Dead on the side of the road- Help! - PeachParts Mercedes-Benz Forum

haasman · #1 05-17-2004, 12:31 AM

The 91 300E stalled at a light and will not start ..... got it back to the house but still no catching of the engine.

I changed the distributor cap, thought that might be the cause so I changed it back to the old one, still not start.

I checked the OVP fuse, looks good. Checked the connections, all seemed cleaned. I smell raw fuel but ....

I also washed the engine, but it ran just fine afterwards for several minutes.

I hear the fuel pump in the right-rear with turning the key on. The tank is 3/4 full.

Any suggestion would be much appreciated.

Haasman

william rogers · #2 05-17-2004, 02:19 AM

Have you checked the coil? I just had to replace the coil on my 86 SE ..........

William Rogers.......

haasman · #3 05-17-2004, 09:13 AM

Started right up this morning ... must have gotten somethng wet?

I'll let it run and see what happens when its warm.

Whew!

Haasman

zafarhayatkhan · #4 05-17-2004, 09:23 AM

I used to wash the engine on my 89 Mitsubishi Galant on a regular basis. One time I got carried away a little and it did not run very well until the next day.

Since then, I have not washed the engine on any of my cars.

haasman · #5 05-17-2004, 12:27 PM

I had my wife check the fuel pump cycling by turning the key off and on and it does make it's noise.

I am wondering if a fuel pump relay can work in the key cycling but then fail as it gets warm?

Does a fuel pump do this?

Haasman

EricSilver · #6 05-17-2004, 04:24 PM

If it has been warm out, and/or the stalling occurs only when the engine is hot, the Crankshaft Position Sender Unit could be frayed. That got me last year.

Easy, quick, approx. $90-100 repair by a tech.

If memory serves, it is a cable/sensor that runs from the back of the engine to the ignition control unit(?)

EricSilver · #7 05-17-2004, 04:52 PM

I should add:

If it is the CPSU, the car will crank and catch for a fraction of a second before shutting down.

The insulation on mine had worn away and exposed the stranded wires -- which were also a bit corroded. When it got hot outside, the heat interrupted the signal between the crankshaft end of the sensor and the ignition control unit end, and the engine would shut down -- usually when the car was stopped.

haasman · #8 05-23-2004, 02:03 AM

Thanks Eric

The car was running great for several days and now is in a dead on the road condition again.

It was hard to start today- changed the cap and rotor to be sure and then fired right up. Went half way around the block and it started bucking, loosing power and finally stalled. Will not restart. $&%^#!

I will try and check the CPSU wiring if I can get it home again.

Also I don't think I heard the fuel pump when I tried to start it.... but it stalled on a noisey street.

Haasman

EricSilver · #9 05-23-2004, 02:44 AM

Those are the exact symptoms I had with the CPSU.

Has the weather been very warm or hot? Does the engine quit only during the day, but not at night? When the car was running great, was the weather cooler?

It could be something else (coil or ignition control unit) but it sounds like CPSU or some other heat-sensitive electrical issue.

cc260E · #10 05-23-2004, 02:57 AM

Eric,

Is there any procedure to test the CPSU. In the manual they just say to measure the resistance (800 ohms if I remember well).

I have the same sneak shut down ( a lot of things have been changed on my car)

260E 1988 Euro 390 000km Great car

stevebfl · #11 05-23-2004, 02:08 PM

The only way to properly test the cranksensor is to break out the signal and view it on a scope. I don't have the pattern saved on this computer so I have grabbed a small picture from my article on AC:
http://www.continentalimports.com/ser_ic60046.html

I have blown it up here and the shape is discernable. This was taken from a 1991 300e at the sensor to controller connection. We have a special tool to break it out but for years we used a device we constructed from the connetor on a old sensor and te connector from a controler. The problem is it is a coaxial signal wire and it can't be backprobed very easily.

The coil is actually a more statistically probable posibility.

Ron Johnstone · #12 05-24-2004, 02:48 AM

There is a chance that the fuel pump relay is involved. Sometimes they intermittently fail. If you want to test the theory, I'll be glad to lend you one. I'm close by in Santa Clara.

haasman · #13 05-24-2004, 10:36 AM

Thank you Ron! I may call upon your offer.

I am now going to replace the fuel pump this morning and see whether that is the problem. I will keep this thread updated with the results.

Haasman

Ron Johnstone · #14 05-24-2004, 12:01 PM

Very expensive to replace the fuel pumps, especially if there are two of them as found on my TE. Try the relay first. I tell you this from experience. Tip: If you do change the pump and it turns out not to be the problem, sell the used one on ebay. There is a definite market out there.

etsa · #15 05-24-2004, 01:20 PM

Hi Haasman:

I had a similar problem about a year ago that Benzmac helped me resolve.

I ended up with two problems. When the engine got hot, the crank sensor went south as well as the solder joints on the fuel pump relay. It drove me crazy for one week.

Crank sensor is pretty easy to get at. It connects from about the bell housing to the EZL. Just follow the wire. It goes under the air cleaner housing.

I found the fuel pump relay by jumping two pins when it failed after I did the crank sensor. I will check my notes when I get home and let you know the pins to jump. It started right up after I jumped it so I changed the fuel pump relay too. Since then, no problems.

I hope this helps.

Aloha,
Eric