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.

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.

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.

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)

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

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?

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....

403 not starting
 

Aplogies, only just seen this thread. If you have or suspect water in the fuel system there are products out there to cure this problem, e.g. Wynns Dry Fuel Water Dispersant.

I believe they work by emulsifying the water into the petrol.

Andy

I have only just spotted this thread as well, years ago on a 403 I had in regular use commuting from Fishguard to Swansea at weekends I had a couple of breakdowns and had to call out the RAC who found water in the carbs, I changed garages but eventually found the problem a couple of small rust pin holes where the fuel filler pipe meets the base of the box it sits in, they were on the top and side of the pipe so in heavy rain some of the water that should have been going past the pipe to the drain in the corner of the box was getting into the petrol. Equally so you could have the same problem with holes anywhere around the base of the pipe especially if the rain water drain is blocked.
I cured the problem by cleaning up the whole of the outside of the base of the pipe where it is welded into the box and sealing it with Petro Patch.
Geoff.

Not sure if that is the case but when I spilt some petrol I found that the drain pipe was blocked. Now cleaned out.

From a previous question I cured the gushing of petrol from the breather by adding a loop and a petrol filter as an 'expansion box' to the pipe.