Howdy. I have a '94 F-150 I-6, my 1st truck, I bought it 3000 miles ago w/130K. One morning the oil pressure stayed at 0. I thought I fixed it by jiggling the sending unit wire, as the pressure became normal. The problem kept recurring, but it became apparent that wire jiggling wasn't the answer. On initial start-up, pressure usually goes right to normal for 4-5 seconds, then bottoms out. Usually if I restart the engine, I get the same result, but sometimes I get no pressure even at initial start. It seems erratic. I'm afraid to let it idle too long in the hopes that the pressure will bob back up to normal. I've replaced the sending unit, and get the same result. I've disconnected the sending wire and attached an ohm meter to the pressure switch, and get the same indications as the in-dash gauge gives. The last thing I did was remove the pressure switch and install a mechanical gauge, and it doesn't move at all (I haven't ruled out that this gauge doesn't work - probably wishful thinking!). Anyway, any ideas what could cause this? According to what I've read here, it's rare for the pump to go out, and I hadn't noticed a gradual decrease in pressure - very sudden. Thanks for all help.

 

When was your last oil change? Have you checked the oil level?

 

If you didnt have any oil pressure then it wouldnt be too long before the engine started making some serious noises .... I assume thats not the case since you made no mention of the engine making any noises . Try another pressure gauge , the oil pressure should go to between 40 & 60 Psi as soon as the engine starts .

 

Thanks for the responses.

I changed the oil as soon as I bought the truck, and changed it again after this problem started (about 2500 miles between). Oil level always good.

I drained the new oil change out and at the advice of an Auto Zone aquaintance, added 3 qts 10w30 plus 1 qt auto trans fluid. I also installed a new mechanical gauge. Still no pressure. I removed oil fitting, restarted the engine, and at first nothing came out, but eventually oil ran out the hole (didn't squirt out). I re-installed oil pressure pipe, still no pressure. During one of the start-ups, I heard a short 'bad' sounding (to me, but maybe I'm a little skittish) squeal-type noise from within - I shut down immediately. I didn't hear it again during 2 or 3 subsequent start-ups.

I'm thinking either bad oil pump, or maybe some clogging of some oil passageway. I have Haynes manual for pump change-out, but I wouldn't know how to handle a blockage. Thanks for further comments.

 

If it was mine I would drop the oil pan and check for blockage at the pump.

Chris

 

I recently read a similar post somewhere. The low/no oil presure in the I6 was solved by changing the filter, it was clogged.

1992 F150 Supercab SB 4x4 302 AOD 3.55 31x10.5 All Terrain on Ford 15x8 Ralleys

 

I also read an article a couple of years ago about someone having the same problem, and I believe it was a bad newly installed "Fram" oil filter.I have used Fram filters with no problems.
Another thought have you added a engine cleaning product? I was advised by a mechanic, not to use engine cleaning products as they can contaminate, and plug up engine oil passages.
Good Luck
Davie

 

You mentioned that you were using the electric oil pressure gauge, stick a good mechanical gauge on there and see if it's truly the pressure or maybe just a flaky gauge. The "jiggling the wires thing" has me suspicious of the gauge.

TundraKat
Anchorage, AK

 

I have a '95 300 I6 with 75000 miles. I had problems with my oil pressure gauge and it was a poor connection at the sending unit. When I had the oil pan changed at about 68000 miles they found the pickup screen half plugged with sludge (apparently the previous owner didn't change oil frequently), but that wasn't causing any pressure problem (at least not according to the electric pressure gauge). I have heard of the auto tranny fluid in the crankcase trick (back in the 70s), but a better idea is to put one quart of Rislone in the crankcase.

 

I have seen the oil pump drive shaft that connects the distributer drive to the oil pump fail. Its just a hex shaft that will somtimes rounds off on one end. Easy to check by removing distributer and pulling shaft out to look at.
Also on a T-bird we once had, the timing chain was plastic coated to help quiet down the chain(brilliant Ford idea)the coating failed and clogged the oil pump screen, resulting in loss of oil press.

 

 

Thanks to all contributions. Here's 'the rest of the story'...
I checked distributor drive first (easiest) - that was o.k. So then I dropped the pan and replaced the pump and pick-up tube. This fixed the problem - with mechanical gauge still attached I got 45psi (equates to end of the 'M' on dash gauge). I think the culprit was the strainer which looked pretty sludgy and oil wouldn't pour through it too well. The old pump seemed to pump oil as well as the new one did when 'hand cranked' with a screwdriver.
Note on sending unit - mine is not the 'on or off' variety, it does send a variable signal to the gauge. If you have your sending unit out, hook it up to an ohm meter then aim a stream of air into the opening. I used a little 12v air compressor. The meter will register variable ohm readings depending on how much air pressure you force into the sending unit. I suppose it may be possible to damage the sending unit if you over-do it, so go easy if you have alot of psi available.
Notes on the Haynes Manual. I've used these quite a bit, and usually they are more helpful than not, but in this case - at least on my truck (1994 2wd 300ci six cyl w/air)- there were several discrepancies.
*no need to remove radiator. I did unbolt the fan shroud (to allow it to rise up with the fan as the engine is raised), and the transmission cooler oil lines bracket on the lower right side of the engine block (to avoid over-flexing them when engine is raised).
*no need to remove starter - it's just not in the way.
*engine does have to be raised more than one inch. I probably had close to two inches between engine mount and chassis brackets. I had to remove one component (don't know what it is) that was bumping into the wiper motor as the engine was raised.
*once the engine was raised enough for the back of the oil pan to clear the torque converter housing, it came right off - no need remove oil strainer before pan would come off.

Hope this helps anyone else in the same predicament.