Typical DI fuel issue

[Mark93]

I have recently got a 2002 GTX DI and done a lot of work overhauling it. I took it out on the water last weekend and noticed that It would run great up until 75% throttle but if you go past that it will bog down. But it will do this no matter if its from a standing start or 5000 RPM (which is the max I can get out of it while in the water). As soon as you got past 75% its coughs and splutters.

I have checked the fuel pressure when I got home while the ski is on the trailer. It is around 107 PSI when cranking and runs great! but when I get to around 6000RPM the pressure starts to fluctuate. I already put a brand new Quantum fuel pump HFP-342DI in along with new regulators and injectors except for direct air injectors. I have heard about the HFP-501DI pump if anyone knows the difference? or any other suggestions for this issue

 

[etemplet]

check your rave system and make sure your air lines are going to the correct location. I installed the rave solenoid backwards on one of the skis. When the races were suppose to open they closed. I wasn't getting good top end at all obviously. Anytime these skis give me trouble between 4 and 6k I look at the raves.

Also check the raves and make sure they move easily and hold pressure. Check also your water control valve on the exhaust and make sure it isn't leaking. These things may not solve your problem but you will have eliminated them.

On the air injector the guy I send my parts to said that often the AIR injector is the problem and people don't get them cleaned and checked.

An air leak will also cause the problems you are describing.

 

[Mark93]

check your rave system and make sure your air lines are going to the correct location. I installed the rave solenoid backwards on one of the skis. When the races were suppose to open they closed. I wasn't getting good top end at all obviously. Anytime these skis give me trouble between 4 and 6k I look at the raves.

Also check the raves and make sure they move easily and hold pressure. Check also your water control valve on the exhaust and make sure it isn't leaking. These things may not solve your problem but you will have eliminated them.

On the air injector the guy I send my parts to said that often the AIR injector is the problem and people don't get them cleaned and checked.

An air leak will also cause the problems you are describing.

I have checked the raves by removing the top threaded cap and they both opened smoothly and then closed when they should. My first thought was Raves as it would bog out at that RPM but they are seemingly fine.

But an air leak is something that I thought as it’s around the same throttle position as the races open also demanding air. Maybe a weak air compressor? But I’m getting full fuel pressure up until the high RPMS …

I have checked the water regulator and I don’t see any evidence of a leak.

But you did get me thinking, I removed the springs from the RAVES and pressure tested them with a small handheld pressure tester only to 15PSI and noticed quite a lot of bubbling from the plunger main seal. So this could be my issue.. do you think a small leak like this could cause this issue?

 

[etemplet]

The raves shouldn't leak. I don't know the proper pressure for the test off hand. Easy enough to fix and sometimes they just need cleaning up. Check that "check valve" coming off the engine casing under the throttle bodies. Make sure it is working properly.

When I connected the rave solenoid backwards it acted a lot like what you are describing.

 

[Mark93]

The raves shouldn't leak. I don't know the proper pressure for the test off hand. Easy enough to fix and sometimes they just need cleaning up. Check that "check valve" coming off the engine casing under the throttle bodies. Make sure it is working properly.

When I connected the rave solenoid backwards it acted a lot like what you are describing.

Hi, thanks for your help …

I am pretty sure I’ve got the rave solinoid hooked up correctly. So much so that I crimped the line between the compressor and the solinoid and I’m still getting the fluctuating fuel pressure even without the raves or solinoid doing anything… I also checked the check valve and that’s working correctly.

I highly suspect the new fuel pump as I know they have issues .. I’m going to try and remove the filters and see if that make a difference to the flow rate at higher RPMS

 

[etemplet]

Yes, fuel pressure would be the problem if it isn't consistent. Check those o-rings on the fuel rail. Sometimes it is that simple. Good Luck !

 

[DooWacka]

Rig your fuel pressure tester with enough hose length so you can monitor the fuel pressure while underway, not just on the trailer.

 

[Mark93]

Rig your fuel pressure tester with enough hose length so you can monitor the fuel pressure while underway, not just on the trailer.

I will do but to be honest I’ll probably not go out now until next season but would like to sort it before then