Sportsman 800 2005 need some EFI help - Polaris ATV Forum
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post #1 of 11 (permalink) Old 06-10-2019, 09:45 AM Thread Starter
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Sportsman 800 2005 need some EFI help

Hello,
I hope you are not to fed up with EFI issues…

I live in Sweden and I have a 2005 Sportsman 800 with 250 h on the clock. It started to run a little bit rich and is now at the point where the machine stalls at idle. These are the symptoms: Idle drops really low, below 700 rpm and finally stalls especially when the machine is hot. It runs a little bit rich but exhaust is not black and it does not smell of fuel. Spark plugs were black (soot). It hesitates a little bit at low rpm:s but pulls rather ok especially before it gets hot. No codes are set. I also have a problem that the fuel level is sometimes showing in the display and sometimes not but I assume it is not related.

What have I done so far. Battery is checked and fully charged. Both spark plugs new. New air filter. As I think the fan is not starting as often as before I have changed the temp sensor. Engine does not get warm (no boiling or warnings) and the fan starts when pulling the wires at the sensor. Crank case ventilation is clear and I can not see anything strange with the wiring to the TPS or T-BAP. I have checked the voltage at the TPS just by measuring voltage when the ignition is on and it was 0,694 V. Turned the TPS so it is now 0,710 V (did not make any difference for the idle). I tried to set the idle by turning the TPS but couldn´t get it above 850 rpms when cold and trickles down and stalls when warmer. I have not changed the idle screw setting. When using the throttle I can´t see anything strange with the voltage readings but that is with my multimeter as I don´t have an analog voltmeter.

I don´t know where to check next. I know wiring issues and the T-Bap sensor is causing a lot of EFI-problems but shouldn´t I have error codes if that was the case? I have not checked the fuel pressure but the fuel pump was changed last autumn. Could the exhaust be restricted?

Ideas?

Thanks,
Peter
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post #2 of 11 (permalink) Old 06-10-2019, 02:12 PM
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Sounds like your pump is going out...
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post #3 of 11 (permalink) Old 06-10-2019, 02:43 PM
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Check the fuel pressure - should be about 45 psi

2006 Trailboss 330
2002 Sportsman 90
2005 TRX400EX (FOR SALE)
2003 LT-Z400 (needs engine work & is for sale)
2004 CRF250X
1971 Triumph 650 Bonneville (has 5 original miles)
1972 Triumph 650 Bonneville (undergoing restoration)
1979 Honda CBX (6 cylinder)
1970 Kawasaki G3SS 90cc Bushmaster
1976 Suzuki RE5 Rotary (not running & FOR SALE)
1981 Kawasaki KZ305-A
1981 Suzuki GS450T (undergoing repair & will be for sale when done)
1982 Kawasaki KZ750-H (FOR SALE)
1989 Honda VT1100C
2007 Vectrix VCTX Electric Scooter
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post #4 of 11 (permalink) Old 06-12-2019, 12:33 AM Thread Starter
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Thanks for your replies! I will borrow a meter to measure the fuel pressure during the weekend so that will be interesting. I assume I need to know the pressure when cold and when warm?

I changed the fuel pump two years ago and the pump I used was a Kemso. If that is now a problem I would like to get a better pump. Is there any particular one that is recommended?

Thanks again,
Peter
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post #5 of 11 (permalink) Old 06-12-2019, 05:47 AM
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Fuel pressure should be the same hot or cold, but check it just for the record. It's not so much the fuel pump as it is the fuel. Alcohol blended fuel can destroy the cheaper pumps in a short time -all depends on the type of alcohol (Ethanol, Methanol or Isopropanol), the % added to the gasoline and how often the machine is run. Alcohol fuel should be used within 21 days of purchase and not let set more than 5 days or the alcohol can separate from the gas. When alcohol absorbs water (from the atmosphere) is separates from the gasoline and algae starts to grow in the water. Can cause clogged filters, damaged rubber parts, stuck float needles and other fuel system problems.

2006 Trailboss 330
2002 Sportsman 90
2005 TRX400EX (FOR SALE)
2003 LT-Z400 (needs engine work & is for sale)
2004 CRF250X
1971 Triumph 650 Bonneville (has 5 original miles)
1972 Triumph 650 Bonneville (undergoing restoration)
1979 Honda CBX (6 cylinder)
1970 Kawasaki G3SS 90cc Bushmaster
1976 Suzuki RE5 Rotary (not running & FOR SALE)
1981 Kawasaki KZ305-A
1981 Suzuki GS450T (undergoing repair & will be for sale when done)
1982 Kawasaki KZ750-H (FOR SALE)
1989 Honda VT1100C
2007 Vectrix VCTX Electric Scooter
1965 Montgomery Ward 3 1/2 HP Tecumseh Mini Bike
1970 Triumph T25 250cc Trailblazer
1968 Triumph 250cc Flat Tracker

Shop Owner and Mechanic with over 50 years experience
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post #6 of 11 (permalink) Old 06-12-2019, 06:59 AM
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The rich running and erratic idle and things sounds more like dirty throttle body/TPS and/or TBAP issues to me. Many times the wires will break INSIDE the insulation and can't be seen. Its more feeling thin or bad connections at the plug. The inner part of the TB (on the engine side) will also get carboned up.

Last edited by polman500; 06-12-2019 at 07:44 AM.
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post #7 of 11 (permalink) Old 06-12-2019, 07:45 AM
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Let us know what you get on the fuel pressure test.
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post #8 of 11 (permalink) Old 06-14-2019, 12:14 AM Thread Starter
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Wouldn´t T-Bap problems render a fault code? I have none. I will report fuel pressure as soon as it is checked.

/Peter
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post #9 of 11 (permalink) Old Today, 06:30 AM Thread Starter
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Ok, so fuel pressure is 40-41 psi when starting the machine cold and it idles steady at 800 rpm. It responds fine to the throttle. The warmer the engine gets the higher the fuel pressure climbs and the lower the idle gets. After a couple of minutes the idle approached 700 rpm and the fuel pressure has now slowly climbed to 58 psi and the engine cuts out. It is possible to start it again but it needs some throttle to start and it immediately dies again. My feeling is that the engine is running sligtly rich and finally gets flooded.

Ideas?

//Peter
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post #10 of 11 (permalink) Old Today, 06:43 AM
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Fuel pressure regulator

2006 Trailboss 330
2002 Sportsman 90
2005 TRX400EX (FOR SALE)
2003 LT-Z400 (needs engine work & is for sale)
2004 CRF250X
1971 Triumph 650 Bonneville (has 5 original miles)
1972 Triumph 650 Bonneville (undergoing restoration)
1979 Honda CBX (6 cylinder)
1970 Kawasaki G3SS 90cc Bushmaster
1976 Suzuki RE5 Rotary (not running & FOR SALE)
1981 Kawasaki KZ305-A
1981 Suzuki GS450T (undergoing repair & will be for sale when done)
1982 Kawasaki KZ750-H (FOR SALE)
1989 Honda VT1100C
2007 Vectrix VCTX Electric Scooter
1965 Montgomery Ward 3 1/2 HP Tecumseh Mini Bike
1970 Triumph T25 250cc Trailblazer
1968 Triumph 250cc Flat Tracker

Shop Owner and Mechanic with over 50 years experience
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