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74 MAG Electronic Fuel Injected Cold start problem

thespeedracer

New member
"I have been experiencing an i

"I have been experiencing an issue starting the engine in my Cobalt when it's cold. In the past I could turn the key, the engine would immediately start up. Now, I have to hold the key and allow the starter to run for a much longer duration. Sometimes, it can take several attempts before it starts, or it may immediately start, but then stalls. Once it starts, I have no issues until it's been sitting for a day or more. The boat is only used at most once a week… So it’s always been sitting for at least several days before I start it cold again.

The engine is a 7.4 MAG Electronic Fuel Injected w/ 335 hours."
 
the label on the engine is 454

the label on the engine is 454 mag mpi

At the begining of the season the spark plugs and fuel filter were replaced. What else should I be looking at?
 
Sounds like a fuel problem. C

Sounds like a fuel problem. Change the pump's filter? Antisiphon valve at the fuel tank may be stuck open allowing fuel in the lines to drain back into the tank via the fuel supply hose. Fuel pump or pressure regulator may be going out. When it starts is there alot of black smoke? Injectors may be dirty.
 
"When was the last time the en

"When was the last time the engine had ignition service? Does it have a fuel/water separator filter? If it does then pour the contents of the filter into a jar and let it sit awhile. Look for water to separate out. Smell the fuel to see if there is a "Varnish" odor to it. If there is water in the fuel and it smells like varnish, you need to pump out the stale fuel.

Next, pour in 1 can of SEA FOAM for each 10 gallons of new fuel. Pour 1/2 can of it into the new separator filter. Do the basic tuneup and then see if it will run.

I'll bet that the throttle body is also dirty. Clean it w/throttle body cleaner and NOT carb cleaner. Also clean the flame arrestor."
 
"I forgot to add... Last night

"I forgot to add... Last night we put fresh gas in as the boat as it almost empty. The boat ran fine until it sat for a few hours. I went to start the boat, it started up and idled fine for a few moments. As I pulled away in idle the engine slowly stalled and would not start for several tries. When it did start there were a few back fires and it stalled.

Today I removed the fuel filter and poured out the gas... There was no water or varnish smell. I reinstalled the filter and the engine started right up with no issues. However within 2 or so minutes the alarm went off. The engine temp was about 175 so it looks like I need to replace the water pump impeller now... Talk about timing
"
 
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