Hi folks. Been fettling the thin topped pump for a pork pie X246. Fitted a new pip and tested in the tank. The pump seems to be drawing up fuel! Took the pump out to test and on pumping it got a big skoosh of fuel all over the place. It seems to draw and push air. I took the NRV to bits again and the pip is seated well. The spring seems okay but I lengthened it a bit for more pressure. I also refurbed another pump and there seems to be a litle bit air coming out of the top (small bubbles appearing with spilled fuel) Must be going wrong somewhere with the pips. Any ideas. Many thanks Brian
Did you use new rubber seals or old stock seals? Old ones might got hardened over time... Might be worth a try to use some nitrile rubber to punch some pips...
I can't imagine why your pump is doing that unless you have fitted the leather cup round the wrong way. Just incase, the cupped side needs to be pointing down into the tank. If this was fitted the wrong way then it is possible that it would have enough force to suck the fuel back out of the tank. Only thing I can think of anyway. Best regards Matt.
Cheers Matt, but sadly not. It's not a new cup but I can't see replacement would cure it. It's like the spring in the NRV is too weak or not there. Cheers
Make sure the new pip in the nrv is thick enough and it seats properly you say you have stretched the spring to aid this. does it move nice and freely? The leather cup on the pump rod should force air down the pump to the nrv but come back up easily when you pull it back, if it does not loosen the nut on the pump rod a bit i have had trouble with the hole in the leather being small as well leather cup should be quite loose see how you go pete
Hi Brian, There should be a bit of play in the rod axis of the pump leather holder. If it is completely tight it will produce the symptoms that you have described. I have seen pumps that have had extra washers added to take up this designed slackness. The pump design is very clever, it needs that play to allow the air to pass the leather on the up-stroke, and then the leather expands on the down-stroke to push the air into the tank. The NRV, if good, just stops fuel feedback, but if your pump is sucking on the back-stroke it will draw fuel back. Hope this helps - Steve.
Hi Brian i have had a few NRV's on various pressure items,have failed even after replacing the pip with a new one,and the cause has been a bad seal on the nrv or pump due to ware. All so a fine crack in the pump tube or joint could have failed
Hello Brian, I make sure that all parts of the pump are very clean and that always helps. The problem which you describe is a common one and I have most often found that the NRV., is the culprit. Try a different pip and spring, stretching the spring can help. Sometimes I have found that the springs are weak, so I have fitted 2 weak springs together and that has cured the problem, Jeff.
Thanks folks. I followed all the tips, checked for old washer etc. The leather was a bit tight and I flexed it a bit to make sure it was supple. Slackened the nut off (which fell off first try!!!) I stripped it down again and cleaned every thing again. I tried it without the spring and with a little bit blowing and sucking, and the taste of paraffin, the pip seemed to be sealing. Built up again and now works so I'm not sure which bit was wrong. Thanks to everyone. Brian
