Oil Pressure Gauge Troubleshooting

I was out flying this evening (Beautiful evening in North Georgia. We don't
get better flying weather than today...) and noticed that my oil pressure
was "stuck" at 100 PSI. I reduced throttle and RPM, no change, I increased
throttle and RPM, again no change. I tapped the face of the gauge. No
change.

Eventually, I shut down the radios and transponder and turned off the master
switch. The OP gauge fell to zero. Back on with the master and it's 100 PSI
again. By the time I returned to my home field, the pressure gauge seemed to
be acting normal again, so I presume it is going to be an intermittant
problem - the absolute worst kind to diagnose.

Anyway, the gauge and sender are both Rochester brand. Probably 6 years old
(4.5 years flying)with 350 or so tach hours on 'em.

How do I diagnose the problem when it recurrs?

Thanks in advance.

KB

Kyle Boatright wrote:

I was out flying this evening (Beautiful evening in North Georgia. We don't
get better flying weather than today...) and noticed that my oil pressure
was "stuck" at 100 PSI. I reduced throttle and RPM, no change, I increased
throttle and RPM, again no change. I tapped the face of the gauge. No
change.

Eventually, I shut down the radios and transponder and turned off the master
switch. The OP gauge fell to zero. Back on with the master and it's 100 PSI
again. By the time I returned to my home field, the pressure gauge seemed to
be acting normal again, so I presume it is going to be an intermittant
problem - the absolute worst kind to diagnose.

Anyway, the gauge and sender are both Rochester brand. Probably 6 years old
(4.5 years flying)with 350 or so tach hours on 'em.

How do I diagnose the problem when it recurrs?

This is a gauge with a remote sender mounted on the engine, right? I
ask that because what you are describing sounds like a wetline gauge
with some air in the line and cold oil.

Maybe the sender is dying. Can you see if the voltage in the
electrical line between the gauge and sender varies with oil
pressure? Then you could eliminate one part or the other.

"Kyle Boatright" wrote

Anyway, the gauge and sender are both Rochester brand. Probably 6 years
old
(4.5 years flying)with 350 or so tach hours on 'em.

That is a lot of time and hours on a sender. I would be surprised if it is
not the sender.

Most senders fail when oil gets past the pressure side, and gets into the
dry side. You really can't usually see the problem, but sometimes, you can
see oil (a small amount) oozing out around where the wires hook on.

If you put voltage onto one lead of the sender, you should see the other
terminal voltage go up and down with RPM. If not, bad sender. You can
check the gauge by inputting differing voltages, from zero to 12 (or 28) and
watch the oil pressure go up and down.

If the sender is fairly inexpensive, replace it. It is due. Your mileage
may vary.
--
Jim in NC

"Jim Carriere" wrote in message
.. .
Kyle Boatright wrote:

I was out flying this evening (Beautiful evening in North Georgia. We
don't get better flying weather than today...) and noticed that my oil
pressure was "stuck" at 100 PSI. I reduced throttle and RPM, no change,
I increased throttle and RPM, again no change. I tapped the face of the
gauge. No change.

Eventually, I shut down the radios and transponder and turned off the
master switch. The OP gauge fell to zero. Back on with the master and
it's 100 PSI again. By the time I returned to my home field, the pressure
gauge seemed to be acting normal again, so I presume it is going to be an
intermittant problem - the absolute worst kind to diagnose.

Anyway, the gauge and sender are both Rochester brand. Probably 6 years
old (4.5 years flying)with 350 or so tach hours on 'em.

How do I diagnose the problem when it recurrs?

This is a gauge with a remote sender mounted on the engine, right? I ask
that because what you are describing sounds like a wetline gauge with some
air in the line and cold oil.


This is an electronic gauge with a sender mounted on the engine accessory
case.

Maybe the sender is dying. Can you see if the voltage in the electrical
line between the gauge and sender varies with oil pressure? Then you
could eliminate one part or the other.

You could, but that would mean working awfully close to a flailing prop.
I'm not up for that. ;-)

KB

"Kyle Boatright" wrote in message
...

"Jim Carriere" wrote in message
.. .
Kyle Boatright wrote:

I was out flying this evening (Beautiful evening in North Georgia. We
don't get better flying weather than today...) and noticed that my oil
pressure was "stuck" at 100 PSI. I reduced throttle and RPM, no change,
I increased throttle and RPM, again no change. I tapped the face of the
gauge. No change.

Eventually, I shut down the radios and transponder and turned off the
master switch. The OP gauge fell to zero. Back on with the master and
it's 100 PSI again. By the time I returned to my home field, the
pressure gauge seemed to be acting normal again, so I presume it is
going to be an intermittant problem - the absolute worst kind to
diagnose.

Anyway, the gauge and sender are both Rochester brand. Probably 6 years
old (4.5 years flying)with 350 or so tach hours on 'em.

