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1995 XP - Priming Fuel Lines ?

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Ernest Jones

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Hi folks!

After many weeks, actually months, I finally got the carbs done on my neighbors 1995 XP. I also replaced all the lines with some really nice stuff.
I went to start it today and of course is has no fuel in the lines.

I forgot to clamp the 3 lines going to the fuel selector so I'll do that tomorrow. In the meantime, how do you actually prime the fuel system when the lines and carb have been redone? I took the fuel cap off and pressurized the tank with my mouth and that's when I learned I forgot to clamp the 3 lines at the fuel selector.

So tomorrow is the big day, but whats the best way to prime the system when the carbs are new along with the lines?

As always, many thanks to those that have gone before and share their knowledge.
 
I have rebuilt many many carbs over the years,,,I have never primed the lines,
Usually,,,I will turn the motor over with the choke on for 5 second cycles,,,to give the starter a rest,,,,
but,,,sometimes I will put some premix in the cylinders,,,the motor will momentarily fire up,,,which helps the carb fuel pump to prime quicker and save the starter.
I will repeat the fuel in the cylinder untill it continues to run,,,
If the air box is off,,,you can easily pour the fuel into the carb throats,,
,,this method has worked for me for many years.
 
Thanks Popps!

I was thinking about it last night and I'm quite sure I mixed the feed and return lines up. The unit was apart for a long time so I had forgotten which went where and I made new lines as well replacing all the old ones. I suspect that when I clamp the 3 lines at the selector (which I forgot) and switch the return and feed lines around it will likely be good.

This brings about another question. How long can you run it on a garden hose? What are the issues with that, if any? I'm just helping my neighbor, he bought it, but I used to own an automotive shop so I have the skills but not the experience when it comes to skidoos.
 
I do the same as Popps, just roll it over a few times, and I also will sometimes put a little pre mix in the plug holes but have started them without doing that as well after a carb rebuild. The top of the baffle is labelled with RES RET ON VENT. I didn’t realize that till this year, makes booking everything back up easy, Fuel selector valve is labelled as well
 
I am still having issues getting this thing to flow fuel.

I clamped the 3 lines going to the fuel selector that I forgot yesterday.
Also clamped the two lines at the fuel filter (forgot those too).
The outlet line on the fuel filter is going to the inlet on the carbs (1995 XP)
With the return line pulled off the plastic tee, if I blow on the tank (pressurize it) I get leaks somewhere at the fuel selector valve. Not a ton, but it does leak.

I cannot get fuel to appear at the plastic tee on the return line with the tank under pressure.

Fyi, fuel selector was not replaced. carbs were done properly with the 'back to stock' Mikuni kits and all fuel lines were replaced one by one.
Very frustrating. I was hoping to get this thing off my plate today :)
 
Take the time to double check all the lines, from the fuel selector RES goes to RES on the baffle, ON goes to ON, OUT goes to the fuel filter, that’s all the lines from the selector valve. The only open fitting on the baffle should now be VENT and RET. which obviously vent goes to vent through the hull and up under the hood I believe and RET comes from carb. Only other line is from fuel filter to carb inlet. Double check those. If still no go you could put 4 pounds of pressure into the pulse fitting on the carb to make sure it holds.
 
OK, the fuel sending unit does not appear to be labelled. The fuel selector is. I have verified that the OUT from the selector is going to the IN on the filter and the OUT from the filter is going to the front carb.

The jet ski did work prior to this and it had the factory grey lines. The factory would have had it right so when I replaced them I did them one at a time to avoid mixing them up.

When I pressurize the tank with my mouth I do get fuel intermittently spitting from the disconnected return hose. Not a lot, but it does spit some. But nothing from the plastic tee that it connects to (the returns from both carbs)
 
Ernest Jones said:
OK, the fuel sending unit does not appear to be labelled. The fuel selector is. I have verified that the OUT from the selector is going to the IN on the filter and the OUT from the filter is going to the front carb.

The jet ski did work prior to this and it had the factory grey lines. The factory would have had it right so when I replaced them I did them one at a time to avoid mixing them up.

When I pressurize the tank with my mouth I do get fuel intermittently spitting from the disconnected return hose. Not a lot, but it does spit some. But nothing from the plastic tee that it connects to (the returns from both carbs)
Click to expand...
Look a little better with a light, it’s embossed on the sending unit but it’s hard to see
 
Yeah, it's covered with black paint. I'm certain the lines are correct at this point. But that leaves the fuel leaking at the selector valve. Are these units sensitive to leaks? Ie, does the fuel system have to be hermetically sealed for it to work properly?

I'm thinking unless the selector valve is changed out, along with a new filter, I don't want to go much further. I pulled the feed line at the carb, held it up while pressurizing the tank, and very little came out. But when the line was lowered it began siphoning on it's own. Very odd.

I'm also guessing the lack of a accelerator pump means that you can't check for fuel flowing into the throttle body by activating the throttle when it's not running.
 
Ernest Jones said:
Yeah, it's covered with black paint. I'm certain the lines are correct at this point. But that leaves the fuel leaking at the selector valve. Are these units sensitive to leaks? Ie, does the fuel system have to be hermetically sealed for it to work properly?

I'm thinking unless the selector valve is changed out, along with a new filter, I don't want to go much further. I pulled the feed line at the carb, held it up while pressurizing the tank, and very little came out. But when the line was lowered it began siphoning on it's own. Very odd.

