How long should SportJet 240 hold fuel pressure after running?

[Saleenmav]

Still chasing down a gremlin on my 2002 X20 - with a 2001 M2 SJ240. At any time you could walk out and bump the key and it will fire right up and run great. Quick off and ons and there’s no issue. After you run it for a longer period and go to restart it just turns over. Let it sit for a few hours and it will start right back up. Engine is cool to touch after running, no codes and I changed the port side temperature sender last time out to no avail. Although, it did work fine most of the day and then stranded us.
I found an older thread where someone had similar problems and it was concluded that the injectors were leaking down and flooding the plugs, causing the no start. Fuel would evaporate after a couple hours and run again. With this information I just ran mine with a fuel pressure gauge hooked up (on the trailer). 33 psi while idling and then it loses a few psi right away when you shut it off and then about a pound a minute thereafter. When it got down to about 10 psi I pulled a plug and it did look a little bit wet. Put it back in and bumped the key and it fired right up with no hesitation. How long should it hold pressure to indicate no injector leak down? Could this still potentially be my issue anyway since it will start right back up after short run cycles? Thanks

 

[Tim75]

Still chasing down a gremlin on my 2002 X20 - with a 2001 M2 SJ240. At any time you could walk out and bump the key and it will fire right up and run great. Quick off and ons and there’s no issue. After you run it for a longer period and go to restart it just turns over. Let it sit for a few hours and it will start right back up. Engine is cool to touch after running, no codes and I changed the port side temperature sender last time out to no avail. Although, it did work fine most of the day and then stranded us.
I found an older thread where someone had similar problems and it was concluded that the injectors were leaking down and flooding the plugs, causing the no start. Fuel would evaporate after a couple hours and run again. With this information I just ran mine with a fuel pressure gauge hooked up (on the trailer). 33 psi while idling and then it loses a few psi right away when you shut it off and then about a pound a minute thereafter. When it got down to about 10 psi I pulled a plug and it did look a little bit wet. Put it back in and bumped the key and it fired right up with no hesitation. How long should it hold pressure to indicate no injector leak down? Could this still potentially be my issue anyway since it will start right back up after short run cycles? Thanks

Fuel pressure can leak down 3 ways.
Thru one or more injectors.
or-
Back thru the fuel pump.
or-
Thru the regulator.

Since your pressure is up for several minutes, it seems you don't have either kind of leak. A leaking injector will not spray directly onto a spark plug.
What may be happening is a problem with the TPS. When it fails, it tells the ECU to go full rich in order to prevent an engine meltdown.
This dumps excess fuel into the crankcase and floods it. Hard start or no start. Let it sit for an hour and it cranks right up.

Many threads here about checking TPS. Or in the service manual.

 

[Saleenmav]

Fuel pressure can leak down 3 ways.
Thru one or more injectors.
or-
Back thru the fuel pump.
or-
Thru the regulator.

Since your pressure is up for several minutes, it seems you don't have either kind of leak. A leaking injector will not spray directly onto a spark plug.
What may be happening is a problem with the TPS. When it fails, it tells the ECU to go full rich in order to prevent an engine meltdown.
This dumps excess fuel into the crankcase and floods it. Hard start or no start. Let it sit for an hour and it cranks right up.

Many threads here about checking TPS. Or in the service manual.

Thanks for that input. I left the gauge hooked up and it had actually only leaked down to 13psi initially and today it was still holding that same pressure, so I think you’re correct that I probably don’t have the common injector issue. TPS was my other thought before reading the threads about the injectors flooding the cylinders. I think the TPS was about the only electronic component not changed on this boat and the last time out it was really loading up and smoking at idle so that makes sense that it could be bad. Going to try and test it tomorrow.

 

[Saleenmav]

So I went to check the TPS and both screws were loose. Which makes sense since the idiot shop that worked on this boat before I bought it had half the fuel line hose clamps loose as well. It looked like it was sitting in about the middle. I put the meter on the brown and blue wires and while it would sometimes move out of the range while I moved it back and forth with the throttle closed, it pretty much was running between about .775 and .875. At full throttle it never hit two volts. Those values are definitely out of the range of where they should be, but with it reading on the lean side it’s odd that I’m seeing the problems I am. Unfortunately it does look like the TPS is likely bad though, regardless.

 

[Saleenmav]

Looks I was ripped off by an old lady. Pulled the TPS and all the wires were coming apart where they went into the sensor. The white wire only had a few strands connecting it. With it being loose they had obviously been messing with it. Now to figure out the cheapest way to fix this thing so I can sell it since my wife and kids no longer want anything to do with it after being stranded multiple times.

 

[Tim75]

Looks I was ripped off by an old lady. Pulled the TPS and all the wires were coming apart where they went into the sensor. The white wire only had a few strands connecting it. With it being loose they had obviously been messing with it. Now to figure out the cheapest way to fix this thing so I can sell it since my wife and kids no longer want anything to do with it after being stranded multiple times.
View attachment 66163

Was made by Cummins in UK. No longer. Becoming harder to find and Mercury knows it.
Stupid expensive part. If you can find old style with round connector, it will work. Just swap the connector. That is what I did 4 years ago.

 

[Saleenmav]

Was made by Cummins in UK. No longer. Becoming harder to find and Mercury knows it.
Stupid expensive part. If you can find old style with round connector, it will work. Just swap the connector. That is what I did 4 years ago.

You wouldn’t happen to know what the old part number is or what engine it would’ve come on?