PeachParts Mercedes-Benz Forum - rough idle hard cold starting

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rough idle hard cold starting

rough idle sounds like injector noise, only at low RPM from idle to 1200 RPM

also when starting cold, it takes cycling the glow plugs a few times so it starts smoothly, otherwise it starts very rough with lots of smoke.

So a couple things: it has had a replaced #22 head and at same time new
Monarch glow plugs. Also new delivery valve seals. This was in 2014 and only driven it maybe 20,000 miles since, and the car has been sitting for a couple years and now I'm driving it again.

First thing after the long hibernation was doing a diesel purge and that did not change anything except while doing the diesel purge the engine ran pretty quiet.

A couple things I'm wondering:

Should I try re-torquing the delivery valve seals? Perhaps at least try cracking each injector line one-by-one to determine if it changes any symptoms?

The other thing is I'm pretty sure the glow plugs that I used were for the earlier head. Should I have used later model plugs for that newer #22 head?

BTW the installed pre-chambers were from the old #14 head if that makes a difference.

1987 300SDl #22 head
240,000 miles

Quote:

Originally Posted by Dudernio (Post 3872440)

rough idle sounds like injector noise, only at low RPM from idle to 1000 RPM

also when starting it cold it takes cycling the glow plugs a few times so it starts smoothly, otherwise it starts very rough with lots of smoke.

So a couple things: it has had a replaced #22 head and at same time new
Monarch glow plugs. Also new delivery valve seals. This was in 2014 and only driven it maybe 20,000 miles since, and the car has been sitting for a couple years and now I'm driving it again.

Fist thing after the long hibernation was doing a diesel purge and that did not change anything except while doing the diesel purge the engine runs pretty quiet.

A couple things I'm wondering:

Should I try re-torquing the delivery valve seals? Perhaps at least try cracking each injector line one by one to determine if it changes any symptoms.

The other thing is I'm pretty sure the glow plugs that I used were for the earlier head. Should I have used later model plugs for that newer #22 head?

BTW the installed pre-chambers were from the old #14 head if that makes a difference.

1987 300SDl #22 head
240,000 miles

Cracking injectors for cylinder contribution is a good step.
Try that. Whichever cylinder doesn't react or reacts weakly is the issue.

The glow plugs required follow the prechambers so they are a bit longer if the #14 prechambers were used. Can you test your glow plug relay and test ohms for your installed glow plugs to ensure everything is working.

Make sure you don't have any air ingress anywhere. I just went through a mind-numbing chase in my SDL where the very first start of the day was really rough with a CLOUD of white smoke. Upper O-ring on the fuel filter banjo bolt was pretty gnarly looking and appears to have been just enough of a leak to let the fuel system get aired up over night, but only enough to cause a rough start.

With that brand of glow plugs. I would check them out carefully first. There for all practical purposes is only one brand to buy and Monark are not it.

I would be surprised if someone got twenty thousand miles out of a set. Personally I consider it a waste to install other than bosh. Even they could create issues but just not as likely at that milage.

Plus you risk the tips swelling on off brand glow plugs. No off brand glow plug ever got a decent reputation and they have been marketed for a very long time. There is another brand that is good as well but not available usually.

All men are not created equally. Nor are glow plug brands.