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  #1  
Old 10-12-2017, 05:14 PM
Robert M's Avatar
Robert M Robert M is offline
 
Join Date: Feb 2006
Location: South Carolina
Posts: 635
Default Oil pressure and the Hobbs

Hi gang!

After I did my first start everything seemed to be doing well except my oil pressure. I never got a reading from the gauge and the "low oil pressure light" never went off. As soon as I noticed, I shut the engine down.

Here's what I have......

The Van's OP gauge has power going to it and it is grounded. A signal wire goes from the gauge to the sender. The sender is attached to the firewall manifold with sealant on the threads. The firewall manifold also has the oil pressure switch attached with an aluminum connector tube between the placement of the sender and the switch. On the OP switch, the "NO" goes to the Hobbs. The "NC" goes to the OP light. The OP switch is grounded.

I want to make sure that I have everything connected properly before I start pulling things off the engine to look for oil (i.e. the filter). I am hoping that someone out there has a schematic/hand drawing/illustration to show the roper installation sequence for the Van's oil pressure sender to oil pressure gauge to Hobbs.

Thanks,

Robert
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  #2  
Old 10-13-2017, 01:27 PM
TS Flightlines TS Flightlines is offline
 
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Location: Ridgeland, SC
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Default

Was going to ask the question that you do actually have oil pressure, right?
Wouldnt be the first time. Check the oil pressure hose to the sender to see if oil is actually there. Hope so!
Tom
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  #3  
Old 10-13-2017, 10:41 PM
Go Guy Go Guy is offline
 
Join Date: Sep 2009
Location: Jenks, Ok.
Posts: 31
Default Oil Pressure

I just went threw what you are experiencing. Start with the cheap stuff first. I have replaced the transducer, hose, check grounds, many hrs of tinkering etc... Turns out the ten year old vans gauge was bad. It's the cheapest part! I didn't take my on advise, that cost me good coin.

If your light didn't come on, chances are the OP is fine. Did your hobbs keep counting? I did hook up a manual OP gauge to double check when mine quit showing pres. Then I started trouble shooting. Grounds can cause some headache.

If you put sealant on the transducer treads, that will not let the transducer ground unless you have a separate grd wire from the transducer to the plane, engine etc...

In my case, the gauge was bad.
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  #4  
Old 10-14-2017, 11:53 AM
drill_and_buck's Avatar
drill_and_buck drill_and_buck is offline
 
Join Date: Feb 2005
Location: Bridgewater, MA - KPYM
Posts: 403
Default

Hmmmm, interesting puzzle

Given:
1. No reading from the OP gauge
2. Low oil pressure light never went off
You have two separate sensors, that share the Oil Pressure port on the manifold, telling you that you have no oil pressure. You didn't mention if you recorded any hobbs time changes. That would be telling. You may have not run long enough to register a time click, but I would check. If you did record a hobbs change the implications are that there was sufficient oil pressure present to close the NO switch. That would be good news in that oil pressure is reaching your manifold.

Given that you have two separate indicators stating that no OP has reached the manifold, I would start there.

A quick check you can make....
1. Remove one spark plug from each cylinder
2. Disconnect the oil pressure hose from the manifold
3. Crank the engine for 10 seconds to see if oil is dispersed from the end of the hose.
4. If you did observe oil, reconnect the hose to the manifold and crank the engine 10 seconds on, 10 seconds off (without plugs) successively 3-4 times to see if you get an oil pressure reading on the gauge. Not sure what the OP switch trip point is for shutting off the light so it might still stay on. Various RVers have used this method to test/build up oil pressure prior to the first engine start.
5. If the above doesn't provide any new information and you have verified that oil is flowing the the manifold, try the following. Pick up an old school, round dial oil pressure gauge and plumb it either directly to the engine or replace one of the sensors at the manifold. Crank the engine again without the plugs and verify that you have pressure. Troubleshoot from there.

Good luck, let us know what you find.
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  #5  
Old 10-14-2017, 10:55 PM
PCHunt PCHunt is offline
 
Join Date: Feb 2007
Location: San Diego, CA
Posts: 1,483
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At the risk of being overly obvious, and I'm sure you've done this, but make sure there is oil in the engine. (You wouldn't be the first.....)

Did you do any kind of pre-oil? Spin the engine by hand with one plug removed from each cyl? Or a pre-oil rig until you saw oil pressure on the gage? Engage starter with one plug removed until you saw oil pressure?

