Okay, so ever since the 240D came to us (super-high mileage, half worn out, details and history completely unknown) we've been trying to go through it issue-by-issue and get it sorted out. When we first got it, it had been sitting for over a year and so it had fuel tank scum problems and was impossible to start. We finally got it running, after a 10 minute battle, with WD40 through the air intake. One tank removal, cleaning, chemical treatment, and about eight filters later, the car started running "almost reliably". It was starting up, while not perfectly, well enough to not be worried about it not cranking in a parking lot. Never had to hold the key more than about two to three full seconds before it was running even on a cold morning.

The engine DOES have fairly high blow-by, because the oil cap dances at an idle, and it probably has never had a valve adjustment in its life. Obviously those are contributing factors or at least theoretical contributing possibilities. It's hard to start because it's just slap worn out and low on compression, possibly.

But I can't ignore the fact that we got almost two months of good, reliable, quick starts out of it before this problem started. An engine, even if it's worn out, behaves more predictably than that.

Now, you can hold the key in the crank position for 30 seconds at a time with the accelerator on the floor, with the thing connected to a good battery with jumper cables, and you could crank for probably three full minutes in 30 second blasts, glowing twice until the relay cuts out between each one, before it would run.

That's not glow plugs. Even an engine without glowplugs should start if you're putting that much heat into it just by cranking it over. Especially since I've had this problem consistently on 70 degree days.

What would bring this on so suddenly? I'm thinking fuel delivery. It acts like an engine that's fuel starved during this cranking process -- but the black cloud behind it as you're cranking sort of negates that possibility. I thought it might be an air leak, so I primed the engine with the (brand new) hand pump right before my last start attempt. Didn't make a bit of difference.

It's a 4-speed so I have started parking it at the top of the driveway hill in such a way that I can just roll start it and get moving. Guess what? Works perfectly. Not so much as a cough or shudder when I pop the clutch in 2nd - it just comes right up to life and will IMMEDIATELY idle and run normally.

Warm starts are absolutely flawless. If you let the car sit for three hours or longer, you'll have to toast the starter to get it running again, or push it off and pop the clutch.

Any theories? A few answers, please, in addition to theories?: Thanks

1. Is priming with the hand pump adequate to ensure that fuel is making it all the way to the injectors even if there was a leak in the system? It definitely primes until I hear the relief valve or whatever opening up.

2. If I wanted to do a volume test by pulling the return line and measuring the amount of fuel cycled through in X seconds, what would X be and what quantity am I looking for to prove the IP is adequately functioning?

3. Could low compression and poor valve adjustment really cause that much of a problem cold starting -- without affecting warm starting the tiniest little bit. It warm-starts like a brand new engine.

4. Doesn't the fact that it roll starts so easily and, more to the point, takes less than five seconds after starting it with the transmission before it's running perfectly for the day, indicate that it can't be anything TOO major? Or else I'd pop the clutch, it would spring to life while it had a hill to roll down, and die as soon as I clutched out again?

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~Michael S.~
Past cars:

1986 300SDL
1987 300SDL
1982 240D
1982 300SD


Current:

1987 300SDL

This reminds me of a "Gus and the Model Garage" mechanical mystery from Popular Science

Weird.

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1972 W115 220D/8 SLS, Coffman Starter "Ümläüt"

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(='.'=) This is Bunny. Copy and paste bunny into your
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90% of cold start problems are caused by a failure in the glow plug system. You don't mention troubleshooting the glow system. I would do that first, then run a compression check. And yes, low compression can cause your symptoms.

Gus would always solve the really tricky problems. This is a simple one.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I can believe low compression causing poor starting all the time, but I can't ignore the month and a half it cold started like it only had 100,000 miles on it before it started acting up.

Sudden failure of a glow plug might explain it. I'll check them out next time I'm at home.

__________________


~Michael S.~
Past cars:

1986 300SDL
1987 300SDL
1982 240D
1982 300SD


Current:

1987 300SDL

Yes, pull each glow plug, and put 12v to the stud and ground it on the main body . . . if it doesnt glow hot, you will know, also could be a relay or wires . . . fuse . . . Does your glow plug light glow like normal? Diesel Giant has a good tutorial!

Also how fast is it turning over? Could it be that the starter is not able to crank it fast enough?

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82 240D Manual 277K and still rolling!
02 Volvo S60 AWD For Sale

It glows some times and not others.

It's turning over plenty fast. I ruled that out by jumper-cabling it to the other Benz while making some of these attempts. Unless the starter itself is going bad... but I'm not going to buy and replace a starter just on a what-if. i'll wait until it finishes dying if that's what it's doing.

__________________


~Michael S.~
Past cars:

1986 300SDL
1987 300SDL
1982 240D
1982 300SD


Current:

1987 300SDL

I'm not sure what you mean when you say the glow plugs glow sometimes and not others. Could you clarify?

Although it's possible for the starter motor to sound as if it's turning fast enough when it's actually not, I wouldn't suspect it at this point.

Are the battery connections solid? When you turn the glow relay on, what kind of voltage do you get at the plugs? When you crank the engine, what kind of voltage do you get at the starter? Does smoke come out of the tail pipe?

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'Betsy the Getaway Car' : 1978 MB 240D, 582k
'The Mistress of the Sea' : 2001 Giant Boulder, 10.30k

I think he means that the light in the dash sometimes works, sometimes doesn't . . . which means to me there is atleast one glow plug not working!

Compare the other starter speed to your other diesel benz . . . or swap them . . .

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82 240D Manual 277K and still rolling!
02 Volvo S60 AWD For Sale

"3. Could low compression and poor valve adjustment really cause that much of a problem cold starting -- without affecting warm starting the tiniest little bit. It warm-starts like a brand new engine."

My experience is that low compression will make a cold engine almost impossible to start, glow plugs or not. I suggest you perform a compression check.

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

Starter sounds about like the other one.

That's correct, the glow plug light seems to randomly choose to glow on some starts and not glow on others. Probably DOES mean one glow plug is burned out but I'm still surprised that one out of four or even two out of four would prevent starting. Make it hard, yes. Prevent it... that's hard to believe given the number of diesels I've worked with over the years (tractors, mostly) that started with no preheating devices whatsoever. Just pure compression.

I'll do some voltage checks next time I get home; I've got the other car at school at the moment. Or if my dad has time I'll get him to check it out. I don't have the car with me at the exact moment but I am trying to make my list of things to check on my next weekend at home so I don't spend all my time guessing.

__________________


~Michael S.~
Past cars:

1986 300SDL
1987 300SDL
1982 240D
1982 300SD


Current:

1987 300SDL

I see it as follows:

1) No valve adjustment has ever been done since you owned it.

2) No checks at the glow plugs have been made to ensure that each has 12V during glow.


So, any conjecture about lack of fuel or the multitude of other possibilities are basically moot points until the above is accomplished.

X2 Since the car will start when you pop the clutch and will start easily when warm, glow plugs are the prime suspect.

This scenario is precisely what happened on my 81 240D. New glow plugs and she started right up.

Codifex
1981 240D SkyBlue (needs an engine)
1983 300DTurbo w/sunroof

x2.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Yep, once you get new glow plugs and do a valve adjustment, try it again.
Mechanical items wear out and you've shortened the life of your starter.

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83 SD

84 CD

I would replace the filter in the tank and run it on some kerosene also do the IP timing and have the valves adjusted to specs and try to start it without the air filter to see if the filter is too old