sullair 85 volks compressor problems

[Pheasant Surprise]

So usually a road tow diesel compressor has an unloader valve on the air inlet to the compressor. You start it up and it just runs in idle to warm up the engine and compressor for a minute or two. Because no air is getting drawn into the screw element of the air end, there is no load on the engine.

When ready to put it into work the unloader valve is opened/activated and the compressor will then allow air in and starts compressing all that air, building a load up, the engine revs will increase, building more and more air. If the taps on the air outlet are fully open the engine will rev flat out and only drop back to idle when the compressor reaches its set maximum air pressure.

Actually they will modulate the revs, based on the air consumption. There is a feedback path from the pressure control valve on the main receiver/oil separator tank going to a little pneumatic actuator which is directly controlling the lever on the injection pump.

Is your compressor building pressure from the off?

 

[Pheasant Surprise]

This is the air path that most road tow diesel screw-type compressors use. I ripped this off an old Atlas Copco manual, but they are all basically the same:

 

[Pheasant Surprise]

im not to sure how to unload the commpressor , in the manual it says to crack open service valve a little on start ups

Oops sorry I missed this in your earlier posts. If this is the case the air end is probably running “loaded” from the get go, that’s why they want you to open the service line on startup.

Nice and simple. So yeah with no other obvious valves on the air end, it should simply build air pressure as you rev the engine.

 

[edbatt]

Oops sorry I missed this in your earlier posts. If this is the case the air end is probably running “loaded” from the get go, that’s why they want you to open the service line on startup.

Nice and simple. So yeah with no other obvious valves on the air end, it should simply build air pressure as you rev the engine.

yeah got engine runs at rpm but no air pressure building so quite honestly kinda give up on it surges up and down and wont build pressure lol

 

[Pheasant Surprise]

yeah got engine runs at rpm but no air pressure building so quite honestly kinda give up on it surges up and down and wont build pressure lol

Is it an actual Sullair rotary screw air end on it? Not been replaced with something else - have you got any photos?

Screw compressor air ends usually last for thousands and thousands of hours, with very little maintenance. Hopefully something simple that doesn't require a rebuild.

 

[Pheasant Surprise]

You don’t happen to be from the states @edbatt ?

Found this thread on these Sullair compressors on a vintage VW forum with a bloke from Shawnee, Kansas who may have the same unit. Might be worth getting in touch?

The manual below has various photo of the carb linkage and governor rod adjustment.

VW Type 122 industrial engine manual, early version (English)

VW Type 122 industrial engine manual, March 1985 (German)