Weird oil gauge movement

After a long time I'm back with a weird problem with my oil gauge on my 88 7.3.
I know that it's just a 'idiot light' and not meant to be moving - but now it does !!! ...but in a 'bad' way:

If i accelerate the pressure drops so far that the engine light comes on. If I let off the throttle it comes back to normal. I know for a fact that I still have oil pressure because I have another mechanical gauge hooked up but I wonder if the top end is loosing oil pressure? My mechanical gauge is hooked up at the bottom oil gallery (the plug near the oil filter just a bit over the oil pan).

What could that be? Any thoughts?
Its not all of a sudden dropping to 0, it's moving with engine RPM. It drops to about 0 at 2000RPM.
(0 as in zero, not O in nOrmal)

By chance are any of the other gauges acting up?

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No. They all work like they should.
I already though of a ground problem, but I think then they should all act up

This occasionally happens to my oil pressure. The slip connection on the sending unit starts to short causing some wild gauge movement. I've had the same issue, acceleration drops it and coasting brings it back. I gently squeeze the actual slip connection with pliers when it gets frequent and that makes everything happy again for awhile.

That means i have to somehow bend me in shape to get behind/underneath the turbo :-\ I'll try to look at it.
Is there a possibility that this could also be the spring in the oil filter head? Or something else?
Engine sounds totally normal with 'no oil pressure'.

Your engine is fine, I can almost guarantee this is an electrical issue

The factory oil guage is basically useless, if you turn on the fan in my truck oil pressure goes up, or turn on headlights, the more eltrical load on the truck the higher the oil pressure lol

I'm no expert on the path that the oil flows in the engine, but I'm pretty sure that it goes from the pump to the filter and the oil cooler, then to the rest of the engine. Unless you've tapped into an oil galley somewhere between the oil pump and the cooler, then your mechanical gauge and the factory one should be reading the same oil pressure. How they display it on their respective gauges, of course, will look different since they're two different designs.

If you have a solid mechanical gauge that you trust, I personally would recommend leaving it alone if it's cumbersome to get to. I have the factory setup, so the sending unit sits on the turbo feed line. Easy to access. Erratic gauges can be annoying, but like many have said before it's just a glorified idiot light.

I will look if i can get to it in a couple days. It would be nice if its right in the turbo feed but I have a aftermarket ATS088 on it and the sending unit is burried in its old place - right under the turbo

Please go read my no oil pressure post. I have no oil psi at the top port at all, but 45 lbs at idle on the lower port. Oil does come out the top one but no pressure. Not to scare you but I been fighting this for weeks now and can not locate the issue

I used Rotella for years until folks on here suggested there were better oils for these particular engines. When I switched to Mobile Delvac it was a noticeable difference on my factory gauge + less oil consumption between changes. Factory gauge is taped into turbo on mine.

pelky350 said:

The factory oil guage is basically useless, if you turn on the fan in my truck oil pressure goes up, or turn on headlights, the more eltrical load on the truck the higher the oil pressure lol

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This.

My 87 6.9's factory oil gauge wanders all over the place. At idle, it bobs around near the first line, making the "Engine" light come and go. It has a mechanical oil pressure gauge that a previous owner installed. At that same idle, it has 12-15PSI when at full operating temperature (higher when cold or partly warmed up). From what I have read, that's normal readings on these engines.

The factory gauge though? It fusses about low oil pressure at idle and screams at you with the engine light, which just isn't true. The tiniest bit of throttle makes the gauge go up drastically and the light turns off. As I understand it, that gauge goes by resistance or some crap. The Ford "fix" was to add a resister which forces the gauge to stay mid way with the key turned, being even less accurate!

catbird7 said:

I used Rotella for years until folks on here suggested there were better oils for these particular engines. When I switched to Mobile Delvac it was a noticeable difference on my factory gauge + less oil consumption between changes. Factory gauge is taped into turbo on mine.

Click to expand...

I've only gone through two oil changes since I got my truck. I don't know what oil (and additives?) it had when I got it but it didn't seem to use any oil. Or not enough to be of concern, anyway. On the first change, I put Rotella T5 (semi-synth) because it as on sale at O'Reilly with double points. It was using the oil pretty heavily, but I also was driving it in mountains across country for a couple months. (I travel/live out of my truck camper full time, so yeah)

Anyway, since it was using a lot, I bought some cheaper Maxlife 15w40 ($15/gallon) after I used up the remaining gallon from the change. (I run the FL-1995 oil filter, with an extra quart required). After I used that up too, I bought the cheap Walmart oil ($10/gallon) since I've read that it's good quality oil. When I did my last change, I switched entirely to that oil. Sadly, it's using oil just as bad as ever. About a quart within 200-300 miles. Hard to say exactly.

However..... I have been around a city for a few months now and I do a lot of stop and go without fully warming up the engine most of the time, so that might be a factor. I added some Lucas heavy duty oil stuff to it (the thick as maple syrup stuff) but I didn't add the full quart. I added some when I noticed the level was down twice. This last time, it had gotten down below "add" a little. So I added about a quart and a half more of the cheap Walmart oil I already had on hand, and a small bit more of the Lucas stuff. It was about 65% of the way up the crosshatch area so I left it at that since it may not have been at full operating temp.

Driving up a very steep hill and trying to maintain 30mph, I was leaving a cloud of..... I'm not sure what color smoke. Grey? Blue? Can't tell by looking in your mirror while in motion. It wasn't black, I know that. I saw that at 8000+ ft in Colorado and thankfully didn't blow my engine. I don't think anyway. Unless it caused higher oil consumption after that?

I only finally installed a proper water temp gauge the other day and the little bit I have driven around town, the highest I have seen it show is 180, with ample heat coming from the AC system. I have yet to see how it does on that steep hill I mentioned, since I haven't been over there since I put the gauge.

But anyway, I have read that the Delvac is good in these.... so I grabbed a gallon and will switch to adding once I start getting low again. Next oil change, I'll put just Delvac (no Lucas, at least to start with) and see how it does.

I use Delvac MX 15W40 in my IDI and Powerstroke. The IDI did consume some oil too before that (whatever the preowner used?) and after I changed to Delvac no oil needed to be added between oil changes. Same with the Powerstroke which is do for an oil change now (almost 5000mls reached).