85 W126 300SD Wont Start!
 

I just bought an 85 300SD. The guy that sold it to me said that it had a ploblem starting. He said that he had, that day, towed it from the mechanic shop. Sure enough it started right up, idled good, and I took it on a test drive and it ran smooth. The next morning 7am i tried starting it and it wouldn't. Naturaly I assumed that it was the glow plugs....I replaced them all. It will start when the outside temperature is warmer but not early in the morning. I tested all the old glow plugs and only one of them was bad. I have power to all G.P. and I tested the new ones to make sure that I was getting ground from the engine to the G.P.....so i know that the glow plugs are working. I can hear the glow plug relay switch off after about 30 seconds. The guy replaced the old battery a month ago and I tested it today and it held 12Volts fine. It has 230,000 with a working odometer and other than the bad starting, is in really good condition. It has the oxidizer trap and some blow by. I have seen more blow by in other engines and they run fine. What could possibly be the problem with this car!!!!??? Thanks, Stephen

one more thing
 

I checked all the fuses and they are all working.
-Stephen

Air getting into the fuel lines? Have you checked all hoses and fuel filters and the tank strainer?

Have you checked for voltage AT the glowplugs themselves?

I would recommend adjusting the valves. I have found that the turbo engines' intake valves tighten up. Valve adj makes a big difference in starting.

fuel?
 

I used the fuel primer and I could feel the fuel running through...a big difference when pumping air. If i can use the primer to get fuel I assume the IP is doing its job.
Again...When i get it started she runs fine smooth idle, no rough idling or missing.
-Stephen

I dont see how adjusting the valves would do anything. The car runs fine once it starts. Once it starts it immediatly finds a nice idle speed and on the road it accelerates fine and shifts fine. If it were the valves when the engine does start and is not at temperature it would idle rough right? This is why I feel that is an electracal problem I have not checked the voltage @ the glow plugs as I dont have an voltmeter. The big fuse for the glow plug relay is obviously new and unbroken. If i am getting power at the glow plugs..with new glow plugs...they should be glowing red hot. If i was not gett ing 12 volts at the g. p., what would be the cause? thanks, stephen

Does it crank very fast? If it cranks too slow it will not start well. Could be a worn out starter....

it cranks ok
 

It seems to crank about average. Not to fast but not to slow. Again remember. It only has this problem when it cold in the morning...once it warms up, it takes a couple cranks to start it but it starts. Now that you mention the starter, it seems to stick a little once I let off the ignition key.
-stephen

That sounds like low voltage, load check the battery and check your battery ground cable.

If by "sticking" you mean the engine is dragging the starter, then its the starter bendix....one of ours did that for a while, then the whole starter died...and we replaced it.

............so, what's the real situation..........??

If it will not start after sitting intermittently it sounds like an air leak to me.

discrepancy revieled
 

when I had the old G.P. out I took a wire connected it to ground and power to see if they would glow red hot. However I did not check how much power I was getting out of the wireharness that connect to the G.P.s
-Stephen

The issue is COLD VS. WARMER
 

As I said before...i load checked the battery...its a new battery so that is not surpriseing....it held 12 volts fine. I will check the ground cable. What explains the NOT starting when it is COLD and starting when it is WARMER?

I think that you've got to confirm that you have 12V at one of the glow plugs before we go any further with more complex problems.