6.2 fuel injection problem

[kenny nunez]

I recently purchased a 18' Donzi 6.2 MPI that will not go over 3k RPM. The sea water pump impeller is new, the fuel injectors have been flow tested, the 93 gas is ethanol free and the tank was drained. The Cool fuel pump was removed and the screen was inspected and was clean. The fuel filters are new.
The boat jumps up to plane @ 2k rpm, and runs perfect up to 2800- 3000 then just noses over until the throttle is pulled back slightly to the 2500 range.
The Rinda scanner shows no codes. With a fuel pressure gauge attached to the rail the pressure is 40@ idle and 43 with the vacuum line removed. When the the engine is between 2500 - 3000 the fuel pressure gauge needle constantly bounces from 30-50 . I am really scratching my head at this point. Any suggestions?

 

[tpenfield]

I would go ahead and replace the fuel pressure regulator . . . or at least test it. If it tests out OK, then look to see if the cool fuel pump is the source of the problems.

I suspect that the 3K RPM limitation is due to the fuel pressure not staying within the spec, which I believe is in the 43 psi range that you saw when you did the static test.

 

[alldodge]

Howdy

Have an engine serial number?

 

[kenny nunez]

Many thanks for the reply. I will pull a vacuum test on the 2 regulators. The one on the cool fuel side may be the problem. I was also reading about the map/ mat sensor voltage. I have to wait until the weather settels down to check it out. This boat had been sitting for the last 2-3 years in Knoxville where I bought it.
I had a stern drive shop from 72-03, so I never got to go to any service schools for the fuel injection systems.

 

[kenny nunez]

6.2 fuel injection problem. I pulled 15 inches of vacuum on both regulators which held. Is it possible that the map/mat could be the problem?
The engine was installed in 07 and I have no serial # s. The invoice just says 6.2 engine with labor.

 

[alldodge]

Pulling a vacuum on a reg isn't going to tell you if its working, it will tell you if the diaphragm has a leak. To check the reg you need to apply air pressure to the inlet side of the reg and slowly increase until you find out when it opens to send fuel back to the filter

 

[kenny nunez]

Hey, thanks, I have a gearcase tester and will give it a shot. What should I be looking for as in the pressure.

 

[alldodge]

Hey, thanks, I have a gearcase tester and will give it a shot. What should I be looking for as in the pressure.

Manual shows 43 psi at 1800 rpm. I would look for open and hold 43 or so

 

[kenny nunez]

I will give it a shot tomorrow, Thanks