Author Topic: Intermittent starting problem  (Read 3281 times)

RickInTex

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Intermittent starting problem
« on: January 30, 2006, 14:18:07 »
Last fall I began to have a slight, intermittent hesitation problem.  The car would start fine from cold, but after a mile or so of driving, then waiting at a stoplight, the engine would sputter and hesitate when I gave it gas to get moving.  This would last a second or two, with no recurrence.  (Interestingly, the exact same thing that I've lived with on my 96 Jetta for about 8 years.  Always for a few seconds, then goes away with or without the aid of gentle massaging of accelerator.)

One December morning, the sl started perfectly, and I drove for maybe a mile before turning the engine off.  15 minutes later, it started fine, but under mild acceleration from rest, sputtered momentarily as above before smoothing out.  Drove a block or two, and it died when I put the clutch in to stop.  Wouldn't restart.  Cranked but wouldn't catch.

Took it to a new mechanic, recommended to me, who seemed to know his stuff--works only on old MB.  With one thing and another, he took a while to get back to it.  Here's what he found:

Nothing coming out of the add-on voltage booster going to distributer.  He disconnected it entirely.

Bad points.  Now replaced.

The problem with starting is now intermittent--sometimes fine; sometimes won't start at all.

He is suggesting it's the distributor, since there's a lot of play, he says, in the plate below the points.  He's talking about a replacement  of the distributor [:0].  I'm skeptical.  At the very least I want to get the distributor bench tested first, to see if there's really a major issue there.

Thoughts and advice?  Can a problematic distributor manifest itself intermittently?  Are there other potential electrical culprits?  What should I have checked in the fuel system?  Cold start system?

By the way, I have less than 5000 miles on a rebuilt top end and injector pump, including new injectors.



Rick
Dallas TX
1967 250SL, 4-speed

Ricardo

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Re: Intermittent starting problem
« Reply #1 on: January 30, 2006, 15:10:45 »
Hey Rick
I don't know how much a replacement dist. costs, but you'll be getting an aluminum replacement (009 or 010) which isn't what your car currently has (Vacuum retard 051 probably). If time isn't a problem, you should send your dist. to our own Dr. Dan. He's the go-to guy for distributor rebuilds and if he has stock he'll do an exchange or rebuild yours. He knows these distributors very well and has the machine to set it up properly. I got rid of my Crane  ignition module after getting my dist. rebuilt by Dan and my car has run great ever since.
I'm not sure what you mean by voltage booster, unless you're talking about an aftermarket elec. ignition module , which often get installed to "cure" a worn distributor, intermittent start problem.
Then again this could still be a fuel issue, though not as likely if you had the pump rebuilt.
Just a thought
Ricardo
'67 250 SL 4 speed
# 1834
(I think we should start a fraternity of Richard's with '67 250's  8)

RickInTex

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Re: Intermittent starting problem
« Reply #2 on: January 30, 2006, 15:18:36 »
ricardo--yes, it's an aftermarket electronic ignition module, which has apparently ceased to supply current out to the distributor.  i wonder if this was installed by the previous owner in order, as you suggest, to cure a start problem in my probably-worn distributor.  then, when the module died, these problems reappeared.

Rick
Dallas TX
1967 250SL, 4-speed

J. Huber

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Re: Intermittent starting problem
« Reply #3 on: January 30, 2006, 15:33:07 »
Ricardo's advice is very good. You might also check into the cold start system. There is a ton of info here on such things. For years I chased a "intermittent starting problem" replete with new points & plugs every time I took it to a shop. This seemed to help for a short while, only to have the problem come back. Then I found George. (Not to be confused with finding God...) We trouble shot my system and found a bad ThermoTime Switch. Car has not missed a quick start-up since (maybe 3 years or so of almost daily driving).

James
63 230SL
James
63 230SL

George Davis

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Re: Intermittent starting problem
« Reply #4 on: January 30, 2006, 23:10:03 »
Rick,

I'm sort of leaning toward an ignition problem.  Ricardo's advice to have Dan rebuilt the distributor is good, at 35+ years old it probably needs it, but unless the advance mechanism is really messed up it may not be the root cause of the non-start.  Ignition coils can fail such that they work fine when cold but quit working a short time later when they're hot.  If you can swap in a known good coil this is easy to test.  You might also consider replacing the wire from the distributor to the coil, it could have a break inside the insulation.  Probably not but easy enough to check.

James, finding God can mean something good or bad, but I won't ask!

George Davis
'69 280 SL Euro manual

Naj ✝︎

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Re: Intermittent starting problem
« Reply #5 on: January 31, 2006, 02:53:07 »
Rick,
 
quote:
Cold start system?


I would ensure that the air is shutting off completely from the warm up device after warm up. It could be leaning out the mix and causing  ...

naj

65 230SL
68 280SL
68 280SL

RickInTex

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Re: Intermittent starting problem
« Reply #6 on: March 10, 2006, 07:13:46 »
Thumbs-up to George D:

Resolution--very belated--to starting problem from December (see below--stalled out, wouldn't start):

Mechanic #1 found no power coming from aftermarket voltage booster; disconnected it.  He replaced points, condenser, coil, and the car started.  However, it kept dying once warmed up.  Many delays, much mystery.  Talk about distributer being the culprit as it's clearly worn.  

More delay, life gets complicated for me; many phone calls and reassurances from Mechanic #1.  Eventually he asks that I take the car back as he is getting a new roof put on the shop.  Seems like a good idea for the car not to be there while this happens--particularly if it isn't getting fixed.

Towed to Mechanic #2, at the shop where I had had major work done in the past.  Started with basics.  Fuel pressure great from pump; injection pump (rebuilt last year) great; plugs and wires fine.  However, points put in by Mechanic #1 are not set right.  Dwell is not correct.  These fixed, but car still stalls out once warm.  Coil tested (new from Bosch, installed by mechanic #1):  weak output.  Bingo.  Coil replaced, and all is good.

The moral: don't assume that new parts are good.  Also, realize that an unknown mechanic's credentials (Mechanic #1 is M-B factory trained, decades of experience) and positive word-of-mouth aren't guarantees.  Not very useful advice, of course, since what else is there to go on with a new mechanic?

Kudos to George D for suggesting the coil!

Beautiful weather in Texas today for top-down driving.  Alas, I have to leave town for a few days!

Rick
Dallas TX
1967 250SL, 4-speed