07 800 fuel pump test - Polaris ATV Forum
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post #1 of 14 (permalink) Old 07-10-2014, 05:13 PM Thread Starter
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Question 07 800 fuel pump test

Hello. So I'm still fighting this start on ether an run on gas problem. I tested fuel pump and if I turn the key on it quickly jumps to 19-20 psi. If I turn the key off it holds pressure and builds to 39 psi on second turn of the key. Is that normal? If I hit it with carb cleaner it fires up and runs and idles all day on gas but it just won't start on gas alone. Any help from somebody that has debt with these machines electrical problems would be greatly appreciated ....thanks in advance
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post #2 of 14 (permalink) Old 07-13-2014, 03:45 AM
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There is your problem. It should build up to 37-39 lbs on first turn of key and hold there. IIRC. Surely either a pump or pressure regulator issue.

What is pressure at idle? Mid throttle?

Does pump make any noise like screeching or anything like that?
How long will it hold 36-39 lbs?

The problem is it should build higher pressure initially.

2007 Sportsman 800
1500 miles, mostly at Hatfield-McCoy trails, WVa.
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post #3 of 14 (permalink) Old 07-13-2014, 03:47 AM
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Will it start if you cycle key (pump) 2-3 times first before cranking?

2007 Sportsman 800
1500 miles, mostly at Hatfield-McCoy trails, WVa.
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post #4 of 14 (permalink) Old 07-13-2014, 04:37 AM Thread Starter
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Thank you Walters.. I did not check long term pressure. Once machine us fired up on ether it runs fine and with normal throttle response.. I read in the service manual about initial Efi pressuring after fuel line disconnect. I'll have to retest after reading about turning the key on and off 6 times to purge any air. Also do u have any thoughts on the pick up coil or crank position sensor and it not sending signal to injectors to pulse and send fuel in unto more engine rpm? Maybe similar to machines that will start with a pull rope but not with electric start?..today will be a day for more testing. Also would the kill and reverse switch problems I've read about allow the machine to start on ether most of the time and then run? Thanks again .I'm not ready to give up the fight lol
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post #5 of 14 (permalink) Old 07-13-2014, 05:00 AM
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Not familiar with kill switch issues.

As I understand it, pump comes on briefly with key on to build initial pressure then shuts off until engine is cranked and efi sees either a certain rpm and/or ANY rpm trigger from a sensor. Then turns back on.

Doesn't explain why it likes ether though.

Crank speed. Is battery up to snuff? If weak it may effect fuel pump and starter crank speed. Checked charge, connections and load tested battery?

Diesel engines sometimes get ether dependent when it is used unnecessarily. We call them ether babies. They wont start without it even when it is not needed.

Any reason to suspect low compression?

Have you checked for diagnostic fault codes?

Report back.

2007 Sportsman 800
1500 miles, mostly at Hatfield-McCoy trails, WVa.
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post #6 of 14 (permalink) Old 07-13-2014, 05:09 AM Thread Starter
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Checked codes none unless I disconnect something. Pleasure tested and both are at 180 give or take a 1lb. Machine never tasted ether till I bought it with this problem. Digital display shows about 480-550 rpm during attempts to start. When it starts on ether it seems like it builds rpm up then fires it's not a instant start up. Battery lives on a 2 amp charge thru all this and yes battery is solid. Would the fuel work half way? By that I mean pump till 20 lbs then stop or pump continuous no matter how long of a test line was hooked up to it?
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post #7 of 14 (permalink) Old 07-13-2014, 05:19 AM Thread Starter
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Also sorry I did not see ur question about starting after I turn the key a few times. No it has never started after that.2 times out of 100 attempts without ether it fired back up after I turned the key off. Almost without fail it will start on ether and then run fine. It doesnt always start on ether but u can hear the engine trying to fire. Ive been thru the wires and nothing other then the t bap wire harness seems to have failed. Im looking for a easy way to test the stator and cps. Ive found a few differnt ways but since u brought up the questions on my testof the fuel pump ive found something I may over looked. I want to make sure my tests are done ccorrectly.
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post #8 of 14 (permalink) Old 07-13-2014, 05:20 AM
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Aside from not building up sufficient initial pressure. Which one would suspect a pump or pressure regulator,.....I WOULD have to research more about the sensor the efi looks to to resume fuel pump operation and then also injector pulses. If the sensor was starting to fail and needed to see a higher rpm to turn on the pump than the starter could provide.....then yes the sensor is suspect too.

2007 Sportsman 800
1500 miles, mostly at Hatfield-McCoy trails, WVa.
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post #9 of 14 (permalink) Old 07-13-2014, 05:24 AM
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I believe initial pump cycle is timed and not pressure dependent. After efi senses rpm and pump is turned back on, it stays on and any fuel beyond what is needed to maintain the specified fuel pressure is dumped back into the tank by the regulator. This is why a weak regulator may cause a failure to build initial pressure.

2007 Sportsman 800
1500 miles, mostly at Hatfield-McCoy trails, WVa.

Last edited by WalterS; 07-13-2014 at 05:33 AM.
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post #10 of 14 (permalink) Old 07-13-2014, 05:25 AM Thread Starter
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Thanks for confirming my understanding of the system. Im having difficulty finding test info on 07's. I know many yrs cross eachotger just seems 07 is to close to the middle. Now to locate the senser test in the service manual.
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