I've got a long standing weep from my fuel pump. The leak is between the joint under the top cover which holds the fuel cut off diaphragm. Despite swapping over various parts including the diaphragm and gasket it still does it. I think I've reduced it but not stopped it and the consequence is when not driven much my fuel consumption drops to about 13 mpg. The fuel cut off diaphragm I find is to stop the fuel in the tank draining by gravity through the pump when not in use. If this and the float valves in the carbs are faulty, fuel can syphon directly into the engine. I don't have this happening fortunately. I thought the mating surfaces between main body and cover could be bad - I got a replacement pump and rebuilt it but to no avail. Has anybody got insight into this?
If you only use it for short journeys 13mpg is probably not so unusual for a 2l type-4. How's your local terrain? Hilly? In the best circumstances on a long run I get under 20mpg.
To go from 20mpg to 13 mpg needs lets say 20 mpg is 0.05gall / mile 13 mpg is 0.076 gall / mile Difference is 0.026 gall / mile or 0.8 gallons an hour at 30mph. Thats quite a lot for a leak in the pump . It would make the side of your engine quite clean and very smelly. Your engine is off tune . The pump is a distraction, even if it is actually leaking.
Hmm. Something else to check, though it's been running fine. It's when it's standing still I'm losing the miles; I've hardly been anywhere since techenders.
So further investigation, and I still can't stop the weep. I'm pretty sure though that this can't be the real cause of poor fuel consumption (I agree @mikedjames - it would be far too much). So next I'm wondering if the pump is pumping at too high a pressure and the weep is just a side effect. My problems seem to go back to when I fitted a new bakelite spacer so maybe if it's not thick enough the push rod is operating too strongly. I've already added a couple of extra gaskets though.
It's original, but it's cobbled together from two separate pumps as I've tried different things out. I also have a modern version but that only lasted a month before it started to fall apart. I've repaired that so I'll probably try it out at some point.
Sorry to hijack but I'm away from my van at the moment and wanted to ask. I'm thinking of replacing all my fuel lines and if I'm replacing everything I need to buy the right size ethanol proof fuel line from the factory fuel pump forward. Do you know the diameter of fuel pipe you are using please?
I've got 5.5 mm biofuel resistant hose from here: https://www.advancedfluidsolutions....-fuel-hose-diesel--petrol-22400400-2015-p.asp
So is the barb on the fuel pump 6mm and so I can replace all through with 5.5mm pipe? Sent from my Redmi Note 7 using Tapatalk
The pump doesn't have barbs, just plain pipe in and out and 5.5 mm works fine. There is an after market pump with barbs (that's if the swollen bit on the end of the pipe is a barb), but I think that uses 7mm hose.
OK an update on this. After a lot of experimentation using parts from a spare pump and a type 1 pump repair kit it seems to be behaving itself. I found that the fuel cut off valve and diaphragm, item 5 on this drawing, was faulty. I managed to get a new diaphragm from a type 1 pump repair kit, but the valve which goes underneath was also faulty. I had another duff diaphragm, but the valve still worked so I had to Dremel the metal parts off and sandwich them onto the type 1 diaphragm with a small weld. It would be great if they made a type 4 repair kit but so far I've not found one.
