No Go, No Fun 240 EFI in 2002 X20

[SeniorChief]

Soooo, my buddy and I spent all day on chasing what we thought was a VST issue. After replacing all the fuel lines, the plugs, and the water separator she still turns over like a champ but will not start. Looks like I am not getting the ground from the ECM to turn the High-Pressure Pump on. We jumped the pump to ground and we tested the rail pressure and it read 60PSI, not the normal 36-to 34PSI. Pulled the plugs and they did not look overly wet. We did check for spark and it is there. I am thinking it is the ECM not grounding the high pressure pump of firing the injectors, but everything I read says that it is pretty hearty and does not fail often. What are we missing?

 

[Tim75]

Soooo, my buddy and I spent all day on chasing what we thought was a VST issue. After replacing all the fuel lines, the plugs, and the water separator she still turns over like a champ but will not start. Looks like I am not getting the ground from the ECM to turn the High-Pressure Pump on. We jumped the pump to ground and we tested the rail pressure and it read 60PSI, not the normal 36-to 34PSI. Pulled the plugs and they did not look overly wet. We did check for spark and it is there. I am thinking it is the ECM not grounding the high pressure pump of firing the injectors, but everything I read says that it is pretty hearty and does not fail often. What are we missing?

What engine are we working on?

Start with checking all your ground wires. Clean and shiny. No green connections. There are at least four, including on the ecu itself.

Have you opened the round connector in bracket? Delicate. How is the connection for the vst?

With the high fuel pressure, it sounds like your regulator is stuck. There is a screen in there that may clog. My engine 240 efi ran at 90psi.
Another stupid expensive Merc part.

 

[SeniorChief]

0E397235 240 EFI M2 Jet Drive. I have not checked the grounds, where are they located? I can take my multimeter and go form each bolt on VST power connections to the engine block and get 12.85, just nothing from bolt to bolt, so a ground issue sounds plausible. The round connector forward on the engine from the ECM did have some cracks on it, but it still mates up good. The gray locking ring was cracked as well, I was going the heat shrink it once I got everything working. I redid the power connections on the VST plus new hoses and clamps on all the liquid lines. I thought about the regulator but it was at 90 with the old VST and stayed there with the new VST assembly so that is two different regulators which again is why I was thinking ECM. It seems to me the injectors are not opening up, I thought that might cause the high pressure?

 

[Tim75]

0E397235 240 EFI M2 Jet Drive. I have not checked the grounds, where are they located? I can take my multimeter and go form each bolt on VST power connections to the engine block and get 12.85, just nothing from bolt to bolt, so a ground issue sounds plausible. The round connector forward on the engine from the ECM did have some cracks on it, but it still mates up good. The gray locking ring was cracked as well, I was going the heat shrink it once I got everything working. I redid the power connections on the VST plus new hoses and clamps on all the liquid lines. I thought about the regulator but it was at 90 with the old VST and stayed there with the new VST assembly so that is two different regulators which again is why I was thinking ECM. It seems to me the injectors are not opening up, I thought that might cause the high pressure?

The first ground is on top of the ecm. There are more on the plate that holds ignition coils. I think there are more, but I haven’t found them either.

Injector failure would not cause high pressure. Fuel makes a loop from vst pump. by the injectors, thru the regulator back to vst. The injectors pass fuel by pulse width in milliseconds. Higher than spec pressure will cause a rich condition. Have you checked injector harness connector? Starboard, low, round, thumb size, 4 wires. It pulls straight apart. Do not twist.

The nut that holds that round 16 pin connector is easily replaced. The old one is broken away, and the new nut snaps on. Reassemble harness. Takes about 2 minutes. Amazon.

 

[ripcuda]

On mine, the fuel pressure regulator had a clogged screen and the fuel pressure was 70psi. I took the FPR off, disassembled and cleaned the screen. Put it back on and fuel pressure is normal now. So it is removable and cleanable.

I've read of others who have rewired the VST high-pressure fuel pump to the ignition switch... bypassing the ECU.

I would like to find that replacement ECU connector "nut" too. My ECU connector is held together by many zipties.

Cheers!

 

[Tim75]

On mine, the fuel pressure regulator had a clogged screen and the fuel pressure was 70psi. I took the FPR off, disassembled and cleaned the screen. Put it back on and fuel pressure is normal now. So it is removable and cleanable.

I've read of others who have rewired the VST high-pressure fuel pump to the ignition switch... bypassing the ECU.

I would like to find that replacement ECU connector "nut" too. My ECU connector is held together by many zipties.

Cheers!

Ok not Amazon.
ECU Harness Coupling Nut Replacement | Power Performance

Or Amazon
Amazon.com
You would have to destroy the inner piece to have just the nut on this.

I have been the zip tie route, too.

 

[SeniorChief]

Sorry been a while since I got a chance to work on the boat. So I traced all my problems down to Pin 2 on the ECM plug which is supposed to be a ground. The same ground goes to pin 86 the fuel pump relay, which is why my primer pump was not coming on either. There is no ground coming off that pin. It is a red and black wire leaving the connector and a red and purple wire going into the ECM. I have checked 2 of the grounds I could find, the one on top of the ECM and the one by the coil packs, I did not see more but I am sure there are some. If I use an alligator clip and ground the pump the boat fires right up. Does anyone have a schematic for the inside of the ECM? Curious about what triggers that ground to kick on the high-pressure pump. Don't want to ghetto wire the boat and put a hard ground on the high-pressure fuel pump.

 

[Tim75]

Sorry been a while since I got a chance to work on the boat. So I traced all my problems down to Pin 2 on the ECM plug which is supposed to be a ground. The same ground goes to pin 86 the fuel pump relay, which is why my primer pump was not coming on either. There is no ground coming off that pin. It is a red and black wire leaving the connector and a red and purple wire going into the ECM. I have checked 2 of the grounds I could find, the one on top of the ECM and the one by the coil packs, I did not see more but I am sure there are some. If I use an alligator clip and ground the pump the boat fires right up. Does anyone have a schematic for the inside of the ECM? Curious about what triggers that ground to kick on the high-pressure pump. Don't want to ghetto wire the boat and put a hard ground on the high-pressure fuel pump.

It is possible that your wire pin 2 is broken behind the pin. Believe it or not, these connectors are available from Amazon.
Your ECM is a primitive computer. I am pretty sure it is all proprietary and no one has a diagram. However- it seems that Brucato has reverse-engineered it and they have made a clone. There are large transistors inside the ECM that are on internal timers that control the ground. That is a potted and sealed unit. Brucato can test and repair your unit.

There is another round connector that you should check. Only about 7 pins.
Keep looking and checking your grounds. Also the positive on the VST. Did you get the fuel pressure corrected? Is your lift pump relay working properly? Your ground to VST is on a timer- 25 seconds I think. Resets when you cycle the key.