Oil Pressure Gauge Troubleshooting

[Kyle Boatright]

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

[Jim Carriere]

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.

[Morgans]

"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

[Kyle Boatright]

"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]

"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]

"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

[Morgans]

"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

[RST Engineering]

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
>

[Cy Galley]

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
>

[Kyle Boatright]

"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

[Cy Galley]

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
>