Steve/Gilly/Techs....Help! - PeachParts Mercedes-Benz Forum

mithra · #1 03-31-2003, 11:39 AM

It is one of those days....try to edit my post and end up closing them...@#%$

The problem...1993 600sel, the car acts like it is flooding...local dealer is saying it is the OVP... I was on cruise at 120kmh, a couple of hours into trip across province, car surged, settled down. A few minutes later the engine surged again, the fuel consumption meter pegged at its highest and stayed there... no warning lights, no overheating, oil pressure normal. The car will start and idle no problem, misses(bogs) on slight acceleration, accelerates normally at WOT. Fuel consumption is astronomical. Blue/black smoke on acceleration, smell of fuel rich exhaust. Any help would be appreciated... Thanx

Gilly · #2 03-31-2003, 11:42 AM

Can you do a scan for codes?
Any malfunction lights on the dash?

Gilly

mithra · #3 03-31-2003, 11:52 AM

Gilly, there are/were no warning lights at all, everything on instrument panel is normal. The check engine light IS functioning during the prestart sequence, goes out on start up. I called local dealer ( in this town) and he indicates that it may be the OVP. Is there any thing that I can check for?

mithra · #4 03-31-2003, 11:54 AM

Gilly, in addition, the only thing different on the dash; the fuel consumption meter is pegged wide open at any speed and does not come back under deacceleration as it normally does

Gilly · #5 03-31-2003, 12:21 PM

The high fuel consumption and smoke would seem to indicate the fuel/air ratio is incorrect. Along with the surging problem, I'd tend to think along the lines of a bad throttle motor assembly, but this is just a guess. A fairly common problem could be a mass airflow sensor. Doesn't really sound like the OVP to me, but maybe the people you are talking to have seen these symptoms with a bad OVP and I haven't. Possible I suppose. If you can find the OVP (I am unsure of the location of it on this model, but I'd start in the area of the right rear corner of the underhood area) you can check the fuse on top of the relay.
Very unusual no code situation (no warning light) if the problem would be either the throttle motor or MAF.
possibly check the rubber "elbows" where the air flow enters the intake manifold to make sure they are tight and no cracks in the rubber.

One thing you can try is pulling off individual spark plug boots (just one or two on each side) to see if it affects operation of the engine. This way you can be sure that both banks are operating. The engine will actually idle pretty good on just one bank, but of course you expect BOTH banks to be operating. If pulling plugs on one side of the engine affects the idle, and not the other, then you know you have a bank shut down. There are individua control systems for each side of the M120 motor, it kind of operates like 2 inline 6's. Like 2 M104 engines to be exact.

Gilly

mithra · #6 03-31-2003, 02:26 PM

Gilly, sorry for the delay on the response.... I will check the car out later this afternoon as you suggest and post the results... Thanx for taking the time out of your day to offer the suggestions. Being away from the home port and in a bit of a panic.... its nice to know that you are there to help. Again thanx

mithra · #7 03-31-2003, 02:36 PM

I don't know if this would play a part in this problem; but I put a new battery in the car last Friday. Coincidence? It is the MB battery.

Gilly · #8 03-31-2003, 04:08 PM

This question probably doesn't matter, but WHY was the battery replaced?
Would you say this problem started immediately after the battery replacement, or a few days after? If it happened immediately after battery replacement, than it's likely related to it. if it took a few days for this to happen, then probably not a factor.
I'm curious if you have a "check engine" light yet, it may take a short time for the light to activate. I'm assuming (possibly incorrectly) that the engine control system (diagnostic module especially) are identical to a US version car.

Gilly

mithra · #9 03-31-2003, 04:22 PM

Gilly, I replaced the battery last Friday along with the battery for the sl, only because of their age, 5+ years for the sel, original for the sl (10 years). Interestingly enough, I had not driven the sel since the battery change, until this morning. I just went outside (within last 5 minutes) to leave from my client's place to go to the motel, the 600sel will roll over (crank) very well, but no start... Now I can't even try your suggestions.

mithra · #10 03-31-2003, 05:07 PM

I have checked the fuses in the base module... they all appear good....car cranks but no go...suggestions? This morning when the problem appeared, I actually stopped and restarted the car a couple of times, now that the car has sat for the day, it wont start.

