84 300SD stalls from cold start when put into reverse

[JiveTurkey]

Heya Diesel Peaches,
I've been bringing the '84 300SD up to steam slowly over the last few weeks. In the last two days a new issue has reared it's head. From a cold start the engine idles more roughly than it used to and stalls when put into reverse. The idle is a little lower (around 500) than it was when I bought the car (around 750). When the engine is warm, or even halfway warm it operates normally at all engine speeds. I havent done a compression test and there's not a lot of blowby.

I've been doing little stuff to the car so far
-new glow plugs (bosch)
-new glow plug relay
-voltage regulator to the alternator
-tightened AC compressor and alternator belts

I've been running good diesel with treatments every fill up since I got the car.

Any ideas?

[4thesporty]

I would say glow plugs, but you just put new ones in.

How long are you glowing before you start it?

[JiveTurkey]

I watch for the light to go out and then wait for the buzzer to stop before starting. I've heard two things about this though,
-People on here largely agree the glow plugs stop glowing as soon as the engine cranks.
-indy Mercedes mechanic I'm friends with says the glow plugs should stay on.

I normally just wait for the glow plugs to "click." so I know they're done heating. I havent checked the rack dampener yet.

[Graplr]

Originally Posted by JiveTurkey

I watch for the light to go out and then wait for the buzzer to stop before starting. I've heard two things about this though,
-People on here largely agree the glow plugs stop glowing as soon as the engine cranks.
-indy Mercedes mechanic I'm friends with says the glow plugs should stay on.

I normally just wait for the glow plugs to "click." so I know they're done heating. I havent checked the rack dampener yet.

On your car, the stock glow plug relay does NOT glow after the starter is engaged. You can buy the "after glow" relay that stays on for 2-minutes after starting, I did and have it on my SD. Haven't noticed much of a difference.

The stalling issue is related to the rough idling. Fix the rough idling and you will fix the stalling issue.

[JiveTurkey]

Originally Posted by Graplr

On your car, the stock glow plug relay does NOT glow after the starter is engaged. You can buy the "after glow" relay that stays on for 2-minutes after starting, I did and have it on my SD. Haven't noticed much of a difference.

Thanks for that info

Since I'm doing "statistical methods for business" homework I decided to take a break from numbers and go tinker with the car. I found that the vacuum connection from the hard plastic line that comes off the banjo bolt had a (bad) tear in the rubber caused by some stupid ******* yanking on it too hard (hint, I might be the stupid ******* ) Thankfully I was able to repair the tear and the line now holds vacuum. The idle is back to where it used to be (smoother.) That big cloud of gray smoke that started on a cold startup two days ago is gone and there is very little smoke on a cold idle again.

My conclusion... Since the off boost fuel wasn't regulated (that vac line wasn't holding vac) there was way too much fuel (hence the big cloud of gray smoke) and the engine stalled. Now that it's repaired the engine is back to it's old self. It does sound almost like it's missing slightly on one cyl when it's on a cold idle. But that miss goes away with any increase in engine speed, or when the engine has warmed up for a minute or so.

I also tested the following;
-resistance on all glow plugs is below 1 ohm
-glow plug wires all showed continuity
-glow plug relay, fuse are working as they should.


I want to add, the plugs are all new Bosch plugs. First I tried "autolite" plugs and they're complete ****. I took them out within a day. The bosch plugs are great! Note, the plugs that were in the car when I got it were Bosch and actually tested well (resistances of around 1 ohm or so.) I cleaned them up and I'm keeping them for spares. The glow plug relay is from Fastlane (so sad to see Phil leave)

[MattBelliveau]

...but it doesn't stall going into D?

[JiveTurkey]

Originally Posted by MattBelliveau

...but it doesn't stall going into D?

I fixed the stalling issue today, so no idea there. I always had to back it out of it's space before I could put it in drive, so no idea.

[JiveTurkey]

I went off half cocked yesterday. It stalled again this morning (same symptoms) when I moved it so I could drive my w114. The smoke is gone though. Since it's just now starting to get colder, perhaps the cold has something to do with it? Thoughts? Help is always appreciated.

[ubertino]

I'm having a similar problem, and I just recently replaced my glow plugs as well. When I start I get the cloud behind the car, and it runs pretty poor until I give it gas. Only once has the car stalled when put in reverse though.

I haven't done a valve adjustment yet, I'm expecting that will solve some of the problem. I also have no idea when the fuel filters were last replaced, so I'm changing those as well, which also might help.