Actual low oil pressure and converting oil pressure "gauge" on 1999 Ford Econoline

[m0zart]

My van:

• 1999 E-350 Super Duty XL Club Wagon with V8 5.4L gas engine, very good maintenance history, 152k miles
• I purchased the van about one month ago and have not yet gotten around to changing oil, investigating thoroughly, etc. yet.
• Oil pressure "gauge" has been erratic/intermittent, showing normal (mid-gauge), then dropping to zero, and randomly coming up again; OPS was replaced already
• I was able to borrow and connect a mechanical oil pressure gauge that in fact confirmed low oil pressure to me (showing 5-15 psi). See video of my real oil pressure reading in the following. Towards the end of the video I rev-ed the engine up to 2500rpm according to ultragauge/ODB-II reading:

  https://www.youtube.com/watch?v=K2Rq...ature=youtu.be

Two items I would like to resolve:

1. “idiot light” style gauge instead of a more sensitive indicator with “real” OPS
2. Low oil pressure

For the longest time I thought the oil pressure sending unit itself or the gauge on the instrument cluster were defective due to intermittent behavior showing either mid- or low- level that was exhibited by the gauge. I replaced the sending unit, singled out the respective wire behind the instrument cluster and cleaned all electric contacts thoroughly. More significantly, online I found out that the gauge is considered an “idiot light” equivalent as the dial of the gauge can only show binary states as per this forum post: https://forums.trailerlife.com/index...print/true.cfm

I understand the top causes for low oil pressure are:

• Low oil level
• Low oil viscosity/wrong oil
• Damaged/worn out oil pump/filter
• High level of dirt/grease sentiment in the engine that cause oil passages to become blocked

The mechanic I was able to borrow the mechanical gauge from was a little shady and charged me “all the cash I had on me” (being $14) to use his gauge, so I want to buy my own. I also want to deploy a “real” oil pressure sensor so I can convert my gauge as per this article: Ford Oil Pressure Gauge Fix


What I am asking or help with:

To tackle both items in one I need to know what the diameter and pitch of my oil pressure sender unit’s threads are. I could unwind the sender, take it to the store and measure it out, but this is messy and somewhat hard to get to, so I am wondering:

1. If there is a standard sized thread that I can look for when purchasing a “real” sender or mechanical gauge and
2. If there is any parameter in particular I can look out for when purchasing a “real” oil pressure sender unit.

Thanks all in advance!!

[arctictraveller]

I think your first order of business should be determining why you have low oil pressure, the mechanical gauge pretty well proves you do. i'm no expert, but I do know that running the wrong oil can cause damage, due to the small oil passages in the engine restricting flow. If someone ran too heavy an oil and starved the bearings, or ran it low, there could main bearing or rod bearing wear that allows the oil to escape before building pressure. I would purchase an oil sample kit and send a sample away for analysis. If they find wear metals, that could help diagnose the issue, but hopefully it's something simple though. There are plenty of folks here more knowledgeable than I am, perhaps they have better ideas. Good luck......................

[daveb]

I agree a oil sample might be a good move. Hopefully you find the cause. My chevy truck had similar issues and it was the oil pump pickup. Not saying that is your problem though. My issue gave me trouble over several years and kept getting worse.

[JWA]

Well sorry to break the news to you but its highly possible your entire engine is on its way out. My '05 E350 with 5.4 had a somewhat repeatable low oil pressure warning light, alarm and OP dash "gauge" dropping to zero before popping back up. I too changed the OPS to absolutely no positive effect--same situation.

Heeding the Work Shop Manual's procedure or specification of OP at hot idle being 25 PSI minimum my first test with 5W-20 syn-blend oil showed a whopping EIGHT POUNDS. A trusted mobile fleet mechanic suggested a concoction of 15W-40 diesel oil and one quart of Lucas Oil Stabilizer---OP at hot idle jumped all the way up to FIFTEEN PSI.

A new engine fixed the OP problem, the replaced engine had about 145K miles, had supposedly been "carefully maintained". Typically oil pressure readings that far below the factory spec of 25 PSI isn't the cause of anything other than a failing oil pump or main/rod bearings worn to the point the engine won't hold its oil pressure.

As for your IC OP "gauge"---rather than muck about with all those mods on an existing E-Series cluster add an aftermarket real OP gauge---I use Auto Meter GS Series myself but cost isn't a consideration. There are other very good quality gauges that would work fine. Once upon a time I too considering buying a gently used IC to experiment with modifying it but in the end preferred the aftermarket gauge.

FWIW the best place for an OP sender is in the same spot Ford installs their own. I kept the factory sender only to shut the IC from sounding off but added a brass t-fitting so both the factory OPS and aftermarket senders could be used simultaneously.

You can also use an oil filter adapter sandwich plate to add a sender point if you're not up to adding the brass tee fitting. This photo shows the factory OPS on top of the tee-fitting, the aftermarket sending unit would be where the blue fitting is now.