1991 7.3 idi f350 questions

[chevyman98]

i have recently aquired a 1991 f350 2wd 7.3 idi with an auto trans. i need to get it up and going for my father to drive back and forth to work. we put new fuel and fluid in the trans with a filter and oil and oil filter. the problem we have is that it shift s fine through all gears but will not lock into overdrive. if there are any suggestions woul be great. also the oil presure guage works off and on and was wondering if maybe the sending unit is bad and could yall tell me where its at. the last question i have is the tact starts to work at around 1300 rpm but if it drops below that it sits at 0. if yall could help us out that would be great. thanks in advance.

 

[Brutis]

Well, it sounds like your tach sensor is not working - mine did the same thing - would drop to 0 at lower rpms. That could also be the culprit for the overdrive issue. Does your Overdrive switch have a blinking light over it? If so it is likely the tack sensor, FIPL sensor or both like mine was.

The oil pressure sending unit is on the very back of the motor behind the air cleaner. You can't really see it without a mirror. Its down in the dip maybe a tad passenger side of center almost where the bell housing meets the engine. Hope that helps.

 

[TwoTone IDI]

just to add, the oil pressure sender is a switch, not a true sender... all it knows is if you are above 5 psi.

 

[icanfixall]

Welcome to the site... We don't usually care what the dash oil pressure gauge tells us. All it really is telling you is that you have at least 7 lbs of pressure. Its really not a pressure gauge at all. Most of the time the wire push pull connecter needs to be sueezed tighter. They loosen up and then you see the needle moving up and down with no reason. The water temp gauge isn't much better at telling you a coolant temp... Just whats the temp when its showing the needle on the M or the O or the L..... Your trans is the famous all electric controlled E4OD trans. There are some good ones with all the upgrades and some terrible ones without the upgrades. Hard to tell what you have from here. The tach problem sounds like the sensor is dirty or gone bad. Its found on the injection pump gear cover to the drivers side of the cover above the water pump. Two black wires going to it. Remove it and clean off any dirt or metal shaving and maybe it will start working. If not just replace it... A ford only part Sorry for that...

 

[chevyman98]

thanks ill try these tips and see what the out come is thanks

 

[chevyman98]

well the sensor for the tact is bad i belive the wire going into it are frayed and thats not good are there any other things to check as far as the transmission not going into overdrive and yes the od switch does have a light on it but when its in od postion no light and when the light is on is when you press it in to keep it from going in.

 

[chevyman98]

i removed the oil pressure switch and installed a manual gauge and im getting good oil pressure 45ish cold and 20ish hot. can i ground the oil switch plug or do i need to run a hot wire to is to make the SEL go off. also the tact sensor is bad i no yall said the oil place you can get it is ford so does that mean even places online you can get it and if so what is the specific name for it.

 

[TwoTone IDI]

just ground it.

 

[chevyman98]

thanks