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Module madness...part 2

Irish1941

Irish1941

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Got a brand for new distributor but had a 399 module in it. Kooky I know but whatever. New GM is new GM.
Now near as I can tell this is a marine module.
Knowing somewhat about boats, I can only assume this module can't be good on the street.
Marine is somewhere around 3200 to 5500 for power where WOT is mostly used and a street 369 is idle to 3200/3500rpm and WOT is rarely seen.
Am I correct in this thought or way off?
I don't know enough about marine vs street in ignition with EFI or TBI for that matter. I'm sure marine TBI ECM must be tabled to WOT performance but never even heard of a marine ECM part number.
Most of Merc marine is just a USCG cert for boat use with no huge difference from boat to truck. Some vents get screens or spark arrestors added on etc...
What do you know?
 
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it's a dizzy module, doesn't have anything to do with rpm range... ECM controls all that.. iirc, that a digital Ignition module used in the early 90's.... but I can check my merc software at work if you need...
 
Thanks for the reply but re-reading, I don't think I was very clear.

I know ECM controls spark timing, advance etc but what I was trying to say was what rpm range would spark fall off for the 399 module?
Stock street modules seem to drop off well before redline/WOT as where boat engines run WOT most of the time so it would need solid spark to at least 6000rpm.
That being said, is 399 amp flow same as street module or higher like a MSD?

The matching coil for this module should be able to handle charge/discharge spark energy needed in higher rpms.
Only coil I could find that seems to be a match, is one from Mercury: 817378

Plus I think some marine applications use small cap HEI without any EFI. That would mean timing curve would have to be in the module but I'm not a boat expert by any means.

Dwell of 399 vs 369?

I can only guess it would have less dwell in higher rpm range to carry spark up to and above 6k rpm with the right coil. The coil saturation circuit you think would be different from marine to street.

Tried looking it up for differences but no luck.
Here are the cross ref numbers for the 399:
GM 10482830, 16139399, D1965A
Merc Marine 811637, 811637T, 850487
OMC 3854003

Might be all moot seeing the truck never goes past 3500 rpm but might be interesting to see differences if any.
 
that's the module in their Delco EST system.. I was reminded when I was in one this morn... :haha:

and yeah, in carb'd apps, the curve is hard programmed in it.. TBI's have it in the ECM... iirc, the timing bases are 14, and 34 at 3200...

keep in mind.. boats don't run those kinda rpm's.. and certainly not WOT for extended periods of time... sure, outta the hole to get on plane you'll put the coals to em, but than you back off to a cruising rpm once on plane...

carb'd motors are lucky if they reach 4 g's, maybe 4200 on a good mill prop combo... new 496 or MPFI? yeah, they'll spin 4600 at WOT, but you generally cruise at 3400 to 3800 depending on hull config, etc...


slippery slope running marine ignitions in vehicles being the EFI's run open loop and no O2...
 
Yeah, there we go. Hard boat numbers. :waytogo:
Guess I was a little generous with my revs for boats. :D Been a while since I owned a watery hole to throw money in. Seem to recall my Black Max twins would redline around 5500 but outboards are apples and oranges in this one.

Answers the curiosity I had. I didn't really want to run it but good to know I shouldn't keep it for a trail emergency spare. With hard curve built in it, my truck would have a melt down.

Thanks!
 
yeah, outboards are a different kettle o' fish...
 
So instead of starting new thread, I'll just add to this.
Had a slight miss on one hole. #1 and no SES light/no codes.
Tach was solid as was vacuum @ 21 from PCV port on TBI.
New GM 369 module. Miss still there.
New GM dizzy today installed, old one had some cracks.
Ghost spark I think. Nope, miss still there.
New Delco wires, plugs coil & cap/rotor from last tune up 400 miles ago.

Nothing but new GM sensors all around.
Temp switch, TPS and MAP both check out voltage wise. All grounds good.

Put timing light on. Timing itself rock solid @ 0 HOWEVER I can see the light acting up.
flash--flash--flash flash flash--flash--flash etc every two seconds...you get the idea.
Try all other leads. Just #1.
Pull EST to set timing and erratic spark goes away.
Only thing left is ECM itself.
What could I be missing?
Does it hot or cold. In gear or park. I'm at a loss. :dunno:
 
Isn't the EST module itself seperate?

