PhilipB Posted April 16, 2016 Report Share Posted April 16, 2016 (edited) Cracking day at Castle Combe on Tuesday but not without a few issues. OGB is a TR2 with twin Weber 45’s and a few other bits but with a standard mechanical fuel pump. First two sessions, the engine’s on song, running well and pulling hard. Towards the end of the second session the engine cut out and I coasted in. Enlisted the help of Carl and Dan from Revington TR (thanks again guys) and it proved to be the pivot pin on the pump lever had fallen out resulting in no fuel to the carbs. Swopped in a new pump, another session, on song again, problem sorted. Went out for the next session but didn’t make it onto the track. It proved to be the fuel pump again, the new one. Diaphragm looks OK and is going up and down but no fuel coming out. Fuel is running free from the tank but blew the line back just to make sure no obstructions. No answers to that conundrum but to get going again, we put the diaphragm and top half of the old pump on to the new bottom half (with the crank that actually pivots). Fuel now being delivered and engine running again. However, under load at 4k plus and it now feels like it’s running on 3 ½ cylinders. The filters were OK and we’d blown back the fuel line to make sure there were no blockages. It did briefly clear which made it sound like a fuel issue so we arranged for another new pump to be sent. Today I fitted the new pump and it’s still running rough under load. The Webers have fuel filters and they were clear, Main jets are OK too. No blockage in the fuel line to the carbs and filters in the pump are clear. It’s a newish aluminium tank so it’s unlikely to debris from there. There were clearly some issues with the first replacement pump but it ran OK for one session until it stopped delivering fuel. There is completely new pump now so given the above, I don’t think it’s a fuel delivery issue any more. So I’m looking for some guidance. Tappets were checked last weekend. Condenser was changed after the second session on Tuesday. Points gap is OK and timing is OK. Distributor cap looks OK. Red rotor arm. Spark plug gaps are fine with light brownish grey deposits. No increase in oil level and no oil in the coolant. Oil pressure and running temperatures as before. The engine is a little lumpy at idle but it runs ok. Floor the accelerator and it hesitates but clears a bit when I back off the throttle a bit. Does anyone recognise these symptoms and/or have any ideas as to what to do next? Phil Edited April 16, 2016 by PhilipB Quote Link to post Share on other sites
stillp Posted April 16, 2016 Report Share Posted April 16, 2016 Dirt between the pump and the carbs? Pete Quote Link to post Share on other sites
PhilipB Posted April 16, 2016 Author Report Share Posted April 16, 2016 (edited) Hi Pete Don't think so, the line between pump and carbs blows through with no problem Phil Edited April 16, 2016 by PhilipB Quote Link to post Share on other sites
stillp Posted April 16, 2016 Report Share Posted April 16, 2016 Fuel tank breather clear? Pete Quote Link to post Share on other sites
graeme Posted April 16, 2016 Report Share Posted April 16, 2016 (edited) Phil, Have you checked the cylinder compressions? You may have burnt a valve. Graeme Edited April 17, 2016 by graeme Quote Link to post Share on other sites
Peter Cobbold Posted April 16, 2016 Report Share Posted April 16, 2016 (edited) Fuel tank breather clear? Pete +1 Tank 'vacuum' might well not show up in normal driving. Two sessions to build up 'suction'. And the new tank has a new filler cap, no vent to atomosphere ? Edited April 16, 2016 by Peter Cobbold Quote Link to post Share on other sites
stillp Posted April 16, 2016 Report Share Posted April 16, 2016 This "It proved to be the fuel pump again, the new one. Diaphragm looks OK and is going up and down but no fuel coming out. " sounds like a non-return valve failure, they're pretty simple things but might fail due to a bit of grit, so if not the breather I'm still thinking there's something floating about in the fuel system. I'd blown through mine several times, but had similar symptoms to yours until I turned the engine over with a needle valve (Strombergs on mine) out. The fuel flow must have washed the offending carp out. Pete Quote Link to post Share on other sites
PhilipB Posted April 16, 2016 Author Report Share Posted April 16, 2016 Thanks all for your input Pete The original pump issue was a pivot pin falling out The second pump worked briefly but then stopped delivering fuel. For that reason the top part of the original pump was fitted to the new, working bottom half and flow restored but running rough The all new third pump, fitted today, has not cured the problem. As I noted, Webers have a filter on the inlet to each and these were at all times clear. Peter The new tank was fitted ~3 years ago but with the original filler cap, no issues experienced on previous track days, or even normal running as now, but I will try again with the filler cap open Graeme That's sort of where I was heading and will check this week. Kind of puzzling though as, to the point at which the second pump failed, the engine was fine. I came in from a session with no problems, engine fine, switched off. Half an hour later, going out for the next session and when the second pump failed, from that point on the engine has been a bit rough. On just searching through the forum on burnt valves, I think I'll also run through the ignition system with a fine toothcomb, especially as the problem did seem to clear for a brief moment whilst on the track. Phil Quote Link to post Share on other sites
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