5.7 EFI random stall

[Strecker25]

Weird one today, wondering what you guys think.

1998 5.7L EFI Alpha 750 hours

engine runs like a top, great compression measured last year (180-100) new distributor, cap, rotor, plugs, wires, and fuel pump. Has run perfect for 10 hours this year.

today I’m cruising along at 3300 rpm and it just quits. No warning signs at all, I have the fox marine gateways and they report no check engine light or reduced power, fuel pump kicks on, etc. Motor fired right back up but died again a minute later. 2 or 3 more starts and then it ran perfect again

went to anchor, sat for 3 hours, ran back flawlessly.

the only thing that seems a little off is the sync gauge is bouncing erratically like that engine is losing revs. The fox-marines do not show any drop in RPM, engines are solid and synced.

I also noticed the alternator on this motor is very hot to the touch and the idle voltage is only 13.1 while my other side is 14.1. I’m going to replace it since it’s old, but 13v shouldn’t cause the EFI to shut down.

We’re in the north and the air was only 75 degrees, shouldn’t be vapor lock. Checked both battery and alternator leads and everything is tight

if it happens again I think I need to get codes pulled. But what say you? Gotta be electrical right?

 

[Strecker25]

I also pulled the cap to check it out. A little bit of carbon tracking but not horrible. I’ll clean that up as well. The cap has about 25 hours on it

 

[SeaRide]

Strecker,

Have a look at the thread below. You symptoms are not identical, but the bouncing synch. gauge is suspicious, leading me to believe it could be a shift interrupt switch issue killing the ignition. Also could be problems with the coil wire, coil and etc.

http://clubsearay.com/index.php?thr...ckfiring-under-load.84388/page-2#post-1104073

 

[Strecker25]

Strecker,

Have a look at the thread below. You symptoms are not identical, but the bouncing synch. gauge is suspicious, leading me to believe it could be a shift interrupt switch issue killing the ignition. Also could be problems with the coil wire, coil and etc.

http://clubsearay.com/index.php?thr...ckfiring-under-load.84388/page-2#post-1104073

Very interesting. I actually have a spare interrupter switch on board so I’ll swap it out. That would make some sense especially the way it died, very sudden with no hesitation

I also have a rinda code reader on the way to see any stored codes.

I remember reading a while back that the tach/sync circuit could actually affect ignition it it had issues. It seems unlikely so I won’t go there yet, but I’m keeping it in mind.

lastly, I replaced the coil proactively but the one last year seemed fine (original) I still have it so if the interrupter doesn’t solve the problem and there are no codes maybe I’ll swap back to that coil to see if the new one is overheating.

Thanks for the link, intermittent problems stink!

 

[SeaRide]

You are welcome. Changing the switch will be easy especially since you have a spare.

Good luck.

 

[cfd95]

Sounds like the ignition coil .
Went through same problem memorial weekend on my port motor .
Was a bad coil.

 

[Strecker25]

Sounds like the ignition coil .
Went through same problem memorial weekend on my port motor .
Was a bad coil.

roger that, will swap it. Any troubleshooting that can pinpoint it for certain? Did it throw a code or anything?

 

[cfd95]

roger that, will swap it. Any troubleshooting that can pinpoint it for certain? Did it throw a code or anything?

It could be the pickup coil in the distributor too.
Your description that it shuts right right down sounds ignition related.
No codes.
My Port motor kept dropping off ,synch gauge was bouncing then just shut down and backfired.
Would start back up ,once on plane would do again.
I keep a spare coil and pickup coil on the boat.
changed the coil ran the rest of the way home like a champ been fine since.
Ordered another coil replaced starboard one kept old one as spare.

 

[Strecker25]

I broke my own rule and replaced more than one part at a time, but I didn’t feel like troubleshooting all weekend.

new coil, alternator, and interrupter switch. Ran 3 hours, solid as a rock. Sync gauge is pinned in the center again. I suspect the coil might have been the culprit but I guess I’ll never know. Thanks all!

 

[Strecker25]

Well, gremlins are back. Ran fine last weekend, same issue back today after only an hour ride.

