Pat McPherson

Hey Guys,
I need some help from the EFI Gurus.
My engine has been running overly rich and does not seem to have full power.
The codes are 42 and 43 as I read them for my code tool.
It seem to me like the engine is stuck in knock mode and retarding the timing.
I have checked the wiring and changed the knock sensor.
The next thing I think I should change is the KS module or spark control module. I looked it up on the BAM web page a nd it is part number 805443 or 805443T.
The problem is that it is no longer available from Merc.
Now What????

Dave_N

Code 42 would mean grounded IC circuit or grounded/open bypass circuit. If this code was active, then you were running in "Distributor Module Mode", meaning you were using the ignition modules internal advance curve as opposed to "Run Mode" where the ECM would be in control of ignition timing. That could explain the degraded performance, but in this mode the knock control system would not be working so I'm not sure what to think about the Code 43 (Continuous Knock).

I thnk I would try to resolve the Code 42, and then clear all codes and run it again to see if they reset.

Pat McPherson

Thanks Dave.
I've been pulling my hair out on this one. I swapped the distributor to one I had from a 1999 7.4MPI today with no change.

Dave_N

Have you checked the IC and Bypass circuits for open or short to ground?

Pat McPherson

That is what I'll do next.
After reading your post last night, I read about trouble shooting the circuit in my Volvo Penta manual.
Thanks for the help...

Pat McPherson

OK Dave, I found some time to work on my boat last night.

The first thing I did was to check the 4 wires between the distributor (IC module) and the ECM (J2 connector). No open circuits and none seemed to be grounded.

I also have a 1999 7.4Gi Volvo Penta engine hanging around so I used the manuals from that as it seems to have more diagnostic info than my Merc manuals.

Anyway I did a test described that checks the signal between the IC and ECM.
First I measured the resistance on pin J2-23 to ground and got 5200ohms. Good.
Then with a test light I applied 12v to pin J2-24. The resistance drops to 1700 but it's supposed to drop to below 1000. So the manual says to change the IC module.

OK, so I put the IC module for my other distributor (the original 1996) and that one does not even pass the first test.
So I guess I have two bad IC modules...???

Now thinking back to what may have happened.
When I first saw the code 42 and 43 I swapped the IC module from my 1999 distributor to the 1996 distributor that was in the engine. Then I swapped the whole distributor and the 1999 is in the engine now. The 1996 distributor has like 700hours and has lots of corrosion so I can understand the failures.
Could swapping the IC for the 1999 to the 1996 (while it was in the engine) blown that module too?

Maybe if I had swapped the whole distributor with IC module the first time, I'd be up and running?

Oh well, I guess the next thing to do is buy a new IC module and go from there. I hope those are available...

Any more insight?

ZXXX Donzi

I have an entire ignition system off a 1997 502 MPI that is laying around if that helps you. Everything is in working order.

Dave_N

So if you clear the codes do they reset right away?

Pat McPherson

Yes.
I have been getting the same two codes, 42 and 43. If the problem is not the IC module then I guess it's the ECU?
The engine starts up and runs OK but real rich and coats the transom black.
I also believe it's not giving full power.

Yesterday, I picked up a new IC module, Cap and Rotor.
I also bought some used parts from a fellow OSO member. 1994 ECU, KS module, wire harness, and injectors. I'm assuming the ECU would need to be reprogrammed from my 1996 roller cam engine?
I'll get back on the boat Saturday.

Thanks for the help...

Pat McPherson

Thanks but a 1997 has the new gen 3 stuff.
My 1996 is like the older engines