50-60 deg. F cold start failure
 

the symptoms of the last month or so:
('81 240D)

-hard to start, rough start in only mildly cold weather. it will usually start after 3-4 5-second cranks. i let the glow plugs heat for 40 seconds or so.
-starts fine when engine warm
-occasional loss of power, esp above 60mph.. not consistent
-a little oil getting into the air filter, apparently through the crankcase cover vent and also possibly through the air intake manifold?
-some oil and/or fuel visible near injector #1. possibly just small oil leak in crankcase cover seal.
-overall burns about a quart of oil per 15-20 gallons of fuel, highway driving.

i partially melted the rubber sleeve on the fuel tank filler neck w/biodiesel. been running B20-B100.

the glow plugs measure the correct resistance (all around .5 ohms). i also can't find any leaks in the fuel lines. all the hose clamps were tight.

any comments/tips or other ideas are most appreciated. this is what i plan to do/check:

-switch to mobil 1 synthetic 5w30. is that the correct grade? would 0w40 be better?
-check for fuel tank vent blockage: check for physical obstruction and check via tank cap..
-check battery, ground connection, terminals clean
-check glow plug relay fuse
-clean injectors by running on diesel purge or equivalent.
-check fuel filter at tank (the other two were recently replaced)


which of those would be most likely beneficial? please give me some input.. thanks :sun_smile

jeff

'81 240D
'78 volvo 240DL wagon
test drove: '05 CDi. this benz is a racecar!
want to build: VW bus w/ 1.9L TDI engine

Check for 12V at the glow plugs when you turn the key to position #2. The relay may appear to function, but the plugs are getting no juice if the fuse is compromised.

2 quarts of oil per 1000 miles is quite high. How many miles on the engine. What's it's overall condition? Compression?

its got 155k miles. glow plugs are getting 11.5V each. overall condition is pretty good, was garaged its whole life. engine runs fine.. just recently i drove it 350 miles at 70 mph nonstop. it won't go faster than about 85-90 though, on flat terrain. i haven't check the compression, i'd like to, but have to buy the tools first.

A. Please describe exactly how you measured the glow plug resistance.

2. How long since the last valve adjustment?

III. What happens when you run on petro diesel?

D. Any custom plumbing for the biodiesel?

glow plug resistance was measured with a standard multi purpose voltage indicator, set to 200 ohms, with one end at the plugs (or at the terminals above the left front wheel well) and the other end on a common, the crankcase cover for example.

no idea about the valve adjustment, but i can try to find out.

no custom plumbing for the biodiesel (yet). what do you recommend, what kind of fuel lines, filters?

OK, what I was getting at was whether or not you had isolated the glow plugs before measuring, which it sounds like you did.

I would definitely check valve adjustment. A Haynes manual will guide you through that pretty well. Sounds like it may not have been done for a while. The valves will get too tight if not kept in adjustment.

From your other posts, it appears that it has not run right since you got it, is that more or less correct? Did the primer pump leakage get resolved?

You didn't comment on the petro diesel. You may want to switch back to petro diesel for a couple of tanks and see what happens, just to rule out any possible biofuel problems. You need to make sure it runs right on petrodiesel before you jump into biodiesel.

i ran it on petro diesel for about 3000 miles before introducing biodiesel. ran fine for another 2000 miles on bio.. still runs fine, just this starting problem.

for the valve adjustment, i could give it a try tommorow, assuming i can get the right kind of wrenches, and if you think that's probably the cause of the problem.. or should i try something else first?

as for the last thread about this car, yeah i just replaced the primer pump and it started right up.. as posted in that thread.


thanks for the replyin!

jeff

Even with tight valves it ought to start at 50 degrees, assuming good glow plugs, good battery and good starter. My gut feeling is that you have fuel system problems. Maybe air in the system, or maybe plugged filters, or maybe even a problem with the fuel itself. Will it start at all? If so, I would get some known good fuel in it and see how it does.

>> OK, what I was getting at was whether or not you had isolated the glow plugs before measuring, which it sounds like you did. <<

actually, your first guess turns out to be the right one: i pulled out the glow plugs and retested them, and found 3/4 to have around 15 ohms of resistance. having replaced them, she fired right up.

i don't exactly understand what i did wrong on testing them the first time.. maybe you
can explain the right way?

so thanks again.. i sure was happy when that thing fired so easily. drove home late at night singin casey jones.


j

Next time, remove the cover from the glow plug relay, then unplug the connector that goes to the glow plugs. Measure resistance from each of the terminals on the connector to engine ground. This tests each glow plug, it's wire and connection. Also, check the glow plug fuse at the same time to make sure it's not cracked or excessively oxidized.

50-60 degree no start is definately a glowplug issue.....my recently acquired parts car was pulled out of a field, had 2 year old diesel in it and it started within 2-3 seconds after a 30 second glow cycle in 18 degree weather.

Now thats better than my good car does............

did you pick up that 79SD someone was trying to GIVE away here on this forum? I hope so.

A quick comment on your oil selection. Mobil 1 5W-30, is not approved by Mercedes. Mobil 1 0W-40, and Mobil 1 15W-50 are.

Additionally, Mobil 1 0W40 is approved by Mercedes for year around use.

Phil

Thats the one I am talking about........motor needs a little tlc..........as its leaking fuel like a sieve........but any diesel that starts that easy in cold weather with 2 year old fuel..........and likely to be summer fuel at that.....is a great engine.