StevedTR4A Posted February 20, 2009 Report Share Posted February 20, 2009 Advice please Just got back from a 20 mile run in my TR3A. Opened the bonnet (engine still running) and saw that fuel was leaking from the rear carb float chamber overflow pipe. Is this likely to be a stuck needle? The engine runs well and the carbs have given no problem, they were rebuilt some 2000 miles ago. I guess this could be caused by dirt in the fuel so is an in line filter recommended? Do I just try tapping the top of the float chamber to free the needle before stripping the float chamber? I am just getting back to SU carbs after an absence of some 35 years so please bear with me thanks in advance Steve Quote Link to post Share on other sites
StevedTR4A Posted February 20, 2009 Author Report Share Posted February 20, 2009 Should have mentioned that I have H6 , AUC878 carbs. Steve Quote Link to post Share on other sites
gamtune Posted February 20, 2009 Report Share Posted February 20, 2009 Advice pleaseJust got back from a 20 mile run in my TR3A. Opened the bonnet (engine still running) and saw that fuel was leaking from the rear carb float chamber overflow pipe. Is this likely to be a stuck needle? The engine runs well and the carbs have given no problem, they were rebuilt some 2000 miles ago. I guess this could be caused by dirt in the fuel so is an in line filter recommended? Do I just try tapping the top of the float chamber to free the needle before stripping the float chamber? I am just getting back to SU carbs after an absence of some 35 years so please bear with me thanks in advance Steve i had this problem steve & it turned out to be a sinking float, try taping it first if it dont stop take the top of the float chamber & check the needle valve or see if the float has sunk .hope this is of some help phil. Quote Link to post Share on other sites
pfenlon Posted February 20, 2009 Report Share Posted February 20, 2009 An inline filter is a must. Tanks are usually grotty and the filter in glass bowl isnt good enough, clean the valves, even better to renew them, then install your QUALITY in line filter. If you dont, the valves will alwys stick open, with possibly blazing results. Quote Link to post Share on other sites
peterc Posted February 20, 2009 Report Share Posted February 20, 2009 i had this problem steve & it turned out to be a sinking float, try taping it first if it dont stop take the top of the float chamber & check the needle valve or see if the float has sunk .hope this is of some help phil. Hi Steve, This problem is more than likely caused by dirt in the fuel system. I would recommend that you remove both floats and clear any debris from the float chambers. This is a problem that I have found and in the end I fitted an in line filter. Amicalement Peter C Quote Link to post Share on other sites
Don Elliott Posted February 21, 2009 Report Share Posted February 21, 2009 Petrol has additives and the big additive (10%) in the USA is ethanol. Ethanol attacks the solder in the floats and will cause a pin-hole leak. This has been reported on several car forums. The petrol gets inside and the float sinks with exactly the results you have described. Try swopping the rear float to the front carb and if the problem now occurs with the front carb, you have identified what the problem is. If so, it may be an additive that did it or maybe it's "age-related" as my doctor keeps telling me. Fix the leak. Someone somewhere is trying to develop a plastic float for all our LBCs where the float might be blow-moulded and the material would be selected so it will withstand all the petrol types and additives. Quote Link to post Share on other sites
vivdownunder Posted February 21, 2009 Report Share Posted February 21, 2009 Hi Steve, Yes, something as fine as a human hair can lodge in a needle and seat, which then fails to seal, and allows the bowl to fill to overflowing. Typically such an inpurity will travel right past the front carbie, and lodge at the end of the fuel line in the rear one. Try tapping the bowl lightly first, then the next step is removing the bowl top cover to clean or replace the needle and seat. There's an outside chance the brass float has pinholed and filled with petrol, rendering it unable to rise and close the needle. Suggest an inline filter between the incoming fuel line from the tank and the petrol pump, so it keeps both the pump and the carbies clean. Regards, Viv. Quote Link to post Share on other sites
StevedTR4A Posted February 21, 2009 Author Report Share Posted February 21, 2009 Thanks guys, thats a great help. Is there a quality in line filter that is recommended. I did recently pick up a WIX plastic filter but not sure if it is suitable. I have heard that fuel starvation is a problem if the filter is not suficiently big. Any particular recommendation? Thanks again Steve Quote Link to post Share on other sites
vivdownunder Posted February 21, 2009 Report Share Posted February 21, 2009 You'd be fine with the Wix fuel filter Steve. They've been around for donkey's years, and long involved with their products in motor racing. You'll need one to suit 5/16 ID fuel hose, and preferably clear so you can see when it needs replacing. This diameter inlet/outlet will only give fuel starvation problems on a TR road tune motor if it gets obstructed. Regards, Viv. Quote Link to post Share on other sites
T Robinson Posted February 21, 2009 Report Share Posted February 21, 2009 You'd be fine with the Wix fuel filter Steve. They've been around for donkey's years, and long involved with their products in motor racing. You'll need one to suit 5/16 ID fuel hose, and preferably clear so you can see when it needs replacing. This diameter inlet/outlet will only give fuel starvation problems on a TR road tune motor if it gets obstructed. Regards, Viv. I have had a leak in the past and fixed the problem by fitting grose jets in place of the needle valves. However, I would also recommend taking the needles valves apart and lapping the needle onto its seat with chrome cleaner. It works! Regards, Tony Quote Link to post Share on other sites
StevedTR4A Posted February 21, 2009 Author Report Share Posted February 21, 2009 A slight tap on the float chamber seems to have cleared the leak - for now! However I will definitely fit a fuel filter and am contemplating Grose jets. The only position for the filter is in the hose just before the carbs as I have pipe to the tap and a braided hose to the pump. Thanks again gents for the reassuring advice Steve Quote Link to post Share on other sites
vivdownunder Posted February 21, 2009 Report Share Posted February 21, 2009 A word about Grose Jets. They were a great thing 30 odd years ago for stopping fuel smells in the cabin, when SU needles and seats were both brass. Now that modern needles have a neoprene tip, they actually work better than Grose Jets, which are still a metal to metal sealing product. Regards, Viv. Quote Link to post Share on other sites
StevedTR4A Posted February 22, 2009 Author Report Share Posted February 22, 2009 Hi Viv I didn't know about the neoprene tip. I guess best to go for this. I had also heard that Grose jets were not the perfect solution. ie variability in quality, height setting etc I will check out the availability of the original type with the neprene tip. Thanks again Steve Quote Link to post Share on other sites
Don Elliott Posted February 22, 2009 Report Share Posted February 22, 2009 I put in Grose jets in 1990 on my TR3A and never had any issues related to the floats or flow to the bowls. I have no inline filter and never had a blockage in 18 years with these jets. But the inside of my petrol tank has been epoxy coated so there is never any rust or other sediment in the glass bowl under my petrol pump. Quote Link to post Share on other sites
StevedTR4A Posted February 23, 2009 Author Report Share Posted February 23, 2009 Thanks Don The car was fully restored in 1998-2003. I have records for most things but have no idea what was done to the tank. Being aware that the guy who carried out the restoration ( his retirement project) was quite meticulous I guess he would have treated the tank if it was needed. There is a little debris in the bottom of the pump bowl so something must be coming from the tank. I dont intend to take the tank out so will for now fit an in line filter. I looked at a suppliers website for new needles and they imply that the latest "conventional" needles with the viton tip are supperior to the ball type. Who knows? - I guess I will go the conventional route for now. regards Steve Quote Link to post Share on other sites
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