Started back up 30 minutes later and was fine.

one thing I discovered was the fuel pump lines laying against the oil pan. I’m wondering if that could cause the pump to cut out?

another spot on top of the intake manifold where that pipe from the manifold to the intake was laying on a wire bundle that goes to the water temp sensor, iac wires, and throttle position sensor. The shielding was melted, in wondering if that could also cause a cutout.

 

[Strecker25]

I can for certain say the injectors and cutting out. Happens for a millesecond or two while it’s stumbling then they quit. During the no-start condition the injectors are not firing. If I wait a little bit they will fire back up and spray.
Seems to be brought on by heat.

swapped ecu - no change. Will test fuel pressure tomorrow

 

[Strecker25]

Hopefully the final post here - turns out it was the distributor, specifically I believe the ignition module. It seems like it was getting hot and cutting out, which from what I can tell will cause the injectors to shut down. I didn’t replace just the module I swapped a distributor in.

I hope that helps somebody.

 

[GoodVibes]

Thanks for the in depth write up. We have same motors in our boat. Just recently purchased the boat. Survey was good good, especially with the motors.

On our third trip out in the lake, last weekend, our starboard motor was roughly 4-500 rpms higher than port. Didnt get a shut off at all and when we came in quickly to dock, they synced right back up. Odd. I am newbie with the boats but have been in car business for 12 years and I at least "feel" that I would be able to feel/hear a difference from operating normal to having slight variations or concerns.

Any ideas here? Again we didn't get a shut off, but our sync was out of whack until we came back to canal to dock. Possibly something similar?

 

[Strecker25]

Thanks for the in depth write up. We have same motors in our boat. Just recently purchased the boat. Survey was good good, especially with the motors.

On our third trip out in the lake, last weekend, our starboard motor was roughly 4-500 rpms higher than port. Didnt get a shut off at all and when we came in quickly to dock, they synced right back up. Odd. I am newbie with the boats but have been in car business for 12 years and I at least "feel" that I would be able to feel/hear a difference from operating normal to having slight variations or concerns.

Any ideas here? Again we didn't get a shut off, but our sync was out of whack until we came back to canal to dock. Possibly something similar?

500 off at idle or on plane?

that sounds like a vacuum leak possibly. The ecu normally controls that stuff with the various sensors, but if you pull the vacuum line from the throttle body that goes to the port side rocker cover the idle will shoot up to 1000-1200.

check that hose For leaks or being brittle and double check the pcv valve on the rocker cover.

 

[GoodVibes]

500 off at idle or on plane?

that sounds like a vacuum leak possibly. The ecu normally controls that stuff with the various sensors, but if you pull the vacuum line from the throttle body that goes to the port side rocker cover the idle will shoot up to 1000-1200.

check that hose For leaks or being brittle and double check the pcv valve on the rocker cover.

More so when we got out in to higher rpms. Really didn't feel like pushing it up over 3000-3200 so stayed slightly under 3000 for the short amount of time we were out. And then they synced back up when we go back to just above idle speed. I've spoke to a few and read some things. Anything from fuel levels, to possibly throttle cables. Mechanic is checking it out today. I am awaiting the phone call. I will keep updates as I get them.

There were relatively choppy waters for our lake also so to feel any big abnormalities was a bit tough anyway. Neighbor in our marina said was top 5 toughest wind and current days in the canal that he has seen in 15 years. Again could mean nothing, but I'm just trying to soak in as much as I can to get educated.

 

[GoodVibes]

500 off at idle or on plane?

that sounds like a vacuum leak possibly. The ecu normally controls that stuff with the various sensors, but if you pull the vacuum line from the throttle body that goes to the port side rocker cover the idle will shoot up to 1000-1200.

check that hose For leaks or being brittle and double check the pcv valve on the rocker cover.

Just noticed you were in Rochester. I am in Watkins Glen. Seneca Lake!!

