Fuel problem, 99 670X

eazyduzit509 · Jan 10, 2010

So, just did a fresh topend rebuild on my 670 and it wouldnt start for anything. Cleaned carbs, checked for spark, etc. Picked up a NEW $90 fuel pump from skidoo around noon today, got back, threw it in and fired up 2nd pull. Rode that bad boy for a solid hour or two and doin about 30 on a trail with 6 other riders, its straight up shut-down. Cruisin about 5-6K rpm's and it felt like someone yank the teather off. WOULDNT resart for anything, got it to kick a few times with the primer but thats it. Towed 'er back to the house and began inspection. Checked for spark again, pulled airbox, carbs, fuel filter in tank and the new fuel pump. Opened up the fuel pump ands its pritty straight forward, no moving parts, just some check valves and fuel passages.

Put it all back togther and let a 500watt light stare at the carbs for a good hour (to elliminate ice problems, only 30 degrees out). Primed it 5 times, cranked 'er over and kicked but thats all she wrote, had 7 guys standing around taking turns pullin on her but nothin happened. Can see lots of air in the fuel lines going to the carbs, tried blowing threw the fuel tank to push it threw but no luck. Pulled it over while someone else checked to see if the fuel was moving and nothin... Made sure the crankcase pressure line was seated properly and connected to the fuel pump.

ALL i can guess is SOMEHOW MABEY the new fuel pump isnt working and straight crapped out. Its hard to grasp though, theres no moving parts inside of it and its pretty simple, i just dont get it. If i get a replacement pump, throw it on and she starts, im'a be pist... What you guys think? Ive tried damn near everything... Its got good spark and sometimes kicks when we prime it, SAME EXACT thing happened with the initial fresh topend start, nothin, nothin, nothin, threw on a new fuel pump and fired right up.

Im stumped..................

Zachmandu · Jan 10, 2010

I am assuming that you have been storing the sled outdoors while it was torn down?? Or was it stored indoors in a heated garage/shop?

Theory - water in fuel. While outside, possibly even when you were riding it last, there was water somewhere in the system, that was frozen, but somewhere it was not causing problems. THEN, you brought the sled into a heated garage/shop, and said water melted. But THIS time, it went somewhere that you did not want it. After doing the top-end, you drug the sled back outside in the cold, this water, now in a bad place...fuel pick-up, fuel line, etc... froze.

Just an idea, and it only takes your time- Take the ENTIRE fuel system apart. remove the tank, fuel pump, fuel lines, carbs, pulse-line.....everything. Get ALL the gas out of everything, and then place all the parts in a warm environment to dry it all out. Once you are SURE that everything is dry, re-install parts with fresh fuel, and add some fuel dryer to cover your butt. Make sure all your fuel line connections are solid and leak-free.

I've had to do this to a couple sleds of mine over the years, where I just could NOT figure it out. Just so happens that I just did one last weekend on a kids' '00 700 Summit that was doing the same thing as yours. Took a couple hours, but we got it running.

Granted, this will only work if your problem is water-related. But it seems that you have done the right thing by covering all the basics. The fuel pump is simple.... a diaphram run off of the crankcase pulses, and two check-valves regulating fuel flow into and then out of the pump. As long as it is clean, and is getting a good signal from the 'case, it should work.

Good luck! Call me if you have any ??

eazyduzit509 · Jan 10, 2010

Ive always used HEAT in my tank aswell. Gonna try throwing a new pump on it tuesday...

Skidoohmx · Jan 10, 2010

If it will not start with the primer I highly doubt it is your fuel pump. The primer bypasses it completely. It should start and run for a few seconds just from the primer shots. Are the plugs wet or dry if you pull and look at them? You do have good compression after doing the rebuild?

Zachmandu · Jan 10, 2010

Good tip on using the primer to check fuel delivery! Did not think of that.

Not fuel related, but....

Had a buddy last year re-build his '01 800 Summit. Thing ran like crap, was hard starting, had no power.....

Tore it down, and discovered that he installed the rings upside down. Flipped them over, put it back together, and the sled ran perfect.

If you say you already bought and installed a new fuel pump, I doubt the new pump is bad, and that it is not your problem. Buying another is probably not going to magically cure the problem. I think that something simple is being overlooked, and when you find it, you are going to be pi$$ed.

