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  1. #1

    Can someone make sense of this fuel routing? HELP! (95 SLT 750)

    Hey everyone!
    First off I'd like to say how thankful I am to have a place I can go to with such friendly knowledgeable people! My name is Josh and I recently purchased two skis: 1997 Arctic Cat TigerShark Montego DLX and a 1995 Polaris SLT 750. The guy we bought them from was an engineer at Lockheed so I was told he took quite good care of them. They ran great all last season except right towards the end. The Polaris would have a rough time starting and then one day going full throttle just didnt open up. Had to ride it 1/4 throttle for a while and THEN open it up. Smelled gas alot etc.

    I took a look and noticed one of the fuel lines had a burn mark in it and was spewing gas, so I figured that was the issue and this season I decided before I took it out to replace all fuel lines. And WOW. I am stumped. I am not an idiot when it comes to mechanics but i've tried every possible way of looking at this and cannot understand how this fuel is routed. It makes NO sense. So Im going to post some pictures and maybe someone could take a look and give me some insight on what the hell is going on and what (if anything) I can do to make it better.

    Click image for larger version. 

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    From what I could see he completely eliminated the separator. Blocked off the res line. And thats where I get lost. Is it going straight to the fuel pump (see picture below)

    Click image for larger version. 

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    By the way (you can't see it clearly) but the other line coming off the fuel pump was the one that was burned and had a hole in it.

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    I feel like such an idiot that I cant figure this out. Thanks everyone for enduring this long post of mine and any and all help/suggestions would be greatly appreciated!
    Thanks
    -Josh


  2. #2
    ripcuda's Avatar
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    Welcome to GH!

    Your SLT 750 is a great ski. I have 2 of them. Their Achilles heal is the fuel system. They came stock with a single outlet, round fuel pump (which you have) that feed the 3 carbs in single file order (one after the other). As the fuel pump aged, it weakened and pumped less... and eventually it got bad enough to starve the last carb in line of fuel... so it leaned out and would commonly burn-down a piston.

    What you need to do, is remove all that modified and hacked fuel lines in your ski... and fix it proper. You need a triple-outlet fuel pump... plumbing an outlet to each carb separately. (removing and plugging the linked supply hoses between them... leave the return lines linked). You need to go through each carb and clean it... and really should consider a full carb rebuild with Mikuni kits to restore them to good as new... they are 20+ years old after all. You need to replace the fuel selector valve and reconnect the main and reserve lines (inspect pickups in the tank too). You should also replace the fuel filter... and hook back up the fuel/water separator. You should shorten the pulse line to the fuel pump... doesn't need to be so long. And be sure you don't loose the restrictor in the return fuel line.

    There is a ton of info... links to thread discussing all the details here: http://polarispwcknowledge.shorturl....is-fuji-engine

    Please avoid the temptation to just go with it as is. It can easily cost you a lot more in the long run.

    Cheers!

  3. #3
    ripcuda's Avatar
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    Click image for larger version. 

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    Cheers!

  4. #4
    johnsonmtz's Avatar
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    RIPCUDA has good advice.

    I would suggest ditching the inline fuel filter and get a water separator from a 780. Those had a stainless steel screen built into them for your filter and flowed much better than that little inline thing you have.

    While rebuilding the carbs you should put new lines on the oiling system as well. The mikuni oil pumps were pretty much flawless, but the tubing can harden over time and crack.

    You can also install a flame arrestor from a 780 or gen Ocean Pros. Turn your high speed needles out an extra 1/2 turn to make up for the extra air flow and it will give you a little more on the top end.

  5. #5
    Hey guys thanks so much for the replies. I am planning on getting the triple fuel pump for sure. But for now, Is it okay to just put new fuel lines on there in the correct order? The res would go to the in of the separator and out to the inline fuel filter? Also, the pulse line is the black rubber hose in the one picture correct? Sorry to ask such stupid questions. I guess im also trying to learn how the fuel is routed so I can learn how to maintain this thing better. The more I understand how it works the more I can troubleshoot when time comes ya know. I just dont get if he blocked off the res line, what happens when I switch the selector to res? nothing? And is it just going straight to the fuel pump? Whats the benefit, if any, of bypassing it and why do you think he would have done such a thing?

  6. #6
    ripcuda's Avatar
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    The fuel selector is bypassed completely by the looks of it. So no switching happening there. The fuel selector valves get old and can leak air into the fuel line. The fuel lines (including fuel/water separator, fuel selector valve, filters) must be air tight... from the pickup in the fuel tank to the fuel pump. This is under a mild suction as the fuel pump pulls fuel out of the tank. Any air leaks in this entire path will mean air bubbles and less fuel getting to the fuel pump and thus sent to the carbs. Perhaps there was a leak in the system and the PO decided to bypass the selector to not have to deal with it. So he direct plumbed from the fuel tank pickup (main, or probably reserve pickup) to the fuel pump... bypassing the separator and selector.

    The pulse line comes off an engine block nipple (under the carb/intake side... towards the rear) to the backside of the fuel pump... it's what makes the pump work. Keeping this line short as necessary is best. It uses the same size fuel hose as all the other fuel hoses.

    Can you just fix the hoses and roll with the old fuel pump? I woud not... unless you know that fuel pump is brand new. As stated, the #1 killer of the blue Fuji Polaris engines is fueling... and that 20 yr old fuel pump is past it's prime. You're just asking for trouble. Buy the $30 new triple outlet round Mikuni fuel pump and fix it right. No sense plumbing new fuel lines twice.

