Tach and speed O going crazy

[Harley]

I just got my truck back going after sitting a while. I put a new injector pump on it and it runs good, however the tach and speedometer moves over to the right side of the instrument panel and bounces up and down. I havent been able to find any bad grnds. or anything wrong. Some times while you are driving down the road it will start working properly for just a few seconds then it start back jumping around. the alternator is putting out 13.8

[trukdoc]

what year model is your rig? elec. tach signal is from alt. mech. signal is from speed sensor that is componet of oil pump drive unit. under rear of intake. check plug.loosing this signal will cause 4l80e problems from hell

[Harley]

the 4 plugs behind the intake all seem to be fine. the ops is new and plug in as well. when i unplug the alt with the white and black wire it does not help the tach or change anything. the trans is shifting and operating fine. I'm not getting a wait to start light anymore, is this because it's 90+ degrees here?

[Harley]

Those four plugs that were behing the intake seemed to be fine, but i took them all apart and then pluged them back up and it fixed it! Thanks






1994 3500 crew cab dually 6.5 TD
complete cooling upgrade, new PMD with heat sink, marine injectors, new glow plugs, K&N air filter stock box, new heads,