Looking for any suggestions

[Berkley1]

So basically I have VP 5.7GXI I have literally replaced every sensor or relay on the engine new injectors new distributor you name it it's been replaced the only thing not replaced has been the ECM I even got a Tech mate diagnostic scanner to look for fault codes. the boat starts and runs great at idle and at any RPM when not under load, the minute I take the boat out after about 20 - 30 minute once I increase the throttle it dies and will not restart almost like it's a fuel problem if I let the boat sit 20 minutes it starts and I can motor in at idle speed or maybe 1000 RPMI no problem. I don't even know where to begin at this point there is nothing on the engine that has not been replaced fuel is good, fuel pump new could it be a fuel tank venting issue? Or is it time to call a professional mechanic? sincerely frustrated.

 

[Scott Danforth]

If it runs for 20-30 minutes, I would check the vent

 

[alldodge]

Put a fuel pressure gauge on the rail

 

[Berkley1]

Put a fuel pressure gauge on the rail

no rail has injectors I had the diagnostic scanner hooked up when it died no fault codes

 

[alldodge]

no rail has injectors I had the diagnostic scanner hooked up when it died no fault codes

It's a GXI it should have injectors connected to the rail. Which gxi ?

 

[Berkley1]

It's a GXI it should have injectors connected to the rail. Which gxi ?

A

 

[Berkley1]

There are two injectors on the throttle body can see the flow coming from the injectors

 

[Scott Danforth]

It may not throw a code if it's starving for fuel from a vent issue. That is where the pressure gauge comes in

 

[Berkley1]

Just ordered a inline fuel pressure gauge should I have gauge on the high and low side and what should the pressure be.

 

[Scott Danforth]

VP runs higher fuel pressures

TBI is 29-30 psi, MPI is 55-60 psi

 

[alldodge]

Just ordered a inline fuel pressure gauge should I have gauge on the high and low side and what should the pressure be.

The A being TBI it will have 30 psi on the high side

 

[ESGWheel]

For fuel starvation thoughts: see post no. 4 of this thread (link) and post no 9 of this thread (link). And if interested in how the combo gas caps work (both fill and vent) see this thread (link)

 

[muc]

Agree to start with fuel pressure.
low side 8psi ± 4
high side 29psi ± 2

Watch injectors with a timing light. You can get a much better look at the pattern.

If you suspect the ECM is overheating --- get a couple of cans of compressed air (air duster for keyboards) when the engine shuts down, turn the cans upside down and blast the ECM until it's frozen. See if that gets it running again. Wear gloves and eye protection! what comes out of the upside down can is not good for humans or animals.

 

[Berkley1]

Agree to start with fuel pressure.
low side 8psi ± 4
high side 29psi ± 2

Watch injectors with a timing light. You can get a much better look at the pattern.

If you suspect the ECM is overheating --- get a couple of cans of compressed air (air duster for keyboards) when the engine shuts down, turn the cans upside down and blast the ECM until it's frozen. See if that gets it running again. Wear gloves and eye protection! what comes out of the upside down can is not good for humans or animals.

I checked fuel pressure it's right at 29-30psi HP how would I know if the ECM is bad the scanner I have shows no fault except TPS low voltage so how can I check to see if the ECM is good?

 

[alldodge]

I checked fuel pressure it's right at 29-30psi HP how would I know if the ECM is bad the scanner I have shows no fault except TPS low voltage so how can I check to see if the ECM is good?

With error of TPS voltage low, this kind of like telling the ECM I don't know exactly where the throttle is, so don't know how much fuel motor is given.

What is the DTC code?

 

[Berkley1]

With error of TPS voltage low, this kind of like telling the ECM I don't know exactly where the throttle is, so don't know how much fuel motor is given.

What is the DTC code?

Code I believe is 22

 

[alldodge]

DTC 22 - if there is a open or short on J2-19 or 26 will be set

Check IAC and MAP and insure 5V reference voltage is at 5V

 

[Berkley1]

DTC 22 - if there is a open or short on J2-19 or 26 will be set

Check IAC and MAP and insure 5V reference voltage is at 5V

I have proper voltage on the map and IAC according to the scanner

 

[alldodge]

Is the 5V exactly 5V?

 

[Berkley1]

Is the 5V exactly 5V?

Yes shows 5V exactly