    And don't loose the restrictor (small brass thing pushed inside the hose... should be marked with a small zip-tie around the hose where it is) in the return fuel line.

    Cheers!

  7. #7
    StevoH@O's Avatar
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    Wow RIP! That diagram and actual picture is worth 1,000 words! Thanks for sharing. I've printed for future reference.

    In the past, I have simply rebuilt the single pump. And then rebuilt each carb. Everything seemed to run fine at that point. I have read about the triple option but I was less comfortable trying it on my own. If I acquire another 750 unit, I will be going your route. I was not aware of the fuel on/off switch being an "air leak" source. I always figured, if they worked, they worked. Would you suggest a simple in line switch much like lawnmowers have?

    Thanks for the ideas and suggestions.

  8. #8
    ripcuda's Avatar
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    I can't take credit for making that picture. It came from a PDF that another member made... I just screenshot it and posted as a picture. The original can be found in K447's awesome Polaris PWC Knowledge site:
    https://sites.google.com/site/polari...is-fuji-engine

    The whole fuel selector valve can leak air into the fuel system... or another common "failure" is when the Main line leaks into the Reserve line. So imagine a low tank, you switch to reserve (deeper in tank) cause the main pickup is above the low fuel level. If the main (now open to air) leaks into the reserve... it's introducing air into the fuel flow. And that's bad. There is a drop-in Seadoo replacement that works... but if I recall the On/Res/Off points different ways. If you want both main and reserve capabilities. You need a fuel selector switch. A simple on/off valve like on a lawn mower would only give you an off switch... but no reserve.

    Rebuilding the stock round single outlet pump will work with stock fuel routing. It will eventually suffer the same fate over time as the original... but that could be 10 years down the road... who knows. A triple outlet pump costs the same and is just better. That's why Polaris used one on their 780 (that and needing more flow).

    Cheers!

  9. #9
    Hey guys!

    RIP, I cant tell you how much that one post has really helped clear things up for me. THANK YOU! Anyways, I did what you suggested and waited to replace the fuel lines until I got the triple fuel pump. Which I got today! Yay! Im really excited to put this thing on, but I'm not the most experienced mechanic in the world, but I think its about time for me to get my hands dirty and try. So with that said, I have a few questions about this things installation. First. When pulling off the fuel lines that are on there now, will I have a bunch of gas spilling? Should I have something in place beforehand? Also. Two. I know its recommended to install this lower in the hull than the original fuel pump so in your experience wheres the best spot? Three. Once installed and lines hooked up, do I need to do anything like prime it or something to get the fuel moving? If so, how do I go about that. Thanks for the image you posted, I think I can follow that easily. Last question. The block off's for the carbs. Are they just things you can get at hardware or auto store? What are they called? Thanks everyone and RIP for all your help. You guys are the best. seriously.
    Take care guys
    -Josh

  10. #10
    ripcuda's Avatar
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    Some fuel will spill when you pull the old hoses off. Not enough to worry about... just have rags handy to contain it as you pull each hose off... and don't smoke. The long hose from the fuel tank to the current fuel pump will have the most fuel in it. Unhook and lift the hose up so it doesn't all leak out... it'll probably drain back into the fuel tank... which is good.

    Are you removing the whole carb rack for cleaning/rebuilding? You should. If so, it's easier to put the plugs (block offs) on... while the carbs are on the bench. All it is is a short piece of hose with something stuck in the end so it won't leak. Your plug should be smooth... not a threaded bolt... as those tend to leak even with a hose clamp. Might have to get creative as to what you clamp in your stubby hose as a plug. It won't be under much pressure at all... 4psi maybe. But use hose clamps on both the carb fitting and the end of the hose with the plug... as seen in diagram pic. And of course, use hose clamps on all fittings both on the carb, fuel pump, filters, fuel separator, fuel tank, etc.

    I've always mounted my triple outlet fuel pumps in the same spot as the original fuel pump... hanging off the rear end of the flame arrestor (airbox) on the stock bracket. You will have to position it however best you can to keep the hose lengths short as they loop around from the pump to each carb. I recall only mounting my pump with a single bolt into the bracket (instead of 2) so all the hoses would route easier. Some folks put the pump a little lower, not on the bracket and mount it somewhere else... but in the same general area.

    Keep track of the arrows on the pump... one IN (hose from fuel separator)... three OUT (to each carb)... one PULSE (backside to engine block fitting).

    Also, don't forget or loose the small restrictor in the return fuel line... coming off last carb... going to return line on top of fuel tank. You might have to cut the old hose and push the restrictor out... then push it in a couple inches into the new return line and put a zip tie on top of it as a reminder.

    Priming. I suck on the main single IN supply line coming from the fuel separator until gas comes out then put that hose on the fuel pump IN and clamp it down. This will fill the separator too. The pump will prime the rest of the lines to the carbs. You will need to prime the engine (spray bottle with a little premix in it) through the carbs to get the engine to start. It'll start for a moment then burn up your primed squirt. You'll need to do this 2 or 3 times... by then the fuel will be primed all the way to the carbs and it should stay running. Be sure to turn on fuel selector switch/valve to ON or RES... and have gas in your tank before you do all this. Don't swallow the gas! Or smoke!

    Cheers!

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