I'm also guessing the lack of a accelerator pump means that you can't check for fuel flowing into the throttle body by activating the throttle when it's not running.
Click to expand...
Not sure about all that but yes if you can see fuel leaking from the fuel selector valve I wouldn’t go any further till it’s changed out,
 
burtshaver2021 said:
Not sure about all that but yes if you can see fuel leaking from the fuel selector valve I wouldn’t go any further till it’s changed out,
Click to expand...
That’s correct, you can’t check for fuel when it’s not running, the fuel pump is activated by the pulses the engine makes. If your pressurizing the tank to prime the fuel system leave your fuel feed line attached to the carb and pull the return line off, you could then blow into the return line which is still attached to the tank. As Popps had mentioned earlier I have never primed the fuel system after a carb rebuild and have had no issue. I will put a small amount of fuel in the plug holes and they fire right up. I do think that priming is not a bad idea though as I find the machines idle pretty high for 10 seconds or so until the fuel system is air free.
 
Aha...found this;

Leave the return line off and blow into the fuel tank check valve to pressurize the fuel tank and keep your thumb over the return line. As soon as you see fuel come out of the carb return fitting put the return line back on and you have purged the fuel system and carbs.

That worked. But....only temporarily. But here's the rub, I had to really blow into the filler neck of the tank to get it to flow. In fact, with the fuel feed hose off the front carb, and with the hose below the level of the tank, it should have self-siphoned the tank dry. Instead, it ran for a short period and then stopped.

So there's something there. It took, in my mind, way too much pressure to push the fuel through. If I were a carburetor fuel pump I would not be able to suck it through.
 
My suggestion, Take the hose of the carb and run it to a jug of premix gas, that will make sure your carb is working, and then add more items in the chain to see where the trouble is. Sometimes it is the selector valve, some times it is a weak connection allowing air in.
 
I think that's a good idea. A small funnel into the feed line held up in the air would use gravity to feed the carbs and remove the entire fuel feed from the issue. I'm just really surprised how much pressure I had to blow into the tank to get fuel to flow. I also expected it to siphon the tank dry with the feed line off and held lower than the tank.

The fuel fumes make it hard to think after a while !
 
Ernest Jones said:
I think that's a good idea. A small funnel into the feed line held up in the air would use gravity to feed the carbs and remove the entire fuel feed from the issue. I'm just really surprised how much pressure I had to blow into the tank to get fuel to flow. I also expected it to siphon the tank dry with the feed line off and held lower than the tank.

The fuel fumes make it hard to think after a while !
Click to expand...
No need for the funnel, the pump will draw the fuel, just put a fuel line from carb into a container of premix it’s attach the line that is there directly to the ON at the baffle
 
Or,,, instead of an exterior jug, I remove the “on” hose that goes to the selector from the baffle, then
I remove the hose from the water separator that goes to the carb,,, and then I put that hose on the now vacant nipple on the “on” fuel baffle,, works like a charm,, and very safe.
 
Update. The upper vent at the front top of the jet ski was plugged with insect nest or something. The second I cleared that out, when I pressurize the tank by blowing into it, it no longer builds pressure to the point where you wonder if the tank is going to expand :) So there is some progress. The fuel leaks at the selector switch turned out to be the clamps, so they were replaced and there is no longer a leak there.

I figured I had it beat at that point, but no dice. It's still not getting fuel to the carbs. I then pulled the sending unit and checked the filter screen at the bottom of the sending unit. It's clean.

I then ran a fuel line into a Gerry can and ran that direct into the front carb. Runs like a top. So we know my carb work is good.

Yet...still no fuel flowing into the carb from the feedline. In my view, when I pull the line from the front carb, it should siphon the tank empty because the hose is lower than the tank. It won't

I'll try again to remove the fuel filter housing.
 
That’s good news, just wondering what size and brand of fuel line you used when you re did those lines? Because the 1/4” ID continental fuel line that I have used would not leak even if there was no clamp at all. Now that you know the carb is good you could put the supply line from the carb directly to the ON at the top of the fuel sending unit. If it doesn’t work, the. You know it’s the sending unit, if it does work, you could try hooking the lines up the way they were except run the line that supplies the carb directly to the OUT on the fuel selector valve, if it doesn’t work then you know it’s the valve, it it does work then it must be the fuel filter because that’s the only other component. Or if you have the tools you could vacuum test the fuel system?
 
Thermoid SAE 30R6 - probably the best fuel line money can buy, but I take your point. Great diagnostic steps! I'm still waiting on a new fuel filter assembly and...what we found after re-clamping the lines to the selector valve is that....now the valve itself is leaking. So basically it seems I'm finding all the weak links. I did pull the sending unit and the plastic strainer at the bottom is clean.

The gas fumes are really messing with my head. It's hard to think straight. Which is why I can appreciate your diagnostic steps so much. I'm going to wait until the new selector valve and fuel filter come in and see if that cases it. When I blow on the return line I can hear/feel the bubbles in the tank. When I blow on the fuel feed line I get basically nothing. The next step up the chain when blowing on the feed line is the fuel filter. My guess is it's hooped. I can't get it open, it will break as it's seized.

But wow, I"m amazed at how my mind can't think right with the fumes. I'm standing over the cockpit and basically huffing all the gas in the hold. Many thanks for your continued help. I'm getting much closer and it sure was nice to hear it run on the overhauled carbs.
 
Have you had the rubber fill
Tube off of the fuel tank? The fitting on the tank is prone to cracking near the base of it. It kind of sounds to me like you have the return line from the carb going to either the RES or the ON, in the fuel sending unit
 
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