 

[Strecker25]

Just noticed you were in Rochester. I am in Watkins Glen. Seneca Lake!!

cool! Beautiful down there. Seneca can become a lot like Lake Ontario at times since it’s so deep when the wind picks up

trust your sync gauge more than the tachs. I replaced mine because the port side was way off. My understanding is the sync is typically more accurate for whatever reason. You could also have the mechanic shoot it with a laser tach to check for accuracy at the dash. Lastly, don’t think your throttles have to match up exactly. Mine don’t in order to sync.

a really cool investment (if you have an MFD/plotter) is the fox-marine gateways. I added them and they’re amazing. They have an app too, shows all kids of stuff. Map sensor, tps, iac, timing, fuel pump output, rpm, fuel flow, etc. when it’s paired with a plotter it calculates mpg as well. It will also tell you if the throttle position on each engine is synced up

 

[GoodVibes]

cool! Beautiful down there. Seneca can become a lot like Lake Ontario at times since it’s so deep when the wind picks up

trust your sync gauge more than the tachs. I replaced mine because the port side was way off. My understanding is the sync is typically more accurate for whatever reason. You could also have the mechanic shoot it with a laser tach to check for accuracy at the dash. Lastly, don’t think your throttles have to match up exactly. Mine don’t in order to sync.

a really cool investment (if you have an MFD/plotter) is the fox-marine gateways. I added them and they’re amazing. They have an app too, shows all kids of stuff. Map sensor, tps, iac, timing, fuel pump output, rpm, fuel flow, etc. when it’s paired with a plotter it calculates mpg as well. It will also tell you if the throttle position on each engine is synced up

I appreciate the insight!! Thanks a lot. Will take a look at the gateways. Pretty informative stuff

 

[Benhole]

Hopefully the final post here - turns out it was the distributor, specifically I believe the ignition module. It seems like it was getting hot and cutting out, which from what I can tell will cause the injectors to shut down. I didn’t replace just the module I swapped a distributor in.

I hope that helps somebody.

Any suggestions based on your experience? Just bought a new boat after performing very well during sea trial and survey. Unfortunately, the day I took ownership and went to start the engines, the starboard turned over but never fired up. I had the previous owner come down and try to start it, just in case I was doing something wrong or was unaware of nuance, but to no avail. I replaced one of the batteries that seemed to be in rough shape, still no firing of the engine. Thinking it was a spark issue, the owner helped me replace the coil and was successful in getting the engine to start.

We took it up to a new marina on both engines until about 15 minutes in, the starboard cut-off. We did get it restarted again as we were coming in to dock about 30 minutes later. The next morning, I went to the boat and was able to fire up both engines no problem, but as I was heading down the alley-way (about 2 minutes in), the engine cut out.

The coil we swapped was indeed a used coil, so perhaps a new one would fix the issue, but it seems peculiar to me that two coils would go bad. I have a mercruiser tech supposedly looking at it over the next couple of days but I am not optimistic that 1) they will diagnose it correctly 2) provide a permanent fix 3) be prompt in remedying the situation.

Any insight would be greatly appreciated!

 

[Strecker25]

Any suggestions based on your experience? Just bought a new boat after performing very well during sea trial and survey. Unfortunately, the day I took ownership and went to start the engines, the starboard turned over but never fired up. I had the previous owner come down and try to start it, just in case I was doing something wrong or was unaware of nuance, but to no avail. I replaced one of the batteries that seemed to be in rough shape, still no firing of the engine. Thinking it was a spark issue, the owner helped me replace the coil and was successful in getting the engine to start.

We took it up to a new marina on both engines until about 15 minutes in, the starboard cut-off. We did get it restarted again as we were coming in to dock about 30 minutes later. The next morning, I went to the boat and was able to fire up both engines no problem, but as I was heading down the alley-way (about 2 minutes in), the engine cut out.

The coil we swapped was indeed a used coil, so perhaps a new one would fix the issue, but it seems peculiar to me that two coils would go bad. I have a mercruiser tech supposedly looking at it over the next couple of days but I am not optimistic that 1) they will diagnose it correctly 2) provide a permanent fix 3) be prompt in remedying the situation.

Any insight would be greatly appreciated!

sure sounds like a similar issue, you can get the module for like $80-100

It could also be a fuel issue, when it cuts out so you see fuel spraying out of the injectors while cranking? Mine were completely dry with no fuel coming out.

I’d also suggest checking fuel pressure - you need a special adapter to do it - but that cause some wackiness as well.

I actually have the special schraeder valve adapter unopened if you want it - I’ll sell it to you for less than new and it’s unopened. Your mechanic should have one though. I also have an ignition module unopened, but you’ll have to make sure it fits your engine. Good luck!