fuel flow problems

Hello Dave,  When your car falters and stops have you checked for fuel in the float chambers ? An old mechanic told me 'it's always the electrics'. I never assume that new coils, rotor arms and condensors will work reliably, having had problems with replacements myself. For what they cost it might be worth trying another lot. Coils usually become progressively worse whereas condensors and rotor arms break down suddenly when warm giving the symptoms you describe, but then when cooled down  will allow the car to run until it warms up again. Good luck. Posted by tf1695 12/09/2012 16:19:35

Hi,  I have checked with both new and old ignition components, plus the float chambers are definitely empty. I can feel the car change as one then two and finally three carbs are starved of fuel. However, hopefully my fuel problems will be resolved by the new tank which I should be able to fit this weekend (It is not easy to fit a new tank on the car when car and tank are in England and I am working in Istanbul!)  Regarding fuel flow, I have seen at least half a pint of fuel flow from an open pipe without obvious problems from the various combinations of pumps that I have tried.  cheers  Dave Posted by DaveT 13/09/2012 05:55:09

Can't wait to hear how you get on Dave, fingers crossed for you! Paul. Posted by pryantcc 13/09/2012 15:14:38

Have you checked the filters in the top of the carburetor float bowl Banjos? Posted by IanHardaker 14/09/2012 23:38:49

Well after all this saga, the car was not ready for the friend's wedding that I had promised to do last Saturday! They had to squeeze into the back of my Jensen 541S (a 2 door GT) instead. As I was doing them a favour for no charge I did not feel too guilty about it but it was certainly a shame.  Getting back to the Alvis, the tank is not yet ready, but in the meantime I bypassed the fuel tap (which I have rebuilt twice and tested with a vacuum gauge after reassembly) and managed to get a good pressure reading and the glass filter bowl was full - this is the first time that I have seen this really work properly for any more than a few minutes. However when I took the car out for a short drive it didn't get very far (about half a mile) before dying again, however the fuel pressure remained good. So suspecting a blockage in the feed pie to the carbs, this pipe has been removed (again!) and poked through with a length of locking wire but I didn't find anything wrong! I will try the flow test at the next opportunity (again). The float chamber lids have also been removed and cleaned a few times but these will have to be checked again.  When the car stopped, I checked all the fuel lines for the possibility of overheating but the exhaust had not fully warmed up and as all the fuel lines were still cool to the touch I do not think that vapourisation is the issue.  I have also cut the choke fuel supply pipe and inserted a length of clear plastic pipe so that I can seen whether the AED is functioning correctly - it is.  The old tank has now been cut up and it is quite obvious that significant quantities of rust in the tank were the initial cause of most of my problems but it is still just not quite right.  Investigations continue... Posted by DaveT 17/09/2012 12:01:56

Do all three float chamber lids have the flooding pin?  If not, do your float chamber lids allow for some air access so that a vacuum is not occurring in the float chambers? Posted by johnlayzell 17/09/2012 22:33:00

Hi,  I have had this thought and all three float chambers have the "flooding pin" and all three (now) have the correct groove in the top flange of the lid to allow air in and out of the chamber above the fuel level.  thanks  Dave Posted by DaveT 19/09/2012 11:34:41

I remember I had a similar problem with a Riley 12/4 with twin SUs. I fitted the latest float chamber needles from Burlens . The ones tipped with some sort of coating instead of just plain brass. I could normally travel about half a mile before the float chambers ran dry due to the vlaves sticking shut even against the pressure of a new SU pump in a brand new fel system. Looking back it may have been that the float level was set too high thus exerting more pressure onto the seating. Even so it took some believing but fitting the old brass needles instantly cured the problem.  Cheers  john Posted by speed20 19/09/2012 19:05:46

Sounds like you are on to it with the fuel tank and its' internal debris. However you try it is almost impossible to get ALL the rust flakes out.  Make sure that there are no "high loops" in the fuel lines where air could collect. Some cars have the pipe to the three carb banjos above the carbs and some below. Below would seem to be better so that any trapped air or vapour can travel to the carb.   Phil 3861Wa Posted by Silver Eagle 25/09/2012 22:02:49

Hi Phil,  thanks for this suggestion (routing of fuel line from below rather than above) - I had not considered this. I am reluctant to discard the original fuel line but have not managed to find any new banjos (or perhaps someone has a 2nd hand assy that I could acquire) to try an alternative routing. My net step is the needle valves in the float chamber but last weekend and this weekend are taken up working on my Jensen 541R which is booked in for 3/4 of a new chassis - a major job on any car, especially one with a fibre glass body.  thanks again  Dave Posted by DaveT 26/09/2012 07:01:40