My whisperlite s about 10 years old now and on my last day of my last trip the pump did not seem to want to pressurize the fuel bottle. I got it to work ok, but just watched the Whisperlite service videos on YouTube and look it apart. The pump cup was not torn but was dry and looked well used. A little pump cup oil helped it work better, but I’m not real confident in it right now.

It looks like a replacement cup comes in the Expedition repair kit, but for about $5 more I could just buy a new pump. Thoughts on his? Has anyone just gotten a pump cup from MSR?

To me, the answer is a no-brainer. You can buy a pump cup and fiddle around with it in an effort to make it work... or for an additional $5.00, you can buy an entirely new pump. No messing around and it's brand new.

Done deal.

We had to do some field repairs on our Whisperlite pump on the first day of our trip this year, despite testing it out beforehand. It was leaking and not staying pressurized. We had to add oil to the pump cup and fuel tube bushing. After this, our pump worked perfectly for the rest of the trip. This pump is probably a similar age to yours.

My opinion is that if there is no visible damage to the pump cup, and you can confirm that the pump works fine following your repair by testing it, then there is no reason to get a new one. Test it a few weeks in advance of your next trip. If it still has problems then after a second round of oil, that's when I would consider buying a new one.

What pump do you have? Old style,
Or new,
Either works, the old style can be brittle and may or may not use leather or vinyl cups. The new style is nylon impregnated and stronger, with a vinyl cup.
Leather cups are getting hard to find the newer vinyl is available in repair kits, or from Needle Sports in the UK. MSR in the USA does not supply individual parts but offers rebuild service, often for free. I think it has more to due with liability issues in the US.
The MSR pump oil is a thin oil, but Primus uses a thick almost grease, in a similar sized tube. Both work fine the Primus seems better, longer lasting, in the pump.

butthead

I have the newer one on the right. I sent an email asking if I could buy the one part but no response yet.

Send me an email, I have extras.

butthead

FYI If you use it more often in cold weather you could also consider one of the arctic pumps (the one with the blue ring). It has a leather pump cup and softer seals in some places. I have one that I use for my XGK EX for winter camping and mountaineering and it has held up better in cold weather vs the standard pumps as advertised. The standard pumps work better under normal conditions though as the nylon cup pressurizes better and requires fewer strokes.