Erratic oil pressure ideas. Have aftermarket gauge.

[jayro88]

This past summer I installed an aftermarket oil pressure gauge in my '88 e250. I have it T'ed in along with the stock one. It is a digital AutoMeter one. When I first installed it I would consistently have about 12psi hot idle and 37psi on the hwy with the cruise set at 65mph. It would follow the expected behavior. It would increase and decrease with load/rpm. As is got into the dead of winter and was consistently staying below 0*F the readings started getting weird. It would bounce around until it had been running at temp for a while.....sometimes almost 10psi. One second it would as 37psi and the next it would say 27psi and then back agian. Now that it is warmed up it has not returned to normal. It seems to get stuck at about 33psi. Oil pressure seems good. Pressure jumps the second I take off. In 3rd gear (c6 trans w/3.54) I have 30-31psi just maintaining 35mph on completely flat ground, but after that it is like the pressure doesn't want to go up. It works its way up to 33psi with the CC set at 65mph. Sometimes after cruising for a while it jumps up to the normal 37psi and stays there, sometimes not.

I am thinking that it is something with the sender and am going to order a new one. The reason I think the pressure is okay and the sender is bad is because if I am cruising at 65mph/33psi and turn off the cruise to let the van just coast the oil pressure stays right at 33psi until the speed drops to almost 40mph (all coasting with no throttle). I would expect there to be a quicker drop if I completely let off the throttle. I will also sometimes get a higher reading, by 1-2psi, when I lessen the throttle input (like going down a hill). Then I may lose 1-2psi when I add more throttle (like going up a hill).

I pulled my oil filter and verified that the oil pressure regulator is shut al the way. Van has 150K on it. I have had it for 30k and consistently maintain it. It is very clean for its age and appears to have been well maintained prior to me having it.

Besides a bad sender, is there anything else I should check. Is there something that could be gumming up that is preventing full flow to the gauge sender location. I ran some AutoRx through it when I first got is 30K miles ago. Is it possible that the pressure regulator valve spring is getting tired? Should I pull the oil cooler block and look at replacing or shimming the spring? Is there an oil additive that I should add to help boost the oil pressure a little?

I could just be paranoid, but I am wanting to drive the van for another 300K miles including family trips and towing. Thanks

 

[79jasper]

Start with the sender and gauge before anything. Gauge being well below freezing, then taking a big pressure spike of a cold start probably fouled it up.
May need a higher quality gauge.

Sent from my SM-G900R4 using Tapatalk

 

[jayro88]

Start with the sender and gauge before anything. Gauge being well below freezing, then taking a big pressure spike of a cold start probably fouled it up.
May need a higher quality gauge.

Sent from my SM-G900R4 using Tapatalk

Ordered a replacement sender. Should be here on Tuesday. Going to start there and see what happens. It's the inconsistency that makes me think it is not an issue with bearing wear and low pressure. I went with Auto Meter since I had heard they made quality gauges. Hopefully it will just be a bad sender.

 

[tbrumm]

Just a little food for thought: I also have an autometer analog electric oil pressure gauge. At least on the regular analog gauges, that sender is pretty big. After the first sender went bad, I mounted the next one "remotely" in a rubber cushioned clamp on the cowl above the fitting in the block. I connected it with a section of high quality grease gun hose. Has been in there for over three years now with no issues. The diesel vibrations probably don't do these sender units any good. I can't remember if the Autometer instructions said something about mounting the sender off the engine or not.

 

[jayro88]

I reread the instructions. It does mention that for high vibration engines you can attach it with a piece of hose and a pair of clamps. I may have to try it that way.

 

[cpdenton]

I connected it with a section of high quality grease gun hose. Has been in there for over three years now with no issues. The diesel vibrations probably don't do these sender units any good. I can't remember if the Autometer instructions said something about mounting the sender off the engine or not.

Did you have to run a separate ground wire to the sending unit installing it this way?

 

[tbrumm]

Did you have to run a separate ground wire to the sending unit installing it this way?

Yes, I did run a separate ground wire - never tried it without one - just figured it would require it. The rubber cushioned clamp certainly insulates the sender from ground otherwise.

 

[IDIBRONCO]

In my opinion, the only way to get a good oil pressure reading is to install a non-electric gauge. I just don't trust the electric ones. I also don't use the plastic oil line that comes with the gauge. I buy an install kit that has copper line. Nothing worse than a cold plastic line breaking.

 

[Agnem]

Just a little food for thought: I also have an autometer analog electric oil pressure gauge. At least on the regular analog gauges, that sender is pretty big. After the first sender went bad, I mounted the next one "remotely" in a rubber cushioned clamp on the cowl above the fitting in the block. I connected it with a section of high quality grease gun hose. Has been in there for over three years now with no issues. The diesel vibrations probably don't do these sender units any good. I can't remember if the Autometer instructions said something about mounting the sender off the engine or not.

That's the way Ford mounted them on the 1983 models, before somebody got cheap and started putting them right on the engine. I'm not a fan of mechanical sensors. I'd rather have a failed sensor, then an oil leak in the cab. The Isspro stuff is really good, and since I started selling them, I haven't had one come back.

 

[jayro88]

So I think I have it fixed. I replace my senders, the stock one and the Autometer one. I took tbrumm's advice and insulated the Autometer sender from the engine vibration with a short piece of 1/4" fuel line, a couple of barb fittings and some hose clamps. I had to add a ground wire since the sender was now insulated.

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Seems to be fixed. I didn't take it for a drive yet since I didn't feel like installing the doghouse and then uninstalling it to do some more work tomorrow (yeah, I was feeling that lazy). I fired the van up and let it idle for a good while. Long enough to bring it up to operating temperature and then some. Hot idle PSI settled at 13-14. Pressure would steadily climb to 36-37 psi when I would give it throttle. This is good since before it would only go up to 33 psi at about 55mph, then drop 1-2 psi and sit on 31 or 32 psi at anything above 60mph regardless of rpm or speed. I guess I will know tomorrow for sure. Thanks for all the suggestions.

 

[PwrSmoke]

Bear in mind that your engine's LIFE rests with a short piece of cheap hose and two 50 cent hose clamps. Is the hose up to years of heat and chemicals? Will the clamps loosen and leak? High quality braided hose with fitting crimped in are usually chose for vital tasks like this. If that hose fails while you are going down the road, all the oil will be pumped out of the engine in a minute or so.

 

[jayro88]

Thanks for pointing that out. I have a braided stainless line on the way to replace it.

 

[PwrSmoke]

Sounds like you are on top of it then. Good man! I was just making sure so we wouldn't have to agonize over hearing your engine had burned up sometime down the road because a hose failed.

 

[chris142]

the copper line brings every engine noise into the cab with it! i added a short piece of plastic line to mine to stop the buzzing

 

[mohavewolfpup]

Ironically I have this going on with a 6.5 diesel currently. Very annoying. (supposedly) another mechanic tore it down and didn't find anything. The stock gauge and a aftermarket one still show screwy oil pressure. It's also been driven probably around 1k (or more) miles since the low oil pressure "problem" popped up, and hasn't left the driver dead at the side of the road. It's parked now, just moved around now and then. But still runs.

Very annoying!