7.4 mph won't restart

D

dodge 403

New Member
Jul 17, 2016
10
buffalo ny
Boat Info
sea ray 280 sundancer 2002
Engines
twin 5.0 with bravo 3
2000 mercruiser 7.4 mpi wont restart after it gets up to temperature then the next day it will start. I replaced cap, rotor ,plugs, wires, IAC, TPS, ICM ,temp sensor, batteries checked, new gas filter, I have spark, fuel pressure, had starter rebuilt, removed plugs and they were wet from gas, any ideas is it flooding what could be causing the no start ,after the starter was rebuilt it was good for couple of weekends back to no start, checked ground wires new ignition switch when it starts it runs great no issues, but after i turn it off it won't restart any ideas
 
won't start turns over read a few other forums seems to be a few out there with a similar problem
 
not likely a flooding issue with a MPI engine.....I have read where the fuel can sometimes return back to the fuel tank after a shut down of the engine when it is warm.....then the fuel pump has to run a few seconds to prime the fuel lines all the way to the injectors....I don't think there is a back-flow preventer in the fuel system.....

one suggestion would be next time you run into this try cycling the ignition key from 'Off - Run - Off' before trying to start the engine a few times to see if the fuel pump will purge the air out of the fuel lines and prime the fuel supply line with fuel.....

cliff
 
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Sounds like no spark. Verify that next time it doesn't start. Ignition coil and sensor can get heat sensitive
 
scoflaw said:
Sounds like no spark. Verify that next time it doesn't start. Ignition coil and sensor can get heat sensitive[/QUOT i


agree with scofflaw. if it uses cap and rotor likely coil or something in the thunder bolt ignition module getting hot. classic symptoms of coil going bad.
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i do agree that ignition coils and control modules are heat sensitive...i have gone through issues with both in the past myself....the only reason I think it might be something beside the ignition coil or the ignition control module is the engine is not dying on its own...the OP said this problem only happens after he shuts down the engine....if a coil or module heats up and opens a circuit it will kill the engine at variable times....

cliff
 
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Has happened to me before it's most likely the fuel in the cool fuel module getting hot after the engine runs .if you run the blower's after shutdown it should be able to restart. the engine room gets hot the fuel vapour locks. try going for a ride coming back try running blower a half hour or so should have no problem


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went to the marina motor started like it should got it up to temperature 170 shut it down waited 10 minutes started and stopped it a few times all good waited 10 minutes try to start it with no luck hooked up scanner no codes have spark, have fuel, engine temp about 140, cranking engine at full throttle no luck ,cycled fuel pump few times no luck , ran starter long time that it got hot ran batteries down ,could starter be drawing too many amps causing a no start
 
it does sound like the classic symptoms of vapor lock in the fuel supply.....

cliff
 
Pick up a can of freeze spray. When it doesn't start, hit your fuel cooler and fuel lines to see if in fact it's heat soak.

You want that battery up to the task.
 
I replaced the thermostat 145 same issue no start after shutting down crank but no start I find hard to believe its vapor lock every single time it won't start engine compartment open ,cooler temps got spark and fuel am i missing something someone said heat soak what temp has the engine have to be that it will not start definitely not overheated thanks anyone know what the starter should draw as far as amps , starter gets hot trying to restart the motor yet the cables are not even warm is that normal thanks
 
dodge 403 said:
I replaced the thermostat 145 same issue no start after shutting down crank but no start I find hard to believe its vapor lock every single time it won't start engine compartment open ,cooler temps got spark and fuel am i missing something someone said heat soak what temp has the engine have to be that it will not start definitely not overheated thanks anyone know what the starter should draw as far as amps , starter gets hot trying to restart the motor yet the cables are not even warm is that normal thanks
Click to expand...

will the engine restart if you shut it down after just a couple mins of running and before it reaches normal operating temp?

if you leave the engine hatch open will it restart after you shut it down when fully warmed up?

if you have proper spark and proper air/fuel mixture at the plugs the only things left are ignition timing and compression....

cliff
 
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To summarize.... Engine starts perfectly and runs as it should from a cold start.. Will run as long as you want it to. ????

If this is correct, then the problem begins on the hot start ???

If this is the case then there are some systems on your boat that can be heat sensitive.

Fuel system...as in vapor lock... fuel gets so hot it is no longer fluid but is a vapor

Coil and ignition sensor are also 2 items that are subject to fail with heat. Doesn't have to be extreme heat if these components are on their way out.
 
is the starter spinning the engine fast enough to restart it after shut down?....if the starter is getting hot it could be dragging and not spinning the engine fast enough to start...

cliff
 
CliffA said:
is the starter spinning the engine fast enough to restart it after shut down?....if the starter is getting hot it could be dragging and not spinning the engine fast enough to start...

cliff
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Good point, starters can suffer from heat soak as well, especially big blocks
 
CliffA said:
is the starter spinning the engine fast enough to restart it after shut down?....if the starter is getting hot it could be dragging and not spinning the engine fast enough to start...

cliff
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motor started yesterday got up to temperature then wait 30 minutes checking temps with a heat gun average temp was 135 tried starting with no luck, put in a brand new starter engine started with no problem engine cranking so much faster a very big difference in cranking started every time through the afternoon with no problem didn't matter how long between starts, air temp was 85 -90 degrees kept engine compartment closed, I think the starter was my problem all the time, thanks for all the input from all of you , i did have the original starter rebuilt thinking that it wasn't turning fast enough I will think twice about dealing with that shop again
 
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