Oil Pressure Gauge Troubleshooting

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.

"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

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

Remove the hose and see if you can look thru it.

"Kyle Boatright" wrote in message
. ..

"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

"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