If I am reading your post correctly, you have TWO indications of no oil pressure. That would surely get my attention!
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  #6  
Old 10-15-2017, 08:32 AM
gasman gasman is offline
 
Join Date: Mar 2007
Location: Sonoma County
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Are you using an anodized manifold? Anodizing insulates.
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  #7  
Old 10-16-2017, 09:21 AM
Robert M's Avatar
Robert M Robert M is offline
 
Join Date: Feb 2006
Location: South Carolina
Posts: 635
Default Oil pressure and the Hobbs Q & A

Quote:
Originally Posted by TS Flightlines View Post
Was going to ask the question that you do actually have oil pressure, right?
Wouldnt be the first time. Check the oil pressure hose to the sender to see if oil is actually there. Hope so!
Tom
Therein lies my problem, I'm not sure if I have oil pressure. I am going to disconnect the OP hose and look for signs of oil

Quote:
Originally Posted by Go Guy View Post
I just went threw what you are experiencing. Start with the cheap stuff first. I have replaced the transducer, hose, check grounds, many hrs of tinkering etc... Turns out the ten year old vans gauge was bad. It's the cheapest part! I didn't take my on advise, that cost me good coin.

If your light didn't come on, chances are the OP is fine. Did your hobbs keep counting? I did hook up a manual OP gauge to double check when mine quit showing pres. Then I started trouble shooting. Grounds can cause some headache.
The light DOES come on, it just doesn't go off. I have only run the engine for a few minutes at a time, I may not have built up enough pressure. Gonna check the lines and test the gauge with a auto OP gauge.

Quote:
Originally Posted by Go Guy View Post
If you put sealant on the transducer treads, that will not let the transducer ground unless you have a separate grd wire from the transducer to the plane, engine etc...
I DID put sealant on transducer threads, that will be the first thing I check after all other "simple things" are checked.

Quote:
Originally Posted by drill_and_buck View Post
Hmmmm, interesting puzzle

Given:
1. No reading from the OP gauge
2. Low oil pressure light never went off
You have two separate sensors, that share the Oil Pressure port on the manifold, telling you that you have no oil pressure. You didn't mention if you recorded any hobbs time changes. That would be telling. You may have not run long enough to register a time click, but I would check. If you did record a hobbs change the implications are that there was sufficient oil pressure present to close the NO switch. That would be good news in that oil pressure is reaching your manifold.

Given that you have two separate indicators stating that no OP has reached the manifold, I would start there.

A quick check you can make....
1. Remove one spark plug from each cylinder
2. Disconnect the oil pressure hose from the manifold
3. Crank the engine for 10 seconds to see if oil is dispersed from the end of the hose.
4. If you did observe oil, reconnect the hose to the manifold and crank the engine 10 seconds on, 10 seconds off (without plugs) successively 3-4 times to see if you get an oil pressure reading on the gauge. Not sure what the OP switch trip point is for shutting off the light so it might still stay on. Various RVers have used this method to test/build up oil pressure prior to the first engine start.
5. If the above doesn't provide any new information and you have verified that oil is flowing the the manifold, try the following. Pick up an old school, round dial oil pressure gauge and plumb it either directly to the engine or replace one of the sensors at the manifold. Crank the engine again without the plugs and verify that you have pressure. Troubleshoot from there.
Good luck, let us know what you find.
No Hobbs change either but I am going to follow your list of troubleshooting items.

Quote:
Originally Posted by PCHunt View Post
At the risk of being overly obvious, and I'm sure you've done this, but make sure there is oil in the engine. (You wouldn't be the first.....)

Did you do any kind of pre-oil? Spin the engine by hand with one plug removed from each cyl? Or a pre-oil rig until you saw oil pressure on the gage? Engage starter with one plug removed until you saw oil pressure?

If I am reading your post correctly, you have TWO indications of no oil pressure. That would surely get my attention!
Yes, I checked again, there is oil in the engine. When the engine was built, special lubricants were places at all of the rotating points of contact. My wife and my self hand cracked the engine for several minutes each, (whew), with no sign of OP on the gauge. I then used the starter to crank the engine (no top plugs) several times with still no OP.

Quote:
Originally Posted by gasman View Post
Are you using an anodized manifold? Anodizing insulates.
No anodizing on the manifold. As a matter of fact, there is no anodizing on anything aluminum in this plane. I have come to understand that anodizing weakens the aluminum. Found this out through RC helicopter pilots. It was discovered that the parts on their practice helicopters (no anodizing) never failed but the same parts that were anodized on the "show/contest" helis WERE failing.

Thanks again for all responses. I have more research to do. I will post my findings.

Robert
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RV-9, N556RM, O-320, Dual PMags, Catto 3 blade.
100% finished - flight ready - waiting for inspection.
Mosquito XEL kit in hangar waiting on RV-9 to fly.
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