ECM is pretty much always a possibility, but unless you have a known good spare it's pretty costly and pointless to replace, unless you've actually figured out it's the problem.

AFAIK all spark is handled outside of the ECM...the ECM controls timing and fuel pump operation via signals from the ignition setup, that's it.
 
Dorian, thanks for reply and yep after thinking about it for a minute I had a idea.
What I think is going on is rotor is phasing inside cap causing spark to jump terminals giving me the double, triple spark I'm seeing.
I'm going drill a extra cap and see exactly what's going on in there.
So odd it'd be doing with new distributor but anything is possible.
 
Just to clarify, I assume the 0* is with the EST bypass disconnected, idle timing is somewhere around 20* with it connected? Your previous post almost makes it look like you have timing at 0* all the time, but based on the fact you know to disconnect EST, I doubt that is the case. But just verifying. :)
 
Yep, at 0 with EST unplugged.
Kinda put the unplugged comment in wrong spot.
Too many beers while thinking will do that to me. :D
 
I think what you are alluding to is that you think the spark is jumping between the different terminals on the cap? I can't see that being physically possible due to the spacing of the terminals...each terminal is 45* apart. or am I misinterpreting what you are thinking?

Can you swap plug wires with #1? (a reason I always keep a few old ones that are decent around) If it's confined to cylinder 1 only, it's gotta be the cap or the wire, only two things that are cylinder specific. Pretty sure a timing light will work even if the plug isn't firing, but if they don't, that would be something else I'd check, as I've broken plugs before, and up to that point, did not realize how relatively easy it is to do.
 
That is exactly what is going on. Rotor is missing contact and I'm catching spark from #2 as it comes on #1. Swapping wire makes no difference. Still there. And noticed it was there with ETS unplugged. Revs were low so didn't really notice it but closer inspection revealed it was still sparking erratically.

I just put a hole in an old cap. Put rotor on and lined up the reluctor in the distributor I just took out. Stuck on the cap.
Take a look where the rotor is pointing. This is what is causing my mis.
IMGP0260_zpsb218e476.jpg
 
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I don't know what "typical" looks like, but the only cause of a rotor/cap mismatch with TDC being measured correctly is rotor not being "keyed" correctly, timing mark(s) incorrect on balancer or tab, or the timing gear set incorrect no?
 
30 yrs of screwing cars & trucks together, I kinda know where TDC is.
The photo is a Delco cap and Delco rotor. As to how it's out that much, got me. Mallory or MSD had an adjustable rotor for just a problem but can't seem to find it.
I find hard to believe that a brand GM new dist & rotor would have same issues. Rotor locks in tight on the shaft. I mean like REALLY tight.
Must be something I'm missing right in front of me...
I guess I need to get a PC craptop and a datalog this thing
 
If it's a mechanical problem like it seems to be, not sure that datalogging is going to help. I've never seen the cap/rotor relationship as you show (installed), so I'm curious to see how much closer "right" is.

Didn't mean to imply you didn't know what you were doing, just that if the engine is at TDC, there are few things that can affect rotor/cap alignment.
 
dyeager535 said:
Didn't mean to imply you didn't know what you were doing, just that if the engine is at TDC, there are few things that can affect rotor/cap alignment.
Click to expand...

It's ok, I didn't take it as such. :D
And agreed, there is only a few things it could be. I thought if I used data log might see the extra ignition spikes and what might triggering it. Never done live view.
Did some looking around online and seems my truck is not only one this happens to.
 
Have you tried rotating the crank by hand and watching the rotor? I have never bought into the worn out/skipping timing chain due to the amount of teeth engaging on both gears, but I could see a (severely) stretched chain causing some weird timing issues, since there is nothing to keep the chain tight.
 
How many miles does the engine have? The timing chain might be worn enough to cause the rotor phasing to be off. Most of the TBI trucks that I see with over 100k on them will have the ignition timing retarded by 4-5 degrees because of worn timing chain. I have seen untouched trucks with close to 200k and I have to adjust the timing up 6+ degrees which could be enough to cause the phasing issues like what you have.:dunno:
 
Only reason I say it's not the timing chain is the timing is rock steady. It be jumping around even with EST unplugged. I put it to zero and it stays there.
Thanks for input so for fellas. I'll get this figured out yet. Or shove it off a cliff.
 
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