Red Line Components Posted June 9, 2017 Share Posted June 9, 2017 1500 pre crossflow single Weber. Running well until going above 4500rpm, after 10-15 seconds seems to be suddenly out of fuel. Dip the clutch and it returns to a weak idle failing to rev. Have checked jets are clear. Floats set correctly. New fuel pump, filter and fuel lines between filter and carb. (New plugs, points, coil and leads) Am usually quite good at diagnosing issues but am getting frustrated with this one! Any thoughts? Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted June 9, 2017 Member Share Posted June 9, 2017 Running well until going above 4500rpm, after 10-15 seconds seems to be suddenly out of fuel. Dip the clutch and it returns to a weak idle failing to rev.If you switch off does it recover by itself after a time?Have you tried removing the fuel filler cap? And do you hear an inrush of air when you do that after it's been running for a time or just after the fault has occurred?Jonathan Link to comment Share on other sites More sharing options...
Red Line Components Posted June 9, 2017 Author Share Posted June 9, 2017 It recovers and is happy again after 20 seconds of spluttering and unresponsiveness. Have checked the fuel filler.. no vacuum. Changed fuel pump 2 months ago due to complete lack of fuel delivery. ( i do have another new pump which was to be my next step) Link to comment Share on other sites More sharing options...
SJD Posted June 9, 2017 Share Posted June 9, 2017 A number of years ago I had a problem with my Series 2 1500 Cosworth which was due to the pipe from the petrol tank, the bend where it leaves the tank, becoming partially blocked with sediment. I'm using a SU electric pump and once the float chambers had emptied the car spluttered and I stopped, then the pump filled the float chambers and off I went for a short distance till it happened again. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted June 9, 2017 Member Share Posted June 9, 2017 Didn't someone describe similar occlusion with silicone sealant?Jonathan Link to comment Share on other sites More sharing options...
Red Line Components Posted June 10, 2017 Author Share Posted June 10, 2017 I will rig up a different fuel tank to check. Thanks Link to comment Share on other sites More sharing options...
Englishmaninwales Posted June 10, 2017 Share Posted June 10, 2017 Worth checking the float chambers when happens. If low points to either a partial fuel line blockage or fuel pump - if mechanical do you have the correct capacity pump ?Malcolm Link to comment Share on other sites More sharing options...
Red Line Components Posted June 10, 2017 Author Share Posted June 10, 2017 Will hopefully out and check the float chambers if it happens with the new fuel tank arrangement. Hadn't considered mechanical fuel pump capacity.. will double check what I bought. Link to comment Share on other sites More sharing options...
Molecular--Bob Posted June 10, 2017 Share Posted June 10, 2017 Modern fuels with ethanol can soften old rubber based fuel hose, if the pump is at the engine end, such as the original ford mechanical pump, the suction can pull the hose shut as the revs rise, then at tick over, suction falls and it opens up again and allows the weber float chamber to refill. Link to comment Share on other sites More sharing options...
Red Line Components Posted June 10, 2017 Author Share Posted June 10, 2017 Thanks for the reply Bob.. it is a mechanical pump at the engine. The tubing get is a hard plastic, and the flexible pipes between filter and carb are new. Will post how it goes with new tank and all new hoses. Link to comment Share on other sites More sharing options...
Red Line Components Posted June 10, 2017 Author Share Posted June 10, 2017 Well.. with a new fuel tank with a new filter and pipe and another mechanical pump it still falters after 25 seconds at 5500rpm. Exactly the same as with the old tank and new pump. It will rev cleanly to higher revs but falters soon. Looks like it's the carb. Link to comment Share on other sites More sharing options...
revilla Posted June 10, 2017 Share Posted June 10, 2017 Could it be as simple as the same kind of blockage that people have been suggesting, but up in the carb itself? Blockage around the needle valve somewhere? Might be worth just cleaning it out next. Link to comment Share on other sites More sharing options...
Red Line Components Posted June 10, 2017 Author Share Posted June 10, 2017 Yup.. that is my plan for tomorrow. (Or fit one of the other carbs that I have) Link to comment Share on other sites More sharing options...
Roger King Posted June 11, 2017 Share Posted June 11, 2017 Have you actually checked the fuel delivery rate to the carburettor? I know it's not so easy with a mechanical pump, but it should be possible to run on the fuel in the float chamber long enough to check flow rate into a bucket.ALL USUAL WARNINGS ABOUT FIRE HAZARD AND THE NEED FOR EXTINGUISHERS, ETC, APPLY TO THIS - WITH KNOBS ON! Link to comment Share on other sites More sharing options...
Red Line Components Posted June 11, 2017 Author Share Posted June 11, 2017 I will try that Roger. What flow rate is to be expected at idle? Link to comment Share on other sites More sharing options...
Red Line Components Posted June 12, 2017 Author Share Posted June 12, 2017 Fixed.. in the end it was a partial blockage at the banjo. Removed the glumpy rubbery mess and all is sweet again. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted June 12, 2017 Member Share Posted June 12, 2017 Well done.Did it look as if a blob could move in and out of the flow, or did it look constant?And when was any work done that could have caused it?Jonathan Link to comment Share on other sites More sharing options...
Red Line Components Posted June 12, 2017 Author Share Posted June 12, 2017 Not a mobile blockage.. more like a build up of decayed rubber hose. Looking all set now for a good cross country trip to the UK at the end of the month and onwards to Donington on 7/7 Car is still for sale! Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted June 12, 2017 Member Share Posted June 12, 2017 ThanksGute Reise!Jonathan Link to comment Share on other sites More sharing options...
OliverSedlacek Posted June 13, 2017 Share Posted June 13, 2017 Glad you've solved it. These things seem simple in hindsight but can be so frustrating until diagnosed. Link to comment Share on other sites More sharing options...
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