The car in question is a 1991 190E 2.6

I have found out through tests i conducted with my tools. The ovp, mass air flow sensor,
throttle valve switch, wiring harness, crankshaft sensor, fuel pumps are ok. But what I did notice something fried my MAS and it wasnt the fuel pumps.

The ovp is getting voltage and seems to be working and many of the other components in the fuel system are getting voltage and meet specs according to the service cd.

The car will start up sometimes easy most of time its hard to start. Once its started it stays running and there will be moments when the rpms dip really low and almost stalls. In general the rpms are erraditc. The car eventually stalls and when its warm its almost impossible to start.

I have done a lot tests and work and nothing seems to solving the problem.

What other components should I look at to solve this problem and what else could fry a mas?

anyone?

Does this car have a mechanical or electronic fuel injection system ? I am not very familiar with this car but if it were happening to my 87, 260E, these are the things I would check.

Coolant temp sensor that sends engine temp to the fuel injection computer and the ignition control unit. On my 260E, the sensor has 2.5 to 3.5K resistance when engine is cold and then the resistance decreases to between 250 and 350 ohms when the engine reaches 80 deg-c

vaccum and fuel leaks

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Saumil S. Patel

it has electronic fuel injection,has the bosch cis-e system

CIS-E is mechanical injection, right ? Do you have an air sensor with a large plate or do you have a heated film or heated rod type air sensor ?

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Saumil S. Patel

CIS-E is the same as KE-JET, I think (continuous injection). Easy to tell, if you have a heated wire MAS it's LH type, air meter plate under the air filter it's KE-Jet

You did not mention ignition parts -- check condition of cap, rotor, wires, and plugs. Carbon tracks in the cap will cause all sorts of trouble.

Check for vacuum leaks (idle control valve, boot between air meter horn and injector seals).

Check the temperature of the fuel pump relay -- if it's quite warm after a short run, replace it (this cured all sorts of starting/idle ills on my TE). If it stalls while driving, definitely replace it.

Replace the OVP -- the problem with it is that it is usually intermittant, rarely goes totally dead right away, and is vibration sensitive. If it has one fuse on top, its original.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Correct if im wrong but if the ovp was broken it wouldnt be getting voltage?
I dont think the mas unit is getting warm but ill look closer tommorow.

This problem is really getting annoying and getting to the end of my wits with this hunk of junk. My vw 96 jetta isnt this kind of pain in the ass to track down a problem like this.

The OVP is a tricky bugger, often it will seem fine cold or sometimes warm, but it is a touchy git and will often be very very intermittent, I would consider a new fuel pump relay and an OVP, excpecially if it is original

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Christopher Henkel
1990 190E 2.6 - Arctic white SOLD
1986 190E-16v - Blauswartze
1993 300CE - SOLD
2003 W208 CLK 320 Cabriolet - Magma Red

I just had a problem like that. It turned out to be the crank sensor on the bell housing. Normally it's about 1000 ohms but I cought it shorted. An indication was the tach going to zero when it quit even though the engine was still spinning, coasting actually. A suggestion would to re-seat it.

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5 speed '91 190E 2.6 320,000 mi. (new car, fast, smooth as silk six, couldn't find any more Peugeots)
5 speed '85 Peugeot 505 2.5l Turbo Diesel 266,000 mi. (old car, fast for a diesel, had 2 others)
5 speed '01 Jetta V6 (new wifes car, pretty quick)
5 speed '85 Peugeot 505 2.2l Turbo Gas 197,000 mi. (wifes car, faster, sadly gone just short of 200k )
5 speed '83 Yamaha 750 Maxim 14,000 mi. (fastest)
0 speed 4' x 8' 1800 lb Harbor Freight utility trailer (only as fast as what's pulling it)

The OVP provides conditioned electricity to the electronics (engine controls, climate control) to prevent a voltage surge from frying them. If it is bad or intermittant, it will interrupt current supply to the engine computer, ignition module, and so forth, giving you erratic running. You have to measure the output, not whether or not it has current supply.

On a 91 you probably have electronic injection, not KE-jet (definitely if you have a MASS unit instead of individual relays). I don't know if the fuel pump is operated via the "big box" or via a standard fuel pump relay.

You need to pull the trouble codes before getting all bent out of shape, that system has on-board diagnostics and will tell you what isn't working.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

The fuel pump is operated by the mas which has the relay for the fuel pump along with other things.
the ovp is reading 20ma by the ehl.
I dont have the money at the moment to buy the special diagnostic tools for the car. Knowing how mercedes makes their cars so you have to bring it to a dealership I most likely wont be able to rent the diagnostic tools.

that ovp has at least two circuits in it,when the one feeding the f.i. computer drops out the car is running in limp mode.i would replace the ovp just on principal first.your car has the fuel distributor with the black eha screwed to the side and when you start car the computer sends signal [40-60ma]to get enough fuel to start.if no power to comp----you get the picture.the other thing you can do is to use a 3mm allen at the tower in front of distributor and push down and twist about a 30deg turn clockwise which should make rich enough for starting.hopefully the ball bearing in top of tower has been removed.

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David S Poole
European Performance
Dallas, TX
4696880422

"Fortune favors the prepared mind"
1987 Mercedes Benz 420SEL
1988 Mercedes Benz 300TE (With new evaporator)
2000 Mercedes Benz C280
http://www.w108.org/gallery/albums/A...1159.thumb.jpg

You MUST eliminate any vacuum leaks before it's gonna run right. Very likely you have bad idle control valve hoses and a bad boot between the air meter horn and the throttle body. Fix those and you will get it started, anyway.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

K ill look for vacuum leaks tommorow

An update. I have just checked my spark plugs and they are BLACk. So my engine is running rich. Something is telling the control unit to send too much gas and choking the motor. Also my water temperature sensor is picking up 1300 ohms at the ezl and that info is being sent to the control unit. this doesnt sound right. And I also forgot to mention this is a calfornia model with 4 plugs instead of the normal 3 on the ezl. So do i have to replace my ezl?