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· Registered
42 Posts
Discussion Starter · #1 ·
Hey again!
My fuel gauge and my tach aren't working right. I can't figure it out...

I have replaced the cluster w/ 5 different boneyard clusters and now everything but the tach and the fuel gauge work ( long story). The sending unit appears to be good and the switch for the dual tank works fine.
Also, the tach won't rev over 1000 rpms???????
Now there is a "mystery" wire that is near the battery-black in color- that runs down toward the starter but i cannot tell where it originates AND!!!!! it dead ends up near the battery. Somehow it got cut by the previous owner(s) and i'm thinking ***? Maybe that is a ground, I have no idea. I'll try to take a pic if need be.

******* fwiw, when the truck was drove from TX to IL, the gauge would read F until it physically reached about 1/2 tank then it would suddenly drop and then work. Now it no more workie-work?!

Thanks Again!!!

· Registered
12,232 Posts
Could be two separate problems.......

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.

Fuel senders have been known to wear out but check the connection on the FSV (fuel selector valve)..... does the tank selector switch the FSV to a new tank......

Check these ohm readings...... they MAY be applicable to yours.

Here are the fuel guage test #s

22 ohms sent to the guage it reads empty "E"

145 ohm sent to the guage it reads full "F"

Here are the sender test #s

Sender at empty stop 14-18 ohms

Sender at full stop 154-162 ohms

· Registered
42 Posts
Discussion Starter · #3 ·
Pete, it me PL405,

My buddy is on the road so i'm checking his post. I got the info you emailed me about 2 wks ago on the vacuum pump, and that helped us solve the problem.
I'll give him a heads up on your thoughts.
Thanks for all your help!!! :)

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