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Help - Mystery Motor issue 07 Ranger 700 EFI

2K views 10 replies 5 participants last post by  Dflynn2204 
#1 ·
Hi and thanks for reading. Any al all help will be greatly appreciated. My Ranger 700 EFI runs but not well. When this started I trouble shot through and repaired several issues each time thinking I had solved it but to no avail. Fuel pressure was lower than acceptable range so pump was replaced. Running steady 40 psi now. Voltage regulator would charge fine on start up then collapse to 5 vdc, replaced with a new one that starts in the 13's then climbs to the low 15's then settles back down once warm to the upper 14's vdc. Battery stays charged now.

Remaining issue is a rough idle, it sounds like it's hitting on one cylinder only but I've dismissed that, both fire the same on a spark tester while running. New plugs properly gaped. New plug wires, just because.

It will drive but again feels like one cylinder or timing is off. This happened all of a sudden one day when coming in from checking cows. Thinking it was a loss of fire on one cylinder I turned it off and towed it in. While idling, it will intermittently spurt a good run, but it's only momentary. I've scoured over all the wiring issues commonly found on the forum but nothing found and no changes when moving wires.
I've have a video clip of the idle and spurts on good run if I can figure out how to post it.

My TPs and wiring is tight. Air filter clean. Running with air filter out did not impact the idle issue. I'm suspecting TPS but don't really want to changed parts that may be good. Certainly someone has experienced and solved this problem.

Looking forward to the suggestions and thanks again for the help and ideas.
 
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#4 ·
Have you checked the plug wires? I'd also check the compression. Number 1 cylinder will often check low with age.
As for valves, that engine has hydraulic lifters. Only thing you can do to the valves is pull the head and clean the carbon out and lap the seats. Those engines do have a tendency to carbon up the valves pretty bad and you won't believe how dirty the inside of the throttle body will be on the engine side. Polaris doesn't use seals on the exhaust valves and those motors puff a little exhaust back into the intake. When valves get lot of carbon and seals get worn they'll leak a little. If you're going that far you should plan on fresh rings too. Clean up the head/valves new seals and the throttle body while its apart.
 
#6 ·
@ polman500

Thank you for the input. I will examine the throttle body this weekend and report back that and compression. As far as the valves, I will check that too but like the other poster said, if I'm going to go that far I'll be looking at a larger job. Thanks again for your ideas and experience sharing.
 
#10 ·
We have a winner!

Just wanted to post an update to the mystery. I finally got around to testing the injectors as suggested by this wise man. One sprayed and the other did not. Purchased remanufactired pair of injectors from EBay and installed. Works like a champ. Thanks for submitting the suggestion. Hopefully this update will help others.
 
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