377 mag mpi dts Hard start after the first time

[silver_power]

Hello,
I have twin engine boat with 2 x 377Mag Mpi Dts Axius. (S/N: 1A605669 & 1A605670)
The problem i have with the starboard engine is that it fires up ONLY the first time of the day. What ever attempt i try during ex. 10time period, it will not fire up and it will flood. It will not start, even with WOT. The only way to start, is to disconnect the power supply of fuel pump and start the engine. It will start at the second attempt without throttle at all.
The engine after it starts, runs perfectly. Something happens, only during cranking, and the engine floods
Checked till now:
1. Change spark plugs (the old were in very good condition and the combustion is very good, no oil, carbon etc)
2. Fuel pressure normally, 38-39psi@idle, 43psi with vacumm hose disconnected and 38-39spi during cranking
3. Voltage during cranking drops to 10.6V, 12.7V @StanD by
4. Change the fuel rail with the injectors from the port engine which starts perfectly without throttle
5. Change the ignition module and the common spark plug wire from the port engine
6. Pull out the temperature sensor and put a 390Ohm resistor so the engine see steady 72oC
7. Flame arrestor clean
8. Swapped the DTS throttle plate from the port engine
9. Fuel Filter new and the screen below them as well,
10. checked the water hose of the cool fuel module for blockage
11. Checked the FPR for destroyed diafragm and change it with new as it ruined during unistallation.
12. Check for faults with Diacom, all perfect (MAPT, etc) and no fault codes...

The next two things is to swap the distributor cap and all the spark plug cables with port's engine, but i am sure that this will be useless as if the cap-rotor -cables would be the problem, the engine would not started after unplugged the fuel pump, give a crank to clean and then connect it again.

Honestly i do not know what to check next........

Do you have any idea??

 

[alldodge]

Is a strange one, but with it flooding I would look closer at spark. Those flat distributor caps are known to look great but be bad. Many keep a spare on the boat because they can fail without warning

 

[silver_power]

I totally agree with you, but the fact that when it starts, runs perfect.......??
Would it run perfect if the cap had problem? I mean, with a weak spark, the engine would not run good during get the boat on plane of at 4000+rpm.....
Except if you have heard something similar......
At the other boat with 350mag mpi , having the same flat dizzy cap, when it failed, i had unsteady rpm during cruise. The rpm fluctuated about 300rpm, obviously because the spark jumped to wrong cylinder.......

 

[Scott Danforth]

check battery connections and other wiring to the starboard engine. if the voltage is low during cranking and is dropping, that would be bad connections somewhere

 

[silver_power]

I already checked them......nice grounds and the voltage during cranking does not drop below 10.5V.....the situation is not better even with starting at "BOTH" batteries.....
I alleady changed the starter with new, since the previous "died" because the lots o cranks!!
I believe and agree with you, that i am dealing with ignition issue.
Except dizzy cap and cables, is it possible the cam sensor cause the engine not to start? Is it easy to swap it from the port engine?
The fact that a twin engine boat gives you the ability to swap and test known well operational components, is very help full!

 

[alldodge]

Right now I of the opinion it's lack of spark, don't know if it's the cap or not only that they are known to have issues. I start with simple stuff than try other things. You have done many things and nothing works until it starts to work again.

Disabling the fuel system is just a coincidence, so what is keep spark from happening. The PCM looks for spark before fuel injectors are fired, it sees something enough to turn injectors on, but maybe not enough to get an actual spark. @muc

 

[Scott Danforth]

I already checked them......nice grounds and the voltage during cranking does not drop below 10.5V.....the situation is not better even with starting at "BOTH" batteries.....

these two sentences are a dichotomy.

if the voltage is dropping while cranking to 10.5 with one battery or two batteries, the issue is either the ground lug on the block or the power connection at the starter, or the ground and power at the cannon plug.

 

[silver_power]

Which is the sequence for the engine to start?...i mean, the pcm sees that engine started rotating from crank sensor and determine which cylinder is at top dead point...but it does not if it is at compression or exhaust stroke.so till now it has no fuel or spark....When the cam sensor synchronises give at pcm the signal and then engine fires the injectors and then the spark?
What happens at the meantime that engine see rpm but no signal from cam sensor?...is there possibility to fire the injectors even if it has not the cam signal?
If yes, then maybe the cam sensor if faulty and as it delays to give the signal to pcm, the engine is allready flooded due to extended cranking time.......

 

[alldodge]

The PCM must see at least 300 RPM, and ignition procedures will energize. Not sure about your motor and that's why I tried to get MUC into the conversation. Your distributor has a Cam sensor but I don't think it has a cable attached, and if no cable is attached then it just uses the crank sensor

The injectors are batched fired which means a few fire one or more times per revolution. The below pic is from a 555 ECM so not yours but just to provide an idea

 

[muc]

Yes, this engine uses and needs the cam sensor to run. Yes, you can swap them. No, I don't know if it's easy.
This engine has 8 injector drivers in the PCM, it fires the injectors in pairs.
I don't know if the CMP effects the injectors, I think it is just used for the ignition.
Are you using the Diacom recording function to check voltage drop during cranking? It is the most accurate because it measure voltage at the PCM (where it's important) not at the battery. With a PCM controlled engine voltage drop is very important. 10.5v is borderline bad with this engine. Especially if your getting the same reading with both batts selected. Red Flag!
The unplugging the fuel pump to get this restarted is very strange. Is this very repeatable? That you need to do this every time you try to start the engine warm?
I would use the Diacom to do a "wiggle test", use the record function KOEO and KOER.

 

[silver_power]

Yes, this engine uses and needs the cam sensor to run. Yes, you can swap them. No, I don't know if it's easy.
This engine has 8 injector drivers in the PCM, it fires the injectors in pairs.
I don't know if the CMP effects the injectors, I think it is just used for the ignition.
Are you using the Diacom recording function to check voltage drop during cranking? It is the most accurate because it measure voltage at the PCM (where it's important) not at the battery. With a PCM controlled engine voltage drop is very important. 10.5v is borderline bad with this engine. Especially if your getting the same reading with both batts selected. Red Flag!
The unplugging the fuel pump to get this restarted is very strange. Is this very repeatable? That you need to do this every time you try to start the engine warm?
I would use the Diacom to do a "wiggle test", use the record function KOEO and KOER.

Yes, i need to unplug the fuel pump every time i try to restart engine, especially warm.
I like the idea of the wiggle test using recording at diacom.....i will do it!