Oil pressure gauge operation

[tommyg 154]

Since I now have a new engine complete with an oil sending unit, I decided to fill the last space on my D180's instrument panel with an oil pressure gauge. Picked up a VDO 0-80 psi gauge to fit the opening. There are 3 terminals. The one marked "+" I have hooked up to the power from the ignition switch when I turn the key. The one marked "S" is hooked up to the sending unit. The middle terminal marked with a green dot is the ground, and I have it hooked up to the ground accordingly. 

When I turn the key, the gauge maxes out at the top of the range. When I start the engine, it stays there. I tried disconnecting the wire from the sending unit but still the same behavior. What am I missing here?

[953 nut 59,327]

Is the sending unit the one that came with the gauge?  Is the gauge wiring the same as the instructions for the gauge? I know that reading instructions is not the manly thing to do but it can be important.

[tommyg 154]

The sending unit is not the one that came with the gauge. It was already on the engine when I installed it. And yes, I sucked it up and read the directions. The only thing I can put my finger on is that the ohm range of the sender needs to match the range of the gauge. Not sure how I measure that.

[gwest_ca-(File Mod) 11,393]

Perhaps the sending unit is for a light. Try turning the ignition  to just on without the engine running. The gauge may go to 0 psi. Most gauges will go to max when the sending unit is open or wire not connected. 

Garry

[953 nut 59,327]

Sounds like you have come up with the solution to the problem, new sending unit.

[tommyg 154]

Perhaps the sending unit is for a light. Try turning the ignition  to just on without the engine running. The gauge may go to 0 psi. Most gauges will go to max when the sending unit is open or wire not connected. 

Garry

Just turning it on the ignition sends the gauge to max psi at 80. 953nut, is there a way to test a sending unit for proper operation? Is there a difference between a sending unit for a light and a sending unit for a gauge?

[953 nut 59,327]

The sending unit for an idiot light is an on/off switch, on without pressure and off at the set-point. For a gauge you have a veritable resistance compatible with your unit.

[tommyg 154]

So it sounds like I need to replace the sending unit with one designed for a gauge. Thanks!

[pfrederi 18,566]

Cheaper solution get a Sunpro Mechanical oil pressure gauge. Works just great on my D200.  About Cheaper solution get a Sunpro Mechanical oil pressure gauge. Works just great on my D200.  About $15

5

http://www.amazon.com/Sunpro-CP8216-StyleLine-Mechanical-Pressure/dp/B000FJS4PO

Your sending unit should show varying levels of resistance as the engine starts and builds oil pressure, problem is that range of variance has to match the gauge...unless the sending unit and gauge are same brand that is unlikely

Edited October 2, 2015 by pfrederi

[tommyg 154]

I took a gamble and ordered a sending unit that appears to match the spec required for the gauge. We'll see when it arrives next week if it will work. So the does the mechanical version just replace the sending unit with connected tubing of sorts?

Edited October 3, 2015 by tommyg

[squonk 43,448]

Sometimes the sending unit for a gauge will work exactly opposite than what's needed for the gauge because of what brand it is. I used to work at a Napa and we had a customer that built seaweed sucking machines for all along the great lakes. They always used Stewart Warner gauges and a certain sender part #. Well Napa dropped SW for a while and the substitute for it was VDO. They were installing these senders on the bottom of the tank. They filled the 250 gal diesel tank and then found out that VDO gauge still read empty. They drained the tank (They weren't happy )  and now the gauge went to full. They really wern't happy about getting that smelly sender out of the tank and having to replace it with a totally different sender so they found another place to get SW.

As a side note, the shop burn't down one night with a just completed unit inside full of diesel. Place was an 1/8 mile from my house. Night sky looked like the 4th of July! 

Edited October 3, 2015 by squonk

[tommyg 154]

I was conscious of that as I searched for the sender. Both the gauge and sender are VDO. Gauge reads 0-80 psi. Sender specs are 0-80 psi. Keeping my fingers crossed.

