Cutting out under load

[Nick Seber]

4a runs fine on the flat with a light throttle, under load up hills, she splutters afer a few hundred yards and then cuts out. Car will restart but barely runs.

took the fuel bowl glass off, separated fuel and junk in the bowl. Cleaned and refitted, using the hand primer hardly puts any fuel into the bowl, car needs to be running to fill the bowl properly. Fuel pump issue?

[RobH]

It might be a blockage in the feed pipe from the tank. Have you fitted an in-line filter? those are known to get blocked. 

Otherwise it sounds like a leaking non-return valve in the pump.  Could be a hole in the diaphragm but then you might notice a petrol smell or fuel in the oil.  

Edited April 7 by RobH

[Charlie D]

Nick,

Are you sure that the lobe for the fuel pump is "Off the cam" when you operate it by the hand lever?

If not then the lever feels like it is working fully, but the diaphragm is hardly moving.

That would account for the fuel pumping when the engine is running.

Charlie.

[Nick Seber]

22 minutes ago, RobH said:

It might be a blockage in the feed pipe from the tank. Have you fitted an in-line filter? those are known to get blocked. 

Otherwise it sounds like a leaking non-return valve in the pump.  Could be a hole in the diaphragm but then you might notice a petrol smell or fuel in the oil.  

No inline filter that I’m aware of. The car gets to exactly the same place on the hill from my house before spluttering so points to fuel starvation?

[RobH]

Yes, fuel problem.  The question is whether it is the feed to the pump, or the pump itself which is the cause.  Of course it could also be a blockage from the pump to the carbs.   If the pump can't push fuel out that way, it can't pull any from the tank to fill the glass bowl.  

If you take the feed pipe off the carbs and put the end in a bottle, can you squirt fuel through easily by operating the priming lever?  

 

[RogerH]

Hi Nick,

what air filters do you use on the carbs.

I had this issue two years ago.  I have K&N filters.

When I inspected the filters, they had shrunk. 

When I had a WOT - usually up hill the filters would collapse and shut off the air.

Take foot off throttle and normal service resumes

This can happen if you clean the filters in petrol, over time

Replace filters

 

Roger

[Nick Seber]

40 minutes ago, RobH said:

Yes, fuel problem.  The question is whether it is the feed to the pump, or the pump itself which is the cause.  Of course it could also be a blockage from the pump to the carbs.   If the pump can't push fuel out that way, it can't pull any from the tank to fill the glass bowl.  

If you take the feed pipe off the carbs and put the end in a bottle, can you squirt fuel through easily by operating the priming lever?  

 

All squirts through nicely 

[Nick Seber]

48 minutes ago, RogerH said:

Hi Nick,

what air filters do you use on the carbs.

I had this issue two years ago.  I have K&N filters.

When I inspected the filters, they had shrunk. 

When I had a WOT - usually up hill the filters would collapse and shut off the air.

Take foot off throttle and normal service resumes

This can happen if you clean the filters in petrol, over time

Replace filters

 

Roger

Oval metal and cardboard filters, new a couple of years ago 

[Footstuck]

Is the car fitted with electronic ignition?
If not, the first thing I would do is change the condenser. The cost is minimal and not wasted as you will have a spare for future servicing.

When it cuts out check the coil temperature, as it could be a resistance problem. If the coil is hot in the extreme, check all your gaps (and cap segments) along with any other resistance causes.