Air compressor expertise needed pls

ssured up and the cut out worked at the appropriate pressure.

e compressor oil (ISO32) and added it to the correct level. The instructio ns said to run it for 20 seconds with the air free flowing to allow the oil to circulate. So I did.

at the compressor/valves are not closing properly. Or somehow not working properly.

nual recommended Machine Mart oil, which is ISO100, SAE30 (I think), theref ore it is thicker. But would that affect things? I guess I could drain th e old oil out, but no point if it's not the oil that is causing the problem and my knowledge or motors/valves make me think that it should be unrelate d.

On industrial compressors, the inlet and outlet valves are usually easily a ccessed. Usually just poppet valves. Sometimes stick. Cheaper ones have reed valves (bits of spring steel) which can break.

I'm not familiar with the air master range. However I have worked with a variety of others. Some employ an inlet valve lifter during starting. Possibly yours has one which has malfunctioned. You could try Google for a parts diagram and spares list.

It does seem odd though that it was working till he put the thicker oil in. Maybe an empty out a flush through in case its grit etc in there and then replacing with the thinner oil. Like you its all a bit of a black art, but things happen for reasons and if something has been working its an awful coincidence. He does not say if he tried it before he put the oil in at home, if that did not work then he would not have put the oil in. I was thinking that left around disturbed and maybe turned over during transit could easily have brought crap from the existing oil in to jam valves. Brian

snipped-for-privacy@gmail.com explained on 30/09/2018 :

I would guess at an unloader valve failing to close properly. To allow the motor an easy time getting up to speed, they use an unloader valve releasing the compression, so it is doing no work as it starts - that is sticking open.

Thanks Brian,

The oil I added was thinner (ISO32, not ISO100). I called the manufacturer s and spoke to an engineer who said he was surprised to hear of a compresso r being spec'd to use ISO100 (SAE30) as he felt it was too thick.

When I got it, I had seen it running. It went up to pressure then cut out, as it is supposed to do. At home, it ran and went to pressure the first t ime I got it out the back of the car. It was only then that I checked the oil level (is there a sump of some kind, presume so?) and found that it was below the minimum level. So I went to buy oil for the little beast.

But that might be what has killed it! I have an 'exploded' diagram sent fr om Machine Mart's help centre, but it is a bit rubbish in detail.

Looks like a dismantle job, but the last engine I took apart was a Morris M inor!

Thanks.

Thanks Harry - I guess that means a dismantle, clean and reassemble. Fingers crossed!

Update:

I have taken off the cylinder head and made sure there is no dirt in the two little metal reed strips that act as valves. All seems ok.

When I first run the motor, air is being pushed out of the outlet and I can feel it sucking (a little) at the inlet. All good, except that it still will not build up the pressure. It only reaches about 30psi.

I have drained off all the old oil and added a little new, not that that should make a difference.

I'm now wondering if the piston rings are kaput. How could I determine that?

There are breather holes on the oil sump dipstick and I can feel air coming from these, but that could just be that there is air moving around below the piston (hence the holes).

If I hold my finger over the outlet, or run the motor for a while so the pressure build a little (to 30psi) then I can feel air coming FROM the air intake. Surely, that cannot be right?

Any ideas on what to try? Thanks to all for your expertise.

You might try lobbing a bit of oil into the cylinders. That often works. I don't know a lot about compressors though.

NT

Thank you. I can try it I guess. I was just trying to determine if it is the piston rings of the valves. But the valves seem so simple that I wonder how it could be them.

Oil in the cylinder does the job of the piston/rings, it gets blown off the valves, so it will tell you which bit is faulty.

NT