Originally Posted by Tango
Just chatted with someone who had similar high altitude starting issues. He made a suggestion that might help since your engine is not computer controlled. His was a turboed 3208 Cat with an intake heater instead of glow plugs similar to what I believe you mentioned your rig had.
His fix was to cycle the key three times back to back without starting which will raise the intake temp up to max...then crank it.
He said it helped him in spite of not really making any sense. The real problem, according to him, is that at high elevations the air is simply less dense. And since diesels rely on pressure to ignite the mix, starting with less pressure means there will be less on the power stroke. He did say that it was also very like a symptom of tired rings as they would contribute greatly to lower pressure which would be much more of an issue at high altitudes.
Don't know if this helps any, but there it is.
That guy is right on the money. However, dred's engine should be computer controlled, unless someone did a conversion to it.
I'm not sure how the grid heaters are controlled on either vehicle, whether it's a fixed timer, or computer controlled based off engine temp. And that would make a big difference on how long to run the heaters.
What dredman could do is wire a push button into the control side of the relay. So when he is at higher elevation he could hold the button in for a few more seconds to get that extra heat. That's what I did for my glow plugs(but that's because the computer failed).
Diesel fuel has a low auto ignition temperature. That temp depends on the specific blend(winter vs summer) and additives. Adding Power Service(white bottle, we use it in the winter time) should lower that temp making it easier starting.
Diesel engines use rapid compression of a fresh intake charge in order to create the heat that is necessary to light the fuel that is injected near top dead center. If you don't remember high school science, pressure and heat are directly related, so that when you increase pressure the temperature should also rise. That's why your air compressor tank will heat up when building pressure and air tools will cool off when used.
Elevation comes into play because at 10K ft, the air pressure is typically 2/3rds what it would be at sea level. So when there is less air to initially compress, your compression pressure at tdc inside the engine will also be less and so will the temperature. So an engine that runs perfectly fine at sea level at 70*F might have trouble at 10k ft at the same 70*F.
I'm 99% sure dred doesn't have a fuel supply issue, whether it be a lift pump or air in the lines. Simply because of the abundance of white smoke when cranking. That to me, shows that the temp in the cylinder isn't high enough to light the fuel, and that could be caused by one of a dozen different things.
My educated guess? It's a combination of the altitude and engine wear, and possibly the grid heaters not working.
What should he do to fix it?
He might be able to hold the grid heaters on a little longer to maybe compensate for it. He could shoot a little ether in the intake horn and that will raise the compression temp (don't do it unless the grid heaters are disabled). He could also spend thousands and have the engine overhauled/ or a new one dropped in.
If it was me, I'd stick with the first two and go back to enjoying life.