85 300SD loss of power - PeachParts Mercedes-Benz Forum

okrhino · #1 10-14-2011, 07:28 PM

My car has very little power while in drive or reverse. RPMS will not go over 1000 and the car barely moves. If it is in park or neutral the rpms will increase like normal. I have changed the fuel filters twice now and no change. I raised the hood while driving so I could see the throttle linkage and they arm moving and go into the position of wide-open throttle but rpms do not increase. Car has also been hard to start at times I will attempt to start for 2 cycles and then it will start fine but usually the 1st cycle it will turn over but no start until I recycle it again. The car recently was not used for 2-3 months related to a locked up ignition but I fixed that and now I am having these problems. 3 months ago prior to the ignition lockup the car ran fine with normal power.

Any ideas where to start or trouble shoot?

Thanks

Any help greatly appreciated

vstech · #2 10-14-2011, 08:26 PM

I would remove the alda and see if you get an improvement.

bigblockchev · #3 10-14-2011, 09:37 PM

With an ignition switch problem I am wondering if the Shutoff lever is being pulled partway down. Disconnect the vacuum line on top of the IP to check, couldn't be cheaper or easier. Push down the lever to stop the engine after checking. Just a thought. Cheers Dan

tyl604 · #4 10-14-2011, 09:50 PM

Did the vacuum line come off the switchover valve? Valve is located on the fender well or the firewall. If it goes bad (clogged up) or the vac line comes off, you will have a very hard time getting RPMs up.

okrhino · #5 10-14-2011, 10:22 PM

Thanks for all of the suggestions.

I am just a rookie when it comes to the DIY but I am learning. I just have a few questions for you guys.

1) What is the "ALDA"? Where is located? What does it look like?

2) What is the "IP"? Where is it located? What does it look like?

3) What is the switchover valve? Where is it located? What does it look like?

Thanks again and sorry for the basic questions.

ROLLGUY · #6 10-14-2011, 11:59 PM

Quote:

Originally Posted by okrhino

Thanks for all of the suggestions.

I am just a rookie when it comes to the DIY but I am learning. I just have a few questions for you guys.

1) What is the "ALDA"? Where is located? What does it look like?

2) What is the "IP"? Where is it located? What does it look like?

3) What is the switchover valve? Where is it located? What does it look like?

Thanks again and sorry for the basic questions.

1) What is the "ALDA"? Where is located? What does it look like?
It is the square-ish looking unit on top of the IP (question 2)

2) What is the "IP"? Where is it located? What does it look like?
Stands for "Injection Pump" The aluminum bodied unit on the left side of the engine with five metal tubes, one going to each of the five injectors.

3) What is the switchover valve? Where is it located? What does it look like?
I think they mean the overboost protection valve. It is a little solenoid with 2 clear plastic tubes: one coming from the back of the intake manifold, the other going to the ALDA. Both are connected with "banjo" fittings (you will eventually ask what a banjo bolt/fitting is). The banjo bolt on the manifold side (12mm wrench) gets clogged with carbon, and will not give a proper boost signal to the ALDA. The overboost protection valve may be clogged, or inoperative as well (preventing boost signal).

ROLLGUY · #7 10-15-2011, 12:02 AM

Quote:

Originally Posted by okrhino

My car has very little power while in drive or reverse. RPMS will not go over 1000 and the car barely moves. If it is in park or neutral the rpms will increase like normal. I have changed the fuel filters twice now and no change. I raised the hood while driving so I could see the throttle linkage and they arm moving and go into the position of wide-open throttle but rpms do not increase. Car has also been hard to start at times I will attempt to start for 2 cycles and then it will start fine but usually the 1st cycle it will turn over but no start until I recycle it again. The car recently was not used for 2-3 months related to a locked up ignition but I fixed that and now I am having these problems. 3 months ago prior to the ignition lockup the car ran fine with normal power.

Any ideas where to start or trouble shoot?

