1990 250hp yamaha 2stroke fuel / pump trouble shooting help please

[boaterjoejoe]

Hi,

I am setting up a 1990 vx250hp (extd)2 stroke Yamaha micro computer ignition and need help with fuel starvation diagnosis please.

While running on the water hose, it pops and fires quickly with a light choke and no idol rev, but soon starves out and dies after 5-10 seconds, however…the electric fuel pump continues to rattle away until I turn the key off.

Here is what I know so far:
-choke clicks on and off.
-Compression is good, spark is good, and plugs are good.
-I am running it on a new clean external gas tank, hard squeeze bulb, new gas, and the oil reservoir pumped itself full.
-The 3 main (unpowered) fuel pumps are new this month.
-When facing the carburetor end of the motor, the top left and middle left carbs are drying out, compared to the other 4 which show a little bit of fuel wetness at the bottom of the main butterfly. These two carbs are the furthest away from the unpowered fuel pumps and are dry.
-With the unpowered fuel pump lines disconnected at the carb, the squeeze bulb pushes out gas for all carbs.
-I have removed the float bowls and all floats/needles are moving freely, bowls were not overly dirty inside.
-With the main output line removed, the electric fuel pump pushes fuel 1-2 inches in the air.
-Not all the unpowered fuel lines have zip ties securing them.


Questions:
Is the electric fuel pump bad, or do I need to fix something else to get it to pressurize and shut down?
What do I need to do to restore fuel flow to the top left and middle left carbs?
How can I test/know if the oil injection is actually working?
Any suggestions on what to trouble shoot / rule out next?

Thanks for the help!
Joe

[GrayBlue]

Hi,

I am setting up a 1990 vx250hp (extd)2 stroke Yamaha micro computer ignition and need help with fuel starvation diagnosis please.

While running on the water hose, it pops and fires quickly with a light choke and no idol rev, but soon starves out and dies after 5-10 seconds, however…the electric fuel pump continues to rattle away until I turn the key off.

Here is what I know so far:
-choke clicks on and off.
-Compression is good, spark is good, and plugs are good.
-I am running it on a new clean external gas tank, hard squeeze bulb, new gas, and the oil reservoir pumped itself full.
-The 3 main (unpowered) fuel pumps are new this month.
-When facing the carburetor end of the motor, the top left and middle left carbs are drying out, compared to the other 4 which show a little bit of fuel wetness at the bottom of the main butterfly. These two carbs are the furthest away from the unpowered fuel pumps and are dry.
-With the unpowered fuel pump lines disconnected at the carb, the squeeze bulb pushes out gas for all carbs.
-I have removed the float bowls and all floats/needles are moving freely, bowls were not overly dirty inside.
-With the main output line removed, the electric fuel pump pushes fuel 1-2 inches in the air.
-Not all the unpowered fuel lines have zip ties securing them.


Questions:
Is the electric fuel pump bad, or do I need to fix something else to get it to pressurize and shut down?
What do I need to do to restore fuel flow to the top left and middle left carbs?
How can I test/know if the oil injection is actually working?
Any suggestions on what to trouble shoot / rule out next?

Thanks for the help!
Joe

Well my motor doesn't have an electric fuel pump, but had recently faced similar issues with air leaks and bad fuel.

Here's what I would do:
1. Isolate that the fuel delivery is on the motor side by hooking up to an external tank (with fresh fuel!!!).
2. If problem is motor side, get a pressure/vacuum gauge and rig it up after the primer bulb. There is a good tutorial on testing the fuel system somewhere around here. Try the FAQ section.
3. I would definitely add zip ties.
4. How would oil injection be relevant? To test, prevent the reservoir from refilling automatically. Put a mark on that tank and run it for a little bit. See if the oil level decreases.

HTH