This morning I fired up the '95 F150 300 I6 and the oil pressure idiot gauge would not come up. Knowing I have had sender problems in the past I let it run a bit to see if it would come up (but a new sender was installed last month and had been working well). Also I once lost prime on an oil change and it took a minute to come up. Then I shut down and looked in the oil filler--no oil in the rocker compartment! Pulled the dipstick and oil was an inch or two above the full mark (suggests possible clogg causing it to back up the dip tube a bit??), wiped it and re-dipped and it was in the safe zone. A couple more starts for a few seconds each, but no pressure. So, what to do? Truck has 100,000 miles, bought with 58,000 and around 65,000 put new pan on and cleaned out pickup screen that was half clogged (though pressure was OK then). Have been changing oil and filter every 3000 since I got the truck and present oil has 2000 miles. Strange that it would do in first thing in the morning (or worse, maybe I drove it a few miles home that way.) I figure the following can be done:

1.) pull filter and prime pump by shooting oil down the filter input hole in the block. Try to start and see if pressure comes up.

2.) change oil as filter may be defective and maybe see if I can get a tiny dental mirror into the drain hole to inspect that oil pickup is not dropped off.

3) Combine 1 and 2 to save a step.

4) get a new sender (but why were the valves dry after running for perhaps as much as one minute total? So I doubt the sender is bad).

5) take to shop for serious diagnosis. (I am not going to pull the pan myself.)

How many times can this thing be cranked over like this before I risk damage? I know there is an oil film remaining in the bearings, but that will wear off in short order.

(Also posted in '87-'96 Trucks and Vans forum)

 

Problem solved. Apparently a clogg in the line from pump to filter. The whole bloody story is in the '87-96 forum:https://www.ford-trucks.com/forums/s...73#post861573. Mostly advice; the results are the 11th post. Now I'm going to the oil and lube forum to talk about engine flushes.

 

Hmm... Interesting story.

I'm looking to purchase a Winter beater truck that maybe has an low oil pressure problem as well.

I wonder if it's worth gambling $500 on to buy this truck. ???

How difficult is it to pull the pan (to replace the oil pump) ???

 

1) How do you know it has a low oil pressure problem? After a certain year (somewhere in the 80s I think) Ford went from a real gauge to a dummy gauge that reads either low or OK, but looks like a guage (basically a glorified idiot light). With the idiot gauge it likely will read lower in the normal zone because the pressure transducer (sender switch) is old.

2) Depending on your income level, $500 is not necessarily a lot of money. If the truck is pretty good otherwise, it might be worth the gamble.

3) My mechanic did my pan when the tranny was out and apparently it was a lot easier to do that way.

A mechanical gauge can be bought for 15 or 25 bucks and screwed into the block as easy as a spark plug. Then you'd know for sure. And remember low oil pressure (within reason) is not always bad if it is low because you have good flow through the system, just as really high pressure could indicate system backup. If you look in the oil filler cap when it is running and there seems to be ample oil on the rockers you can see, it may be reasonable to assume that oil pressure is adequate.

 

Looks like a gauge to me. It's located in the Upper Right corner of the 87s dash (if that helps).

When the key is in the Run Position (Engine Off), the needle is pointing to the 9 O'clock postion. When it's idling (warm engine), it's on the bottom edge of the Low mark. It goes up a tad when the engine is revved up.

Quote:

A mechanical gauge can be bought for 15 or 25 bucks and screwed into the block as easy as a spark plug. Then you'd know for sure.

Where is it screwed into the block ?? Where the sending Unit goes ??

BTW, it looks to have a Newer (clean) Sending Unit on it right now (doesn't mean it's good though).

 

Your description sounds like a real pressure gauge, but the year seems too late. Although the flippy needle could be caused by poor electrical contacts in a dummy sender I suppose. Also, could get weird if a gauge sender were used with a dummy gauge as they are different I am told. The mechanical gauge screws in in place of the sender, so it is one or the other but not both at once. Given your description of the gauge needle I would be inclined to want a positive test with the mech gauge--one that reads the PSI. Tough and dirty rule is about 10 PSI per 1000 RPM, though perhaps a tad more at idle. I think there is a shop-type mechanical gauge strictly for testing pressure, but a dash mount gauge maybe could be screwed in too. Also, could the owner have installed a real gauge; the stock gauges I have seen would only range from about 9:30 to 2:30 of the clock face.

 

Yea, that's about the range of the marks, but the Needle "pegs" counterclockwise at around 9:00 (with the Key in the ON position/Engine Off).

Is this Normal or is the gauge maybe out of Calibration ??

 

That makes sense. Mine sits in the normal range after shut down, but drops to the bottom when I turn the key on and then comes back up when the engine starts.

 

This one will drop down to about the 7 O'clock Position on Shutdown, but when the Key is turned to the ON position, it will then go counterclockwise (backwards) to the 9 o'clock position.

That leads me to wonder if the gauge itself is out of Calibration...

 

Yeah. Sounds like the gauge is in sideways.

Did you get a chance to look into the oil fill hole to see if there was oil flowing in the rocker area? Take a flashlight.

 

Not yet...

I forgot to mention, when the Engine IS running, the gauge will read just above the Low reading. It will move a tad bit higher when the RPMs are raised.

It only goes to the 9 O'clock position when the key is ON with the Engine Off.

 

Did you ever buy this truck? If so, now you can get an aftermarket gauge installed, but if the valves are getting oil and no ticking bad, then it probably will suffice as a winter beater.

 

TallPaul-

I have read all about your engine oil clog and I can't understand how you would get a clog at that point of the system. Only very small particles can make it past the pump (it is like a meat grinder). The only other place you could get a clog would be at the gasket surface between the pump and block due to excess gasket sealer, or a gasket that slipped. In any case you could have 60-80 PSI pushing at any clogging substance which would tend to push it out of the way and into the filter quick. I don't run a gasket there on my engines. I make sure the surfaces are smooth and flat and bolt the pump up tight.

Was your filter defective?

 

Thanks for the analysis. You bring up a good point. Some things just don't add up here. I would not expect a clog at that location either. I was thinking whether material could have dropped back down into that outlet, but this seems unlikely also. And the fact that the pump outlet was filled only suggests a good antidrainback valve. As for the weed whip cord meeting some resistance, that could be just because it and the passage had curves. I did not actually see any chunks come out of the passage. The filter was tested only for anti drainback valve. I put my thumb over the outlet hole and turned it upside down and saw that no oil came out the valve. Otherwise I could drain oil out the outlet hole. It was a Motorcraft filter too. The only facts are the gauge indicated no pressure, the sender was three weeks old and had functioned fine and does now, after 20-30 seconds of running there was no oil in the rockers at the front of the engine, with the new pre-filled filter and the exit line drained and refilled the oil pressure came right up. Loss of prime does not seem like the problem as the oil exit line would have been empty. So the only thing I can conclude is there must have been some kind of clogg in that line. I think the exit line takes a turn right about where it comes out of the block and perhaps there is a depression that can collect junk. Guess we'll never know for sure, but as Issac Asimov once said, "It would be very unexpected for the unexpected not to happen sometimes."

 

i just fought for 5 days to track down a loss of spark and after replacing everything on the ignition i traced voltage back and found a broken ign. wire at the 2.2k resistor on the drivers side firewall/fender area and NOW I HAVE IT RUNNING BUT NO OIL PRESSURE!!!!!!!!!!!!!! I have no oil at all visible through the fill tube. The sending unit is the large one but is so rusty it can't be functioning properly if at all. Would that cause my sudden and complete loss of oil pressure? After all i've been through already with this thing i really appreciate whatever help u got