I just bought a decent 78 300D with a no start condition when cold. The previous owner had replaced fuel filters and glowplugs. This did not help so I immediately did a run down of the glow plug system with my manual and a voltmeter. According to the meter all is in specs EXCEPT the light stays on far too long. With a small shot of ether (I know this is a no no) the car would start and run perfectly...no misses, no valve noise and no excessive smoke. I consulted my local injection pump guru and he said it may be losing prime. I hand primed the pump and this did not work either. No. 1 leak off leaks some but the engine DOESN'T miss! Upon further consultation, contaminated fuel became an issue. I pulled the fuel tank and low and behold there was a gas smell!! There was lubricity in the fuel so it did have some diesel left in it. I pulled the tank and flushed the sustem out and filled with known good fuel, changed filters agian and I still have the problem. Finally, my question is this: I know that gas can take out the pump, but why does it run so well? This also doesn't address the glow plugs when cold. I should add that once at op temp (175-180) the car can be shut off and restarted up to 30 minutes later although the crank time increases proportionly to the length of time it sits. PLEASE HELP, I AM AT MY WITS END WITH THIS CAR!!!!!!!!!!!

....this probably isn't the issue but it sounds alot like my volvo diesel. I have such low compression that 40 degrees outside will keep it from starting. On the other hand, when plugging it in or running it warm it runs perfect. Generally speaking, I have about 1 hours time in the winter before it won't start. Therefore, she runs at idle much of the time or is plugged in. I hope your issue is simpler than compression.

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DAILY DRIVERS:
'84 300DT 298k (Aubrey's)
'99.5 Jetta TDI IV 251k (Julie's)
'97 Jetta TDI 127k (Amber's)
'97 Jetta TDI 186k (Matt's)
'96 Passat TDI 237k (Don's
'84 300D 211k Mint (Arne- Undergoing Greasecar Conversion)

SOLD:
'82 240D 229k (Matt's - Converted-300DT w/ 4 speed

Valves not adjusted properly, burned valve(s), incorrect timing.
Undersized battery causing it to not crank fast enough to start. Oil to high viscosity (maybe it has 30wt, try 10w_xx).
How many miles ?

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Palangi

2004 C240 Wagon 203.261 Baby Benz
2008 ML320 CDI Highway Cruiser
2006 Toyota Prius, Saving the Planet @ 48 mpg
2000 F-150, Destroying the Planet @ 20 mpg



TRUMP .......... WHITEHOUSE
HILLARY .........JAILHOUSE
BERNIE .......... NUTHOUSE
0BAMA .......... OUTHOUSE

Greetings,


I am thinking along the same lines as Bill, I'd remove the glow plugs and physically check them regardless of their readings. I'd also look at my clear return fuel lines and see if fuel isn't leaking back out of the line, bubbles or air gaps show this, line is either cracked and sucking air or check valve on pump is allowing it to leak back. I also think I would do a compression check to see if cylinders are somewhere within operating spec. As mentioned before, valves and IP timing will play an important part in not only starting the engine while cold and providing good compression while running but maintaining a decent MPG going down the road.


Charles

I've had a similar problem. If there is the tiniest of leaks in the return lines above the main fuel filter, it will give this problem.

Let the car sit overnight, then pull the soft line from the top of the main fuel filter that goes to the number one injector. Fuel should run out, if it does not, there is a leak in the return lines somewhere. Check the cigar hose and the soft lines. If the leak is at the top, it will leak air, but not leak fuel showing you where the leak actually is.

I went through this on my daughters car and found the cigar hose leaking at the clamp. I trimmed off about 3/8", put it back on and all's well, at least with that portion of the car.

Good luck,

Larry,

That was a good finding of the no-start problem. Thank you for sharing.

David

I have two 240D cars. One will start when it very cold and one will not start if it is below 40 degrees. The quick way to tell which one has the problem is to take off the oil filler cap while it is running and the engine is warm. If the compression is bad there will be a lot of exhaust blowing out the filler hole. I think this is the first thing to check for when looking at a used Benz. If the compression is real bad they will have trouble starting when hot also becauset the oil is thin on the cylinders.