If this is the wrong forum, I apologize!

O.K.- Heres whats going on, then my questions:

I was towing my boat, which is around 2500 lbs loaded with gas, coolers, etc
The truck is a 1993 F-150 straight 6 300 cu.in. w/ automatic transmission.
I have always read on the boating forum I belong to that its best to keep overdrive off when towing, especially if you are going thru hilly areas.
I put a tachometer in the truck (came without one) because it seemed to me that the engine sounded like it was turning more revs when I drove with O.D. off.
With the tach in, the truck goes about 1200 rpm's @ 50-55 mph with O.D. on.
With O.D. off, it runs about 2000 rpm's at the same speed.
As I was coming back from the lake, I noticed my oil pressure gauge fluctuating, then dropping off to no pressure. When I took my foot off the gas, the pressure climbed back up.

I stopped, checked the oil level (just right) and checked to see if the engine was excessively hot (no more than normal)

Started back down the road, and oil pressure was fine for a while, then did the same thing. Since I was in relatively level ground, I stopped and switched the overdrive back on. The oil pressure gauge stayed where it is supposed to then.

I took it in to have a oil pressure test, which came back fine. Good pressure, compression, oil levels, filters, etc. The mechanic was sorta confused as to why what happened did. He suggested I get a new sender to the existing oil pressure gauge, and also to 'T' off at the port where the sender goes in, and run a tube from there to a mechanical gauge I should install.

Any ideas why my pressure dropped?
I am assuming that the oil pickup is functioning fine, as well as the pump since the engine passed the oil pressure test.

(I was dreading a bad pump, lifting the motor and removing the crossbar! Yikes)

Well, I installed the mechanical gauge. Another question from that:
Does it matter if the sender for the existing gauge if horizontal or vertical?

 

It seems to me the wire that connects oil press switch is been randomly grounded or disconnected so gauge reads cero or blinks...

In that truck there is no oil pressure sender, just an oil switch normally open, wich close contact to ground if oil pressure pass over 7 psi. There is aproblem with switch, wire or gauge but not real oil pressure droop.

just drive as always and compare readings from mechanical gauge to cluster "idiot" gaugem, we'll see...

No matters switch/sender possitions...

 

The same thing happens to me in my 85' 4X4 i know it is the sender but i have a mechanical guage and it says 55-60psi cold 11-12psi hot idle and 45psi cruise.

I just like to keep both hooked up to see how jacked up the ford guages can be.

DT

 

never trust the ford idiot lights with pointers.

 

I have a fluctuating gauge also. I have 94 300 6 cyl, i just hit the dash and the gauge goes back to normal. Thats my fix,,,,,

 

by the way, i changed the oil pan gasket and liftd the motor ect. For the life of me there was no room to drop the pan. the front axcel was in the way i believe and it was a pain in the ***. I tried for two hours with the motor lifted. The haynes manual said lift the motor and thats all ya gotta do. BS. I manged to put the new gasket in, but I wanted to change the oil pump while I was in there. Oh well.

 

mine came out Very easily with a 2X4 layed flat between the mounts and the frame. i could of done it with out jacking it up but i couldn't get my torque wrench in tight places.

My truck is a 4X4 i have heard it is harder with a 4X2

 

ya your right 4x2 is harder. Wish mine was that easy!! Other problem unrelated to this thread, is oil pans on the newer ones rotting out!!!

 

I installed the mechanical oil pressure gauge (see my gallery) and love it. Didn't T the old dummy gauge, but covered it up. I found 5w30 was getting 35 psi hot at 2000, so switched to 10w40 and get about 42 psi hot at 2000, which I like better (spec is 40-60 psi at 2000 hot).

 

I did 'T' it, and towed the boat to the lake this past weekend. Its is about 50 psi at startup, then 25 -35 running, and then 10-15 hot idle.

I couldnt find anywhere handy to mount the oil gauge, so I ended up fitting it in the little shelf/pocket just under the instrument panel to the right of the steering column. A little silicone, and it fits nicely, easily seen, but unobtrusive.

The tach, since it was just wiring and no capillary tube, went on the 'shelf-it' up above. The body of the tach was too big to put much of anywhere else.
A pic of the tachs in my gallery, dont have one of the oil gauge.
I'll put one up soon.

 

if u didnt replace the sending unit and check the grounds.

good call on the mech guage, very valueable.

id invest in a trans temp guage and a LARGE aux. trans cooler for ur E4OD as well. possibly a shift kit...

 

See my gallery. I have the tach in the dashboard on the right where the electronic 4WD controls would go. OP gauge is on top of the steering column. You might try 10w40 to boost the pressure a bit.

 

I just put mine in the dash and sliced into the dashlights for the guage light so the light comes on with the switch.

I know your's is a 93 but there might be a place to do that to yours. Like a blank panel for an option. Just make sure to take the thing off before you cut it.

DT