Speed limiter

[iddy]

If I drive at around 50/55mph, eventually, after about 4 miles the car splutters to a halt. If I wait a minute and then turn the ignition on the fuel pump chatters like fury for a few seconds and then the car starts and away I go for another few miles before it happens again. When I take the car to work this will happen 3 times over a 10 mile trip. If, on the return journey, I travel at a steady 40mph I have no problem.
I'm assuming it's a problem with the fuel supply not keeping up with the demand. The pump seems to be ok - it will just tick occasionally when driving, and only tick frantically when the car has cut out.
I can drive the car around town all week without a problem, it only happens on a run at those speeds.
Any ideas?
Idris.

[Cam]

Check the connections to the fuel pump. You might have an air leak somewhere. Also, the carb/fuel bowl area for fuel leaks.

That is an odd one, but if the pump is chattering then it's pumping air or the fuel line from the pump is not pressurising due to a leak.

[andrewsxt]

the fuel pump chatters like fury

This happened to me yesterday when i ran out of petrol so does sound like a fuel supply problem.
More an observation than any help

[ColinP]

Hi Idris,

I ran into odd problems similar - run for 4 miles, engine dies, wait 10 minutes goes again ...

I'd order up a new set of contacts for the fuel pump, take the old ones off and give them a jolly good clean!

While you're doing that (it's mich easier to take the pump out of the car), you can check the filters as well.

And just for bonus points, there's the flexible pipework jubilee clips to check.

- There goes another week-end

All the best

Colin

p.s. i ended up with new points for the fuel pump

[Willie]

It is possible that you have an air lock in the petrol tank as it only
happens above a certain sustained speed, you could try undoing the
petrol cap the moment the car stops and see if the pump starts
ticking immediately. Then again it could be that you are overheating
at the 50mph speed but not at the 40mph although vapourisation
due to heat would normally cause the pump to tick furiously BEFORE
you actually stop. The simplest check of all is to give the pump
a smart tap when the car stops and see if it immediately starts
ticking which would indicate that the pump itself is at fault.

[Cam]

vapourisation due to heat would normally cause the pump to tick furiously BEFORE you actually stop.

Yes, that's our 'early warning - get to the side of the road, you are about to stop' system!

[bmcecosse]

Never had fuel vapourisation problem ! Much more likely is vacuum in the tank - but have you tried it with the tank well filled right to the brim ?

[Cam]

Fuel vapourisation is VERY common on Minors and a lot suffer with it in hot weather. The vacuum in the tank/blocked fuel cap is a good place to examine though.

[Multiphonikks]

Yes, that's our 'early warning - get to the side of the road, you are about to stop' system!

Having said that, I once managed to get from the Bath M4 turnoff to the M32/Bristol Ringroad junction with the pump making dire pumping sounds... :/

It was fun though

[iddy]

Thanks for the tips guy's.
I'm buying a fuel pump from one of the chat boarders (Charly), it's only had about a month's use. If that doesn't work I'll put a temporary plastic fuel cap on with a breather hole cut in it.
An old sage told me yesterday it could be the float at fault not delivering enough petrol, he said it can be adjusted. I had a peep at it this morning and can't see any adjustment - it just hangs from the top on a hinge. I see in the manual a photo of a metal strip (?)for adjustment. Is this for earlier carbs? Mines a 1968 1098.
I also should have said in my original note that it cuts out at 50/55 mph either on the way up hill or after I get over the crest, depending on the incline (or is this coincidence?).
It does this whether the tank is full or half full, and I've listened for a telltale whoosh of air when removing the cap but heard nothing.

Idris.

[rayofleamington]

I'll put a temporary plastic fuel cap on with a breather hole cut in it.

The temporary caps won't need a breather cut in them! Try not to use them with a full tank as (unless they are different now) they don't even pretend to seal

The fuel pump ticking rapidly means the carb wasn't full. Therefore the comment regarding the float setting should be discarded (if the float setting was wrong then the carb would still be full and you wouldn't get the racing pump at key-on).

This can be just an unreliable pump which stops when hot, or a vacuum in the fuel tank. If it's anything else I'd be very surprised but with Minors, annything is possible

[Packedup]

Pinhole leak in the fuel line allowing some air to be sucked in - Enough to run the carb dry when under heavy load.

Blockage in the tank outlet (or at a push line) allowing only a small amount of fuel to flow - So sufficient for tickover and lower speeds, but not enough for higher speeds, carb runs dry.

Those are my 2 contributions if the other suggestions don't work out - And I've had both happen to me, each one was tricky to track down.

[TerryG]

I stopped getting fuel vapoirisation when i put a guard behind the carb infront of the engine so there is a bit of metal keeping the heat of the exhaust and engine away from the carb and fuel pipes