Starting After Carb Rebuild

[SeaDooNewb]

I finished rebuilding the carbs on my '96 SPX and have all the linkages and hoses hooked up again. What do I need to do to get it to draw fuel in? It cranks and cranks but doesn't want to start at all.

 

[seadoosnipe]

Choke?

Someone else had this problem a couple weeks back and I gave him the following solution to try. It worked for him, so I'll repeat it for you.
Pull the choke out, or block the carb intakes with your hand. Turn the motor over. The vacuum created in the throat, will suck the fuel into the carbs. Providing you have no major air leaks.
Caution, do not run the starter for more than 30 seconds at a time. There are a lot of cranking amps being used and you'll heat up your wiring coming from the battery going to the starter. If you have to do it more than once to get the fuel to the carbs, grab your battery wires now and again to see that they aren't getting to hot.
It worked for him......hopefully it'll work for you!........
:hat:

 

[Wheels & Waves]

Make sure your return fuel line and supply fuel line aren't backwards. Also, check if there is any fuel restrictions from the tank to the carbs. This includes the strainer and fuel valve. I know you stated all hoses were back on, but double check the impulse line to the pump. I know someone who has left if off before and couldn't figure out why the pump wasn't working....was one of those late nights at the shop.....:redface:

 

[SeaDooNewb]

Snipe, thats pretty much what we did. Pulled the choke out and cranked it while working the throttle. We just were'nt getting any fuel. Tried spraying carb cleaner down the bores and that didn't work either.

Wheels, I thought that too since I had everything torn apart and had to make a new PTO carb out of a MAG carb but I looked at the manual and at some pics of another forum member who is rebuilding his same carbs and I have it right.

What I did notice from Scoop's pics is that I think I left off the hose that goes on the nipple under where the throttle cable goes. Is that the return? It's only on the MAG carb, not the PTO.

 

[Wheels & Waves]

There should be four lines attached to the MAG carb and two to the PTO. Looking at the MAG carb first, there should be a line coming off of the fuel pump cover facing into the cylinder. This line should be hooked up to the impulse line off the engine case. On the bottom, around the bracket the cables attach to, is the fuel IN fitting. Your fuel supply line from the fuel valve goes there. On the cylinder side of the MAG carb are two fittings. The bottom goes to the PTO carb and the top goes to the fuel return line. The PTO carb will have one line coming in from the MAG, fuel supply line, and the other "Y's" into the fuel return line.

 

[SeaDooNewb]

There should be four lines attached to the MAG carb and two to the PTO. Looking at the MAG carb first, there should be a line coming off of the fuel pump cover facing into the cylinder. This line should be hooked up to the impulse line off the engine case. On the bottom, around the bracket the cables attach to, is the fuel IN fitting. Your fuel supply line from the fuel valve goes there. On the cylinder side of the MAG carb are two fittings. The bottom goes to the PTO carb and the top goes to the fuel return line. The PTO carb will have one line coming in from the MAG, fuel supply line, and the other "Y's" into the fuel return line.

Well I had what each hose was for a little off but I have them hooked up as you mention above.

How finicky are those pump check valve disks? They were a pain to put in and I'm afraid they are not sealing so the pump is not pumping.

 

[Wheels & Waves]

The pump discs are not that bad to get in right. There is a special tool from Mikuni to install them, but I use a small punch pin with a nice rounded tip to push the rubber holders through. Add a little WD-40 to the holder and it pops right in. You do need to pay attention to a couple of things. One is that the discs have a colored stripe on them. This stripe is to go UP and away from the sealing surface. The other is to make sure you did not puncture the grommets when you pushed them through. You can test the pump for leaks by using a low pressure pump (same as you use for checking pop-off pressures) at the impulse line inlet. You should be able to maintain about 4-5 psi without leaking down. If you have a Mity-Vac, you can check negative also.

 

[SeaDooNewb]

There should be four lines attached to the MAG carb and two to the PTO. Looking at the MAG carb first, there should be a line coming off of the fuel pump cover facing into the cylinder. This line should be hooked up to the impulse line off the engine case. On the bottom, around the bracket the cables attach to, is the fuel IN fitting. Your fuel supply line from the fuel valve goes there. On the cylinder side of the MAG carb are two fittings. The bottom goes to the PTO carb and the top goes to the fuel return line. The PTO carb will have one line coming in from the MAG, fuel supply line, and the other "Y's" into the fuel return line.

This is a little different than the shop manual and Mikuni manual show it. There is no drawing that I can see that shows the nipple under the bracket on the PTO carb (although there is one there). They just show the pulse nipple, the return nipple (cylinder side top) and the supply (cylinder side bottom). In the Mikuni manual there is also a primer nipple that is not there on the carb.

But I know you're right with the way you described it, thats the way it came off the ski. So with nothing blocked off if I can blow on the bracket side supply nipple and when I suck it is much restricted but not totally sealed off. If I suck and/or blow on the pulse nipple it seals and I can feel/hear the diaphram moving when transitioning from suck to blow. The bottom cylinder side nipple I can suck and blow on easily and the top cylinder nipple is the same.

I took the carb off (obvisously from all the sucking and blowing) and some gas came out of the supply nipple. I'm getting ready to take the pump portion apart again to ensure that the disks are installed correctly and the grommets not pierced (I used a ball ended allen wrench to install them). Assuming it is all correct, is there a way to prime the carbs? I wouldn't think this should be that hard.

