7.4 Ignition Module

H

hd2002hd

Member
Jul 20, 2010
457
St. Louis
Boat Info
1996-Sea Ray 215 Express Cruiser/1996-Sea Ray 330 Sundancer/1998-Sea Ray 400 Sundancer/1996-Sea Rayd
Engines
5.7 Mercruiser/454's/454's w/V drive/120HP
1998 sea ray 400 with 7.4’s. About 3 weeks ago the starboard engine wouldn’t start. After calling a mechanic he suggested changing the ignition module. I couldn’t find a marine module so I got one at the local automotive store per his suggestion. Once installed it fired right up. I ordered a marine module right away. 3 weeks later same thing. Starboard wouldn’t start so I installed the marine module. So, what would cause these to go bad? It feels like there may be another issue that is lurking and it is showing up by causing the ignition module to fail or is this just a coincidence?
 
If the 1st one wasn't ACDelco it was probably Chinese junk. Using the good grease too, right ?
 
Well, I just replaced the whole distributor 2 years ago. I’m not sure if the brand. The second one was a Durolast. The 3rd one (replaced yesterday) was a Sierra. I used the grease that came with them and costed them good.
 
scoflaw said:
Is your alternator voltage in the sweet spot ?
Click to expand...

I’m not sure. How would I check, just on the volt meter? If so, it seems to run around 14v. It does wonder up to 15 or so sometimes though.

I just put another module in and it fired up and then died and won’t restart.
 
13.9 - 14.7 is the spec. Too much or little isn't good for electrical parts. Your boat gauge probably isn't that accurate either.

Maybe a chaffed wire or connection issue. Do more research on what dizzy you bought
 
Possible high voltage, intermittent voltage spike or poor ground.
Obviously, we can't monitor charging system voltage or amperage when its's not running so I would start with a voltage drop test from the distributor housing to the center of the negative battery post.
 
I have not had a chance to switch coils yet, but I have been reading up and I found and old thread about ignition issues, but it turned out to be a bad distributor cap followed by a bad distributor cap (if I read that correctly). Mine is for certain blowing the ignition module each time. So, with the advice I received here and what I received from mechanics, it seems most are either in the alternator is providing too much voltage or the coil is bad. I did read about the ECM as well, but would assume since it starts if I change the ignition module, that hopefully that is not an issue?? Changing the coil seems to be the easiest first attempt and since I cannot get a voltage read on the alternator since the engine won't run. I assume I can have an auto parts store test the alternator and it would tell me if it is overcharging?
 
The pick-up coil could be bad and it plugs directly into the module. Check for any of those wires going to it for a short to ground. Distributor body grounds thru the hold down clamp.
A service manual will tell you how to trouble shoot the ignition system
 
scoflaw said:
The pick-up coil could be bad and it plugs directly into the module. Check for any of those wires going to it for a short to ground. Distributor body grounds thru the hold down clamp.
A service manual will tell you how to trouble shoot the ignition system
Click to expand...

So, if the pickup coil is bad you have to pull the distributor shaft out of the block to replace it?
 
scoflaw said:
Forget...there is a pronged washer that holds it on and it can corrode.
Click to expand...
Are you speaking of a pronged washer on the ignition module? I don't recall a pronged washer. Looking at a drawing, I see a couple of retainers. One is above the "shield" (Their terminology) that is above the coil that is inside the distributor that plugs into the ignition module. The other is associated with the external ignition coil.
 
Interesting. So I assume the answer is electrical cleaner to spray in there or is that a no no?
 
Yeah, I saw your comment on that earlier. I looked on line and saw a couple of download options. I don't think my service package came with one. Is there a preferred place to download the service manual?
 
More follow up: I checked all battery connections and found a loose battery cable on the starboard engine. I cleaned and added dielectric grease to all and tightened. I loosened the engine grounds, cleaned and added more grease there as well. I was told by an ignition manufacturer that most of the failures of the ignition module they see is due to corrosion on the distributor bolt as it grounds the distributor. I marked the distributor, removed the bolt, sanded the all of the surfaces down, applied grease and re-tightened. Cleaned the internal part of the distributor, applied grease and installed a new module. It started up several times so I took her out. Ran about a mile up the lake and had lunch. I verified it would start after shutting it down. Fired up and ran back. Tried it again later and it started as well. I did notice on the run up, that both amp gauges moved ALOT between 14 and 16 amps with the starboard side staying mostly and amp or so higher than port. I also have a digital gauge and it ran at least an amp lower and generally around 14 or a little more. I did see it go near 15 at one point for a moment. Initially I thought maybe an alternator was overcharging and maybe that is still the case. I'm not sure. I've also been told that an alternator will move up and down as it cycles through charging. I don't have a good feeling I have resolved anything, but other than removing the alternators and having them tested, I'm not sure of what direction to go. Any thoughts?
 
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