Just picked up a 1994 E320 wagon to go with my '84 300TD. Was bringing the car home on 100 mile trip. The coolant light came on a few miles into the trip but car ran about 80C. Since then the coolant light has been intermittent.

Made it about 90 miles going 60mph then all of a sudden the power dropped and I limped it home running 4500rpm going 55mph. Car was running really rich. Parked it in the driveway, shut it down, then tried to restart. I had to crank it about 15 times and give it some pedal....it fired, then went into a stall, caught fire again and leveled out. Drove it a couple miles, shut it down. Fired it and it fired right up.

During this time I also noticed the oil pressure was really low....like zero. A couple hours after the car cooled down and I could get the needle to jump more when it was cold and pegged at 3 bar one time. As it got hotter and I drove it harder, the needle went back to zero and rarely moved.

I was thinking battery or voltage even though battery is new. Checked voltage across battery and got 12.6. Got 13.1 when running. The first reading seems high to me and the second seems low. I plan to hook up a good battery tomorrow and see if the symptoms persist.

The car was running great for the first 90 miles but now it seems to have lost its mind! I appreciate any ideas you guys can give...thanks!

 

12.6 Is a good battery voltage.

13.1 When engine running i believe is too low, should be around 14.4volts

Oil pressure should rise to 3 bar as shown as you rev the engine, assuming the gauge is working correctly.

Sounds like you have battery / alternator issues which need sorting though. If the oil pressure was too low i bet it would sound like your TD engine!

 

oil pressure sending units do go bad.it is located below the oil filter
can be changed from underside of car easier if car on lift.
as long as you take oil cap off and oil splashing around and engine not noisy as starved for oil you can run with out problem oil sending unit around $30.00

 

While you're sorting out the electrical, remove the voltage regulator to check the length of the brushes. Consider replacing the over voltage protection relay, because it is evil! Well, also because it can fail slowly and cause intermittent electrical problems. I carry an extra one in the car.

 

Thanks for the replies. Am going to clean out the oil pressure sensor today and see if that does anything. I am confident the car is circulating oil though after playing with it last night....oil is splashing and car seems to run fine now even under heavy acceleration.

What I'm more concerned about is the fact all of a sudden the power dropped and the very rich condition. I was also thinking maybe the cats got plugged up. That could cause the power loss condition, but a couple hours later after it cooled down the car ran/runs fine.

Voltage seems to be constant when I measure it so I'm wondering if that would have affected the car in this way (power loss).

 

Has the engine wiring harness been replaced on this car? Except for the oil pressure reading issue, the potpourri of problems you describe seems consistent with a degraded harness. Do you have a check engine light?

The behavior you describe for the oil gauge sounds like a sender failure. The senders typically fail "open" (read low) because the diaphragm inside leaks with age. If you really had no oil pressure you would have been picking up pieces of your rod bearings on that 100 mile trip home.

 

So I checked the battery and alternator and found I had a bad alternator. Got a new one ($140!) and installed it.....and promptly snapped the tensioner rod. So, time to fix that and then see if the alternator fixed my problems.