Weber 40 DCOEs - Engine Cut - Will not Restart - Fuel not Getting Through

[4129R]

After starting easily, running reasonably well, and 180 miles of driving, the engine just cut out at about 3000 RPm as if no fuel was getting through.

Even the AA breakdown man could not work it out, and had to tow me 2 miles home.

The engine will run on the fuel pumped in by opening the butterflies and pumping fully 3 or 4 times, but then just cuts out as if fuel is not getting picked up by the main jets and sucked through to the central venturi.

I have thoroughly cleaned both carbs, all jets and passageways with compressed air, checked the fuel pump, there is fuel in the float chambers but the engine just runs very slowly for 3 or 4 seconds, and cuts out.

I then repeat the pumping, and the same things happens time after time.

I have run out of ideas. Any suggestions?

[Triton]

I would take the fuel supply pipe off the carbs ,put the end in a bottle and crank the engine over to check the fuel pump.  If it was running ok before it does not seem to be a problem with the carbs.

[S2Zetec54]

….just trying to remember…will a failing condenser give those symptoms…..weak spark at low revs and cutting out at high revs. ?

[4129R]

I would take the fuel supply pipe off the carbs ,put the end in a bottle and crank the engine over to check the fuel pump.  If it was running ok before it does not seem to be a problem with the carbs.

Fuel pump works fine. I had to put a pressure limit valve on it, as it was over pumping and fuel was dripping out of a 4 trumpets.

[4129R]

….just trying to remember…will a failing condenser give those symptoms…..weak spark at low revs and cutting out at high revs. ?

Thank you for that suggestion, I will try replacing the condenser.

[Elanman39]

Will it run on the choke Alex?

[BDA]

Grasping at straws, is your fuel level correct? I like to check it using a caliper. (https://www.youtube.com/watch?v=meaGMoH4Pmw) It should be 25mm.

[4129R]

Will it run on the choke Alex?

No, I tried that this morning thinking the extra fuel would work, but it made no difference.

[Elanman39]

Does sound like an ignition issue then.....  Pop round some time if you want, I'm anout to put the S2  body and chasss together for the last (Ihope) time.

[4129R]

Grasping at straws, is your fuel level correct? I like to check it using a caliper. (https://www.youtube.com/watch?v=meaGMoH4Pmw) It should be 25mm.

I checked the float level this morning. 1 carb was slightly low, but the other carb was correct.

That made no difference.

Currently I have ordered a new distributor as the flimsy wiring for the condenser/points earth was horrible, it was a vacuum advance dizzy, and I have no vacuum take off. I am hoping a faulty condenser/earth wiring is causing the spark to fail under load/speed.

[Fotog]

You're not running out of fuel in the tank, are you?

Poor precision / accuracy of the fuel gauge makes it hard to tell what's going on.  I ran out a couple of times in short succession before I fully understood.  Duh

Despite the inter-tank crossover tube, you should put fuel in both tanks.  I know from experience.

[jbcollier]

Sounds like plugged idle jets to me.  Worth a look.

[4129R]

You're not running out of fuel in the tank, are you?

Poor precision / accuracy of the fuel gauge makes it hard to tell what's going on.  I ran out a couple of times in short succession before I fully understood.  Duh

Despite the inter-tank crossover tube, you should put fuel in both tanks.  I know from experience.

Because of the inaccuracy of the fuel gauge, I check how much petrol is in the tanks using a long wooden dipstick, calibrated with the number of litres with 57 being the maximum. That was actually the first thing I checked.

[4129R]

Sounds like plugged idle jets to me.  Worth a look.

I removed all 4 idle jet screws, cleaned the holes with compressed air, cleaned the screws and tried various openings from 1 1/4 turns to 3 turns, and that made no difference.

I removed all the brass jets, cleaned all the jets and cleaned all the holes in the carb body with compressed air, and there were no apparent blockages.

For the engine to just cut out at around 3000 rpm in 5th, something happened to make all 4 cylinders stop working at the same time.   

[314159td]

When you run out of carb problems to have, get suspicious of the ignition system. Particularly when it's a certain RPM that seems to cause the issue, as ignition things like to die at speed if they're worn out. Condenser (capacitor) is already mentioned, but coil, rotor, distributor cap, wires, and plugs are all worth taking a look at and swapping out if you have them on hand. And of course make sure everything is getting good power and ground.