I HAVE A 300SD 1982 IT RUNS GOOD STARTS GOOD WHEN COLD BUT WHEN IT IS WARMED UP IT TAKES 10 SECONDS OR MORE CRANKING TO RESTART. ALSO WHEN I TURN IT OFF IT STILL RUNS FOR A FEW SECONDS. WHAT IS WRONG AND WHAT CAN I DO TO FIX IT THANKS FOR ANY HELP.

aliensiege,

Believe it or not, one of the problems can be the starter. As they get old, the insulation in the stator windings loses some of its dielectric strength, and once it is hot the typical insulation performance degrades significantly with every 10 degrees F increase in copper temperature. So, a hot starter will not be able to spin the motor fast enough due to internal insulation failures to generate enough heat from compression in the cylinders to fire right away. I had this with my 1982 240D and came close to giving up on the car last summer. A new starter from Fastlane fixed the problem and the car runs better now than ever before. I also changed the motor mounts at the same time as they were so broken down I concluded they contributed to the starter motor damage.

Hope this helps and good luck, Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

Aliensiege,

I would first check to make sure the glow plugs (GP) come on. An easy way to do this is to turn on the inside lamp above the mirror before turning on the key. When the key is turned to the run position (not start position) this light should dim slightly but significantly enough to be noticed. This is caused by the voltage drop in the wires from the current drawn by the GP.

If the light doesn't dim, check the GP relay. Pull the terminals off and replace them. That fixed mine. If you have someone else turn the key to run position, stand by front fender and you should be able to hear the relay closing and even feel it if you put your hand on it.

I agree to the explanation about the starter, but if the starter is bad , you should notice a decrease in how fast it cranks the engine. Does it seem to crank faster cold? Does it sound like a weak battery when hot? These are indications of a bad starter.

P E H

THE STARTER SEEMS TO TURN THE ENGINE QUITE WELL HOT AND COLD .GLOW PUGS WORK OK . wHAT DO YOU GUYS THINK ABOUT THE VALVES .MAYBE TO TIGHT ON THE LASH?
PS: THANKS FOR THE ADVICE

Aliensiege,

It could be the valves. How long has it been since they were adjusted? The valves will tend to leak more when hot. Just a slight leak will reduce the pressure inside the combustion chamber which can reduce the temperature below the ignition point of the fuel.

Take off the valve cover and check clearance cold. Intake 0.1 mm=.004 inch. Exhaust 0.35mm=.014 inch.

If it starts OK cold, the rings are not the problem, they would cause hard cold starting if they were loosing compression.

Just an aside, Last week I was going to adjust the valves on my '79 300SD with 200,000 miles. It was 25,000 since they were adjusted last. They were all within my spec: + or - .001 inch from nominal checked with gauge stock feeler gauges that are + or -.001 inch from nominal. They are used a go/nogo gages. I always try to set the valve clearance on the high side IE maximum clearance.

P E H

I GUESS I'LL PULL THE COVER AND TAKE A LOOK
OOOO BOY WHAT FUN I'LL HAVE..