[pfrederi 18,566]

I took a gamble and ordered a sending unit that appears to match the spec required for the gauge. We'll see when it arrives next week if it will work. So the does the mechanical version just replace the sending unit with connected tubing of sorts?

Gauge comes with nylon tubing that you run from the port on the engine to the gauge unit.

[tommyg 154]

Looks like I'm going to have to go  with a mechanical gauge after all. Not because the new sending unit didn't work. Rather it didn't fit between the engine block and the bottom plate of the air filter where it's located. Grrr. This is becoming a time consuming project! But at least I've learned a thing or two.

I'm curious, Paul, these gauges are really inexpensive compared the electrical ones. $5 each on Amazon. Thinking about replacing the entire set with these except for the hour meter. I can get away with $15 (plus shipping) for the oil pressure, oil temp and volt meter. How do you think I would replace an electrical temp gauge on my D180 (the sending unit is on the hydropump) with a mechanical one? Would the adapters they include fit? It comes with 72" of capillary tubing and 5/8" NPT fitting. Also includes 1/4, 3/8, and 1/2" adapters. What do you think?

Edited October 8, 2015 by tommyg

[JackC 617]

"Rather it didn't fit between the engine block and the bottom plate of the air filter where it's located. Grrr. 

Is there a plumbing fitting you can use to re-position it off the port like a 45 degree elbow?

[squonk 43,448]

If it's a std. pipe thread, a 45 deg brass street elbow should do the job.

[tommyg 154]

Already looked at that idea. It's so tight underneath that filter housing.  A 90 deg elbow won't work because it will hit the throttle linkage. I'll look one more time with a 45 in mind, but I have a hunch that's not going to work either. 

[JackC 617]

How about a picture of your engine and situation?
As they say, there is usually more than one way to skin a cat.
We have a ton of cat skinners in the membership.
I am very interested because I would like to do the same thing you are trying to do.
Are you working with a D-160 with the ONAN 16hp engine?
 

[pfrederi 18,566]

Tommy... The mechanical temp gauge for the hydro temp will NOT work.  Been there tried that.  The bulb (sending unit if you will) is to long to fit into the hydro pump housing.  

[tommyg 154]

Well, I thought I had it figured out. I installed a 1" brass straight fitting and then 90 deg fitting followed by a 4" brass tube. That allowed me to install the sender out from underneath the air filter. Feeling pretty proud of myself, I tightened the nut that held the wire to the sender and managed to twist the brass threaded pin in half. Didn't realize it was actually hollow. Took very little torque to pretty much destroy the new sender.

I quit. I ordered the mechanical gauge that Paul recommended. Anyone want a VDO oil pressure gauge, I'll send you mine if you pay for shipping. You just need a new sending unit. (sigh)

[953 nut 59,327]

[tommyg 154]

Are you working with a D-160 with the ONAN 16hp engine?
 

Nope. I actually re-powered my rig with a Kohler Command Pro recently.

[pfrederi 18,566]

Are you working with a D-160 with the ONAN 16hp engine?
 

Nope. I actually re-powered my rig with a Kohler Command Pro recently.

I forgot about your repower.  I couldn't figure out why you had space issues with the sender.  On the K series the port is wide open.  I put a coupling in the oil line about even with the flywheel.  Makes it easy to disconnect when you have to move the engine to work on the hydro pump and/or coupler.   Something I have had to do way too often.

[tommyg 154]

I forgot about your repower.  I couldn't figure out why you had space issues with the sender.  On the K series the port is wide open.  I put a coupling in the oil line about even with the flywheel.  Makes it easy to disconnect when you have to move the engine to work on the hydro pump and/or coupler.   Something I have had to do way too often.

 

Yeah, that would have been an easy one to figure out. I ordered the same mechanical Sunpro you suggested. $4.95. Would have saved me some money had I gone that route the first time. Oh well. It's not like it's the first time I've thrown $$ down the toilet!