91 FJ80 - Oil pressure question (1 Viewer)

[Matty N]

My 1991 LC (FJ80 - 3FE) oil pressure gauge pops right up to the 2nd line on start up/idle and just sits there regardless of driving conditions. Even when I punch it it doesn't move.

Truck is running well. Has 10w30 synthetic in it. Oil level is good.

I have read lots of threads in here on this topic and seems likely that the gauge isn't to be trusted so I guess I need to hook up a snap on gauge with PSI readings to know for sure what's what.

Wondering if anyone else has had this particular issue?

 

[Howard705]

Funny thing is I've had that for 15 years in my '79 40. Swapped a sender from another and still that way.

 

[Matty N]

Funny thing is I've had that for 15 years in my '79 40. Swapped a sender from another and still that way.

Thnx. Can the sender be working but the gauge still be broken?

 

[Offroads4x4]

Thnx. Can the sender be working but the gauge still be broken?

Yes

 

[SUMMIT CRUISERS]

The next time you do an oil change, I would change your oil to 15w40 and see if your oil pressure gauge increases. Another way is to add a quart of Lucas Oil Additive. Both will thicken up your viscosity and will increase your oil pressure. Your oil pressure gauge should correspondingly rise. If not, other is needed.

 

[Matty N]

The next time you do an oil change, I would change your oil to 15w40 and see if your oil pressure gauge increases. Another way is to add a quart of Lucas Oil Additive. Both will thicken up your viscosity and will increase your oil pressure. Your oil pressure gauge should correspondingly rise. If not, other is needed.

Thanks for that. I was thinking I might need a different oil.

But I still am massively suspicious that the pressure gauge is not working right. Granted, I am not nearly as knowledgable as most everyone who posts here but doesn't, as a matter of basic physics, oil pressure need to rise as the RPMs rise?

The only scenario I could understand this maybe not happening is a massively powerful engine and a very gradual acceleration. (Not the case, like I said I can peg the engine and the oil pressure needle doesn't budge).

Keep in mind, I am an idiot, so if there is another mechanical explanation (other than gauge malfunction) please lemme know.

Also worth noting... 219K and I don't think the HG has been done but (very) recent block pressure check was solid and no hydrocarbons in the radiator. No signs of over heating.

I will test the oil pressure manually soon. (Or maybe have my mechanic do it). Not sure how much I need to spend for good snap on gauge.

 

[SUMMIT CRUISERS]

BTW, don't get to worried about the HG on a 3FE. Cast iron head, and not known for HG failures. My son's 92 now has 350K on the original just about everything. Biggest bang for the buck to help possible future overheating and AC issues is to change the fan clutch fluid to 10k or 15k cst. Cost less than 10 bucks and works amazingly.

 

[powermad]

To plumb into the oil system with a gage you will need a BSP thread to standard adapter T-fitting.
I went to the local screw store and got an adapter fitting.
Thread the adapter into the hole for the sending unit. Have a pan handy as it will dump the filter when you remove the sender.
Thread the sender into one side and the gage into the other.


The sender is not a 1/8 pipe and it is not a 10mm x 1.5 straight fitting. It is a BSP tapered fitting.
Now you have a place to plumb in a mechanical gage as well if you want to run one.
I'm partial to Autometer with pillar pod mounts.

 

[Matty N]

BTW, don't get to worried about the HG on a 3FE. Cast iron head, and not known for HG failures. My son's 92 now has 350K on the original just about everything. Biggest bang for the buck to help possible future overheating and AC issues is to change the fan clutch fluid to 10k or 15k cst. Cost less than 10 bucks and works amazingly.

Thanks!

 

[Matty N]

To plumb into the oil system with a gage you will need a BSP thread to standard adapter T-fitting.

Thanks so much for pic. I was reading about this in the 'don't trust your oil sender' post and the pic really helps.

But do I need this for temporary psi check?

 

[powermad]

You will need either a T or straight adapter to check the pressure.
A T fitting allows you to check the dash gage against the tester to see what's going on.

Cornwell has a tester set that may have that adapter in it. $142 though.
http://www.cornwelltools.com/webcat...d-Transmission{47}Engine-Oil-Pressure-Tester#

Or a generic tester from Harbor Freight and a $3 fitting.

 

[Matty N]

Thnx. I will report back after I do a manual check. I think I can borrow a tester. If not I'll have my shop run the check.

 

[maxamillion2345]

Stock senders are really not very accurate. Nothing to be concerned over. Most modern ones are a switch, either you have oil pressure or you don't.