Hi,

I've just been reading some stuff from industry sources that mentioned some odd failures in the OBD1 era trucks.

The first was magnetized distributors. Not sure how this would ever happen, but it apparently causes the PIP (ignition trigger ) signal to be faulty. Since PIP is generated using a magnetic system, I'd say it was possible.

Their repair was to replace the distributor. I'm guessing that it could be demagnetized - you'd still have to take it out ( and possibly remove some of the PIP components).

The second involved diodes and the fender mounted solenoid. They said that there was a diode between the 'S' terminal and ground -- to prevent spikes from the solenoid coil. ( that's a common cure). What's interesting is that they said that if the diode fails, it usually goes open. They specifically said that on Fords, this can cause hard starting-- or even no starts because it temporarily jacks up the computer. Don't know, but apparently you can try adding a heavy duty diode between the S terminal and ground. The cathode ( banded end) should be on the S terminal. I think that they recommended a 1N4005 or better. ( I looked it up, and it seems adequate).

Adding that diode shouldn't hurt anything -- worse that can happen is that it would fail short, which is unlikely -- it's onl a 1 amp unit.

Just some things I found interesting,

hj

 

The distributor in these trucks is cast aluminum which is non-ferrous.. so good luck magnetizing that. PIP modules can fail but it's rare the TFI modules were the weak link on these trucks, there was an overheating problem with the early distributor mounted units in hot climates and the solution was to move it to the fender and mount it in a heatsink. And the diode thing looks fine, I don't think that it will hurt anything but I don't know if it's really fixing a problem either.

 

Thanks for the response -- I've read a lot of your posts, and I've always enjoyed them.

I know that the TFIs were problems, but the guy was talking about 'oddities'. Maybe the shaft could be magnetized ( that is steel right?).
Maybe he was just wrong.

The point of the diode was that if there was one, and it was blown out, it could cause some unusual starting issues. It would be easy enough to try, and I do see the logic.

But whatever, I don't have my 89 any more -- really loved the I6

hj