Gilly · #11 03-31-2003, 05:57 PM

You need to be able to check to see if the fuel pumps are running and if there is fuel delivery to the rail, and also if you have spark at the spark plugs. Once you know this, then it would be a question of if you are getting the correct amount of fuel, if the throttle motors are operating, and if the spark timing is correct.
We can assume you have engine compression, as a sudden loss of compression is usually preceded by some REAL expensive sounding noises under the hood.

Gilly

mithra · #12 04-01-2003, 12:09 PM

Gilly, to keep you posted/updated... I asked my client to run me by the local MB dealer, and I picked up a fresh set of sparks. As you suggested to check for spark; I thought, "heck, I'll just install a new set to be sure." I installed them in his parking lot (embarrassing), took less than 30 minutes.
Turned the key, and the car started instantly, ran smoothly. The plugs that were removed had gaps that were about twice the opening of new plugs, and the center electrodes were substancially worn away.
There was about 60,000km (40, 000 mi) on these plugs since I last changed them. Until I got this car, I had been driving vehicles with extended plug life intervals (100, 000mi), and never really thought about plug life for this car.
I will be getting the manual out now and reading up on what I should have before.(maintenance intervals).
I will get the oil changed here, and have my home dealer read the codes for faults (when I get back to home base).
Judging from the wear on these plugs, they look like a high wear rate item (in this car anyway).
The plugs from the driver's side bank were black, wet and gassy smelling.
The plugs from the passenger side were a dark tan colour (like leather) and dry.
On startup (just now), no exhaust smoke, no smell (fuel or otherwise), smooth idle, quick response to the throttle, proper idle speed.
Gilly, thank you very much for taking the time out of your schedule to help sort this out for me, and keep me mobile.

mithra · #13 04-01-2003, 01:51 PM

Well, it's kind of hard to blame anything or anyone but myself for the panic and grief that I just put myself thru..... ...
I have in my hands, as I type, the maintenance booklet for the car.
Ahem, .... every 15000mi (24000km) Check spark plugs. Replace if necessary.
every 30000mi (48000km) Replace spark plugs.

Considering that there was a minimum of 60000km on the plugs, it's no wonder the car acted up and didn't want to run.

My face is red.

Again thanx, Gilly.

Gilly · #14 04-01-2003, 08:29 PM

Yeah, those big 'ol 12 holers can be real foolers, run real nice and smooth and powerful. Until, as you experienced, they just puke right out on yah, not much warning that they're getting "sick".
You can drop a whole bank and not really notice it all that much, runs pretty good on one bank. That's probably what has been going on, and now the "good" bank wanted some attention as well. ONE of the banks has to run! LOL!
It's real nice how they have that engine set up as far as getting to the plugs. Hardest part of the whole job is carrying all those plugs to the engine. Getting used to it though with these twin plug engines.

Gilly

mithra · #15 05-08-2003, 01:52 PM

Gilly, the car ran perfectly after the change of sparks until yesterday. I am motoring across the 401 to the same client where the issue first manifested itself, low and behold doesn't the car start acting up again. I'm beginning to think this client is hexxed. I pull into a service area, turn the car off, go inside to use the facilities and try and figure out WTF is going on. After about 2-3 minutes, I head back to the car, as I am exiting the building I notice black smoke billowing in the parking lot. Then I realize that the car is trying to barbeque itself. I got the car started and pulled it away from the other parked cars to a wide open area, shut it down, and headed for the back of the car. Got the trunk open, and grabbed my favorite "Mountain Gear" pullover and began to beat the flames out (rear bumper cover). In the background, I can hear "click, click, click" as I am doing my damndest to save the wax and polish job that I had done on the weekend. I get the fire out, turn around, and here are people off a tourist bus getting some neat vaction pictures for their collection. Total damage... one rear bumper cover, one pullover. Floated the car to the local dealer. Dealer's diagnosis.. one MAS gone wonky (passenger side which governs driver's side bank). Dealer indicates that when the MAS goes south, it fails to full fuel. The ambient outside temperature was higher yesterday and probably contributed to the correct mixture for combustion, the first time the ambient outside temperature was near freezing probably preventing a fire that time. Dealer indicates that the cost of the bumper cover and paint will be considerably more than the MAS. I guess the part that gets me is that the MAS worked alright after the initial change of plugs, and did not act up in any way, shape or form, until yesterday.
Anyway, the car is apparently fixed mechanically now, and just waiting for the cosmetics to be repaired. I am at the other end of the province with the wife's sl; I best not scratch, dent, or burn this one.
Mithra.