that you know is either missing because Junior used it as a scratch pad to write down the waitress's phone number at Gert's Gas & Go, or is at the bottom of the glove box fused into a geletanous mass with melted candy, gum and some unidentified objects we don't even want to contemplate. Of course that also assumes the driver can read.

    One thing the glowplug system does teach is that a block heater system is definately worth the trouble. Also a good anti-gel additive in the fuel in cold weather.

  4. #3
    Join Date
    May 2001
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    Eugene, Oregon, USA
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    We've had a TDI New Beetle for almost 5 years now, and I can attest to it's wonderfulness. The TDI techies who have a web site claim that the glow plugs coming on with the door being opened idea is indeed an urban myth. (See www.tdiclub.com.) Our salesman told us this, too. Who to believe? We also didn't find the indicator light for a few years, since it goes out so quickly. My '82 VW Pickup, however, is a bear to start on a below-freezing day, runs rough, etc, so it probably has some glow plug issues. Also maybe a stuck thermostat, too; it took 20 minutes to get decent heat in the cab the other morning when it was 25 F. Now that I have the Westy sorted for the time being, I can spend my time dealing with the pickup.
    -judlandis

  5. #4
    Join Date
    May 2002
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    Nanaimo BC Canada
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    103

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    I had a problem with my diesel not starting while cold. It would crank, but not start. Normally it starts very easily.

    I determined there was fuel - vapour out of the exhaust on cranking, and disconnecting the fuel line revieled diesel.

    So checking the glow plug circuit as follows-

    1) Attach a volt meter +ve to the glow plug bus bar, -ve to the battery -ve

    2) Turn on ignition (yellow light goes on for 7 seconds) check the voltage - it should be 12v

    3) If no volts, then to check to see if the glow plugs are the problem, turn ignition on, wait 7 seconds until the yellow light on the dash goes off, take an 8 guage wire and connect the battery +ve to the glow plug bus bar for 7 seconds. It will spark like boosting a battery. Be careful

    4) Try to start the engine and it will probably start.

    Once you know it is the glow plug circuit, check the relay by removing it. Attaching -ve to terminal 85, +ve to terminal 86 (it should click) Then test the resistance between the two big connectors - if it is ok it should be zero. If not the relay is your problem.

    The answer to the not starting on my van was - metal fatigue - the fuse - the piece of aluminum had worked loose to the point that it had fallen off one side of the fuse box - visually it looked fine until you checked the resistance of the fuse!

    Regards

    Mike
    '82 Westy Diesel

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