1995 SeaDoo SPX - Carb not getting fuel

[kenkuntz]

Hi all,

I have a 1995 SPX I'm trying to get up and running. Spraying fuel directly into the carbs will make it start, otherwise seems like its not getting fuel through the normal process.

Sorry for the lengthy details, but I'm not sure what I'm missing....seems like something obvious, but I can't find the problem. I'm looking for some other ideas.

Here's what I've done/tried:

• rebuilt the carbs.....twice. I was given a couple new rebuild kits the first time so I used those. I posted on these forums with the same issue and was told to make sure I used genuine Mikuni kits, so I ordered and installed the new ones today, following the guide on these forums
• tuned the popoff pressure of the carbs. both are around 28-29 psi. Spec sheet showed 22-37psi so I aimed for the middle.
• reset the low/high speed adjustment screws as per the spec sheet (low 1-1/8, high 0)
• reinstalled carbs onto engine
• tried to start engine. engine cranks but wont start
• took off fuel line to carb (no gas dripped out), cranked engine, and felt for a vacuum on the fuel inlet valve. didn't really feel anything but im not sure what to expect here. Tried a piece of paper towel next to it, but it didnt suck in
• took off pulse line from carb, cranked engine and felt for pulse. pretty decent pulse coming from engine...again not sure what is normal here
• hooked a gas bulb pump directly from gas tank to carb inlet. removed return line from carb. tried to pump gas through the carbs and out of the return valve, but it wouldnt pump through.....expected? basically just built up pressure, but nothing was coming out of anywhere
• tried to start engine, no go
• dripped some gas into carbs, cranked engine....it started up for a couple seconds....then obviously ran out of gas
• reconnected all the fuel lines, tried again, nothing
• disconnected fuel line, blew air into it, heard bubbles in gas tank, reconnected.
• disconnected and removed fuel selector valve. RES side looked gunked up so gave it a good clean out, and the other valves too
• removed fuel bowl and filter, inspected and cleaned out

There were a couple times where it appeared I was getting gas in the fuel line to the carb. when i disconnected it, some gas would drip out. I'm not sure what is expected here but at least saw some gas.

I really cant see the carb being an issue right now. Rebuilt them completely, twice. They really looked pretty good on the inside, no real corrosion, little dirt, etc.

What else am I missing? Or what other things can I test or try? Am I looking at an issue with the fuel pump on the carb? Or is it fuel system related?

Thanks for the help!

 

[mikidymac]

Are you sure the fuel pump check valves and seals are in correctly?
Fuel should easily flow from the inlet fitting out the return fitting and that’s how I prime the carbs after a rebuild.

Remove the return line off the rear carb wye fitting and plug the hose back to the tank. Then blow into the fuel tank check valve to put pressure in the tank and with the fuel selector on after a few seconds fuel will come out of the return wye and the fuel systems and carbs are primed. Reinstall the hose and the ski should fire right up.

 

[kenkuntz]

Yea, I used the brake cleaner technique to figure out which side the check valves went. And double checked all the seals are correct and in the right spots. I could disassemble and take pics of my process/build if there's a chance something is off on the rebuild?

Couple questions on your suggestion.
- remove return line off rear carb - no problem
- plug hose back to the tank - just put a plug/thumb into the return line to the tank?
- blow into fuel tank check valve - what/where is this?
- fuel will come out of the return wye - this is just where I had the return line plugged


Is there any reason my method of using a bulb pump and pumping gas into the carbs would not prime the system? I could not get fuel to come out of the return....or maybe I gave up too early? Felt pressure on the bulb, so quit pumping. If this should have worked, what is the likely culprit(s)?

 

[Ckrawiec]

Question: Did you re-connect the PULSE line to the carb? I was chasing a fuel delivery problem, drove me nuts until I realized I forgot - DOH! to put the pulse line back on....sometimes in our troubleshooting we get TOO involved.....

