KRB

I've driven the truck enough now to know that the speedo keeps working so the poor ground connection(s) were the culprit.

As a bonus prize, my intermittent "no first start" was cured too. For a couple years I was tolerating an occasional no start on the first key over. It always started immediately on the second try. I couldn't figure it out and assumed it was a loose connection - but where? Couldn't find anything. After maybe a dozen startups it's not done it since. Can an injector pump fail just sitting? - Page 2 - Dodge Diesel - Diesel Truck Resource Forums The leak self healed too btw.

KRB

Well the saga continued. My speedo seems to be bipolar. Recently it just stayed pegged to the right. I'd leave it unplugged but then I have no OD. Noticed the odometer will vibrate some when sitting, don't know if it's the diesel vibration or what, weird...

I've traced wires and checked to the best of my ability for shorts and bare/pinched wires. Unplugged and cleaned PCM. Nada. My next step was to remove the gauge and check that connection but wasn't ready to try that just yet.

So, out of desperation and defeat I decided to remove the ratio adaptor and just entirely take it out of the equation (even though it "appeared" to work correctly when I first started diagnosing) completely. Drove about 30 miles on a wood cutting expedition and the speedo behaved. Still holding my breath but this weekend will be a test, I have a 300 mile road trip planned. I'll report back next week.

cougar

Way back when, my 91.5 had an instrument panel gremlin that drove me wacky. Got tired of it one weekend and ripped the whole dash apart. Found a large wiring bundle had chaffed through and was intermittently shorting out. Repaired the wiring and problem solved.