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403 not starting

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Old 29-08-22, 12:51 PM
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Default 403 not starting

The car failed in an embarrssing way a couple of nights ago (second time).

Previously the electric fuel pump failed (two years old). Bypassed it and it ran on the mechanical pump. Fitted a new electric pump and it ran OK.

Then it stopped 'mid flight'. By passed it and primed the cars. Nothing, except the pump was working (forgot to disconnect it). Reconnected it, still nothing.

Checked the plugs and they are in good condition and sparking. Took the air manifold off and sniffed the carbs and could not smell petrol.

There is pressure in the supply line.

What could be happening?

Also, the middle carb isn't connected to the choke. It that normal? There is a hole in the linkage bar and a spring is connected to the arm but no linkage.
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Old 29-08-22, 02:03 PM
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Default No fly 403

Sudden loss of power plus decent spark does imply fuel blockage. Old ally tanks do give off cheesy crud which can block jets and fuel lines. Petrol pumps will struggle to suck enough fuel past the blockage. Maybe that's why you have both sorts of pump? Blow the fuel line clear backwards with an airline. New ethanol fuel is said to make rubber pipes swell up inside. ( eg flexi hose to fuel pump - should we be changing these?) And double check electrics; points, coil, plug leads , and inside the distributor anyway. Good luck- such a lovely car.
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Old 29-08-22, 06:10 PM
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If there is no hint of any firing at all, then it sounds like no fuel in the float chambers, given that you have a good spark. When you primed the carbs with the lever on the mechanical pump, did the lever go "slack" as it should when the float valves shut ?
With the mechanical pump, when priming by hand, you should see the fuel level rise quickly in the glass dome until it reaches the brass gauze filter.

If that doesn't happen, then:
Try switching to reserve, even if you have plenty of fuel - there may be a split in the main pickup tube in the tank, above the fuel level, causing it to draw in air.
If that doesn't work, then try using a tube directly from a container (with some petrol in it) to the input side of the pump, to eliminate blockages, or air leaks, in the supply line.

I think there should be a choke connection on all three carbs.
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Old 30-08-22, 11:20 AM
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Thanks for the replies.

The fuel tank is a recent stainless steel tank - no reserve.

I have both fuel pumps because I was tired of lifting the bonnet and priming the carbs every time I wanted to drive the car (plus getting oily fingers)!

I'm getting pressure up to the banjo feeds to the carbs (only checked the end one)
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Old 30-08-22, 04:20 PM
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Potential explination. The carbs are full of water and presumably an estimated 1/3 of the tank, hence the lack of petrol smell from the carbs!
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Old 31-08-22, 10:43 AM
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Quote:
Originally Posted by peterg View Post
Potential explination. The carbs are full of water and presumably an estimated 1/3 of the tank, hence the lack of petrol smell from the carbs!
That certainly explains it! And the tank doesn't have to have much water in it before the pickup pipe is seeing it. You will want to work out how the water got there in the first place too.

Mike
403-1402
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Old 02-09-22, 10:13 AM
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The situation wasn't as dire as I thought. I believed that water sits on instead of under, as with oil.

You are right, it is amazing how little water is needed. The nice thing about an electric pump is that it pumps! I took a few samples and the water has dropped from about 15mm to very little but the petrol looks cloudy.

Now the engine runs but is a little rough (after embarrassing me at the top of the road, fortunately I could roll down the hill).

The water could only have got there from the petrol or condensation. Usually I fill the tank right up before leaving it to minimise condensation. Would putting E10 in help to reabsorb the water?
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Old 02-09-22, 04:06 PM
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If it was me I'd drain it all and start again - the other option might be to fill it with the highest octane petrol you can get and see how you get on....
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