Priming a fuel pump.

[Deleted]

I'm sure this is going to be really obvious to most on here but...............
I went to help a guy who has bought a P5b,long time off road,but looks like a decent project. When I got there he was rigging up a syringe to prime the fuel system having filled with fresh petrol.The car had last run two or three months before and fuel had drained back to the tank. I loosened the pump bolts and rocked it back and forth the fuel could be heard going into the carbs and then stopped with them full. A turn of the key and the old girl was running (sounded well too).
I thought this was a simple and well known dodge but the new owner seemed not to know it.
I often do this to my transit V4 which is stood for long periods of time,I'd assumed it was common knowledge.

[Phil Nottingham]

All mechanical pumps once had a priming lever - it was strange BL did not specify one for the new P5B as they were fitted on Land Rovers for years after P5B's went west.  Our P2 had a hand priming too and a carb tickler.


Perhaps it was penny-pinching by BLMC rather than paying extra to AC to modify to the already under-spec'd one. They could have carried on with the P5's double SU pump but made parallel but that would have been far too expensive

[Deleted]

That post brought back some memories Phil. I used to run an old long wheel base BMC threepenny bit as a breakdown/recovery truck. It had a six cylinder petrol engine (maybe a C series?) After a day or so the fuel would run back down to the tank and it would mean laying on the seats taking off the hatch and getting an arm covered in oil pumping away on the little lever under the pump.
A great thing to drive,the front windows by your feet and the view of the whole bed out of the back window meant it could be shuttled about in tight spaces with ease.
Another vehicle that used to be a common sight,I've not seen one for years.

[Ken Nelson]

I have just cleaned out my fuel system on my 3-litre P5 Coupe. The fuel filter in the gas tank was missing, but I don't see any major reason to replace it. The fine screen in the AC filter and fuel bowl under the bonnet was 1/2 blocked with crud which I cleaned out, and I blew all the old fuel out of the fuel lines. But now the SU pumps (both of them) won't push anything but air through them. They apparently need priming, but are there any suggestions for how to do this? I disconnected the fuel line at the carb and that didn't help, and I lowered the SU pump intake hose in the boot and submerged it in a can of gas and that didn't get fuel going either. Everything ran fine before, so I doubt any air leak (and I left the lines alone). Thanks in advance. From: "Mystified in Michigan"

[enigmas]

Well Ken you could try this.
Place the fuel outlet line from the tank into a suitable jar. Ensure the fuel outlet line is lower than the bottom of the fuel tank. If you have a compressor, direct the air line into the filler tube (stuff a suitably dense rag around the air line in the filler as an air dam) This should cause the fuel to start siphoning out of the outlet line.

If fuel fails to exit, the logical conclusion is that the fuel outlet line is clogged with debris.

[Ken Nelson]

Thanks Vince, I'll let you know.

[Phil Nottingham]

The SU pumps do not need priming - they should self prime in seconds. The drop tubes/pickups should have the filter on as debris will block the filters in the SU pumps

[Ken Nelson]

Indeed you are right Phil, the SU pumps don't need priming. Mystery is solved, and lesson learned. I did not know about the fine transparent membrane in the outgoing fuel chamber and when blowing out the fuel lines I ruptured this transparent membrane with too much air pressure. I replaced it with a used one and the pump primed itself without problems. I also put a used filter on the pickup in the tank as Phil suggested. Thanks to all for suggestions.