7.4 MPI intermittently hard to start/rough idle

[Mischief Managed]

Re: 7.4 MPI intermittently hard to start/rough idle

Tested continuity from the DLC to the ECM connector, it's good. Scratching my head...

 

[tpenfield]

Re: 7.4 MPI intermittently hard to start/rough idle

I sent you an email . . . not sure if it helps.

Going to get my place in the line of traffic now.

 

[Mischief Managed]

Re: 7.4 MPI intermittently hard to start/rough idle

I got the email Ted, thanks. I already have the manual printed and in a binder though.

 

[Mischief Managed]

Re: 7.4 MPI intermittently hard to start/rough idle

My manual states that the DLC connector B pin should be connected to ECM connector J1 pin 7. As near as I can tell, it's connected to J1 pin 23. No matter how I count, There does not seem to be any way the it's connected to pin 7. Does anyone have a diagram of the J1 connector showing how the pin count works?

If DLC B is indeed supposed to be connected to J1 7 and is not, I can see how this would prevent my ECM from going into diagnostic mode.

 

[Mischief Managed]

Re: 7.4 MPI intermittently hard to start/rough idle

Disregard my request for a diagram above, I found it on page 5C-29.

 

[tpenfield]

Re: 7.4 MPI intermittently hard to start/rough idle

Seems weird that the wiring is not matching up to the manual & schematic . . .

Are you still managing to do some boating this weekend, or has the engine hatch been up so far. ???

 

[Mischief Managed]

Re: 7.4 MPI intermittently hard to start/rough idle

So now that I found a connector diagram, I took a look at my J1 connector and it has a completely different wiring configuration than Service Manual 16, 1996 edition describes. I guess they changed the wiring between the publication of the manual and the manufacture of my engine, or I am missing something key. I think I'll take it to a shop if it happens again; I don't think I can justify the cost of a scan tool/Rinda software-cable...

Boat is running perfectly right now. Will be taking it to Maine for the weekend later today.

 

[Don S]

Re: 7.4 MPI intermittently hard to start/rough idle

I took a look at my J1 connector and it has a completely different wiring configuration than Service Manual 16, 1996 edition describes.

Probably because it's the wrong manual. You should be looking in Service Manual #23

After you download it, go to page 5E-40 and see if that works better.

 

[Mischief Managed]

Re: 7.4 MPI intermittently hard to start/rough idle

Thanks Don, that's perfect!

Ran the boat all weekend for water sports etc. and it always started and ran perfectly. I did put 30 gallons for fresh gas in the tank, cleaned the throttle body, and R&Rd the fuel filter to make sure it was sealing well; perhaps one of those things fixed it??? Planning to take it on the Gulf of Maine for 100+ mile day cruise next week, fingers are crossed that it does not strand me...

 

[warsaun86]

Don, I have seen that you are an expert with Volvo Penta engines and I have been facing a problem for the past 3 years and gone through 4 engines and thousands of dollars with mechanics and with my most recent engine I am still facing my original problem. After running about an hour my Engine starts to lose power . . . I usually try to run around 3000 RPM however if I run WOT the engine will lose power faster. I broke down and bought the diacom marine diagnostics tool and am trying to tackle the issue myself. Below is a link to the engine readouts and the engine bogging down after over an hour of use, you can see it jumping between 3500-3000 causing it to jerk back and forth . . . I'm hoping maybe you will see something out of wack based on the reading I am getting (no trouble codes). Thanks for your help!!

https://www.youtube.com/watch?v=tS2IY1NCfB8

 

[warsaun86]

I should also state that my engine is also a 7.4 MPI but it is a Volvo Penta 7.4 Gipbycce

 

[GA_Boater]

Don, I have seen that you are an expert with Volvo Penta engines and I have been facing a problem for the past 3 years and gone through 4 engines and thousands of dollars with mechanics and with my most recent engine I am still facing my original problem. After running about an hour my Engine starts to lose power . . . I usually try to run around 3000 RPM however if I run WOT the engine will lose power faster. I broke down and bought the diacom marine diagnostics tool and am trying to tackle the issue myself. Below is a link to the engine readouts and the engine bogging down after over an hour of use, you can see it jumping between 3500-3000 causing it to jerk back and forth . . . I'm hoping maybe you will see something out of wack based on the reading I am getting (no trouble codes). Thanks for your help!!

https://www.youtube.com/watch?v=tS2IY1NCfB8

Don is looking down at us. RIP.

Closed.