Re: Power loss after approx 1 hr of running
with a Kv tester and a fuel system pressure/vacum guage this sort of issue can normally be found inside my 1 hour diagnostic time.<br />hook up the fuel system vacum guage like I said and see if system vacum exceeds 4"Hg, some carbs have a filter in the inlet nut that never gets checked as well. normal fuel system vacum for that motor will be 1 to 2"Hg, less and it could bve an air leak or bad pump, more and its a restriction somewhere. when its dying check the fireing voltage, it should be between about 7Kv and 10 Kv.<br /> mecanical issues dont come and go, so right off the bat we eliminated engine mechanicals, mostly
.<br /> the rest is fuel,or lack of, in the intake manifold and spark, or lack of, at the proper time, at the spark plug gap.<br /> that motor has 4 cycles, suck,squeeze ,bang and blow. everything else helps it go.<br />dont let the complexity of the entire packege pop a brain cell.<br />normally, if the carb works well its ok, however if the carb has no fuel or not enough it cant get fuel to the intake manifold.<br />gotta isolate it to a restriction before the pump or the pump. as most pumps are mechanical they normally work well all the time or not at all. but not always.<br />had a 5.8 PCM that worked well to 4200 then would lean out and blow off a plug electrode, bad fuel pump. found it with the pressure guage.<br />took 3 techs and the customer spent 700 buxs on work not needed.<br />so look at your symptoms, evaluate what may or may not be happening and test accordingly.<br />never saw a sock on a marine draw tube.<br /> however most had a screen just below the tank bung in the draw tube that can drive an untrained tech slam up the wall.<br />however the vacum guage can catch that in the first 20 min or so.<br /> when the motor is losing power do you get any backfireing at all ?