How do I diagnose the problem when it recurrs?

This is a gauge with a remote sender mounted on the engine, right? I ask
that because what you are describing sounds like a wetline gauge with
some air in the line and cold oil.


This is an electronic gauge with a sender mounted on the engine accessory
case.

Correction, this gauge is mounted on the firewall, and has a 12" or so hose
connecting it back to the oil pressure pick-up port on the engine.

KB

"Kyle Boatright" wrote in message
...

"Kyle Boatright" wrote in message
...

"Jim Carriere" wrote in message
.. .
Kyle Boatright wrote:

I was out flying this evening (Beautiful evening in North Georgia. We
don't get better flying weather than today...) and noticed that my oil
pressure was "stuck" at 100 PSI. I reduced throttle and RPM, no
change, I increased throttle and RPM, again no change. I tapped the
face of the gauge. No change.

Eventually, I shut down the radios and transponder and turned off the
master switch. The OP gauge fell to zero. Back on with the master and
it's 100 PSI again. By the time I returned to my home field, the
pressure gauge seemed to be acting normal again, so I presume it is
going to be an intermittant problem - the absolute worst kind to
diagnose.

Anyway, the gauge and sender are both Rochester brand. Probably 6 years
old (4.5 years flying)with 350 or so tach hours on 'em.

How do I diagnose the problem when it recurrs?

This is a gauge with a remote sender mounted on the engine, right? I
ask that because what you are describing sounds like a wetline gauge
with some air in the line and cold oil.


This is an electronic gauge with a sender mounted on the engine accessory
case.

Correction, this gauge is mounted on the firewall, and has a 12" or so
hose connecting it back to the oil pressure pick-up port on the engine.

KB

Man, I can't get things straight this morning. The sender is on the
firewall, fed by the 12" hose.

Sheesh. No wonder I rarely post in the AM.

KB

"Kyle Boatright" wrote

You could, but that would mean working awfully close to a flailing prop.
I'm not up for that. ;-)

How about checking it at the back of the gauge? If you can't do that, Hmm.
Replace the sender?
--
Jim in NC

Yeah, it looks like your snippit button fails at midnight also.

Jim


"Kyle Boatright" wrote in message
...



Sheesh. No wonder I rarely post in the AM.

KB

Is the hose clear? Sounds almost like you have a check valve in the line.
Did you make up the hose by putting on ends? If you made the hose or had it
made to length, there is a possibility that a "donut" has been cut out of
the hose side wall making a flapper valve. Happens when someone doesn't use
a mandrel.
--

--
Cy Galley - Chair,
AirVenture Emergency Aircraft Repair
A Service Project of Chapter 75
EAA Safety Programs Editor - TC
EAA Sport Pilot

wrote in message
...

"Kyle Boatright" wrote in message
...

"Kyle Boatright" wrote in message
...

"Jim Carriere" wrote in message
.. .
Kyle Boatright wrote:

I was out flying this evening (Beautiful evening in North Georgia. We
don't get better flying weather than today...) and noticed that my oil
pressure was "stuck" at 100 PSI. I reduced throttle and RPM, no
change, I increased throttle and RPM, again no change. I tapped the
face of the gauge. No change.

Eventually, I shut down the radios and transponder and turned off the
master switch. The OP gauge fell to zero. Back on with the master and
it's 100 PSI again. By the time I returned to my home field, the
pressure gauge seemed to be acting normal again, so I presume it is
going to be an intermittant problem - the absolute worst kind to
diagnose.

Anyway, the gauge and sender are both Rochester brand. Probably 6
years old (4.5 years flying)with 350 or so tach hours on 'em.

How do I diagnose the problem when it recurrs?

This is a gauge with a remote sender mounted on the engine, right? I
ask that because what you are describing sounds like a wetline gauge
with some air in the line and cold oil.


This is an electronic gauge with a sender mounted on the engine
accessory case.

Correction, this gauge is mounted on the firewall, and has a 12" or so
hose connecting it back to the oil pressure pick-up port on the engine.

KB

Man, I can't get things straight this morning. The sender is on the
firewall, fed by the 12" hose.

Sheesh. No wonder I rarely post in the AM.

KB

"Cy Galley" wrote in message
news:lFh5f.442882$x96.137443@attbi_s72...
Is the hose clear? Sounds almost like you have a check valve in the line.
Did you make up the hose by putting on ends? If you made the hose or had
it made to length, there is a possibility that a "donut" has been cut out
of the hose side wall making a flapper valve. Happens when someone
doesn't use a mandrel.
--

--
Cy Galley - Chair,
AirVenture Emergency Aircraft Repair
A Service Project of Chapter 75
EAA Safety Programs Editor - TC
EAA Sport Pilot


The hose was from a mail-order racing parts supplier (Summit Racing, IIRC)..
It is one of their stock lengths. No idea if they use mandrels or not.

KB