BTW: Welcome to the "chasing the MF fuel delivery problems with these older skis".....I'm in the midst (AGAIN) of chasing a fuel delivery problem. Your story is mine, as well...pretty much to the letter....PATIENCE, patience, patience....sigh!

 

[SigEp368]

I saw you checked popoff, but did you do a pressure hold test on the carb and the fuel system?

you should be able to check it with the carb on the unit.

 

[kenkuntz]

I saw you checked popoff, but did you do a pressure hold test on the carb and the fuel system?

you should be able to check it with the carb on the unit.

Yes, I did a pressure hold test using 10psi for a couple minutes

 

[kenkuntz]

Question: Did you re-connect the PULSE line to the carb? I was chasing a fuel delivery problem, drove me nuts until I realized I forgot - DOH! to put the pulse line back on....sometimes in our troubleshooting we get TOO involved.....

BTW: Welcome to the "chasing the MF fuel delivery problems with these older skis".....I'm in the midst (AGAIN) of chasing a fuel delivery problem. Your story is mine, as well...pretty much to the letter....PATIENCE, patience, patience....sigh!

lol...I wouldnt put that past me! Ha.....but yes, the pulse line is on and tight. I do have a theory I'm about to check.....but I hope I'm wrong.....haha

 

[Ckrawiec]

lol...I wouldnt put that past me! Ha.....but yes, the pulse line is on and tight. I do have a theory I'm about to check.....but I hope I'm wrong.....haha

Keep us posted.....maybe you'll find the holy grail. I'm following this thread with KEEN interest.

 

[kenkuntz]

ok....quick question.

Sea Doo PWC Carburetor Reference - shows 22-37psi popoff

The Seadoo Service Manual says 16-21 psi for dual carbs.

Which do I tune to? And would that have anything to do with fuel delivery?

 

[Ckrawiec]

ok....quick question.

Sea Doo PWC Carburetor Reference - shows 22-37psi popoff

The Seadoo Service Manual says 16-21 psi for dual carbs.

Which do I tune to? And would that have anything to do with fuel delivery?

That is a dilemma......the easy answer is -> to whatever works....which is of absolutely NO HELP to you right now.
And YES, it has everything to do with fuel delivery, as the needles release at a specific pressure and fuel flows accordingly....this IS a pita! HMMMMM...I wonder if the Carb Ref values are too high? Trial and error may be in order here....not what you want to hear but I'm going to be driving that boat myself soon so -> here we go! I guess I'll be tweeking my carbs to mid-range of both specs and see what happens !!!!!

 

[claysimo]

I'm thinking maybe your fuel filter 0 ring is bad and when your engine tries to pump in fuel its sucking air in through that instead. I installed an in line filter to avoid this happening. Also when you took out the fuel sending unit in the tank did you inspect that no gunk had clogged up your straws? Id check that and for 10 bucks buy a new fuel selector valve. Even though I cleaned mine out like you had it still was sticking and not allowing as much gas to come in. Just my 2 cents

 

[Ckrawiec]

I'm thinking maybe your fuel filter 0 ring is bad and when your engine tries to pump in fuel its sucking air in through that instead. I installed an in line filter to avoid this happening. Also when you took out the fuel sending unit in the tank did you inspect that no gunk had clogged up your straws? Id check that and for 10 bucks buy a new fuel selector valve. Even though I cleaned mine out like you had it still was sticking and not allowing as much gas to come in. Just my 2 cents

It is NOT recommended to install any additional components into the seadoo fuel system, especially inline filters which could cause a fuel starvation issue. That is a common collective wisdom of the forum recommendation btw.

The fuel/water separator in the nose of the ski, should have the O-ring checked for sure.

Fuel filters are internal to the carbs.

The easiest way to test for air leakage into the fuel system (tank, hoses, selector switch, etc... is to feed fuel directly into the carbs from an IV bottle type setup, thus bypassing everything up front...that'll give some clue if air infiltration is suspect somewhere.

 

[claysimo]

It is NOT recommended to install any additional components into the seadoo fuel system, especially inline filters which could cause a fuel starvation issue. That is a common collective wisdom of the forum recommendation btw.

