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OM617 Running Worse as Temperature Drops

9K views 39 replies 18 participants last post by  Forcedinduction 
#1 · (Edited)
It's fall and temperatures are in the 50's and 60's. With the temperature change my turbo 1981 300TD is starting to need significantly more cranking for cold starts, unless I give it a little gas in which case it starts up immediately as normal. After its started the engine hunts slightly faster and slower for the right idle RPM. Once fully warmed up the idle seems more rough at idle than it did during the summer. Last winter I had a very low idle on cold start problem that was getting progressively worse as winter progressed, the problem disappeared as warmer spring and summer temperatures arrived and the car was used extensively throughout the summer without issue. It sees regular highway driving/moderate to high loads, currently has 5w-40 full synthetic oil, injectors rebuilt ~12000 miles ago, IP pressure relief valve spring restretched to spec, valve adjustment ~8000 miles ago and will be done again soon, newer style IP primer pump and glow plugs that tested decently well two years ago. I think the low idle on cold start problem is coming back and will likely be worse this time. What could be the issue?

Here's a video from last winter:
 
#2 ·
The main causes for these engines to not start is 1.) low compression and 2.) not properly working glow plugs.

Low compression may be remedied by a valve adjustment, but sometimes you do require an engine overhaul. That's what I had to do on Donkey.

The glow plugs not working could be due to the glow plugs, or due to carbon build-up around the glow plugs preventing the heat from reaching the air inside the pre-chamber. I would remove the glow plugs and ream the glow plug holes. Test the glow plugs while you're at it.

You know, the usual.
 
#3 ·
If the idle straightens out after a few minutes, you might want to check your glow plugs. If not, you can basically eliminate that path. I had a similar issue, and adjusting the valves cured it. As everyone usually suggests, start with a valve adjustment and go from there. But this sounds more along the lines of low compression. As for your oil you should stick with 5w-40, it's probably the best for your situation.
 
#4 ·
If you've still got summer grade diesel in the tank then you'll be having trouble sucking it through the lines as the temperatures get close to freezing (consider night time temperatures as well as day time temperatures).

New engine oil nearly always helps the starter to spin the crank faster.
 
#5 · (Edited)
So @ 4 minutes there is no coolant temperature rise? What is the engine temperature after driving for 10-15 minutes? Maybe your thermostat is stuck open and its time for a new one. Also, I would raise the idle a couple hundred rpm (900-1000rpm) and see if that helps while you are troubleshooting and performing maintenance as previously suggested... then, lower the idle once the problem is isolated and solved. Lastly, a block heater or coolant heater to get things warmed up may help considerably.

There is usually a week down here each year where temps may get into the low 30s F and while my F350 7.3L will start @ those temps it takes some cranking... so I plug in the block heater if I need the truck on those days to help preserve the battery's (there are two (2) in the F350) and reduce the strain the starter.
 
#7 ·
It's not low compression, it's not summer grade fuel, it's called "you have a diesel". The principal of how a diesel operates requires heat. It's always going to be harder to start when it's cold. It would be weirder if it wasn't hard to start in the winter.

If you're already having problems in the 50s and 60s then what other people said could help - winter weight 5W40 oil and new glowplugs. If it gets down around 0ºF you'll need a block heater. 5W40 oil isn't going to make it run smooth right away, just easier to crank.

I also had some cranking issues over the winter and needed to replace my battery cables. They were so corroded that even with another car hooked up for a jump I couldn't get enough energy to the starter.
 
#9 ·
It's not low compression, it's not summer grade fuel, it's called "you have a diesel". The principal of how a diesel operates requires heat. It's always going to be harder to start when it's cold. It would be weirder if it wasn't hard to start in the winter.
WWWWHAT!!!

No one ever warned me of this :laugh
 
#11 ·
Two years ago there were no problems with the cold idle, I'm also thinking it may be time for glow plugs. I can't imagine compression would drop so severely, due to wear, in less than 15000 miles running full synthetic oil for most of that, however a valve adjustment will still be done soon. The engine runs at 80*C and the thermostat seems to be opening at the right time based on radiator temperature checks. It's warm up time seems normal for the OM617, although I do wish it warmed up faster and held its heat better.
 
#12 ·
Hi Master7Chief, I had similar issues when I first got my car (although I am in CA and winter temps never get super low). However I have taken it to places where it snowed and/or were very cold and had similar symptoms to yours.

Firstly, as everyone suggested - a proper valve adjustment should help some.
- check glow plugs, if necessary replace with new ones.
-is your lift pump ok? If it has never been taken care of, that can be an issue especially in colder weather. There is a cheap rebuild kit that can be found online if you are willing to do the work.
-I recently tried Archoil fuel system products and the results were great. The effect it had was similar to doing a diesel purge etc.
-properly calibrated OFV spring from Greazzer from the forums. It restores correct IP pressure and made a difference in my car.
-about 1 week ago I had my injectors rebuilt by Greazzer as well, he did an excellent job. While my car now has more perceived power, I realized in the process that my lift pump is weak. This has been verified by other forum members, myself and my local indie mechanic.

Hope you get a chance to go through these things and bring things back to normal or better.
 
#13 ·
+1 on injectors, if they are leaky or crudded up they will contribute to hard cold starts. My last diesel had problems with misfiring at idle due to fuel leaking out overnight, and a low initial fuel pressure on start up.
 
#14 ·
One also should be aware that first gen w123's(pre 1980) when ordered for a warmer climate, came with a low power starter....

Another thing, is I cannot stress enough about the importance of a good starter. A starter after so many years, will develop lots of gunk and the grease will become rock hard. When your in a colder climate, the grease gets even harder in the cold....

Thus this will greatly hamper the starters attempts to turn over the engine....

