On a 1991 240, after removing and reinstalling the intake manifold to change the heater hoses, the speedo is running 100 mph, and the car won't start. Also, overdrive does not work, and getting the car into and out of park is difficult. Turning on the lights takes the speed down to 80 mph, and speed changes with any electrical load - so its pretty clear it is an electrical problem.

My best guess is that it is related to the shift interconnect to the electrical system to prevent starts except in "park", possibly related to overdrive problem. I am thinking the speedo wiring and the shifter switch system are somehow shorted together?

Anyone else have this much fun with your 240? Any ideas of how to sort out this wiring issue? We need some help!

Tom Jones

 

I assume it was okay before you removed the intake? Did you get all the wires back to the same place?

 

Is the speedometer guage "PEGGED"?

 

Well - here is the skinny!

When we removed the intake manifold to get to the heater hoses, we had to uncouple a plastic harness. That plastic in those cars completely and 100% sucks - touch it and it breaks. In this case, when the harness was reconnected, instead of the wires making contact, they simply pushed out the back side of the plastic harness so that they looked connected, but were not.

Solution - removed the harness coupler, installed male and female connectors on each individual wire. After connection, car started fine, ran fine, speedo 100% o.k. (not pegged).

Still have a problem with the tranny - overdrive will not work - but we figure it is a wiring problem in the shifter (put in a fuse and it immediately fails - indicates shorted wire).

But, we got this car back on the road!

Thanks for the help here!

Tom