NL oil pressure

[Wotname]

Originally Posted by Olly75

When the oil pressure switch is wired up if I hold down the preheat and shutdown bypass the genny will start and stay running, if I let it go the genny automatically stops. However when the oil pressure switch is disconnected the genny will continue running when I let go the preheat switch.

OK, that makes sense now, thanks. I must have missed the starting procedure somewhere upthread...

Back to trying to solve the low oil pressure problem...

[kmacdonald]

Originally Posted by Olly75

The sending unit is tee'd off the same joint as the pressure switch unfortunately.

Just removed the pressure switch and cranked it, and once running there was a significant flow of oil so looks like the line isn't plugged.

The pressure switch is a single wire switch, that when wired up wont let the genny start because of the low oil pressure, but when detached the genny will start. If that makes sense...

Remove the T and screw the sending unit directly into the block. Or better yet screw the mechanical pressure gauge into the block. Post a picture of the engine. I know someone said it wasn't a Kubota but it could have been rebranded by another manufacturer. If so we know what the problem is.

[a64pilot]

Originally Posted by Wotname

Whoa - that doesn't make sense.

If wired correctly, the genny will start with zero oil pressure but if running it should stop if the oil pressure drops to low.

It’s a normally closed switch, just like ones used for a LOP light.
As long as the circuit is competed it’s not allowed to start, assumption via the fuel shot off solenoid.
During starting it’s bypassed, oil pressure opens the switch and then it will run.
I don’t like it wired this way because of course if the wire breaks, comes off etc the generator loses its protection and you would never know.

My Nexgen is a normally open switch, with the circuit open the fuel shut off solenoid is de-energized and no fuel flow is allowed. It’s bypassed when the starter circuit is energized. I believe by simply powering the starter and solenoid off the same circuit. My solenoid is held open electrically and a spring closes it. I believe.
It has two wires and requires a closed circuit to energize the fuel solenoid and run, if a wire breaks, comes off or whatever the engine dies.

[skipperpete]

Originally Posted by Olly75

The sending unit is tee'd off the same joint as the pressure switch unfortunately.



Just removed the pressure switch and cranked it, and once running there was a significant flow of oil so looks like the line isn't plugged.



The pressure switch is a single wire switch, that when wired up wont let the genny start because of the low oil pressure, but when detached the genny will start. If that makes sense...

Could you block the oil flow by pressing your finger over the pressure switch hole, 5psi should be easy to hold back but if the line pressure is higher, like 60 psi, much harder.
I had a thought that it might have had a crack in the rocker box or a blown out oring in the head, on your 643 there are 2 types of overhead arrangement as in the attached pics, on either setup, the oil would dump back to the sump via the pushrod gallery so no external leak.

[skipperpete]

The attach point of the oil supply tube of each variant is circled in red. Try undoing the supply pipe banjo bolt then pinch the banjo with 2 fingers and give er a spin, under normal circumstances you should barely be able to hold the pressure.

[Olly75]

I have the version in the top picture.

I can block the oil with my finger over the pressure switch joint.

And.... I took off the banjo bolt,pinched the banjo joint and started her up but couldn't hold the oil back! ( it's amazing that what's probably going to be an expensive problem to fix has actually made me excited!)

When you say a blown o ring in the head, I'm assuming you don't mean the rocker cover gasket, but something more internal?

[skipperpete]

Originally Posted by Olly75

I have the version in the top picture.



I can block the oil with my finger over the pressure switch joint.



And.... I took off the banjo bolt,pinched the banjo joint and started her up but couldn't hold the oil back! ( it's amazing that what's probably going to be an expensive problem to fix has actually made me excited!)

Good work , progress at last. It’s not easy to do a pressure check anywhere else other than that overhead gear oil feed line but you might be able to work out a connector to your gauge that utilizes the banjo. You could be dumping oil out of the rocker shaft, dismiss the idea of the oring between the head and the block, there isn’t one.
Pete.

[Compass790]

I think you need another pressure gauge which is why I advised to ask mechanic to bring one. skipperpete beat me to the bush test. Sounds really promising for a cheap fix & great you wont have to pull engine.

[a64pilot]

So a freeze plug type of thing blew out of the rocker shaft?

[Wotname]

Dunno about easy and cheap yet but yes, Skipperpete has certainly got Olly75 pointed in the right direction.
So plenty of pressure coming into the head (at the banjo bolt) but it is getting lost as soon as the feed is reconnected.

Maybe a left field idea but would it be worthwhile connecting an air hose to the head (where the banjo bolt goes in) and pumping air into the oil passages to try to work out where it is getting dumped?

If Olly75 has an air source of course!

EDIT: Or a long line filled with oil and use the air to push the oil into the head and see where the oil escapes. I did think of connecting a water hose to the head but I know that would be too rough for you guys - me too unless I had my back against the wall

[Olly75]

Originally Posted by Wotname

Dunno about easy and cheap yet but yes, Skipperpete has certainly got Olly75 pointed in the right direction.
So plenty of pressure coming into the head (at the banjo bolt) but it is getting lost as soon as the feed is reconnected.

Maybe a left field idea but would it be worthwhile connecting an air hose to the head (where the banjo bolt goes in) and pumping air into the oil passages to try to work out where it is getting dumped?

If Olly75 has an air source of course!

I have a dive compressor, would that work?

[Wotname]

Originally Posted by Olly75

I have a dive compressor, would that work?

Good start

Maybe the real mechanics will have better ideas!!!!

[DougR]

Start the engine with the rocker cover off and watch for the oil escaping...

[a64pilot]

I think Skipperpete is familiar with this particular engine and has an idea of what is going on.
I don’t have any familiarity with it, just general knowledge.

[Compass790]

Originally Posted by a64pilot

So a freeze plug type of thing blew out of the rocker shaft?

I think the freeze plug thing applied to a Kubota & the engine concerned is a Shibaura tho they may have the same setup