Correct plug for stock 454 Mag MPI?
07-22-2020 | 06:15 PM
#22
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Joined: Jul 2003
Posts: 49
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From: Shady Shores, TX
We have a very hot spark at the plugs.
Only running fresh, Non-Ethanol & haven't found any water again.
Exhaust leak, don't think so. Runs great & don't hear anything indicating one.
07-22-2020 | 09:11 PM
#26
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Joined: Nov 2004
Posts: 14,154
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From: On A Dirt Floor
Good luck under 200 rpm. Most need 250-300 rpm to fire.
Years back we used slow turning starters to lower compression gauge reading for rules racing. Engines became near impossible to start under 200.
Years back we used slow turning starters to lower compression gauge reading for rules racing. Engines became near impossible to start under 200.
07-22-2020 | 11:59 PM
#27
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Joined: Jun 2011
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Like SB said, I don't believe the MEFI will even fire the ignition if below 250-300 rpm. If slow that is likely an issue.
But it could also be something else.....Next time it happens try this. Open the throttle to 50-75% and attempt a start. This will trigger flood clear mode and shut off the injectors. The vapor lock issue with the MEFIs is often confused with an actual flooded engine because the VST can percolate fuel into the manifold under hot conditions in certain circumstances. The fact that you have what appears to be 'fouled' plugs leads me to believe this is happening.
But it could also be something else.....Next time it happens try this. Open the throttle to 50-75% and attempt a start. This will trigger flood clear mode and shut off the injectors. The vapor lock issue with the MEFIs is often confused with an actual flooded engine because the VST can percolate fuel into the manifold under hot conditions in certain circumstances. The fact that you have what appears to be 'fouled' plugs leads me to believe this is happening.
07-23-2020 | 11:43 AM
#29
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Joined: Jul 2003
Posts: 49
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From: Shady Shores, TX
Like SB said, I don't believe the MEFI will even fire the ignition if below 250-300 rpm. If slow that is likely an issue.
But it could also be something else.....Next time it happens try this. Open the throttle to 50-75% and attempt a start. This will trigger flood clear mode and shut off the injectors. The vapor lock issue with the MEFIs is often confused with an actual flooded engine because the VST can percolate fuel into the manifold under hot conditions in certain circumstances. The fact that you have what appears to be 'fouled' plugs leads me to believe this is happening.
But it could also be something else.....Next time it happens try this. Open the throttle to 50-75% and attempt a start. This will trigger flood clear mode and shut off the injectors. The vapor lock issue with the MEFIs is often confused with an actual flooded engine because the VST can percolate fuel into the manifold under hot conditions in certain circumstances. The fact that you have what appears to be 'fouled' plugs leads me to believe this is happening.
I also have tried the flood clear method on the throttle, no luck.
07-23-2020 | 02:31 PM
#30
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Joined: Feb 2001
Posts: 4,303
Likes: 1,459
From: Virginia Beach
Good infvo possibly.^^^
I had a carbed Mercruiser small block boat cone in years ago. Had all ignition components replaced alongvwith new batteries for crank no start when hot.
I take a look and fires right up cold. Drive it gor 1/2 hr...,,holy fk does it labor to crank. It starts I shut it off a little later again and it cranks so slowbitcwon’t fire.
Check for hydrolocking. That’s fine.
Check for over advanced dist setting, that’s fine.
Replace starter (late model pg 260 type) because cables and batteries fine and I have nothing else to think of.
Bang ! Quick turn of the key. Swear the motor jumped outvofvthe bilge and gave me a great big hug. Boat been totally fine ever since. Customer struggled with it for a few years I guess.
I have not run into this before and not since.
Starters usually stop working, not slow crank. Guess not.
Been working on vehicles over 30 yrs.
I had a carbed Mercruiser small block boat cone in years ago. Had all ignition components replaced alongvwith new batteries for crank no start when hot.
I take a look and fires right up cold. Drive it gor 1/2 hr...,,holy fk does it labor to crank. It starts I shut it off a little later again and it cranks so slowbitcwon’t fire.
Check for hydrolocking. That’s fine.
Check for over advanced dist setting, that’s fine.
Replace starter (late model pg 260 type) because cables and batteries fine and I have nothing else to think of.
Bang ! Quick turn of the key. Swear the motor jumped outvofvthe bilge and gave me a great big hug. Boat been totally fine ever since. Customer struggled with it for a few years I guess.
I have not run into this before and not since.
Starters usually stop working, not slow crank. Guess not.
Been working on vehicles over 30 yrs.
