I think most diesel engines that are designed to work with glow plugs will have great trouble starting cold without them. Of course, they can be designed to work without glow plugs, but that’s different.
People I know who own/owned diesels here in NH and upstate NY…only needed to use the glow-plugs in winter. Cold start in summer and - not needed. Temps needed to be low (usually below 0) for the glow-plugs to be necessary.
We will never know. Maybe the timing belt gave up.
That doesn’t explain why OK had to fix many VW diesels with no-starts from dead glow plugs in Oklahoma.
The diesel engines in cars 40 years ago weren’t very impressive.
Perhaps those VW diesels had compression ratios on the low end of the diesel compression range, around 16 to 1 and so need glow plugs when the engine was cold,
A lot of truck and industrial diesels have compression ratios in excess of 22 to 1 and along with direct injection (no pre chamber) start right up without any help from glow plugs.
Several points to make.
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Forty years ago I wasn’t working on VWs.
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The older VW diesels had compression ratios of something like 23 to 1.
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I enjoyed working on diesels and requested every one that came through the door. Big time money makers. A rebuild for 4 injectors paid 4 hours flat rate. I could do all 4 in an hour.
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Nevada has made a habit lately of trolling me. Now that I’m mentally scarred for life I will just say that Nevada can eff himself.
This BS all started with that Audi oil change regimen post where I stated that “I respectfully disagree…”.
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I completely agree. They were noisy, smoke, and low on performance. Years ago the shop I worked at had a 1970’s MB diesel come in with the complaint of poor performance. I got in trouble for mentioning that for this car “poor performance” was actually a compliment. Anyways, one of the techs worked on it, I went on the test ride with him. We measured the 0-45 time on a day planner. Yet the customer commented how much better it was running.
I’m no expert but I do know there are various diesel engine designs. You can’t use diesel engine as an absolute term as if they are all the same. How the fuel is heated for combustion varies across designs. Some older military diesels don’t even have electrics at all. They are designed to start under any conditions. Glow plugs are only one way to overcome the need to achieve combustion temp in engines that cannot do it by pressure alone.
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My Olds had a wait light telling me when the glow plugs heated the chambers enough to start. In the winter the wait time was longer but in the summer I still had to wait a few seconds but not as long. Who knows whether the glow plugs were actually going on in the summer or not but it sure seemed so.
I had had the $500 injector pump replaced and the guy that worked on it was a former GM mechanic. He set the pump timing according to the manual and I verified several times that it was set according to the instructions in the factory manual. Still had problems with it so took it to an actual diesel shop. They set the timing slightly off of what the factory said and it never ran better with a lot more power. Later on I was replacing my own injector pumps but always took it back to the diesel shop for a final adjustment. They said Mercedes pumps were a lot more forgiving than the GM Stanadyne pumps. I hated that car eventually but just too cheap to get rid of it.
As a former owner of a 2011 Jetta TDI wagon who has tried to start it in a -25º morning in MN I have to agree with OK4450.
Technically, if you can keep cranking and cranking the engine, the heat of compression will eventually heat up the cylinder enough to allow for ignition, but that requires FAR more energy than you will ever get out of a battery at -25º F, so Yes, glow plugs are required for this engine.
The vehicle is in Albuquerque New Mexico, I don’t know what the temperature was but for myself a cold start in July is 100 F.
It’s hot, but I asked a general question, not a specific one, and appreciate the discussion. This wasn’t near home; I don’t know the guy; I was just trying to help; I knew what to check next on gas engine, not on a diesel.
I’ve actually worked for 2 VW dealers over the years and trust me; II’ve seen countless diesels towed in for a no-start condition. The usual cause was a fractured glow plug fuse.
The glow plugs draw 40 amps steady current with roughly a 75 amp surge. It’s not difficult to see what’s going to happen to that 50 amp fuse over time.
A visual of the fuse will show it to be good. A pocket screwdriver inserted underneath will reveal a razor cut in the fuse. A lot of diesel owners were very happy that the problem was a 1 dollar fuse instead thousands for an injection pump or whatnot.
And it’s plenty hot in OK. A 110 the other day with a 100 being the norm.
If the VW in question was running fine and if there were no starting problems before it died I suspect power was lost to the fuel shut off in the injection pump or the timing belt broke.
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I had a 79 VW Rabbit diesel and what @ok4450 reported happened in my car. The fuse was a metallic strip, not a glass fuse or a bayonet fuse. That strip broke or burned out. The car would crank and seem to start, but as soon as I let go of the ignition key it would stop. It drove me nuts until I found it.