Possible fuel pump problem?

[donald]

Help, please!
My Morris won't start. When I turn on the ignition, instead of hearing the rapid pumping of fuel gradually slowing, it seems to keep pumping at a slow beat.

I've disconnected the fuel hose at the carburettor, switched on the ignition and the pump is pumping fuel at a good rate. Fuel is getting to the fuel pump, and to the float chamber so I'm pretty sure fuel is getting to the carburettor ok. (Incidentally, there is a spark at the plugs.)

We are now having heated family discussions about whether it is a fuel pump problem or a carburettor problem. Can anyone help me keep the peace and get my beloved morris back on the road?

Thanks

Ann

[moggles]

It could be either, or a couple of other causes.
a. When you disconnect the fuel line at the carb, does the pump run at the same speed as it does when connected to the carb?
b. If you stick the carb end of the fuel line into say a litre container, does the pump keep ticking at the same speed until the container is full, or does it slow down after a while?
c. If you hold the end below the fuel in the container, do bubbles come to the surface?

If answer to a. is yes, then the pump is not able to achieve and hold pressurise in the line to the carb.
If in b., the pump slows down after a while, the pump is not able to suck adequate fuel from the tank.
If in c. bubbles appear, there is an air leak somewhere between tank and pump.

The possible causes that come to mind are:
1. Blocked fuel cap breather so pump can't suck enough fuel to maintain pressure.
2. Blocked inlet filter in pump - same result
3. Air leak between tank and pump so pump is filling carb with air not fuel (probably loose union on inlet of pump)
4. Grit in pump valves/faulty valves allowing fuel to leak back across the pump
5. Float valve stuck open in carburettor (remove air cleaner and check for signs of fuel in carb throat)
6. Leak from carburettor or fuel line - should be obvious!

Hopefully that will give you sufficient pointers.

[bmcecosse]

Obviously - if the fuel is being pumped to the carb - it's not a fuel feed problem. To finish the arguement - pour an egg-cup of fuel down the carb throat and crank it - does it start? If not - look to the ignition system for the problem.....

[moggles]

I don't know that fuel IS being pumped to the carb - if it is, why does the pump keep constantly ticking? - hence the query about whether the free air ticking speed is the same as when it is connected to the carb. It should be a lot faster when disconnected than connected. If it is sucking and pumping air, or the pump valves are sticking, or the diaphragm is leaking, it will appear to deliver fuel when pumping in free air with no resistance, but won't deliver fuel to the carb against pressure in the fuel line.

[MarkyB]

I'm with Roy on this, if it pumps petrol into a container, its working well enough to start the engine.

Has anything been done to the engine recently? If so, look at this first.

The engine needs sparks as well as petrol to run.

[bmcecosse]

It may simply be flooded - are the plugs wet?