My 93 ford f350 7.3 idi tach doesnt work when trying to start the truck tach jumps up and down after its running it doesnt move,i checked the wires at the unit by the oil fill and wires are in good shape and unit seems good,any ideas what may be causing this issue would be greatly appreciated ?

 

Did you try wiggling the wires and connector, sometimes the fan wind will cause wires to do silly things. You could remove it and test it........

My blurb....

A dead tach sender should/would send the automatic (E4OD) trans into a "failure management mode" (limp mode) with harsh engagements and firm shift feel and an abnormal shift schedule. It has no effect on a manual trans only the Tach readings.

Check the wires where they exit the big nut on the oil filler housing , known to short out due to bare wire.....

Replace the tach sender on the oil fill housing a big 1" nut with 2 wires. Ford only part Engine RPM sensor E5TZ-17B384-A about $50. You can remove and clean it but usually changed later too.

You can test it too, hold it in the air away from ferrous metal, using an ohm meter lead on each wire you need DC resistance between 2000-3000 ohms.

 

Well i think i found out why tach wasnt working correctly, dash caught on fire today must have been short somewhere in harness now i need complete dash harness,anybody got one? nothing but problems for me one right after another,Thanks for info on cleaning the sensor didnt get a chance to try it.

 

I know where i can get you a entire dash or anything you need off a idi parting it out want me to get the number for the guy

 

Hello if you could get the number i would apreciate it,