The fuel/water separator in the nose of the ski, should have the O-ring checked for sure.

Fuel filters are internal to the carbs.

The easiest way to test for air leakage into the fuel system (tank, hoses, selector switch, etc... is to feed fuel directly into the carbs from an IV bottle type setup, thus bypassing everything up front...that'll give some clue if air infiltration is suspect somewhere.

There is an external fuel filter that is known to have o ring leaking issues. Checking the O ring for leaks is a minimum. As far as putting in an inline filter that is clear and has the same diameters might not be recommended, but nor is installing any aftermarket part. I prefer to see my filters and know there is no chance for air to get sucked in, but that's just me. Also you would think it would cause the opposite effect creating a less restrictive flow to the engine from the fuel selector valve.. maybe I need to study back up on fluid dynamics . Anyway I wouldn't touch it if youre not comfortable other than to check the 0 ring.

 

[Ckrawiec]

ok....quick question.

Sea Doo PWC Carburetor Reference - shows 22-37psi popoff

The Seadoo Service Manual says 16-21 psi for dual carbs.

Which do I tune to? And would that have anything to do with fuel delivery?

For reference....

 

[SigEp368]

For reference....

This is great, where did you find this?

 

[Ckrawiec]

This is great, where did you find this?

I don't remember exactly....just something I came across somewhere...most likely somewhere on this forum.....800 or so posts ago maybe

 

[mikidymac]

As said before if your bulb primer sent pressure to the carbs and nothing came out of the return line then something is wrong with the fuel pump side of your carbs. Also don't run it with the bulb primer or you can starve for fuel.

If you run the correct spring and needles and seats you shouldn't have to mess with pop-off as long as you didn't bend the spring arms.

 

[kenkuntz]

ok...further troubleshooting steps....leads to another question...

On the PTO side (non-fuel pump) carb.....I took the fuel inlet/return plate.....should I be able to blow through the return valve? I dont see any check valves, but cant get any air through...

 

[Lothsahn]

Couple dumb questions:
1) Are you still using grey fuel lines? If so, you need to replace those. They dissolve into green goo internally, which gums up everything. You could have a blockage in one of those lines and you certainly don't want to keep using them as you'll just end up with another problem in the future. I used 1/4" Napa carb fuel hose for my 1996 GTX (not sure what size hose yours uses).

2) Do you know that the fuel lines are connected correctly to the fuel sender unit on the top of the fuel tank? There's 4 lines (fuel out, reserve out, fuel return, and I forget). If you or someone else connected them wrong, it won't work right.

 

[kenkuntz]

1) no, not using grey lines anywhere.

2) I'm currently trying to determine if i have a blockage in the PTO carb. As per my last post, I'm unable to blow air through the return outlet. I was thinking I should be able to, since its completely removed from the carb, no gaskets/valves or other parts to prevent air flow that im aware of.

 

[mikidymac]

Yes, air should come out of the outlet.

 

[kenkuntz]

Yes, air should come out of the outlet.

I am not sure how it is blocked, or how to get anything in there to remove the blockage. Any ideas?

 

[claysimo]

yea I had to put carb cleaner in there and then used an air compressor to force the crap out. Can get clogged from the old fuel lines and from previous inadequate carb cleanings.
You haven't really messed with those carbs till you've taken them out at least 5 times lol.

 

[kenkuntz]

yea I had to put carb cleaner in there and then used an air compressor to force the crap out. Can get clogged from the old fuel lines and from previous inadequate carb cleanings.
You haven't really messed with those carbs till you've taken them out at least 5 times lol.

should i blow it out through the return valve? or from the other side, somehow?

 

[kenkuntz]

Ok....here's a couple pics.

The return valve is the one with the 90 degree angle. That is the one I can not blow air through.

If I should be able to, I am not sure how to clean it out and what hole connects to the return. I can easily tell the inlet comes oit of the bigger hole, but I'm not sure where the return is fed from.