Dodgy Fuel pump or something else?

[paulallyedwards]

My 1971 s2 2+2 is driving me mad! It stalls after about 30 mins from cold.
I have had the carb’s refurbished
Changed the coil
Changed the balancer
Changed the plugs
Changed the ht leads
Checked for a blocked filter/debris
in the fuel tank (there wasn’t one)
Tested the voltage across the pump, 12.5 when ignition on and strangely 10v when the ignition is off.

When the cat stops is starts run fractionally rough for a minute or so, not miss firing just a little rough, then it just stops.

You can’t then start it for about 15 mins

The only thing I notice when it stops is that when I try to start it the pump does not tick, but it does after 15 mins when it starts fine.

Can anyone offer any ideas please?
Regards
Paul Edwards

[1954Etype]

Non vented fuel filler cap?

[Gfhug]

Paul, you say you’ve changed the coil but to what? Some of those available online are not that good and can then break down after a while (say 30 mins).
Although your car starts, it is well worth following the advice in post #4 in this topic:
viewtopic.php?f=3&t=20806

And check what Angus has said above. He knows these cars very well.

Also read post 5 here about coils depending on having a ballast resistor which your car might well have:

viewtopic.php?f=3&t=19599&p=159329&hilit=Coil#p159329

Geoff

[Gfhug]

Paul, a couple of other details to help. Is it triple SUs or twin Stranglebergs?
Please click on your user name top right and add these sort of details to your signature.
Have you changed the rotor arm for one from the distributor doctor?
The pump doesn’t necessarily tick after a brief stop as the fuel is already in the line. Is it a standard pump?

Hopefully a few more details can help the knowledgeable to point you in the right direction.

Good luck

Geoff

[mgcjag]

What carbs are you running..who refurbed them...and who fitted them....what do the plugs look like ..black and sooty....when it stalls is there fuel in the glass filter bowl..Steve

[politeperson]

As Steve says, I would go straight to the fuel bowl and see if its empty.

I once had an E type with an internally corroded blocked main fuel line.

It would run for 20 minutes then die. The fuel pump would not tick because of the back pressure in the line.

A small piddle would eventually fill the carb bowls and off we would go again.

If you pull the fuel line off the carbs, you should get a good strong spurt out of the line into a collecting bowl with the ignition on.

Worth a try?

[paulallyedwards]

Thank you all,
The fuel bowl is full when the engine stops.
The carbs are triple Su’s and were refurbished by a local mechanic.
I put the multi meter across the coil and this showed 13.1 v when idling, dropping to 12.6v when the fans kicked in, I didn’t see any drop either at the coil or at the pump when the engine cut out. So I think the spark side of things looks ok.
I also tested the fuel filler cap… it is so old there is no chance it is causing a vacuum.
The rotor arm is a new one from Martin Robey… I am pretty sure it is functioning ok.
Annoyingly the bloody thing idled for a whole hour earlier today and didn’t cut out… the first time that has happened in a year or so … ahhhh
BTW Is it usual for the pump to show a power reading when the ignition is off?
Paul

[DWW]

Have you replaced the distributor rotor?

[mgcjag]

Danny...poster said above he's changed the rotor arm...
Paul.. ignition off then no power to the fuel pump..do you have a circuit diagram....as mentioned vented fuel cap..when it stalles remove the cap..does it hiss as it suckes in air....when it stalles remove the dashpots and pull out piston with needle...is there fuel just down in each jet......Steve

[paulallyedwards]

Thankyou Steve, the circuit diagram is not particularly helpful, it simply shows a direct connection to the fuse. I thought it might go also to the ignition switch, but that is not shown.
I will definitely look down the carb pot next time it stops… a great idea, I am not sure why i didn’t think of that!! Thankyou for helping me I am really grateful.

[mgcjag]

Hi Paul....the diagram shows the fuel pump connected to the fuse block...it isnt fused....and connection block connected to battery via the ignition switch...note you dont look down the dashpots....you remove the pots/piston and needles and look down the jets...Steve