F115 4 stroke fuel issue

[jay00f4]

Someone suggested that I have a bad fuel pressure regulator. Can someone tell me how to test that?

 

[BaileysBoat]

Re: F115 4 stroke fuel issue

There is a threaded fitting covered by a plastic cap. Similar to what you would see on a Ford or Chevy with multiport inj. Using the correct adapter install a fuel pressure gauge on the fitting. You should have 37.7 psi at idle,
45 psi with the vacuum hose disconnected from the reg.

Get a manual.

 

[jay00f4]

Re: F115 4 stroke fuel issue

I am assuming there is no way to test this if I can't get the boat running?

 

[BaileysBoat]

Re: F115 4 stroke fuel issue

The pump should cycle for 3-4 seconds when the ignition is turned on.

 

[jay00f4]

Re: F115 4 stroke fuel issue

I understand that yes and the manual says It should have 44.1 PSI and then drop to 35.6 when running. If I get 44 psi with key on how do I determine from there that it is bad if the motor won't start?

 

[BaileysBoat]

Re: F115 4 stroke fuel issue

You can apply vacuum with a hand pump to simulate 16" of vacuum at idle.

High vacuum = lower fuel pressure, but not below spec.

If you get fuel from the vacuum port the reg is defective.

 

[jay00f4]

Re: F115 4 stroke fuel issue

Bailey thank you for all your help. The boat started and I was able to test the regulator and 38 psi at the rail at idle and jumped to 47 when I unplugged the vacuum line.

I shut it off and went to restart and it wouldn't start. I couldn't hear the vst pump running. I put my meter on it and was getting the expected reading of 12 volts for 2-3 seconds the drop to zero but sometimes the pump would run and sometimes it wouldn't. Is it possible for the vst pump to be intermitten like that if it is defective? Is there something else it could be that isn't allowing the pump to run when it is getting the 12 volt signal?

 

[rodbolt]

Re: F115 4 stroke fuel issue

pump has 12V applied at the red yellow wire any time the key is on, the ground path,blue wire is grounded for about 5 seconds at key on power the ungrounded until the engine is running.
ground path is completed by the ecu.

 

[jay00f4]

Re: F115 4 stroke fuel issue

So if I am getting 12 volt reading at the pump when key on for 5 seconds and when running but the pump isn't running it is bad. Correct? There is nothing else that limits the pump from running? It is possible for the pump to be intermitten?

I just want to make sure before I buy another $300 fuel pump. It was just replaced last season.

 

[hobohro]

Re: F115 4 stroke fuel issue

If you haven't already, read this thread. I found that the YDIS was a great help in determining that my ECM was bad. You can cycle the pump at will with the software. If it doesn't cycle on command then the ECM is bad. Mine was intermittent.

http://forums.iboats.com/showthread.php?t=274234

 

[BaileysBoat]

Re: F115 4 stroke fuel issue

As Rod stated, battery voltage any time the ignition is on, but the ground path is through the ECU.

Check the pump wiring for excessive resistance before you condemn the pump.

 

[jay00f4]

Re: F115 4 stroke fuel issue

I spoke with yamaha tech in Ga. He said based on the test I have performed the pump is defective. He also said if it is intermitten I may be able to clean it. Anyone every heard of this? Do I use like Mercruiser power tune? Is it affective?