What happens if you don't use the glow plugs before a cold start?
 

I work in hotels at times, have to leave my car with the valet people. Hours later, I'm just wondering what happens when the valet guy gets it, despite me telling him to use the glow plugs, when he gets in it and just turns the key to start it. What kind of damage does it do, and what happens if someone did that on a regular basis?

THanks,

Jeff 1991 300d

More wear on the starter, and theoretically a tiny bit more un-burned fuel can get past the rings into the oil.

The '91 has "afterglow" where the glow-plugs run while he's cranking, so it'll eventually start (provided there's enough battery).

I had the same issue at the car wash today. Told the guy "it's a diesel, so glow the plugs before starting." He looked at me like I was crazy. "The what?" Anyway, I don't think it causes any harm, except for maybe the starter and a slight issue with overfueling before igniting. But someone with more expertise than me should weigh in.

I had heard that Daimler was considering with the Jeep Liberty diesel putting in a glow system that would be activated by the keyless entry, so the cylinders were warming without any dumb valet even knowing it. True?

I did the 90-91 Afterglow conversion on my car

I have wondered this as well, since this is my first diesel. So, not using the glow plug puts a greater strain on the starter because it's cranking while the cylinder is heating up rather than waiting until it's hot enough to combust?

That's about the worst of it, maybe a little fuel gets past the rings, that's negligible and would for the most part rapidly cook itself out. You just crank longer to start is really all there is to it, making heat from compression rather than the glowing. Engine damage is really nonexistent from it, the cyl's are still being lubed with fuel, truth be known, unless you as the owner did it on a daily basis, (or let a LOT of valet's have at it) realistically you'd prbably never even know/see any difference in the starter's life.

A cold engine cranks a lot to start that way, a hot engine makes no difference unless its heavily worn.

Usually the valet comes back and says "sir, your car won't start" at least thats what happens to me, even though telling them it's a diesel beforehand. Last time though the guy figured it out and had the cars out quickly.

The solutions I guess would be 1) install a remote start (there's a write up on it somewhere on this forum) or 2) avoid valets.

I choose the latter because with mine, the average valet won't understand the pull/push start switch on the old diesels, and not only would there be a starting issue, I cringe thinking of someone trying to turn the key off without pushing the knob in to stop the engine first. Then there's the "pull up" interlock for reverse gear on the manual transmission - that's asking for trouble too, not to mention my bad 1st & second gear synchros (how many people habitually double-clutch these days?)

I was in Pasadena, CA a few years ago and happened by a big fundraiser event where all these movie-star types were headed into a mansion dressed in their expensive clothes. The "valets" (college kids I'd bet) were parking cars along the residential street which was on a slight hill. I watched one grind gears, stall a few times, and hit the curb a few times too while trying to park. He seemed amused by it, too. Good thing the owner didn't see it and the car wasn't a Lamborghini or anything. And you're supposed to TIP the valet after they mess up your car?

No-glo starting
 

Glow plugs are there to supply some heat to help ignite the fuel mixture when the engine is cold since a stone-cold engine may not generate enough heat in the cylinder under compression alone, to fire. The diesel is a very high compression engine that relies on the upcoming piston to squeeze the air so much that the temperature rises to combustion level and when the injector pops off and introduces a bit of fuel at the optimum time, she fires. In warm weather, a good engine will go without the pre-glow. If it has been run and has some residual heat, she'll go on the first revolution. If one has to be cranked a long time, the starter may get a little hot and theoretically would have a higher wear rate--especially if done all the time. However, these starters are built pretty stout and will take a heck of a beating. I'd not want to grind for longer than fifteen seconds -----and, if it takes that long to start, longer grinding is probably not going to start the motor. I've been through the difficult starting routine here in South Dakota for a long time but I have a few tricks and rarely go away defeated. We do have block heaters to warm up the coolant and she pops off right away at twenty below. This is a heat engine and just wo'nt go if it cant get hot in the combustion chamber.

Also, beware of cranking and cranking away until the injected unburnt fuel washes the thin oil coating off the cylinders. Then compression goes down and yer stuck. But that is getting into the magical area of diesel operation.

Don't worry if somebody doesn't use the glow on occasion. If it eventually starts, drive away. I've worn the battery down to just a grunt often enough and didn't harm the starter. But, sure, use the glow and enjoy.

Sparky