Another upgrade, is to upgrade the battery cables....As with the starter, age effects the cables as well....strands will break and cables will corrode under the sheath....Thus when it is colder, it is harder for the battery to get full CCA's to the starter.....

I also cannot recommend enough, for one to upgrade to 2 gauge battery cables....cheap improvement that is well worth the coin....

I experienced all this, when I first came up here from Cali in December....Freezing cold! And the 78 wouldn't start....Starter was a low power version, since discontinued, battery cables were original....Starter over heated to the point of melting the paint off the starter, thus killed the battery....Now for the last three years, I have had no issues with starting in the cold after I upgraded to a turbo starter, 2 gauge wires and I believe a 900CCA battery...
 
#16 · (Edited)
Update: Did a valve adjustment, all exhaust valves were tight and all intake valves were still in spec., the glow plugs also tested good, heat is concentrated at the tip. I checked and addressed any potential fuel supply air leaks. Rebuilt monark injectors were installed 15,000 to 20,000 miles ago.


The problem persists and the engine oftentimes hunts at cold idle (RPMs continually go up and down) for the first minute or two, it seems to be temperature dependent as well. It almost refuses to start purely from cranking however, apply light throttle and it starts on the first crank. This seems like a fuel control problem specifically at startup, it runs great once partially or fully warmed up. Any ideas?


BTW, adjusting the rack damper bolt to its far limits did not effect the hot idle.
 
#20 ·
How old is the rack dampener bolt and what is the condition of the lift pump? Spring inside an old rack dampener bolt can weaken over time especially in cold weather. New bolt after adjustment typically solves it.

It does seem like a fuel control issue, not a starting issue (it starts well).
 
#19 · (Edited)
This comes from the manual....You very well may be experiencing normal cranking...



Remember these cars aren't equipped with a automatic computer, the driver is the computer....Sometimes involvement is needed between the user and machine...


I think your both right! Used the block heater until the engine was warm to the touch, ambient temps around 25*F, went to start it with no improvement; the engine also stalled with no applied throttle. I checked again and see I actually am getting air in the fuel line! I'll install new 5/16" (?) fuel hose this week; too bad the fuel tank is full...I'm anticipating a mess. :eek:

Every ECU controlled engine I've observed has a high idle command when started cold, these cars really do need this driver input which makes sense.
 
#21 ·
It's not too bad. I was redoing the filters anyway, and I think I just put a new prefilter in the middle of two lengths, detached it from the pump and reconnected the new bits. Be even easier with two people, just have one to put their thumb over the end of the lines. The only rough one is connecting to the solid line from the fuel tank.
 
#22 ·
-10degree fahrenheit is doable in my old om616 but thats the limit, and it has almost the same amount of blowby as there is exhausts. 1min+ glowing...
check the valve clearence, that was my problem, and yes, a good oil makes a huge difference, not to mention the oilconsumption you get if you are ... stupid enough to do like me and drive a few trips at -5to-10 with a 50w oil.
was more of a fill up oil and check the diesel level
 
#24 ·
"Every ECU controlled engine I've observed has a high idle command when started cold, these cars really do need this driver input which makes sense"

On my 240D, + other diesels previously owned, there is a small, unlabeled knob below the instrument console. Its about 10 o'clock position from the steering column. Depressing the fuel pedal + rotating knob clockwise gives a fast idle if linkage and cable is adjusted properly(most aren't & sometimes unhooked). Some newer models don't have the knob but you could probably get the parts at a pick n pull if yours is missing. Don
 
#25 ·
This is one of the nice advantages of the non turbo OM61X engines compared with the turbo which I believe has never had the fast idle knob. (Well from the factory - I'm sure there are many 240Ds with OM617 turbos fitted that still have the fast idle knob - although probably not connected)
 
#27 ·
My coldest start thus far this winter...with block heater on for hours and double glow, the 200D started instantly and idled very nicely !

I am happy, having feared the worst since I had yet to start the car this cold.
 

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#29 · (Edited)
The car still refuses to start without applying light throttle even in this 90*F weather, but with light throttle it will start on the first crank.

The idle speed seems normal but quick blips of the throttle can make it stall. In fact, with the AC compressor engaged (additional load), if I rev to 3000RPM in neutral and suddenly let off the engine will consistently stall as it decelerates. Weird test I know but it highlights the problem.

It seems the governor does not supply enough fuel for start up nor does it respond well to quick changes in RPM. I'm not sure what else it could be other than the IP. Any ideas?
 
#32 ·


The part that's in the guy's hand. The W123 has a manual primer pump, which is (IIUC) connected to the lift pump which is driven of the IP. The lift pump draws fuel from the tank into the IP, while the IP pressurises and times the delivery to the injectors.
 
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#33 ·
Thanks Plane. I get it now. My GMC truck had a lift pump as well but it was an electrical pump underneath the vehicle midway between the tank and IP. I keep this car's lift pump would be similar to the old GMC. So this one is driven if a small rotating cam much like the vacuum pump, correct?
 
#35 · (Edited)
I'm stumped on this cold start issue so I caught a quick video last week. Again, all my glow plugs physically tested good (glowing at the tip), I temporarily reversed the fuel lines to the tank to rule out a clogged fuel tank strainer, confirmed no air intrusion into fuel lines, completed valve adjustments, fuel filter change outs, etc. with no improvement. Glow time has no effect although increasing idle speed to ~850 rpm helped.

3 years ago it ran fine, 2 years ago it would start at 7*F but idled low, this year it stalls without applied throttle on a 50*F day.
Once the engine head is only warm to the touch it idles perfect; about 2 minutes running. I'll be doing a compression test soon, but would compression really change so much in 30,000 miles?


How do your cars run initially on a cold start?
Two years ago...


Last week
 
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