High fuel pressure issue

[Ed Yez]

Alpha drive, Circuit 423 white wire goes through shift interrupter with MEFI 1. This is where the ECM makes the motor stumble to shift out of gear

423 should vary based on rpm

I didn't realize 423 went through the interruptor. Initial wiggle test seems ok but I will look at that circuit more closely.
BTW, the 423 and 424 voltages were taken by backprobing the IC connector. I haven't confirmed the ECM is seeing the same values.

 

[Ed Yez]

I'm EFI all the way but yes they can and do VL

I'm in the auto industry, very new to boating. Never heard of VL on an EFI car. How does that happen on a marine engine? Not trying to argue but to learn. You seem very knowledgeable and I greatly appreciate your help thus far.

 

[alldodge]

I'm in the auto industry, very new to boating. Never heard of VL on an EFI car. How does that happen on a marine engine? Not trying to argue but to learn. You seem very knowledgeable and I greatly appreciate your help thus far.

Mostly talking about MPI, not so much with TBI

Autos have flow thru ventilation and excess fuel is returned to tank

Most marine (not all) there is not much ventilation when motor shuts off and the excess fuel returns to the canister fuel filter. So heat builds up, boils gas in fuel rails. Excess pressure pushes past Regulator to filter.

Finsh floating around or eating lunch, motor starts and then dies. Crank, crank, will not start. Bleed air out of fuel rail and she fires right up and your good until next time. The hotter the air temp the more often it happens

Merc changed from VST to cool fuel to help stop it. Then they added a extra boost pump and that didn't help much. So they keep changing the fuel module to get rid of the issue. The main problem is no return to tank and Merc doesn't want to do it

Builders like Ilmore have return to tank and no issues. I changed my MPI to return to tank and fixed mine also

There are a lot of threads on all forums about VL

 

[jimmbo]

More hoses to and from the Tank, means more potential for Leaks

 

[alldodge]

More hoses to and from the Tank, means more potential for Leaks

Oh no, were all going to die

 

[Ed Yez]

Oh no, were all going to die

That made laugh! Thank you, I needed that!

Most modern automotive fuel systems are returnless. The regulator is in the tank and bleeds off excess fuel right there, no need to run a return line.

Now you have me thinking I should do the same to this boat, run the excess fuel from the regulator to the tank. That would take care of my high fuel pressure.

 

[alldodge]

Now you have me thinking I should do the same to this boat, run the excess fuel from the regulator to the tank. That would take care of my high fuel pressure.

Probably but is most likely just be a bandaid fix for your issue and wasn't my point when discussing VL. I have a hard time getting that it won't stay at 30, and more so that few pounds more causes it to run worst.

Currently wonder if the Reg is not the correct part number, and that injectors may be leaking. I would be thinking about a clean and flow test of them

 

[alldodge]

Oh and USCG requires an antisiphon valve on fuel supply line, one way check valve. No issue with return lines.

 

[jimmbo]

Oh no, were all going to die

No, but the ones who don't keep up on Maintenance, might

 

[Ed Yez]

Probably but is most likely just be a bandaid fix for your issue and wasn't my point when discussing VL.

I agree but I'm starting to get frustrated.

So I put the ohmmeter on the interruptor switch and if I wiggle the wires right where they come out of the switch, the resistance varies, sometimes even up to 8 ohms. I bypassed the switch and it still runs bad. I cleared the codes but had to step away and haven't checked if the 42 is back. Will get back to it later.

The regulator is an OEM replacement part.

 

[Ed Yez]

Out of desperation, I replaced the IC module again with no change. Still have code 42. It seems the only thing left is the ECM.

 

[alldodge]

Code 42 may be the ECM
Running rich I'm not so sure

Have you thought more about having it tested, or contacting OBDiagnostics to see if that kind of issue can be tested for?

 

[Ed Yez]

Code 42 may be the ECM
Running rich I'm not so sure

Have you thought more about having it tested, or contacting OBDiagnostics to see if that kind of issue can be tested for?

I called and spoke to Bob. Going to send him the ECM to check out. Thanks, I didn't know this service was available. Also thank you for your help and insight, it is much appreciated!

 

[Ed Yez]

So I sent the ECM out to be tested and was told there's nothing wrong. Waiting for it to get back to me. I also ordered their diagnostic software so I can see what the computer is seeing and hopefully find out what's going on.

 

[alldodge]

Glad there is nothing found wrong, hope there is nothing

 

[Ed Yez]

I was kind of hoping they would have found something. Hopefully the diag software will show something I'm not seeing.