1995 E300D power issues
 

Hey Guys,

I have a question on my 300D. I tried a 0 -60 run today and it took 33 seconds to reach 60.

The fuel filter has been changed, but I have not yet checked the strainer.
I do not think that the strainer is the problem since this all seems to have started after the tach stopped working. It appears that the OVP is bad and I have not changed it yet.

The question is if the OVP could have anything to do with this. I cannot see how high the engine revs when I floor it and also when stopped at a light it does idle very rough. It seems like not enough fuel is getting there. I know from my SDL that when the ovp is removed the engine starts to idle rougher and lower and you loose a little bit of power.

The o rings on the IP are very dry as well. When i start the car the engine runs rough for about 5 to 10 seconds.

I wonder if all this could be related to the bad ovp?

I'm not sure, but I'm wondering if it's possible a bad OVP is triggering those intake flaps to stay shut perhaps? Can't say for sure, sorry, but I know someone with more 606 knowledge (it's still new to me as well) will chime in and have a better idea.

Also as additional info. I recently bought the car and the tach was working until i started Tig welding on it. After I welded a few spot the tach was not working. More indication that the OVP blew because of the MIG welding.

The 1995 E300D was the most electronic of the 124 diesels; it's entirely possible that something blew up due to transients induced from the welder. If you're lucky, it was the OVP, because it's designed to protect much more expensive items downstream.

The tach not working is certainly a sign of possible OVP failure. Your engine needs the idle speed control (ISC), resonance flap controller, and EGR controller to run properly. Although I can't be positive without wading through a lot of schematics, it's likely that these items all get their operating current via the OVP. Therefore, you should replace the OVP and see if that helps.

Jeremy

Do this first.

I'd be concerned the welding may have caused other electrical issues.

0-60 should be about 12 seconds, this engine really pulls hard once ahead of 2500 rpm. First check the OVP fuses, the OVP provides power to the ELR and EGR controllers, the EGR also controls the intake flaps that tune the manifold depending on engine rpm, if the flaps are shut or dont move your engine will starve for air.

SO I got a new OVP today and put it in. It did not do anything.

The AC compressor definitely never comes on.
The tach does not work.
The flap on the front left side for the recirculation does not move either. Usually that moves back and forth when in idle. When I bought the car this was definitely working.

I am not sure where else to start looking. I do not think that the welding could have caused anything to blow out. I have mig welded so many times on cars and never did it cause a problem. I also do not see why it would cause a problem. The current would not have passed through any electronics.

What do you guys think I should try next. I am not really sure what else to look at.

check the fuses in the fuse box and also check the rpm sensor impedance - its connector is right by the battery.

Also check if any water has been dropping on the control units, it can happen if the windshield tray drains are connected to the pipes that carry it down. If they are not connected the whole electronics section gets flooded. and with a battery living there too check for any acid corrossion that might have eaten any wiring.

I did check there and the are no signs of water getting in. I also checked the fuses and they seem to be alright as well.

Where are some of these cables located that are coming from the OVP. It definitely appears to be OVP circuit related since the typical items stopped working. This just seems strange. I would like to check the cables but do not see any issues.

are the fuses the newer copper style, the original tin ones are quite a nuisance they look perfect but may lose contact due to corrossion.

Let me dig up the power diagram, I think fuse 6 is tied to this system. it should be 16A if memory serves right.

On my way to work this morning the Glow plug light stared flicking on and off. Seems like bad contacts and wires issues. I do have some of the tin fuses. I will buy a set of fuses today and change them to be on the safe side.

I am really interested in find where the wires are for all these cicuits, if they are all run together somewhere. I found 2 cables sets running along side the air cleaner box. could these contain any of the wires?

The wiring from the OVP runs into the car from the drivers side and also the passenger side, if you remove the battery, tray, control unit holder frame (two sheet metal screws) you can see the wiring and where it leads, the junctions for the body connections are inside the fuse box under the fuse panel and under the steering wheel panel.

The wires running by the aircleaner contain wiring for the EGR vacuum controllers, the RHS headlamp and its wiper.

btw it seems that you have a bad ground somewhere, the main ground for about half the circuitry in front the car is behind the gauges, and there is also a ground right beside the negative cable on the shock tower infront of the battery. It may also be a bad ignition switch.

This car is not very "electrical" as some say, the most electric diesel W124 are the 2.5 300D (those have an ECU controlling boost) which then dictates power output. This engine only has electronic idle control which is that one ELR relay thing behind the battery and one EGR controller

I have a printed out wiring diagram of the engine wiring at home, I cant stand referring to such things on a computer screen. I'll look and see what wire tests what.

If you have the wiring diagrams I can also take a look. Is it possible to send them to me.

Also, the FSM is online free from MBUSA:

STAR TekInfo

On the left column, select "MB Workshop Resources". Click through to page 2 for Model 124 Service Library, where you will gain access to the two disk FSM.

So there is one ground in the dashboard. Is that correct.