Thanks

Any help greatly appreciated

Could be a clogged muffler, or if it is a California car, the trap oxidizer (CAT converter) could be clogged.
I doubt removing the ALDA will help with this problem, but the vacuum shutoff could be suspect (as stated above in post #3). The shutoff is located on the rear of the IP. It has a brown plastic tube going inside the cab to a valve on the ignition switch. There is another brown tube that is connected to a vacuum source (on the large diameter vacuum line going from the vac pump to the brake booster). By removing the brown tube from the connection on the shutoff valve, you can easily rule this out. If the car revs fine under power, you have found the problem. You are getting an amount of vacuum to the shutoff just sufficient enough to run, but not under load.

vstech · #8 10-15-2011, 09:53 AM

Quote:

Originally Posted by okrhino

My car has very little power while in drive or reverse. RPMS will not go over 1000 and the car barely moves. If it is in park or neutral the rpms will increase like normal. I have changed the fuel filters twice now and no change. I raised the hood while driving so I could see the throttle linkage and they arm moving and go into the position of wide-open throttle but rpms do not increase. Car has also been hard to start at times I will attempt to start for 2 cycles and then it will start fine but usually the 1st cycle it will turn over but no start until I recycle it again. The car recently was not used for 2-3 months related to a locked up ignition but I fixed that and now I am having these problems. 3 months ago prior to the ignition lockup the car ran fine with normal power.

Any ideas where to start or trouble shoot?

Thanks

Any help greatly appreciated

ok, re reading your post it does sound like you have classic clogged banjo bolt issue.
as for the hard to start part, how cold is it where you are?
when you say "attempt to start for 2 cycles and then it will start fine but usually the 1st cycle it will turn over but no start until I recycle it again." are you considering the glow light time as a cycle? that light is simply an indicator that your plugs are working. the actual time the plugs stay on is MUCH longer. if it's cold, it's best to turn on the key, and count to 35 before attempting to either recycle the key or start. you can leave your door open, and listen to the relay click or watch the dome light, it will brighten when the glow plugs have cycled off. then start it, I bet you get MUCH better performance from the starting.

kerry · #9 10-15-2011, 10:18 AM

I'm going with a problem with the shut off valve related to the replacement of the ignition switch. Remove the brown vacuum from the shut off valve at the back of the injection pump down between the injection pump and the oil filter housing and see if the problem goes away. If it does, the source of the problem is discovered. You'll have to shut off the engine with the shut off lever with that line removed.

okrhino · #10 10-15-2011, 02:45 PM

I removed the vac line off of the IP and car drives fine now! Now what do I do to fix this problem?

Thanks again to everyone!!!

okrhino · #11 10-15-2011, 02:54 PM

When I replaced my ignition if I put the 2 vac lines on incorrectly could that be the cause of my problem?

kerry · #12 10-15-2011, 03:04 PM

Yes.

okrhino · #13 10-15-2011, 04:07 PM

I thought if I got the 2 vac lines reversed on the ignition that I would have problems with the car not wanting to shut-off instead of a loss of power like I had a problem with.

auspumpen · #14 06-12-2012, 01:08 PM

Quote:

Originally Posted by ROLLGUY

Could be a clogged muffler, or if it is a California car, the trap oxidizer (CAT converter) could be clogged.

Has anyone here actually experienced a clogged trap oxidizer on an '85 Cal-spec OM617? I ask because I'm working on one at the moment, and it just doesn't want to rev quickly and produce much power. I've tested the ALDA (holds 10psi), and cleared the banjo bolt, and bypassed the switchover valve...but, still no dice. Timing is at 15 ATDC, chain is 1 degree stretch. Unlike the OP, this one will rev up to redline, but it just doesn't do it with authority and feels like it's being held back. I also suspect that the intake is all coked up due to the EGR, so that might be contributing.

The problem is very acute when its cold and gradually gets somewhat better as it warms to operating temp. The trans is also struggling to shift correctly, and the VCV* is dead.

*Can these be opened up safely and serviced? The plastic seems really brittle and there doesn't appear to be an intuitive way to disassemble without prying on stuff needlessly. Does anyone have a known good unit in the Puget Sound area?

kerry · #15 06-12-2012, 02:13 PM

I believe MB has a recall to replace the trap oxidizer on the 85's. There are pictures on here of a disassembled VCV somewhere I think. Maybe Brian Carleton posted them. Be careful, they aren't available anymore (I think) I think the pictures were posted in reference to adjustment procedures.

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