tr6wilts Posted April 3, 2014 Report Share Posted April 3, 2014 (edited) I am looking for some help with two issues that may be the same: Car is a PI converted to SU's 1. Car runs fine at speed , and in traffic before it warms up, but once it has been driven for 20 mins plus it runs badly in traffic, it seems like a fuel / carb issue and it seems quite hot under the bonnet... Could it be the carbs getting too hot from the exhaust manifold and causing issues, and once the car is up to speed it gets enough cool air? 2. The previous steel tank was shot and full of ****, so I have replaced it with an alloy one, and due to issue above pulled out the pump and filter that seemed to still have some rusty **** in, now as the car seems to run ok at speed I dont think 1 above is related to this, but the questions is since both seem to have been filled with rusty **** (at the filter was on the output side of the pump)it is probably worth replacing, and if so what with? The current pump seems to be a "fuelflow"?? with a Bosch filter, presumambly I dont need to go the Lucas or Bosch route for the pump as it is SU's ie something like a facet fuel pump? I also have a malpassi fuel filter / pressure regulator inline in the engine bay. Edited April 3, 2014 by tr6wilts Quote Link to post Share on other sites
TRseks Posted April 3, 2014 Report Share Posted April 3, 2014 Could also be a bad coil that will start to misfire when it get hot, has happened to me and was difficult to trace down. Quote Link to post Share on other sites
kdb550 Posted April 3, 2014 Report Share Posted April 3, 2014 (edited) what colour are the spark plugs sounds like it is running lean once it has warmed up. could be it requires a different needle or just basic carb setup start with the basic SU setup and checks first. After 20 plus years of racing minis with su's fitted have found people always look for complicated answers to basic problems. good first thing to check would be tae the piston caps off turn the ignition on and make sure the float vavles are doing there job and stopping the fuel when the bowls are full. Also make sure the float valves are set to the correct level and you have the correct pool of fuel in the jet. Edited April 3, 2014 by kdb550 Quote Link to post Share on other sites
Peter Cobbold Posted April 3, 2014 Report Share Posted April 3, 2014 (edited) The fuel might be boiling off butane in the jet area at tick over, at speed the flow is faster and the fuel stays cool. There's a lot of radiant heat coming off the exhaust manifold that can be intercepted with a simple reflector made from ali sheet. Bolt it to the SU mouth flange where the filter fits. Principle shown here: http://www.teglerizer.com/triumphstuff/75w_heatshield.htm Try wrapping the float chamber/jet hose in ali cooking foil as an experiment, if it works you've found the problem. Peter Edited April 3, 2014 by Peter Cobbold Quote Link to post Share on other sites
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