87 300TD Wagon question - PeachParts Mercedes-Benz Forum

lovethydiesel · #1 06-13-2007, 04:47 PM

Hi, and thanks for looking at my first post on your forum. I could really use your help on this. I would like to know if my injection pump has a rack dampner screw like the MB '83 SD. From another forum I gathered that this screw could be the cause of an idle roughness that doesn't smooth out when the engine warmed up. I first noticed my idle roughness when I pulled into a rest stop after a few hours of hard driving. So I did a lot of stuff to see if I could fix it; pop tested my injectors, ran a diesel purge, new timing chain, new fuel filters, did a compression check. None of that fixed my idle roughness, although it did help my starting and fuel economy. It wasn't until I read about someone's 83 SD with a rack dampner screw that I new I had to determine if my car has one, and if so would I be able to replace it myself without any special tools and such. Thank you for your interest and best of luck helping me out.

deanot442 · #2 06-13-2007, 09:50 PM

Quote:

Originally Posted by lovethydiesel

I would like to know if my injection pump has a rack dampner screw like the MB '83 SD. )

nope, no dampner screw on the 87.

are there any other symptoms associated with the rough running (all guages working, all fuses ok, any electronics disabled under the hood...?)

lovethydiesel · #3 06-15-2007, 04:00 PM

I started to go through my list of maintance again. Since it had been 5,000 miles since I inspected my injectors, I decided to pull one at random last night and found a deposit of carbon on the end of it. Pretty black and thick. I had a new one on hand, and put it in. The idle remained rough with the new injector in it. I would like to go through the rest of the injectors this weekend and see about carbon. Which I hear can be scrapped off with a wooden paint stir stick. I may even try to R&R them, but I admit I have never taken one of these apart. Anybody like to tell how that should be done correctly? Please, include torque specs if you would.

Thanks

justinperkins · #4 06-15-2007, 04:16 PM

You should take your injectors to somebody who knows how to rebuild/test them and has all the tools that one would need.

Order yourself the service manual from MB for torque specs.

oniondip1 · #5 06-15-2007, 11:07 PM

Have you had your compression tested? How many miles on the car?
If there is a big compression difference between cylinders it could cause a rough idle. If this is the case it may be something you have to live with or rebuild it. The 87 has an electronic idle control which could also be responsible I think. Someone with some more 603 experience may be able to tell you.

#6 06-15-2007, 11:55 PM

Quote:

Originally Posted by justinperkins

You should take your injectors to somebody who knows how to rebuild/test them and has all the tools that one would need.

Order yourself the service manual from MB for torque specs.

or torque them as hard as you can, that works good too. not with a breaker bar though. just "really tight". and new heat shields.
and there is a relay-like thing with a 10 or so amp fuse on top near the window under the hood that regulates voltage to the battery and that can break and cause weird idle too. it has a name, some nerd will know

777funk · #7 08-28-2007, 09:58 AM

On the 603 IP there is something that controls the idle mechanically that most people don't ever mention on this forum. It's got a lock nut and an adjustment screw much like the rack damper. It's close to the ELR electronic Idle keeper plug. Look in the FSM on injection system and it talks about this.