90hp Fuel pouring out of Carbs.

Brad_Ct

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I have a '94 Baja Blast with a 90hp Sport Jet. The problem I am having is that gas pours out of the throats of all three carbs. when I crank the engine. I bought this boat last year and per the repair slips I got from the previous owner this was a problem before I got it. I have pulled the carbs. cleaned them, adjusted the float levels, checked the needles and seats and installed new gaskets but still have the same problem. Any ideas of what could be causing this?
 

gm280

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Re: 90hp Fuel pouring out of Carbs.

I have a '94 Baja Blast with a 90hp Sport Jet. The problem I am having is that gas pours out of the throats of all three carbs. when I crank the engine. I bought this boat last year and per the repair slips I got from the previous owner this was a problem before I got it. I have pulled the carbs. cleaned them, adjusted the float levels, checked the needles and seats and installed new gaskets but still have the same problem. Any ideas of what could be causing this?

Well is obvious that it is a fuel issue. And understanding how carbs work, the needles shut off incoming fuel once the floats float up enough to push the needles to their seats. So unless your fuel pump is pushing unbelievable amount of pressure it still has to be the carbs. Knowing the possibility that all three carbs are doing the same is the part that throws that assumption into left field. But it still points to the carbs. Are you very sure the floats are not soaked and not shutting off the income fuel? I?d check all three floats for leaks AND the fuel pump pressure for starters... JMHO!
 

Brad_Ct

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Re: 90hp Fuel pouring out of Carbs.

After posting I pulled the carbs back off and checked the floats, they are fine. I also tried blowing into the fuel inlet with just the weight of the float on the needle and could not blow past it. I have never heard of a vacuum fuel pump producing to much pressure before but I will check that on Sunday.
 

jerryjerry05

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Re: 90hp Fuel pouring out of Carbs.

First do a compression test.Make sure you remove all the plugs.
Then check the diaphram in the fuel pump.
Then remove the carbs and check the reeds.Post the results of the tests.
 

gm280

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Re: 90hp Fuel pouring out of Carbs.

After reread your problem a number of time now, I have to wonder IF the PO tried to enlarge the main Jets and either changed them or drilled them out. Too big of main jets would allow fuel to basically pour out of the carbs. I don't know, just thinking out loud. You didn't state if the engine actually starts or not, I suspect not. Are the chokes closed during this situation?
 

Brad_Ct

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Re: 90hp Fuel pouring out of Carbs.

I had it running several times last fall after replacing the triggier, flywheel, switchbox and rebuilding the carbs. There has always been a issue with trying to start it if I choked it because it would flood. Without chocking it would start and I did not have a issue with it dumping fuel, I am thinking that once I get it to start it burns enough fuel to stop the bowls from overfilling and because there is so much fuel it will start without the choke.
 

Brad_Ct

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Re: 90hp Fuel pouring out of Carbs.

I just took a look at the manual I have and noticed that on a two stage pump the pressure from cylinder #3 is used to push the fuel to the carbs. I am thinking that part of the diaphram may be bad and it allowing crankcase pressure into the fuel system. Need to pull the pump apart and check the diaphram as advised by jerryjerry05.
 

jerryjerry05

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Re: 90hp Fuel pouring out of Carbs.

They used 2 types of pumps on that motor?
Make sure that the check valves on the older style are working correctly and not broken..
The newer style is the little square one.
I was doing maint. on my boat after I got it.
Was gonna do fuel pump diaphrams and hoses etc.(we fished way offshore).
The check valve on one motor/pump came apart when I opened it up.
It was still working???? Don't know how??
There is a good PWC section on this site.Lots of knowledgable guys there.
The motor a basic Force the rest a Merc,I think??
 

Brad_Ct

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Re: 90hp Fuel pouring out of Carbs.

I put a 60psi gauge in the pump outlet fuel line and cranked the engine, it pegged the gauge. I pulled the pump apart and I do not see any holes in the diaphragm and all 3 check valves are working properly.
 

stevecur

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Re: 90hp Fuel pouring out of Carbs.

This post has helped me a bunch. Had the same problem today. After reading this thread I pulled my fuel pump apart and the diaphragm has a half inch split in it. Thank you. I was lost with the problem.
 

pnwboat

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Re: 90hp Fuel pouring out of Carbs.

