Fuel Vapourising

[Rich]

Nice warm day today.....

Unfortunately plenty of traffic in town and the car has conked out on me three times today, tipping water over the carb does the trick but I've had to do my water fairy act in the middle of a four lane roundabout, in the outside lane of a dual carriageway and on the motorway slip.

The car has no undertrays or side shields, I'm using a mechanical pump and the radiator fan is cutting in and out as it should.

I can't be the only one with this problem, has anyone got any fixes for this?

Rich

[Hans Efde]

Obviously I have a completely different system, but I have had my recent share of engine cutting out at idle. This was due to the CO setting too low (about 1%, with the idea to decrease the fuel consumption). I have played with the timing and set the CO a bit richer, I think close to the 3% and it seems to idle happily now.
On my previous coupees, one with a 1380 Avonbar and one with a standard engine (with MG airfilter) I never had problems with engine cutting out. And those had the splash guards and forward undertray in place. Only once I had a problem but that was in the Austrian mountains on the Grossgluckner Hochalpenstrasse (probably also a mixture problem due to the low oxygen).

An engine running lean won't show on the temp gauge, it just cuts out a low revs. Therefore make sure your engine doesn't run lean. Give the CO a bit more and make sure the carb doesn't suck in false air, or make sure you have the correct needle in the carb (that matches the airfilter). I noticed you have the MG airfilter on your engine, make sure your needle matches.

[Rich]

I'm running a Pipercross now, my CO tester is out of action so it's set up by ear at the moment, perhaps it's time to sort out the rolling road session at Tipton?

[Hans Efde]

I do it on feel. A quarter turn of the CO screw at the time and a testrun after every change. If your PiperCross is sucking in more air (what it is supposed to do) you need a thinner needle anyway. Maybe you can have one ground when using a rolling road. I think this is one of the biggest drawbacks of the SU carb.

[Rich]

It's already running a modified needle, presumably from when ACDodd built the engine. The place I'll be using has years of A series experience though they haven't set up a Megajolt before. Tipton is run by Richard Miles who used to work at Downton.

[M.Ouvinen]

Mine's a Mk2 Bronze, but...

I've had vapour lock or vapourizing problems too. I replaced the metallic diagonal fuel line from the pump to the carb with a rubber hose routed straight up and around the carb. I'm hoping this will solve the problem. The only problem is, that I won't know without running it in the city traffic and seeing for my self.

I did think about installing one of those wireless roasting thermometers to see how hot the fuel line is running. I think there is still an issue with engine bay temperature, because after a while of driving the idle speed jumps up...

[manifold]

I dont have vapour lock problems with steel hose whatsoever, but maybe thats because I use an electric fuel pump and the carbs are at the front of the engine near an intake vent and the pipes/carbs dont go anywhere near the exhaust system so dont get hot at all?

[M.Ouvinen]

Mine went right next to the exhaust manifold, diagonally from the pump to the carb in a metallic tube, not a braided hose or whatsoever. So it's no wonder it vapourized, since the metal pipe was under a centimeter from the headers.

[Rich]

I've bought a pair of R1 fans to pump the hot air out of the engine bay, haven't had time to fit them yet due to work pressures and having to prioritise fitting the speed sensor for the dash in the rear drum.