Hi Folks,
My 92 Four Winns with 5.8L/Cobra loss power at hole shot and I had made sure it's not engine overheating. I followed by doing fuel system check up and pickup tube, anti siphon valve, vent hose on fuel tank are all ok. Then I connect a cleat t-connector with vaccum guage and clear tubing like Don described on fuel system diagnosis. The t is placed in between fuel tank and fuel filter. The fuel filter is new, replaced 2 wks ago. Then I conducted the test. On the curbside, engine started smoothly and continued for 5 min. During this period, guage showed -3.5 Hg steadly with a few air bubbles went through. Then I reved up to 2000rpm and the pressure remained at -5 Hg. Then I put it at idle and clamped the tubing to cut off the fuel supple right after fuel tank and no change on vaccum, still -3.5Hg and the engine continued running. The guage is accurate which I checked with a lab vacuum pump and cut off by clamping is verfied later. However, the engine will not die after the clamp off even I rev it up to 2000 rpm. What's going on here?
With this no load test, I guess a new fuel pump is needed but just wondering where does the engine got the fuel from after clamping. How long the fuel in the carb bowl can supply the engine?
Frank
My 92 Four Winns with 5.8L/Cobra loss power at hole shot and I had made sure it's not engine overheating. I followed by doing fuel system check up and pickup tube, anti siphon valve, vent hose on fuel tank are all ok. Then I connect a cleat t-connector with vaccum guage and clear tubing like Don described on fuel system diagnosis. The t is placed in between fuel tank and fuel filter. The fuel filter is new, replaced 2 wks ago. Then I conducted the test. On the curbside, engine started smoothly and continued for 5 min. During this period, guage showed -3.5 Hg steadly with a few air bubbles went through. Then I reved up to 2000rpm and the pressure remained at -5 Hg. Then I put it at idle and clamped the tubing to cut off the fuel supple right after fuel tank and no change on vaccum, still -3.5Hg and the engine continued running. The guage is accurate which I checked with a lab vacuum pump and cut off by clamping is verfied later. However, the engine will not die after the clamp off even I rev it up to 2000 rpm. What's going on here?
With this no load test, I guess a new fuel pump is needed but just wondering where does the engine got the fuel from after clamping. How long the fuel in the carb bowl can supply the engine?
Frank