sportsman 800 won't cold start

[jimcharger]

I have a 05 sportsman 800 efi with about 130 hours that does not cold start properly. The fuel pump runs and the engine turns over, but I must crank it for prolonged periods before it tries to start. When it does start it runs normally, and it will restart properly once the engine is warm. It will still have this problem after sitting in a 70 degree shop overnight.

The fuel pressue is ok, about 40 psi.
I have replaced the plugs.
I have swapped in tbap, coil, ecu, from friends machine that works.
The computer shows no flash codes.
If I give it a shot of carb cleaner while cranking it starts right up.

It seems like the efi is not enriching when cold starting.

Any help would be apreciated greatly. The techs at my local dealer do not seem to have any ideas.

[Bruce!]

Welcome to the board!

[Stealthepooty]

Did the techs do a leak down test (compression)?

[Stealthepooty]

Did the Tech Check:
Engine Tempurature Sensor Test
Throttle Position Sensor Test
TEMPERATURE / BAROMETRIC AIR PRESSURE SENSOR Test
CRANKSHAFT POSITION SENSOR Test
Fuel Tank Vent Line clear?

Diagnostics Using “Blink Codes”
To enable the blink codes, turn the ignition from “OFF” to “ON” 3 times, leaving it 'on' the 3rd time, within 5 seconds.
Any “blink codes” stored in the ECU will display a numerical “blink code”, one at a time, in numerical order, on the instrument
cluster LCD. The word ‘END’ will display after all codes have been transmitted.

Did the Tech check the ECU?

[jimcharger]

I have not done a leak down test yet.
have tested engine temp sensor, ok
have replaced tbap from another working machine
tank vent is clear

not sure how to test crank sensor and throttle sensor at home.

no blink codes stored.

have switched ecu with on from another working machine.

unit runs great once started, and restarts properly once warm.

[Stealthepooty]

Throttle Position Sensor Test (looks like a tech needs to do this test)

From the Service Manual:
The throttle position sensor (TPS) is used to indicate throttle plate angle to the ECU. Mounted on the throttle body and operated directly off the end of the throttle shaft, the TPS works like a rheostat, varying the voltage signal to the ECU in direct correlation to the angle of the throttle plate. This signal is processed by the ECU and compared to the internal pre-programmed maps to determine the required fuel and ignition settings for the amount of engine load.

The correct position of the throttle body stop screw is established and set at the factory. It is calibrated for idle air flow. Do not loosen the throttle body stop screw or alter it’s position in any manner. If the stop screw is repositioned / adjusted, the throttle body assembly must be replaced.

The throttle position sensor (TPS) reading can be checked by using TPS Tester Adapter Harness (PU-47082) and TPS Tester Regulator (401264). The throttle position sensor (TPS) is a nonserviceable item. If it is faulty, it must be replaced.



CRANKSHAFT POSITION SENSOR Test
Sensor: 560 ohms, +/- 10% @ room tempurature (68 degrees F)

Download a service manual from partshark.com to see how to do this test.