More than 60psi fuel pressure is way out of line. It should only be 3 or 4 psi. Like Jerry said earlier. Do a compression check.
 

jerryjerry05

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Re: 90hp Fuel pouring out of Carbs.

I think he's saying the pressure from the fuel pump port was over 60# You need to do a compression test on the motor itself. I think they loan them at Auto Zone.They have AZ in Africa? Where you located?
Profile,location? you might be close to someone who can help.
 

Brad_Ct

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Re: 90hp Fuel pouring out of Carbs.

Yes the pressure from the pump is over 60#, I have a compression guage and will do a test tomorrow.
 

gm280

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Re: 90hp Fuel pouring out of Carbs.

Yes the pressure from the pump is over 60#, I have a compression guage and will do a test tomorrow.

Unless you are running a fuel injection engine with a fuel pressure rail, that fuel pressure IS your problem...period! There is something wrong if you have over 60 PSI fuel pressure coming out of a diaphram vacuum pulse type fuel pump... No need to look any further. you need to check out your fuel pump... Not surprised to hear your carbs are flooding fuel out of them... I'm surprised they still have fuel float bowls on them yet...:jaw:
 

Brad_Ct

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Re: 90hp Fuel pouring out of Carbs.

To start with I feel like a idiot, after reading up on two strokes I realized there is no way I should have 60# of fuel pressure so I checked the gauge I was using and found that is was in inches of water. So I have no idea what I have for fuel pressure. I did check the reed valves and do a compession test. The valves look fine none are broken or bent, the compression readings were as follows. cyl.1 127# cyl.2 133# cyl.3 142# these were taken dry with the throttle wide open.
 

gm280

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Re: 90hp Fuel pouring out of Carbs.

Recheck your fuel pressure with a simple pressure gauge. You should only have 3 to 6 PSI pressure coming out of the fuel pump. If it is anything like what you previously posted, the pump IS still your problem... With the compression readings very good and the reeds lookng good and the carbs been rechecked, it has to be fuel pressure/delivery. There is simply is no other thing that could cause three carbs to do the same things like you posted about... Wait a second, you stated that the PO had the same problem. Did anybody do any work on the engine before you bought it? Check to see IF the reed plate is turned around facing outward instead of inward... If they are turned around that could allow the crankcase pressure to push the fuel out instead of sucking it in... Just another thing to check for...
 

Brad_Ct

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Re: 90hp Fuel pouring out of Carbs.

I have to wait until I get the parts for the fuel pump before I can check the fuel pressure again. The history of this boat is that is was bought running in Fla. in 2007 and trailered to NY and would not start, in '08 he gave it to his sister who had a new stater, battery and a used trigger put in. At that time it was noted that the used trigger was bad and the carbs. needed to be rebuilt because they were flooding into the boat. The boat was then bartered non running in 2010 for plumbing work. I bought it last Aug. and so far have replaced the trigger, flywheel, switchbox, starter and rebuilt the carbs. I was able to get it running last fall but still had the issue with fuel flooding. In short it has been sitting around non running since '07.
 

jerryjerry05

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Re: 90hp Fuel pouring out of Carbs.

Now were getting somewhere.
The 60# or more is NORMAL and needed to operate the pump.
The output fuel pressure should only be 2-6#
The compression 127/133/ 142 could be a problem???
The readings should be all within 5# of each other.15# difference between 1 and 3???
It's possible???? The head gasket between #1 and 2 is bad???
I'd try it again with a different guage??
I had 145# on all 3cyl.The motor ran terrible???
Turns out it has a small leak on #2 cyl and was getting water in.
 

pnwboat

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Re: 90hp Fuel pouring out of Carbs.

Are you 100% sure the floats are set correctly? Back on post #2, GM280 mentioned the floats. Turning the carburetor upside down and blowing into the fuel inlet is not a good test if the floats are not floating properly. I've had problems with some of the black foam type floats before. If I set them to factory specs, (parallel to the body of the carburetor when inverted) they leak. I have to set them so that free end of the float is about an 1/8 inch farther away from the carb body than factory specs when the carb was inverted. Then no more leak. Only thing I can think of to cause this is that the floats are old and have lost some of their buoyancy.
 
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