I rennovated this 240D 1.5 years ago and it has been running well. In warm weather, it always immediately started after a few seconds of glow plug and < 1 - 2 seconds of cranking. I have a manual glow plug with a push button, buy the way.

Now, it just doesn't want to start. Even when I give it 10-15 secs of GP, I can crank and crank, and nothign but diesel vapor out of the exhaust.

I verified that the glow plugs are getting 12v when I press my button. I've not pulled them yet. BTW- I replaced these 1.5 years ago when working on the car.

All I can guess is maybe the plugs have gotten carboned up? I have a reamer, so maybe that is the next step. Actually, I need to pull them and make sure they actually glow.

Any other ideas? It is clearly getting fuel because of the vapor out the exhaust.

There's a couple of common things that will cause vapor but no ignition:

1: Lack of heat

2: Lack of compression

Getting voltage to the GP's is only part of the game. You need to verify that the plugs are actually good and glow. You'll still have 12V present with bad glow plugs.

If your glow plugs are good, check your valve adjustment. If too tight, that can be a source of compression loss.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Same problem with my 300SD until I had the valves adjusted; solved the problem.

I did adjust the valves- I even brazed up special wrenches. Maybe things have changed and the clearances have gotten smaller? I'll check the glow plugs first. Thanks

Some of these older engines are addicted to all the glow plus working. At least it seems that way. With only one or two burnt out the engines sometimes do not like to light off.


I even had one that wanted a touch of glow plug activity even when hot to restart. Yet it lit off easily first thing in the morning with a normal glow cycle.

Resolved!

The problem was the manual glow plug relay. I bought the kit from Mercedes Source, so I figured it would be good quality, but no. The first one was actually stuck on permanently, so they sent me a replacement. This worked for several months, but started making a resistive connection, yielding the results in my OP.

So- I ordered a new solenoid relay and this works fine. I got one rated at 150A continuous. We'll see how long this one lasts!

Does mercedesource supply the older ford fender mounted starter solenoid as the relay? If so it usually lasts. He might be supplying an inferior aftermarket product. There are no shortage of then out there now.