The kid last week with the 700 told me that he used Heet as well. Only after we cleaned and dried the whole fuel system did he get it to run. Just a thought.

banditpowdercoat · Jan 11, 2010

Have you c hecked plugs, Compression test? Fresh rebuild, were you checking jetting? Sounds like a possible one cyl went lean. It will "try" to fire with primer sometimes. I know, Just leaned out my MAG cyl. Take head off and have a look at piston's Or Compression test will tell you right away!

eazyduzit509 · Jan 11, 2010

Just talked to another sled tech, he seems to think it may be the Stator... Hmm...

eazyduzit509 · Jan 11, 2010

More info, found a small hole in my Impulse line going from my engine crankcase to my airpump, when i blow threw it i can hear it seeping out... Would that effect my problem?

Zachmandu · Jan 12, 2010

Yup.

As for the stator.... The sled was running perfect until it got hot and burned down right? So why would it go bad as soon as you rebuilt the top-end? Possible, but not likely.

eazyduzit509 · Jan 12, 2010

Kina, it shut off once randomly and hasnt done it before, restarted right after though, then it just started losing power and finally died. all within an hour.

eazyduzit509 · Jan 13, 2010

It was the rotary valve! Guess a piece of ring got thown into the intake side and stripped the rotary gear (said there not sure if they found a piece of bearing in it (rotary gear) from the crank, i'll look carefull when its open). Skidoo wants $600 for parts and labor

. I think im gonna bring her home and make it my new project. Cant let it go to waste, new $250 top-end with 10 miles on it, $100 fuel pump and lots of work put into the sled, i'll tear her apart when shes home. Never pulled a sled engine before, letalone opened up the bottum end. Leme know what ya guys think, comments, tips, etc. Thanks!

Zachmandu · Jan 14, 2010

DOH!! ...and what did I say?? Something simple right?? lol

Let me know what you find when you get it apart. I should have all the parts you need. Usually, the softer brass gear on the rv shaft strips out, leaving the crank ok. Might have to clean up the 'case where the RV rides. Hopefully nothing is scarred up that badly. I have an extra rv shaft, brass gear, shaft seals, rv's, and another 'case if needed.

I should be in the shop all day tomorrow, give me a call.

banditpowdercoat · Jan 14, 2010

Your probibally going to need a new RV shaft too. When the gear strips due to impact like that, it usually bends the shaft as well.

But, unless you have a clutch puller and a flywheel puller, I suggest taking it to the shop to have just these 2 items removed. For the flywheel, one of those bolt on style pullers that look like a peace sign work good, just heat up the center of the flywheel with a propane torch to loosen the bond when you pull it. I've stripped holes right out of flywheels before because they were super tight!

eazyduzit509 · Jan 14, 2010

Sweet, i'll call ya tomorrow then. I was also told i might need a new RV shaft... Do you have a 501 rotary valve zachmandu? what about crank bearing? I have a list of things i may need.

Zachmandu · Jan 14, 2010

I have several different RV's. Not sure of the cut on them. I know I stuck one 501 in Mutt, and I think I may have another. I'll have to stick them on a degree wheel and see what I have. I do have another RV shaft, and gear. I've also got RV covers, and a spare 'case. Crank parts, your on your own. I have one spare crank, and I am kinda saving it for a rainy day.

Rotax-Guy · Jan 15, 2010

If you want I've got a clean 99x with 144x2, d&r, boss seat, rox riser, make you a heck of a deal!

eazyduzit509 · Jan 15, 2010

Rotax-Guy said:
If you want I've got a clean 99x with 144x2, d&r, boss seat, rox riser, make you a heck of a deal!

you've alos got a REV...

what you want for my twin sled?

Rotax-Guy · Jan 19, 2010

I dont know, might have to keep the old girl. Rode her hard all day at the poker run even did some nice fire-breaks with her. Let the wife ride the Rev!

cams · Jan 19, 2010

compensator

when you get the engine out take the compensator out from under the engine plate and clean it...water usually collects there

eazyduzit509 · Jan 19, 2010

will do.

http://www.backcountryrebels.com/showthread.php?t=3197

Fuel problem, 99 670X

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