02 GTX DI 951 crank no start

[Jman5002]

So I got this jet ski with a blown motor (PTO cylinder). It ran on one cylinder but I used a camera and saw a bad piston. This was 6 months ago.

Finally got time ordered new head cylinder and pistons. Rebuilt the top end I broke the solenoid valve going to the exhaust valves/air compressor. Replaced that with a used one (only thing that changed).

It’s cranks and cranks but will not fire. I put a tiny amount of gas down the spark plug hole 1 or both cylinders and it fires Immediately and dies right after.

I’ve got 119 psi compression in both cylinders. I’ve checked the air compressor that’s 81 psi. I have good spark the fuel and air injectors both spray when cranked over. I don’t have a fuel pressure gauge but might have to buy one but again it sprays good fuel out the injectors.

I’m at loss it seems like a lack of fuel problem but I don’t want to just throwing expensive injectors at it when I don’t know if that’s the fix. Am I missing something silly.

Any help will be appreciated.

 

[mikidymac]

You need to check fuel pressure. It is very important on these.

 

[WaarrEagle]

Regardless of fuel pressure, which you absolutely need to check, sending off the fuel injectors for testing and cleaning is a good move. I used Yamaha Fuel Injectors a few years ago for my DI injectors.

It may be a clogged injector or poor fuel pressure that led to the engine failure in the first place.

 

[Jman5002]

Thanks for the replies guys I’ll update with more info when I have it this weekend

 

[Jman5002]

So I’m pretty confident it’s the fuel pump. As the initial pressure when hooking up the tether was 5 psi and the max it will go to cranking is 70psi. I’m pretty sure I read in another thread it’s 35psi on initial and 107psi when cranking. I attached a photo of how I hooked up the fuel pressure gauge to be sure I did it right the gauge is attached to the brass fitting by my thumb.

 

[mikidymac]

You should have 27 psi with key on and engine off, 107 psi when cranking. It has to be 107 psi. At 70 psi it will not run.

 

[Jman5002]

You should have 27 psi with key on and engine off, 107 psi when cranking. It has to be 107 psi. At 70 psi it will not run.

Ok but I hooked up the pressure tester right at fuel pump before the fuel filter is that correct? And could the be the fuel regulator not allowing pressure to build cause low readings?

 

[mikidymac]

Here is a good discussion on it... DI fuel pump what's the truth

ski-doo
"The fuel pressure regulator regulates the fuel pressure at 27psi HIGHER than the air pressure in the fuel rail. In no way is it adding to the fuel pressure so saying 80 psi air pressure + 27 psi fuel pressure = 107psi running fuel pressure is not how the system works. The back side of the fuel regulator diaphragm is exposed to the air pressure and it will maintain the 27psi pressure difference.

No engine running means no air pressure and the fuel pressure will be 27psi which is 27 psi higher than the 0 psi air pressure. When the engine is running, the air pressure is regulated by the air regulator at 80psi so then the fuel pressure shoots up to 107psi to stay 27psi higher than the air pressure.

So, fuel pressure is 107psi +/-2psi and air pressure is 80psi while running."

 

[WaarrEagle]

Ok but I hooked up the pressure tester right at fuel pump before the fuel filter is that correct? And could the be the fuel regulator not allowing pressure to build cause low readings?

In theory either the fuel pressure or air pressure regulator could be bad, but it is far more likely that the pump is the issue. DI pumps have a pretty high failure rate, especially as they age. It may be possible to clean it by running it in a bucket of solvent. Search for prior threads on that topic.

The complexity mentioned above is why a full testing of the fuel and air system is necessary to really nail down where the issue is.

 

[Jman5002]

Thanks guys I think I’ll try putting the fuel pump in the ultrasonic cleaner with some solvent to try to fix it tomorrow. Since it did run on one cylinder last fall I feel like the sitting maybe maybe the ethanol gum it up. If that doesn’t work I guess nothing left but buy a new fuel pump.

 

[mikidymac]

Thanks guys I think I’ll try putting the fuel pump in the ultrasonic cleaner with some solvent to try to fix it tomorrow. Since it did run on one cylinder last fall I feel like the sitting maybe maybe the ethanol gum it up. If that doesn’t work I guess nothing left but buy a new fuel pump.

Where are you getting a new fuel pump?

50/50 mix of gas and toluene for pump cleaning.

 

[Jman5002]

Think I’m gonna get this one off Amazon and ok I’ll use that mixture thanks.

 

[mikidymac]

Think I’m gonna get this one off Amazon and ok I’ll use that mixture thanks.

Ain't going to work.
There was only one time I heard of an AM pump working but I don't remember who found it or what one.

The issue is that the OEM pump is high pressure but low amp. All of the aftermarket ones that make the pressure pull too much power and mess with the ECU so they just don't work.

 

[Jman5002]

Gotchya iguess it’s good I got returnable then then thankyou.

 

[Mark93]

Gotchya iguess it’s good I got returnable then then thankyou.

The pump you showed worked for me but they made another one recently which I have tested fine on my 2002 GTX DI and supposedly it is better for the DI’s and you don’t need to modify the fuel module.

Like previously mentioned fuel pressure is critical and without confirming you have it don’t even bother looking at anything else.

 

[Mark93]

Ain't going to work.
There was only one time I heard of an AM pump working but I don't remember who found it or what one.

The issue is that the OEM pump is high pressure but low amp. All of the aftermarket ones that make the pressure pull too much power and mess with the ECU so they just don't work.

I don’t agree with this as I had two seperate pumps from quantum and both worked fine!

 

[mikidymac]

I don’t agree with this as I had two seperate pumps from quantum and both worked fine!

This is great to hear. We definitely need recent recommendations here as to what is working.

 

[Jman5002]

So I bought an entire used fuel assembly to avoid the power draw problem I through the gauge on it and it fire right up. So problem was definitely the pump. I might return that thought if I can use the quantum pump I posted and return the used pump as it’s $200 cheaper. I think I should still replace the air injector that got beat up when the rear piston went bad.

 

[Jman5002]

I don’t agree with this as I had two seperate pumps from quantum and both worked fine!

Can I ask you how long you’ve run the quantum pump without problems?

 

[Mark93]

Can I ask you how long you’ve run the quantum pump without problems?

To be honest it’s only been in for about 9 months and only done around 10 hours so can’t comment on the longevity of the pump.

 

[Jman5002]

Well after a top end rebuild a fuel pump fuel injector and air injector she runs like a top thankyou all for your help.

 

[mikidymac]

Well after a top end rebuild a fuel pump fuel injector and air injector she runs like a top thankyou all for your help.

Please list the fuel pump. We need good reliable data on viable replacements.

 

[Jman5002]

Please list the fuel pump. We need good reliable data on viable replacements.

I bought a used OEM fuel pump