87 300d still low on power - PeachParts Mercedes-Benz Forum

Jim Wickham · #1 04-02-2007, 02:35 PM

My saga continues with my 1987 300d. I've been working with it for about a week. I thought I was being judgemental because my current daily driver is a supercharged Regal GS, but my wife beat me soundly in a 1999 Dodge 2500 Cummins with a 5 speed... she is by no means great with a stick shift.

It is Gutless.

I have done:

* pulled cross over and it was pretty gunky so I cleaned it out good and let it dry, re installed.... no result
* Pulled overload circuit out and hooked boost hose directly to ALDA... no result
* tapped boost line to ALDA and installed boost guage... looks like little to no boost
* Looked at EGR and Air Recirculation Valve, both have been removed from the vacuum system and the vacuum lines that go to them plugged at the connection just above the vacuum pump.
* Noticed Trap has been replaced with a goofy looking pipe that is about 2 inches in diameter (factory retrofit?)
* Pulled the EGR, it is closed. I then started the engine, it seems to rev more freely with EGR off and I can hear the turbo spin.

Any other ideas on what my total lack of power is from?

2.5Turbo · #2 04-03-2007, 01:05 AM

First, check fuel and air filters. You might want to check the tank screen as well just to be sure. Check your wastegate, it could be stuck open. Make sure all the ALDA line fittings are cleaned out, and that all rubber connectors are not cracked and leaking. Not much else on these cars that can cut boost, you've done some pretty thorough testing. What's your 0-60 time? Should be in the neighborhood of 10-11 seconds on a 124 with a 603 motor with stock pump and boost levels. Make sure you're checking your boost under load; just sitting there revving the engine in park won't produce any usable boost.

Also, I think these cars had a cat installed after the trap ox was removed under the factory recall. Be sure it isn't plugging up either.

Knightrider966 · #3 04-03-2007, 01:10 AM

I don't know much about these engines, but I'd check valve adjustment if it's possible on these. Valves out of adjustment will make a BIG difference.

greasybenz · #4 04-03-2007, 02:58 AM

Quote:

Originally Posted by Knightrider966

I don't know much about these engines, but I'd check valve adjustment if it's possible on these. Valves out of adjustment will make a BIG difference.

They have hydraulic lifters....the 603 engines dont need valve adjustments, they do it on their own.

muleears · #5 04-03-2007, 06:49 AM

Is it slow 0-25? Or slow all the way to 70? If it is low speed acceleration, you may want to adjust the alda, made a big difference on my car. My $.02 Hope it helps.

babymog · #6 04-03-2007, 01:00 PM

Could be the shift points, not the engine. Try shifting it manually to see if that helps.

dieseldiehard · #7 04-03-2007, 04:16 PM

Its the Turbo, guys, either the bearings are worn and dragging or the wastegate valve is stuck open.
Forget the ALDA if you see fuel in the pre-filter its not that. Look for why no boost!

Jim Wickham · #8 04-03-2007, 04:27 PM

It's an 87 w/ garrett turbo, how do I tell if the wastegate is stuck?
do I need to disassemble or can I work it from the outside?

Could a plugged cat not allow the turbo to spin freely and thus not build pressure?

Car does rev more freely when I remove the EGR and leave that port open. It takes it two or three seconds to make revolutions to 4K with EGR in place, maybe 1.5 without.

dieseldiehard · #9 04-03-2007, 04:47 PM

"Could a plugged cat not allow the turbo to spin freely and thus not build pressure?"
Oh my God You don't have the Nasty Trap Oxidizer or Trap in it do you? I forgot about that

Yes if the NTO is there TAKE IT OUT and see if it runs!!!!!
I also saw a Trap that was plugged from lack of regular driving (regular menaing heavy footed) - short runs choke these traps and things up!

Jim Wickham · #10 04-03-2007, 04:57 PM

The thing refered to as a "trap" is up in the engine compartment correct? this one is gone and replaced with a piece of cast manifold/pipe thing.

There is also a "cat" underneath. This is still in the car.

Brian Carlton · #11 04-03-2007, 05:02 PM

Quote:

Originally Posted by dieseldiehard

"Could a plugged cat not allow the turbo to spin freely and thus not build pressure?"
Oh my God You don't have the Nasty Trap Oxidizer or Trap in it do you? I forgot about that

Yes if the NTO is there TAKE IT OUT and see if it runs!!!!!
I also saw a Trap that was plugged from lack of regular driving (regular menaing heavy footed) - short runs choke these traps and things up!

He doesn't have the trap Reid, but, the symptoms surely point to a partially plugged cat. The fact that the engine revs faster with the EGR exhaust port exposed surely is a bit of critical information.

I'd disconnect the downpipe and take it for a drive..........see if it's an exhaust restriction in the cat.

Brian Carlton · #12 04-03-2007, 05:02 PM

Quote:

Originally Posted by Jim Wickham

There is also a "cat" underneath. This is still in the car.

This is what I suspect may be partially blocked.

Jim Wickham · #13 04-03-2007, 06:19 PM

I just doublechecked the hose barb that leads to the overload and the alda and its clean through to the inside.

I don't know if I'll get the downpipe off today as I have to go to my wife's mom's house for dinner.

thanks a bunch for the information/advice Brian, and the rest who have tried to help me out. I think I'm going to either know the fuel/induction system on this 603 or atleast have a much better appreciation for the guys who do when I finish getting this thing back to its orginal glory (power).

dieseldiehard · #14 04-04-2007, 12:07 PM

I agree with Brian that the trap (under the car) is suspect.
I had an experience with a 603 that wouldn't even start and it was due to the trap (under the hood) that was completely plugged, I was almost at my wits end, remember Brian?
A replacement to that straight pipe you have on yours was covered under the factory Open Campaign and they replaces it with the trap thing under the car which is actually more like a CAT. Whatever it is, I know they also plug up because the local Indy had a 603 that was running poorly and it was because of a partially plugged Cat/Trap (whatever it is) under the car.
One member recommended cleaning this thing out using a long drill bit until all the matrix is lying on the ground! A rotorooter would suit me just fine!
Cursed things do not do well on diesels especially if not driven hard!

Jim Wickham · #15 04-04-2007, 05:35 PM

boy it looks like everything and everyone is pointing a finger at that thing. I'm disappointed that the weather is nasty here tonight or I'd be out there with my cordless sawsall right now. Could put it in the garage but I'm using the whole thing for a cabinet shop right now. Oh well gotta pay bills before I play with toys. I did insure it today and should have it registered by the end of the week. I really hope this is the fix... I'll be doing a jig, seriously!!!