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Old 12-06-2009, 06:54 PM
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Join Date: Dec 2003
Location: Metro Detroit, Michigan
Posts: 17,357
Cold starting a diesel.

If you own a diesel long/old enough, you will eventually have a cold starting issue ..

What causes it, (several of these issues tend to occur together) :

* Wrong viscosity engine oil - too thick for the temperature.
* BAD and/or contaminated fuel......
* Plugged air filter.
* Plugged trap oxidizer, (where applicable = if your car has one).
* Air leak in the fuel system O-rings and hoses (cold contraction opening micro holes, possible damage from alternative fuels).
* Primer pump air leak, (1985 and earlier engines).
* Air leak Fuel pre-heater (1986 and newer engines).
* Plugged filters or tank screen (filter and/or screen contracts sealing the few remaining micro holes).
* Damaged steel fuel feed line, (pinched/crimped by road junk impact).
* Bad fuel tank vent = hard vacuum in fuel tank.
* Valves out of adjustment (1985 and earlier engines).
* Bad Lift pump valves (cold thick fuel, chewed up plastic valve face).
* Wear/damage fuel bypass valve = zero pressure to supply injection pump.
* Bad glow plugs or heavy carbon on them.
* Weak/bad starter.
* Weak/bad battery, (a bad voltage regulator/alternator may contribute to this).
* Damaged injectors, (generally leaking = flooding).
* Injection pump wear/damage.
* Bad injection timing.
* Engine wear/damage = compression loss.

Last edited by whunter; 12-06-2009 at 07:42 PM.
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Old 12-06-2009, 06:59 PM
whunter's Avatar
Join Date: Dec 2003
Location: Metro Detroit, Michigan
Posts: 17,357
Links that may help you

Alternative fuel links (Diesel)
Air Intake
Diesel Injection
Engine Electrical
Engine Mechanical
Fuel Delivery
Trap Oxidizer, LINKS thread
Trap Oxidizer, LINKS thread

Related data:

Ignition Cylinder Tumbler replacement; mixed diesel/gas

Broken Neutral Safety Switch and replacing shifter bushings

Last edited by whunter; 12-06-2009 at 07:46 PM.
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Old 12-06-2009, 08:15 PM
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Join Date: Apr 2006
Location: up high
Posts: 81
Not sure whether to thank you for such an excellent comprehensive list, or whether to go cry in my room over such a long list of things that may be wrong with regards to my recently-become-problematic 300sdl w126. for now i'll settle for thanks, so thanks.
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Old 12-06-2009, 08:47 PM
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Join Date: Sep 2001
Location: central Texas
Posts: 17,277
I do not see ' failure to follow the FSM instructions ' for leaving the glowplugs engaged for close to 45 seconds plus in a single ' heat' .....( ignore the light going out ) when my wagon started acting up this made all the difference. Amazing how smart those guys were that wrote the Factory Shop Manual !!!
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Old 12-08-2009, 01:16 AM
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Join Date: Jun 2008
Location: Simi Valley, CA (SoCal)
Posts: 454
Many of these will cause not only cold start issues, but general running issues, e.g., bad/contaminated fuel, damaged fuel feed line, fuel tank vent, injector/injector pump worn, and so on. Symptoms may be more prevalent when trying to cold start, but are not limited to that. I'd guess that if you have a cold start problem, you can look at this list and try to determine if any additional symptoms could clue you in to narrow down the cause. Perhaps this list with additional symptoms when engine is running would be helpful. Like what would be an additional symptom of Bad Injection Timing? Smokey exhaust? Poor acceleration? I'm not good enough at this game to get to the final round, but maybe some of the Jeopardy champs out there could help out. Remember to phrase your answer in the form of a question!

'84 300SD 119KMi (Liesl der Diesel)
'84 300D 326KMi when the oil left (former parts car)
'82 300SD 253KMi (new parts car)
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Old 12-08-2009, 11:40 AM
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Join Date: Dec 2003
Location: Metro Detroit, Michigan
Posts: 17,357

Have a GTG at your place, free food and drink always draws a crowd.
They will probably have your car running in a couple of hours..

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