I had similar situation recently, high idle RPM was the cause of no effects.
I had almost 1000 instead 750-800, when adjusted to 750 things got better
with new gold pin.

p.s as I have been told new nozzles also need some mileage to settle fully


cheers

.

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w126 500SEC gen II euro, powered by OM617 turbo stolen from 84 300SD 2.88 diff,EGR blinded
next wish/project: w114 coupe OM603 powered

Water or other contaminate in the fuel may have damaged some injector pump elements. As the injection pump warms up and the fuel thins a little pop off pressure or fuel quantity may not be enough from one or more of the elements.

I would give the injection pump a good soaking internally with either laquer thinner or acetone . It could be pretty dirty in there and that may have some undesired effect as well.

This will not help a worn element though. Make sure the fuel is returning from the return line on the injection pump as well. This aids in cooling the fuel.

If you started the car in the driveway and let it warm up. If the idle problem started then. I would attempt to cool down the injection pump. Or do the test again keeping the injection pump cool at least until the engine would normally start the roughness.

Really though you should have a fuel pressure gauge installed and look for air ingress into your system after the warm up period first of all. Those common things can cause issues like you are mentioning.

yeah i didn't think about the lift pump maybe being the problem; i'm gonna get the rebuild kit and see. this engine only has about 70,000 miles on it so i'm hoping it's not anything related to the IP. i tried playing with the idle: if i set it at ~550 the engine will stall after being revved (but doesn't shake); if i set it at ~900 i get run-on (not returning to idle) but the engine doesn't shake. so now i have it set at ~750 but it shakes. if i decide to soak the IP in acetone how long should it stay in there without doing any damage? i think there is only one rubber part inside of my IP if i'm not mistaken; wondering if the acetone would damage to that? thanks for all the suggestions and sorry to the OP, i didn't mean to hijack the thread

How is everybody adjusting the idle? Is it just the screw that the throttle linkage hits when no throttle is applied?

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1982 300D Turbodiesel, daily driver. Mods so far: Fram 8038 paper filter, 4 brake light mod, Gen II w126 (front) rotors/calipers, boost turned up to 12lbs, non-egr manifolds, water/methanol injection, 4-speed manual
1980 300SD Turbodiesel, project car, nearly ready to hit the street

1974 240D, New paint

the big slotted screw that sits behind the IP, you have to loosen the 14mm nut first, then turn the screw clockwise for more idle. sometimes the idle screw is kinda rusty so spray it down with PB blaster (otherwise the screw will turn while you're trying to lock in the 14mm nut)

Ok thanks, I was just wondering because my car idles really high, about ~1000 rpm or so. My car is also starting to get a good shake to it when its idling (after it warms up, also it has good motor mounts so I know that's not the problem) so I guess I need to look into adjusting the rack damper bolt as well.

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1982 300D Turbodiesel, daily driver. Mods so far: Fram 8038 paper filter, 4 brake light mod, Gen II w126 (front) rotors/calipers, boost turned up to 12lbs, non-egr manifolds, water/methanol injection, 4-speed manual
1980 300SD Turbodiesel, project car, nearly ready to hit the street

1974 240D, New paint

I was not specifically thinking about the life pump being the culprit. A pressure gauge is much more useful than a rebuild of the lift pump right now with no absolute indication that it is needed.

Doing so is part and parcel of the shotgunning approach to troubleshooting. Most of the time an expensive and frustrating way to procceed overall. If the engine and accessories really only have only 70k on them. I would really spend some time to make absolutly sure air is not an issue first of all. Actually regardless of milage i would do so.

You may have some reading in the archives ahead of you. It can be productive in expanding your knowledge. On any diessel it is normal to always change out the fuel filters with any indication of fuel related problems. A pressure gauge installed avoids the cost as it tells you if flow volume is there. It takes a 0-30 pound liquid filled gauge fed from the area past the main fuel filter and the injection pump. On a car burning alternative fuels like wvo especially I would consider it a long term cost saving requirement. Personally I would not leave home without it.

Any pictures of where to install the gauge, or links to well built gauges suitable for the application?

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1982 300D Turbodiesel, daily driver. Mods so far: Fram 8038 paper filter, 4 brake light mod, Gen II w126 (front) rotors/calipers, boost turned up to 12lbs, non-egr manifolds, water/methanol injection, 4-speed manual
1980 300SD Turbodiesel, project car, nearly ready to hit the street

1974 240D, New paint

There is a chinese 0-30 pound fluid filled and dampened gauge that has reasonably good quality for about 10.00 at harbour freight and other places. It is the one that probably 90 percent of the guys that have used one buy. There is further information in the archives as well.

yeah i was tired when i wrote that, i don't like to just throw parts at a problem. now i did check the pressure coming out of the IP a few months ago (i think i tied in on the back after the check valve- please forgive me i have memory problems from time to time); i didn't have a liquid filled gauge, but it did read 19 psi at it's highest pulse which is what the spec called for i believe but i know i need to get a liquid filled gauge to make sure. can i just tie in a gauge right after the primary filter or was the way i was checking it correct?

What did you do to adjust the damper bolt? I just fixed the identical problem on my car a few days ago.. by giving the damper bolt about a 5 degree turn deeper into the pump. That's a very small change that completely eliminated the issue, so the IP can be very, very sensitive to getting the bolt just right. I don't even have the upgraded, gold colored bolt either.

So, yes, if you think you might need to fiddle with the bolt a bit more, you might have to -- you could have the bolt set wrong by that small of a change, and cause the problem.

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'83 300DTurbo http://badges.fuelly.com/images/smallsig-us/318559.png

Broadband: more lies faster.

Each engine seems to vary, my brother's 300D idles perfectly smooth around 650....I have mine set in the 700 vicinity to get its sweet spot with no shaking. My dad's 83 SD we had to bring up close to 900 to resolve the shaking. His current one idles at around 650 but shakes....still have tuning to do on that one.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Mine shakes like a dog trying to dry off!! When it was at 1000 it wasn't too bad, just adjusted it down to ~750 the other day and it is pretty terrible. Adjusted the rack damper as tight as it will go, and it didn't seem to make much of a difference, so I guess that means I need a new one :/

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1982 300D Turbodiesel, daily driver. Mods so far: Fram 8038 paper filter, 4 brake light mod, Gen II w126 (front) rotors/calipers, boost turned up to 12lbs, non-egr manifolds, water/methanol injection, 4-speed manual
1980 300SD Turbodiesel, project car, nearly ready to hit the street

1974 240D, New paint

First of all make sure all the cylinders are firing a idle if that rough. Well our dog has a middle length fur coat.

I agree. However, mine would "lope" at exactly the right tempo to mimic a missing cylinder. On mine, I know one of the cylinders has slightly lower compression than the rest, so I've been convinced for years that the car was actually missing on that cylinder instead of being a rack damper problem. Now I suspect that cylinder fired just a little differently than the rest and set the insufficiently damped rack into a "lope".

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'83 300DTurbo http://badges.fuelly.com/images/smallsig-us/318559.png

Broadband: more lies faster.