Oil pressure gauge problem.

Messages
49
Location
Hartford CT.
About 3 months ago I installed an Autometer mechanical oil pressure gauge. The feed line comes from the extra port near the factory oil switch and the gauge is mounted on the A-pillar. Everything was working fine, then one day while cruising down the highway, I notice that the gauge was reading about 10psi lower than normal. I tap the gauge and it jumps up to about where it should, I toss it off as just a little sticky. Problem is, that it's still doing it and tapping the guage now, does nothing. At idle the reading is right on and when cold it does read above the cruise pressure. I also have an Accusump with a pressure gauge on the air side. The two gauges used to follow each other closely but now the oil one lags behind. Is it possible that the gauge is only sticky within a certain range, 60-70psi??? Or is there something else going on??? Is it possible that my Canton Mecca filter is getting clogged at only 6800mi?? KG
 
Messages
13,132
Location
By Detroit
Sounds like you should talk to an Autometer customer service tech as maybe the gauge is defective. As for your other speculations, I really would not know. Some have said air in the line can cause problems, but I was told by a gauge company that air in the line does not matter and all both my mechanical gauges (Autogauge by Autometer) work fine that way.
 

kgcobra320

Thread starter
Messages
49
Location
Hartford CT.
Yeah, I emailed Autometer and they gave me the standard, "We don't know, but if you send it to us with the receipt we'll look at it". I had asked them about the air in the line when I first installed them and they said it was fine. You would think if my fullflow was getting clogged that it would have been more gradual. KG
 
Messages
13,132
Location
By Detroit
Sometimes better to talk directly with the tech. Could replace the filter and see if it changes, but a messy job. Gary Allen may have some insite as he has studied pressure and filters a lot.
 

kgcobra320

Thread starter
Messages
49
Location
Hartford CT.
I have the canister type so changing it is easy but the elements are expensive. I suppose that I could just put the old one back in if it wasn't the problem. I was hoping that Gary would be around to provide some input as well. KG
 
Messages
13,132
Location
By Detroit
So I am wondering if you are still having the problem or if maybe it has resolved itself with a bit of driving? Maybe a fleck of crud blocking the relief valve partway open and if fell dislodged after a while.
 

kgcobra320

Thread starter
Messages
49
Location
Hartford CT.
The idle pressure started showing low as well, so I changed the filter. The idle pressure now shows normal but the cruise pressure is still about 10psi low. I'm fairly confident that the pressure is normal because the gauge on the air side of the system does not reflect this problem. Just seems like a weird failure mode for a pressure gauge. I can see sticky or having a permenant offset but this is just strange KG
 

kgcobra320

Thread starter
Messages
49
Location
Hartford CT.
Problem solved! Anyone trying to decide between mech and elect oil pressure gauges might want to consider this: I have 2 mech oil pressure gauges in my 99 cobra. One is plumbed into the extra block port and the other is connected to the air side of my Accusump. After the install I noticed that during cold operation the pressures push the 100psi mark and beyond. I was a little concerned but everthing seemed to be functioning perfectly, for about 3 months that is: Then sometime during September I noticed that the pressures wern't normal. Low at cruise, ok at idle, the 2 gauges not correlating anymore???? What happened????.........The cool September mornings here in New England is what happened. It took a while for me to figure it out but that's what happened. The pressures were already pushing the limits of the gauges and when the temps dropped, the pressures increased. Both gauges are now internally damaged and now have a permenant offset of about 10psi!!!!! They were expensive and difficult to install and now they're ________!!! I could send them back to Autometer and they would probably fix one of them but it will be obvious to them that the limits have been exceeded and would probably not fix both. Most mech oil pressure gauges have a limit of 100psi and will not work at mod motor pressures, especially during cool weather.(Maybe ok if you live in a warm climate zone?). I did see that Autometer does make one oil pressure gauge that goes to 150psi in the Phantom series and should work just fine. Unfortuneately at this point I already have a bunch of the Lunar series. Also I believe that the elect. gauges will not be damaged during pegged operation and would probably be a better overall choice. The elect oil pressure sending units are prone to failure though, due the vibration when mounted on the block and would require remote mounting. KG
 
Messages
13,132
Location
By Detroit
I once had the bright idea of testing a mech oil pressure gauge with my electric air pump. Good thing the gauge only cost me $5. I flipped on the air pump while hooked to the gauge and pegged the needle. Turned off the air and the needle was somewhere midway. I manually twisted the needle back to zero and it seems fine now, but I don't want to use it anymore. I have better gauges anyway.
 
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