Hope someone might have air compressor experience to give me a steer.

I bought a second-hand AirMaster. Saw it working - all seemed good. Pressured up and the cut out worked at the appropriate pressure.

When I got it home and checked the oil level, it was low, so I bought some compressor oil (ISO32) and added it to the correct level. The instructions said to run it for 20 seconds with the air free flowing to allow the oil to circulate. So I did.

Then it will not pressure up. Grrrr!

There feels to be air coming FROM the air intake, which makes me think that the compressor/valves are not closing properly. Or somehow not working properly.

I am no expert on air compressors, so any ideas what it could be. The manual recommended Machine Mart oil, which is ISO100, SAE30 (I think), therefore it is thicker. But would that affect things? I guess I could drain the 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 unrelated.

Help! Thanks.

On Sunday, 30 September 2018 11:59:27 UTC+1, wrote:
Hope someone might have air compressor experience to give me a steer.

I bought a second-hand AirMaster. Saw it working - all seemed good. Pressured up and the cut out worked at the appropriate pressure.

When I got it home and checked the oil level, it was low, so I bought some compressor oil (ISO32) and added it to the correct level. The instructions said to run it for 20 seconds with the air free flowing to allow the oil to circulate. So I did.

Then it will not pressure up. Grrrr!

There feels to be air coming FROM the air intake, which makes me think that the compressor/valves are not closing properly. Or somehow not working properly.

I am no expert on air compressors, so any ideas what it could be. The manual recommended Machine Mart oil, which is ISO100, SAE30 (I think), therefore it is thicker. But would that affect things? I guess I could drain the 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 unrelated.

Help! Thanks.

On industrial compressors, the inlet and outlet valves are usually easily accessed. 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

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"Cynic" wrote in message
...
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.

On Monday, October 1, 2018 at 12:26:21 AM UTC+1, Brian Gaff wrote:
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

--
----- --
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"Cynic" wrote in message
...
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.

Thanks Brian,

The oil I added was thinner (ISO32, not ISO100). I called the manufacturers and spoke to an engineer who said he was surprised to hear of a compressor 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 time 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 from 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 Minor!

Thanks.

explained on 30/09/2018 :
There feels to be air coming FROM the air intake, which makes me think that
the compressor/valves are not closing properly. Or somehow not working
properly.

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.

On Tuesday, October 2, 2018 at 10:04:08 PM UTC+1, Harry Bloomfield wrote:
explained on 30/09/2018 :
There feels to be air coming FROM the air intake, which makes me think that
the compressor/valves are not closing properly. Or somehow not working
properly.

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 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.

On Tuesday, 23 October 2018 14:55:03 UTC+1, wrote:
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