Note: I did not use a low pressure pump or mitivac for anything. I used the same spring in the rebuild kit that was in the carbs. I suppose if the needle is not coming unseated then there would be no gas getting to the carb portion of the carb.

 

[SeaDooNewb]

I took the pump base off. There was a good amount of crap stuck in the well where the fuel comes in from the bracket nipple. Both check valves were intact and seemed to be holding pressure when I blow against them the wrong way. There was fuel in the other well so it would appear that the pump is working but I don't see how those cheesy check valve disks could be considered a "pump".

Getting ready to put it back together but I am still not confident that it's working correctly. I have cranked and cranked but it doesn't appear to be sucking gas into the venturi. It just seems like it would be hard to suck it all the way through one carb, out to the other carb within a reasonable amount of time from being rebuilt dry. I'm working the throttle so it can't be that my low speed circuit is not tuned correctly unless the needle is never unseating.

I want to tackle this but I'm getting ready to give up and take it to the dealer and open the checkbook which would be a shame given the amount of work I've put into it already.

 

[seadoosnipe]

Check book!

You mean you got one!........my wife keeps ours hid. Good thing though. I spend to much.
Don't give up. At least till you finish the carbs and give it a shot!...The fuel only has to flow over the top. Once you overcome the top of the tank, the siphon effect will take over and help prime the carbs......yeah, I know they look cheesy, but hey, they work. Anytime a mechanic opens up a part to an engine, carb or what ever, if they find crap, crud, junk, what ever you want to call it, they usually say, "ah ha!...I found my problem" and you know what? Nine times out of ten, that was indeed the problem.
Give it a shot!....what do you have to lose. Have some patience....you'll get it.

 

[SeaDooNewb]

I'm not sure where that crud came from in the pump well since it was freshly rebuilt but after cleaning it out and putting the pump side back together I took the fuel circuit apart and there was gas there so the pump and pop off/needle valve had to have been working, although not well because there didn't appear to be any fuel going to the PTO carb. Anyway, I put it all back together and it was cranking away again (although this time it was because I didn't turn the gas knob on - DUH), the wife came out because she heard all the cranking and asked if it had gas in it. I said, "Of course it does but I'll top it off to appease you". It took ~1 gallon, maybe 2 until it was full, so I know there was some gas in there because it's a 9 gallon tank according to the manual, but after I did that and turned the fuel knob on it only took a few seconds before it fired up!

So there were a couple things that happened; I took both the pump and fuel circuit covers off, cleaned out the junk in the pump well, and topped off the tank. Not sure what action fixed it but I have to admit that maybe since the fuel pump is so rudimentary that topping off the tank provided more head pressre to help the fuel pump out.

Either way it's running, although rough and VERY smokey (white) but I'll start another thread for that. I didn't get to play with any of the carb screws since it was pretty late.

:cheers:

 

[seadoosnipe]

Well done!

Well, I'm glad you got it running. I think I'd tell the wife that she was a great help. That topping off the tank made all the difference in the world. We both know if didn't, but it'll make her feel good.........LOL
I'll look foward to your next thread. The heavy smoke on start up could be from an oil build up from when you were trying to crank. Remember, the oil injection pump was still pumping the oil to it every time you turned it over. Unless of course, your using the premix method.
Great job. Glad to hear it's running. See you on the next post!...:hurray:

 

[SeaDooNewb]

Well the hard starting persists. Yesterday it cranked right up after I topped off the gas and....cranking it for a long time. Today it acted the same way. I had to crank it and work the throttle for ~20-30 seconds before it fired up. After the initial long start if I let if run for a few minutes and shut it off it starts up immediately but if I leave it off for ~20 minutes it goes back to hard starting. It's like the fuel is leaking back if it sits.

What could be causing this?

 

[Wheels & Waves]

Check the fuel tank vent check valve. It should keep about 1.5 to 2 psi in the tank. The vent line from the baffle will tee off and one end will go to the vent in (a directional check valve there that allows air in) and the other will go to the vent pressure relief valve (directional check valve allowing only excess pressure to vent out). If you tank is not venting properly, you can have a pressure problem. If the tank is not letting air in when the fuel is used, it will cause a vaccume and keep the fuel pump from working properly. If the tank is keeping too much pressure, it won't let the fuel return work properly. Hope that made sense.
Also, check all your fuel fittings. If you have a loose fitting or connection at the baffle, you can get air into the fuel lines and cause poor fuel pressure.

 

[SeaDooNewb]

I think you hit the nail on the head Don. I ran out of clips for all the fuel lines and pulse vacuum hose. I was one short and I didn't have a clip on the main fuel line. While it was on tight enough to not really be concerned with it coming off it could be sucking air in at that point. I put a clamp on it and have started it a few times after that with plenty of time in between and it is starting right up so far. The real test will be in the water. Hopefully we can test it out before it gets too cold for it down here.

Thanks :cheers:

 

[seadoosnipe]

Great!...

Wow, that's good to hear. I'll keep that little bit of information in my data base (my brain) for future reference.
Don really seems to be a whiz at this stuff, just glad he's here on the forum to help out!...
Hopefully that was the key to your problem....great work Don!....:cheers:

 

[SeaDooNewb]

Yep, I should have known that the lack of a clamp would not fly after seeing all the threads about replacing fuel lines. Any bit of air it can suck in reduces the vacuum that the fuel pump can pull. Thanks to everyone for the help along the way. The forum has been very helpful.