91 sdl idle problems - PeachParts Mercedes-Benz Forum

madsen · #1 09-03-2019, 05:55 PM

I have a 91 sdl with poor idle and have been reading that it is supposed to have an electronic idle adjustment to set the idle higher.I have seen the pictures but I have no such adjustmwnt knob anywhere near the fuse box. Does my car not have this ? Off idle it runs good with no shake and minimal smoke.
I am considering turning up the adjustment of the idle on the actual IP ITSELF ?
Am I crazy blind or correct ?
Please help !
Thanks in advance
John

Diseasel300 · #2 09-03-2019, 07:14 PM

90/91's don't have the adjustment wheel. What is your engine idling at? If the EDS system is working, it should be ~650 RPM in park. If you disconnect the plug from the big red round thing on the back of the injection pump you should have the RPM drop.

You haven't mentioned if you have serviced the injectors, fuel filters, or glow plugs is the recent past.

jbach36 · #3 09-08-2019, 10:44 PM

Pour some enzyme stuff in the tank, or the tank strainer could be clogged but then you'd have problems with fuel all the time like when accelerating or going up a hill.

Have you changed your fuel filters?

Do you use a fuel additive to help lube the injectors?

madsen · #4 09-15-2019, 07:11 PM

So it turns out some of my idle problem was a broken injector body.
I sent the injectors of to mark AKA Greazzer and he tells me one of my injector bodies is broke and I need a replacement
I need at least a body. he thinks all the pintles will clean up and be ok.
Any one have a line on a used but serviceable injector for a 603 engine ?
John

Diseasel300 · #5 09-15-2019, 08:06 PM

Good luck. The inclined/angled/oblique injectors aren't common. You can buy a Bosch reman from the sponsor on this site and send the cracked one back as a core. I had to resort to that earlier this summer for the same reason.

You must specify which type of injector you want when you're asking for used. You need the one for the OBLIQUE injection (also known as angled or inclined). The earlier 617/603 injectors for the vertical injection prechambers will NOT fit your engine.

Squiggle Dog · #6 09-15-2019, 10:26 PM

Quote:

Originally Posted by Diseasel300

You must specify which type of injector you want when you're asking for used. You need the one for the OBLIQUE injection (also known as angled or inclined). The earlier 617/603 injectors for the vertical injection prechambers will NOT fit your engine.

Really? Then this might effect what head number I'm able to use on my roommate's car. The injectors are on an old #14 head, and have already been rebuilt.

Diseasel300 · #7 09-15-2019, 10:42 PM

Quote:

Originally Posted by Squiggle Dog

Really? Then this might effect what head number I'm able to use on my roommate's car. The injectors are on an old #14 head, and have already been rebuilt.

Yes. The '86/87 603's used the 617 style injectors with vertical injection. The '90/91 (and 602 turbos) use the oblique style. You can use the early style in a later head if you swap the prechambers and swap the hard lines over.

madsen · #8 09-16-2019, 07:08 PM

So I was working on getting the injector nozzle seals out of the prechamber and at least one had 2 seals in it.
what does the bottom of the prechamber look like ?
Mine appears to have another injector seal
The hole might be slightly larger than on the seal
I had to grind the head off of a long 16 p nail and use it to pop the seals out.
have a number 22 head on this motor if that makes any difference in how the bottom of the prechamber looks.
TIA
JOHN

Diseasel300 · #9 09-16-2019, 08:04 PM

The "bottom" of the prechamber is basically just a beveled area with a hole in it.

madsen · #10 10-01-2019, 03:05 PM

Ok
So I got my injectors back from Mark. Thanks Mark for the great service !!!!
The injectors are installed and torqued and new clear return lines installed.
There are no leaks but I still have the same poor idle and unburned diesel smelling smoke. All the return line are clear and I have air in them.The amount of air in the return lines has gone down alot with 15 minutes of running but the idle and smoke level stay poor.
I checked all the glow plugs while the injectors were gone and one was bad so I changed that one out.
It clears up considerably when get rpms up to 1500 plus.
My next thought is replace all delivery valve washers and o rings.
There is no leak from them but I do have the parts on hand
The fuel tank vent is clear. All the filters are new. The clear fuel filter has no air bubbles in it. Getting the motor up to temperature made no difference

Any thoughts or ideas ?
No obvious leaks from the tank forward to the motor.
TIA
John

Diseasel300 · #11 10-01-2019, 03:52 PM

My '91 350SD would lose a cylinder at idle. A very obvious skip that would go away above 1000 RPM. If you've ruled out compression problems, the DV service is done, and you have no other obvious problems, the delivery valves themselves may be worn out. Replacing the DV's in my car was the cure for my problem, it went from idling like a rock crusher to smooth as glass, sometimes you think it stalled at a stoplight, but no, it's just running smooth and quiet.

madsen · #12 10-01-2019, 04:40 PM

So what does the replacing delivery valves involve?
Sending the IP out to be checked and repaired ?

I have not yet done the o rings on the DV seals.
Is that a way to go on this problem ?
Or should I be doing other things first?

Is the air in the bypass hoses indicating an issue or just some thing that happens?
I am building an adapter to check compression thru the injector hole by welding an adapter to my cracked injector body.
Thanks for responding
John

madsen · #13 10-03-2019, 01:52 PM

Bump
Anybody ideas on poor idle and smoking ?
John

madsen · #14 10-26-2019, 07:51 PM

ok so finally got back to working on the car. Got the delivery valve seals all replaced. No change in idle or smoke level. So today I replaced all the fuel lines and rebuilt the fuel heater, Actually just changed the o ring seal on it. What a pain. Still have the poor idle but it does not immediately idle poorly. But after running at like 2500 rpm and the letting the throttle off it slowly starts to idle bad and the smoking gets worse. I would say that I have improved the idle significantly from where it started but it certainly is not idling like it can or should.
I still have the air in the overflow lines coming off the injectors so I have air getting in somewhere maybe ???.
It was really hard to get it to start after replacing the fuel lines and putting the o ring in the fuel heater. Had to recharge the battery a few times because I cranked it so long the battery died. I tried bleeding each fuel line at the injector with it running at 1500 rpms, Seemed to not clear any of the air in the overflow lines.
I need some ideas of what to check next ???
JOHN

madsen · #15 10-30-2019, 11:51 AM

Well I finally found the problem. After being urged to put on a clear fuel line I put two on and found that my lift pump is leaking and I have other leaks from fuel lines I assume because it seems to intermittently show large amounts of air in the return line off the secondary filter going back to the tank.
So the plan is to purchase metric fuel lines and proper style clamps and have no old fuel line from the primary filter forward.
I have also sent DISISEAL300 AN EMAIL Hoping he has more of the o rings for refurbishment of the lift pump.
Not my best moment as a backyard mechanic by haphazardly fixing things and shooting the parts bazooka only to get back to doing the obvious and necessary easy repairs first.
Of course I am hoping that this will be "THE FIX"
JOHN