1995 E300D power issues - PeachParts Mercedes-Benz Forum

kolnerspieler · #1 05-29-2012, 08:02 PM

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?

thatguy · #2 05-29-2012, 08:14 PM

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.

kolnerspieler · #3 05-29-2012, 08:19 PM

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.

Jeremy5848 · #4 05-29-2012, 08:36 PM

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

engatwork · #5 05-29-2012, 09:15 PM

Quote:

replace the OVP and see if that helps

Do this first.

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

Zulfiqar · #6 05-30-2012, 10:23 AM

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.

kolnerspieler · #7 05-31-2012, 07:54 PM

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.

Zulfiqar · #8 05-31-2012, 08:23 PM

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.

kolnerspieler · #9 05-31-2012, 10:41 PM

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.

Zulfiqar · #10 06-01-2012, 10:18 AM

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.

Air&Road · #11 06-02-2012, 06:31 PM

Does this engine have the resonant intake system the same as the 96 model E300D?

Zulfiqar · #12 06-02-2012, 06:59 PM

of course it does.

kolnerspieler · #13 06-03-2012, 09:40 AM

I do see a voltage when the ignition is switched on.

sixto · #14 06-03-2012, 10:39 AM

If the OVP relay is new, can you get your hands on a known good ring gear sensor? Check the wires to the sensor on the bell housing flange below the oil filter.

Sixto
87 300D^2

Zulfiqar · #15 06-03-2012, 01:25 PM

If you have voltage at fuse 6 and continuity to the relay and the relay has its ground, the relay is relaying voltage from the main 3 pole connector then the relay must be working, you can verify this by removing the ELR relay and checking for voltage there, it also spiders off the EGR and other bits n pieces.

check the rpm sensor connector too.