Primus 991 losing pressure?

A in the title really, I can't get it to light and it seems it's not holding pressure. How can I identify where is being lost? I wondered about using washing up liquid like when looking for a puncture?

 

Remove the hood and the glass, then pump in plenty of pressure and submerge the lantern in water and you will see air bubbles coming from where it is leaking, Jeff.

 

It's generally the tank lid that's the culprit on simple lanterns like the 991.

But to make absolutely sure, you just need to dunk the pressurised lantern into some water to show where it leaks.

Remove the top and the glass.
Make sure the tank has no fuel in it. You only want air in there.
Place the cleaning needle in its top position (this will help keeping the pressure in the tank long enough for the test).
Pump it up good and remove the pump.
Quickly dunk the whole apparatus in water.
Once all air has evacuated from the pump tube, all you shall see is a very thin stream of bubbles coming out from the jet. This is normal since you don't have a positive shut off valve on these lanterns. (Sometimes the cleaning needle still manage to block practically all air from the jet, but normally it don't.)

Any other evacuating air is where you have your leak.

Good luck. You can't really fail with a lantern as simple as the Primus 991.

 

Thanks that is such an obvious solution now you've told me. One other thing, the pump on mine has no seals bar the leather and I can't see how it doesn't leak from there. Should it have a seal where the leather carrier bolts to the pump shaft?

 

The pump itself doesn't seal the tank.
You have a non-return valve at the bottom of the pump tube.

 

So how is the non return valve replaced should it be at fault, I can't see how it's got to. Thanks again

 

I presume I will have to sacrifice the mantle too in order to submerge it

 

You might be able to save the mantle if you keep it above the water level.
Any leak that will be troubling you will still be below that point.

Search the forum for NRV and NRV-tools.
There's tons written about this...

Here's one example.
You don't need any fancy tool to get the NRV out.
A slotted piece of steel like I show in that link is just as good as any other.

But even if it turns out that your NRV is leaking, you should try to cleanse it first.
You do this by removing the pump, then fill the pump tube with paraffin.
Re-install the pump (which of course shall be working well) and give it a firm push all the way down, forcing it to squirt all that paraffin through the valve.
Sometimes this will fix a leaking non-return valve.

 

Thank you very much, will soon have a working lamp for my shepherds hut.