2003 Sportster starts and dies

[Jrells]

I thought this might help someone else like all these posts helped me. I have a 2003 Sportster with the Monsoon 335hp 5.7L engine. After de winterizing I had it out for 2 or 3 hours when it started not idleing. At 1500 rpm and above it would run decent but not like it was before and would surge at idle. I started with the fuel and filter and no change. Then spark plugs, wires, cap and rotor, still no change. I then replaced the TPS, IAC, MAP sensor, still no change. I noticed when it was cold it would idle for a while but then start to surge from 600rpm to 1300rpm till it would finally die. I read a few posts and a vacuum leak was mentioned a few times, also heard this model of GM engine was known for loosing intake gaskets. So removed the intake and plenum, the intake gasted had a tear so I was proud of myself for finding the problem... replaced all the gaskets and put it pack together and fired it up... and same problem. Pulling my hair out... I moved to the injectors, pulled them out and cleaned them and put it back together. It ran good for 10 mins and started surging again... I tested fuel pressure and it was at 72 psi, I heard most like to be about 40 but my friends 04 Sunsetter runs at 70 so thought it was fine. By chance I releived the fuel pressure on the tester while it was running at it started running purfect. I noticed while relieving pressure the gauge was at 40 psi, so I thaught fuel preasure regulator. Replaced it and still same problem and same preasure. I pulled the lines out of the tank and everything looked good, fuel was being drawn on the pickup and flowing back on the return, and the tank vent is clear. I romoved the hose from the fuel regulator and blew compressed air through it and there was a lot of restriction but still passed air. I started undoing fittings on the return line and found it was partially pinched behind the fuel tank (with 38 gallons of gas of course) at a clamp. So it was allowing just enough fuel through to show 70 psi on a guage and probably was affected by heat so it would run when it was cool out. I relocated the clamp and replaced the fuel line and it runs perfect. So I have learned this engine shares a lot of parts with a 96 vette vin 5 vortec 5.7L engine, like fuel system, injectors and stuff, pre vortec ignition system cap and rotor and stuff, vortec plugs, kind of a mix of years and genertions of the GM engines. Oh and all this took about 4 days in 105 degree heat to figure out...Cant wait to get back on the water. My point is there are a lot of friendly knowlegable people out there that will share their experience and minds to help other boaters work on their stuff. Thanks Malibucrew...

[SmoothWaterMan]

I think you are saying that after all that it's working fine. But it shouldn't be if it's still showing 70 psi of fuel pressure. Your pressure regulator is either not working or still clogged. Without pulling the specs I think your 03 was 30-40 psi.

Peter

[electricjohn]

37 to 45.