Clogged trap cataylist symptoms - PeachParts Mercedes-Benz Forum

stephenc03 · #1 07-29-2008, 04:52 PM

Last night I parked my 85 300SD with no problems. When I went to start it this morning i didnt crank it long enough and she started but died shortly there after. Since then I have not been able to get her started. I primed the pump and I could feel fuel rushing through the pump. I recently replaced all of the glow plugs with bocsh. She has high cranking rpm and a charged battery. I replaced the starter two months ago with a bosch rebuild. I was having problems with this before the starter went out and after replaceing it I thought that I had fixed the problem. Acording to mercedes dealership the trap oxidizer was replaced in 97 with 100,000 less miles on it then she does today. What are symptoms of a clogged trap cat? She idles realy good and up until yesterday had power accelerating. If it wern't for the fact that she idles good, i would check the valves but I have no reason to suspect that. After the trap cat is replaced has anyone ever heard of them clogging up again? When I crank her she puffs out a thick "dry" soot. I also do alot of town driving...barley enough time for the car to warm up...but I have only put a thousand or so miles on her since I got it.
-Stephen

Jeremy5848 · #2 07-29-2008, 04:58 PM

I have not heard of clogging problems with a trap catalyst on an OM617 but it could happen if a car were driven extensively at low speeds, much idling in traffic, etc., and never given the opportunity to burn off the collected soot. There is a factory procedure for measuring the back pressure using a pressure gauge connected to a port at the rear end of the exhaust manifold, just before the trap cat. I don't remember the spec -- the book isn't in front of me -- but an excessive back pressure indicates a clogged trap.

stephenc03 · #3 07-29-2008, 05:15 PM

Quote:

Originally Posted by Jeremy5848

I have not heard of clogging problems with a trap catalyst on an OM617 but it could happen if a car were driven extensively at low speeds, much idling in traffic, etc., and never given the opportunity to burn off the collected soot. There is a factory procedure for measuring the back pressure using a pressure gauge connected to a port at the rear end of the exhaust manifold, just before the trap cat. I don't remember the spec -- the book isn't in front of me -- but an excessive back pressure indicates a clogged trap.

I recall some one mentioning that port on the manifold before. I think some one said that if there is alot of carbon and such in that area after you take the bolt off....it is an indication of a clogged system. I s this correct?
-Stephen

Jeremy5848 · #4 07-29-2008, 07:13 PM

I have not heard that, but it is possible. The pressure test is the key. FSM says 1.3 bar is the limit (about 19 psi). More than that = clogged trap cat.

LUVMBDiesels · #5 07-29-2008, 07:59 PM

Make sure that the shut off valve is not stuck. Unplug the vacuum line to it and try again.

stephenc03 · #6 07-29-2008, 08:02 PM

Quote:

Originally Posted by LUVMBDiesels

Make sure that the shut off valve is not stuck. Unplug the vacuum line to it and try again.

i never thought of that...does this happen often? how do I replace it if it is the culprit?

stephenc03 · #7 07-29-2008, 08:39 PM

I got it started but was unable to test to see if it was the fuel cutt off valve. After it started it had a big cloud of grey smoke. It didn't smell like diesel though. It smelled very chemicaly if that makes sence. Has anyone experienced this before? thanks, stephen