Priming the fuel pump

[cleverusername]

After changing the fuel line rubbers I couldn't get the Sprint to start, looking in the float bowls revealed why; no fuel. I manually primed the section over the axle, thinking my new copper fuel line might have been crushed at a bend and blocked. Ended up covered in fuel, so that isn't the issue. However when I tried to prime from the front, couldn't draw any fuel.

Tried to get the thing going by filling the float chambers. That fired it up and then it died on me, out of fuel again. At this point I am out of ideas. It could be a blocked pipe but everything was working fine before I changed the hoses and the only new bite of metal pipe I put in isn't blocked.

The only thing I can think of is the pump won't work if it doesn't have any fuel in it but I have no idea how to prime it.

[triumphdolomiteuk]

Get a length of clear plastic tubing and attach it to the outlet pipe on the pump. Put the end of the tube in your mouth and suck like your life depended on it. When you see fuel coming up the tube stop sucking or you will get a mouth full of fuel. Reattach the fuel hose to to the pump and brum, brum. I tried this myself very recently to get my car started as it hadn't run for two years.

[Carledo]

What Andy said^^^^^^^

Which he got from me, though he added the clear tube idea as he doesn't enjoy the taste of petrol! Come to think of it, neither do I, but usually risk it rather than go looking for clear tube!

For some reason, Dolomites in particular seem to suffer from a fuel pump that can run fine if there's some fuel present in the line, but not if it's completely empty.

I also met one recently (on a Sprint) where this "suck through" idea worked fine until left overnight. If you sucked the fuel through initially, the car would run well past the amount of fuel in the float chambers, long enough to get up to operating temp then go round the block a handful of times. If switched off, it would restart immediately. if left off for an hour it would restart immediately. But leave it overnight and it would not start in the morning, or, if it DID start, would only run out what was left in the float chambers and then stop iretrievably, unless sucked through manally again.

This turned out, after a lot of head scratching, to be down to what I think is the anti-runback valve in the fuel pump having come adrift (it's only a push fit) and turned on it's side inside the pump body. This was invisible till I took the pump apart (and not immediately obvious when I did) and didn't affect the pump working as a pump, I took it off and tested it by working the arm while dipping a pipe off the inlet into a container of petrol and it produced a fine quantity of fuel.

I had a spare new pump of the same (QH) make, and if it had been the same arm type, i'd probably never have known why the fault occurred, just fitted the new pump and shrugged it off.

But, as it turned out, the original pump was a "short arm" type and the new pump was a long arm type, requiring a spacer I didn't have in stock. So, being short on time, I took both pumps apart in a bid to swap the arms over. This also turned out to be impossible as the arm pivot was peined into the lower case. I ended up using the old lower case and arm with the new upper case, with non return valve fitted, diaphragm and post, filter and lid. It was only when I turned the old upper case upside down that the loose NRV fell out, alerting me to what the REAL problem was!

I have at least 2 other Triumphs around here (both 1500s) that will not self prime and need a good suck through to get them started after a layup of more than a few weeks. I'm beginning to wonder if this problem is more widespread than just a 1 off!

Steve

[Magenta Auto Sprint]

I have similar problems on the 1850 and the sprint, I blame the new fuel pumps. I think it is that little soft discs of plastic that make up the non-return valves. when they have no petrol on them, they dry out and curl up a fraction, once they have the weight of the petrol on them again they are fine, tilkl they dry out again.

I use this hand pump for priming my carbs.,

https://www.amazon.co.uk/ePathChina%C2% ... 6083&psc=1

[cleverusername]

What has me slightly worried is I have attempted to prime the line just below the fuel pump and I can't get any fuel. This was using the primping bulb off an old Xantia, sadly the only bit of that car left. I am beginning to suspect there is a blocked fuel pipe underneath the car somewhere.

[cleverusername]

Fixed it, I had fitted one of those plastic fuel filters and when I removed and inspected it, there was a hairline crack in the casing. Replaced it with a bit of copper tubing and the engine fired up.

[triumphdolomiteuk]

What Andy said^^^^^^^

Which he got from me, though he added the clear tube idea as he doesn't enjoy the taste of petrol! Come to think of it, neither do I, but usually risk it rather than go looking for clear tube!

I should have credited you, Steve. Of course the idea was yours, I just enhanced it slightly as I happened to have a few pieces of clear plastic tubing to hand. As you do.

[dollyman]

I have similar problems on the 1850 and the sprint, I blame the new fuel pumps. I think it is that little soft discs of plastic that make up the non-return valves. when they have no petrol on them, they dry out and curl up a fraction, once they have the weight of the petrol on them again they are fine, tilkl they dry out again.

I use this hand pump for priming my carbs.,

https://www.amazon.co.uk/ePathChina%C2% ... 6083&psc=1

I have been on about these for years every Dolly should have one fitted unless its a daily driver. Just think how much wear it will save on the starter and temper when it wont start first time
Tony.