Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help

Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Tech Help

LinkBack Thread Tools Display Modes
Old 02-20-2017, 05:28 AM
Registered User
Join Date: Jan 2014
Posts: 45
I'm starting to think I need to replace my injection pump: (

I know it's a rare problem but I'm not sure where else to look. I've got a best beautiful 81 300d. It's got 125k and by the look of the rest of the car I think it's been well cared for, I even have original purchase receipt from Lubbock Texas. From the time I bought it about a month ago it's shaken like a paint shaker and I cant seem to get idle to lower enough by adjusting idle adjustment. I'm not sure what it is but it's obviously a little high and when in drive it wants to push the car almost. I've changed both fuel filters, changed injectors with another set off another car(and new heat shields, did valve adjustment, I checked injection pump timing and it's good, engine compression check showed even in all cylinders, engine mounts replaced, it also has vibration driving down highway slightly. I don't see air bubbles in the hard lines. What else can I check? I'm running out of ideas. Not my first one. I've also got a 240d and used to have a 300sd with an odometer that stopped at nearly 300k. That car ran great! I was really excited about this one. It's a beautiful car

Reply With Quote
Old 02-20-2017, 10:51 AM
Registered User
Join Date: Jun 2013
Location: PNW
Posts: 242
Get the factory service manual and read it. These have instructions for TESTING various systems to find problems. That is MUCH less expensive than randomly replacing parts.

Also if just replacing parts trying to fix a problem, you can introduce new problems which can turn the car repair into a nightmare! Something may be the wrong part or not be installed properly.

And it is typically less expensive to take your car to a mechanic than to replace a bunch of parts. I know a guy who spent $1500 replacing parts and problem not solved, so he sold the car. The new owner took it to a mechanic and the cost was $300.
Reply With Quote
Old 02-20-2017, 01:29 PM
sixto's Avatar
smoke gets in your eyes
Join Date: Jun 2000
Location: SF Bay Area
Posts: 20,797
Have you done things like having the injectors serviced (forum member greazzer offers this service) and a compression check? Does it run like this all the time or only when cold or at temperature? Is it easy to start?

83 300SD
98 E320 wagon
Reply With Quote
Old 02-20-2017, 01:51 PM
Registered User
Join Date: Jan 2014
Posts: 45
Well I haven't randomly replaced parts yet except the injectors which I had already. The other stuff was just service that I figured I should be doing anyways, I replaced the engine mounts cause they needed it. Yes did a compression check and even in all cylinders. Haven't had injectors services. Might be cheaper to just build an injector tester from a bottle jack I guess. But the fact I replaced injectors and didn't change has me thinking it's not that. It doesn't matter if the cars warm or cold. Does it all the time at idle and feel a little engine vibration even down the road. But it does smooth out significantly at increased rpm.

Just to be clear this is a very bad shake. The hood shakes when closed at idle.
Reply With Quote
Old 02-20-2017, 02:01 PM
Registered User
Join Date: Jan 2014
Posts: 45
Oh and yes it starts up easy.
Reply With Quote
Old 02-20-2017, 03:33 PM
Senior Member
Join Date: Nov 2002
Posts: 736
sounds like the idle rack adjuster is worn. google it for more info. good luck, chuck.
Reply With Quote
Old 02-20-2017, 07:52 PM
Registered User
Join Date: Jan 2014
Posts: 45
No rack adjustment on 81 non turbo. That's the first thing I thought to
Reply With Quote
Old 03-05-2017, 12:00 AM
300E Portline
Join Date: Mar 2017
Location: Denver, Colorado
Posts: 7
You replaced injectors with more bad injectors. Bad pumps -- all run lousy.
Reply With Quote
Old 03-13-2017, 04:38 PM
Diesel Preferred
Join Date: Oct 2007
Location: Charleston SC
Posts: 2,735
I'd recommend that you try to diagnose by loosening each injection line slightly to stop that injector from working, see if the idle is affected, and then tighten the line up and move to the next line. The lines that do not change the idle quality indicate where the problem is. What you describe is the classic symptom of leaking delivery valve seals (copper washers). The leak is internal - not visible on the exterior of the delivery valve / injection pump. If you can isolate the problem by injector line(s), then you can try moving the injector to see if the problem moves with it. If not, then that delivery valve is suspect.

If you cannot isolate by this method, then you can try rebuilding all the delivery valves with fresh copper seals. Research the procedure - you DO NOT want to mess this up, because then you may need to replace the injection pump.

If rebuilding delivery valves does not solve this, then having all the injectors tested and the pressures reset would be my next recommendation.

If the injectors are all proven good, THEN you may have a problem with the injection pump and should consider getting a rebuilt pump.
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

Last edited by Maxbumpo; 03-13-2017 at 04:41 PM. Reason: Added more diagnostic steps
Reply With Quote
Old 03-13-2017, 04:59 PM
oldsinner111's Avatar
once a happy man
Join Date: Nov 2008
Location: bristol,tn
Posts: 5,774
tank screen,and fuel pressure too.
I created you,I love you,don't love me? burn in hell forever. sounds like a human
Reply With Quote
Old 03-13-2017, 05:09 PM
engatwork's Avatar
Join Date: May 2000
Location: Soperton, Ga. USA
Posts: 12,642
Disconnect the linkage from the injection pump and start it up to see how it idles. That will indicate whether it is the linkage or something else.

Reply With Quote


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

All times are GMT -4. The time now is 12:51 AM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page