I need help with 454 pre-ignition problem

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TobyZ
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I need help with 454 pre-ignition problem

Post by TobyZ » Tue Oct 23, 2012 4:34 pm

I have put a brand new 454 engine on my boat, and replaced everything else you could replace, runs great but will not sut off when you turn the key off. we have tried just about everything we can think of to elliminate this problem and can't stop it. the lastest thing to try I just heard today was to install a diode on the ignition wire coming from the alternator with would only allow the current to travel one direction. Anyone ever heard of that, or is there any tricks that I may not be aware of? Makrs Airboats in LA told me it was probably the Holly Carb I had, so I put an Eldebrock and it stills does it. We've played with the timing, changed the distributor to one without a vacuum advance etc and still fighting this problem. I would appreciate any advice.

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skinny99
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Re: I need help with 454 pre-ignition problem

Post by skinny99 » Tue Oct 23, 2012 4:54 pm

Do you mean literally won't shut off, like keep idling or do you mean run-on/dieseling? If it the first you have a wiring issue. You are backfeeding power somewhere. Hard to find without looking at set-up.

If the latter then there could be a few things. But most likely it is too high of an idle combined with too much timing.

Read this thread.
http://www.southernairboat.com/phpBB3/v ... t=solenoid

BTW most people have not had a whole lotta luck with an Edelbrock carb on an airboat.
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crowhater
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Re: I need help with 454 pre-ignition problem

Post by crowhater » Tue Oct 23, 2012 5:02 pm

your carb is out of adjustment! Unless you mean it keeps running like the key is still on.

Try this just to check things out! Take your idle adjustment screw all the way lose so that it does not touch anything and see if it shuts down when you turn the engine off.

Because you never said I am just guessing right now but if you have a Holley carb did you check your float levels? If you are running an electric fuel pump do you have a fuel regulator? Do you know for a fact that you are not getting more than say 6PSI of fuel pressure to your carb?
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Re: I need help with 454 pre-ignition problem

Post by TobyZ » Tue Oct 23, 2012 5:22 pm

we have adjusted the carb in and out, up and down, we have played with the timing and currently have set at 10 and 30. Dieseling is the problem, it does it worse after it is hot. When we changed the Holly to the Eldebrock it did get better. It has a mechanical fuel pump, I thought about putting an electric pump but Im tired of just changing parts. There has to be a solution to this that we're missing. Thanks for your input.

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glades cat
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Re: I need help with 454 pre-ignition problem

Post by glades cat » Tue Oct 23, 2012 5:25 pm

Is it an old engine or a fresh build.
Carbon deposits in the combustion chamber can cause "dieseling", running-on, etc.

The easiest is a throttle solenoid.
Might try chemically de-carboning the chambers.
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skinny99
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Re: I need help with 454 pre-ignition problem

Post by skinny99 » Tue Oct 23, 2012 5:29 pm

When you say brand new, Do you mean freshly rebuilt or Crate engine? How much compression? Have you done a compression test? How much
cranking pressure?

What RPM do you have it idling? How low will it idle? Have you done a thorough vacuum leak check?
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akblackdawg
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Re: I need help with 454 pre-ignition problem

Post by akblackdawg » Tue Oct 23, 2012 5:32 pm

what speed does it idle at. it will help if you adjust idle to as slow as possible, maybe 500 rpm if it will idle that slow, then before shut off let it idle down a moment before turning off. hope this helps. Bud
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Re: I need help with 454 pre-ignition problem

Post by Ruagatr » Tue Oct 23, 2012 5:35 pm

Either it is getting fuel & oxygen or it has deposits holding fuel in the combustion chambers. Do like Crow said and close the damn throttle with the screw all the way out. The quickest fix for this is the old air conditioning solenoid in the linkage that will slam shut the throttle butterflies when the key is turned off.

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Re: I need help with 454 pre-ignition problem

Post by TobyZ » Tue Oct 23, 2012 5:44 pm

I have heard about the Sylinoid deal but have not tried that yet. The engine is brand new from GM and has about 3 hours on it now, I have it idleing at 600 RPM, I have have tried to let it idle for a good min or two before turning it off. we have leaned out the carb to a point we thought it could cause problems and that helped when the engine was not very hot, but we were scared to run it along way and burn a piston up. What doi you guys think the timing should be set at, currently we have it at 10 at idle and 30 at 3500 RPM.

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Re: I need help with 454 pre-ignition problem

Post by Birddog247 » Tue Oct 23, 2012 5:52 pm

Just went through some similar issues with my new build. I would advise you to give Alan @s&s performance carburetor a call 281-445-7996. Tell him your issues and he will lead you in the right direction.
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Re: I need help with 454 pre-ignition problem

Post by flying fish » Tue Oct 23, 2012 6:03 pm

Got to get your butterflies shut.

Sure would be nice to hear you had a good A/F meter checking your burn across the circuitry.
This way your A/F ratio would be correct, and then you could work on getting your butterflies shut.
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Re: I need help with 454 pre-ignition problem

Post by Birddog247 » Tue Oct 23, 2012 7:40 pm

When you set your timing with the vacuumed advance I was told to set it while the vacuumed line is disconnected. Once timing is set reconnect vacuumed line. Also might want to run 93 octane if not already.
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Re: I need help with 454 pre-ignition problem

Post by crowhater » Tue Oct 23, 2012 11:52 pm

Listen to me I know Allen at S&S very well and the solenoid is a band-aid for a carb that is not set up right. Do this!!!!!! Take the air cleaner off and run the engine, when you shut it down if it does not turn off " put a towel over the carb" . I bet you money it shuts off. Your butterflies are not closing all the way and you are dribbling fuel into the intake. Do you have a blown power valve? This will cause excess fuel to get by.

With the engine off look down your carb and make sure it is shutting all the way! I have seen butterflies get caught on a carb gasket and this keeps them from closing all the way. Your bottom butterflies should be 100% shut.

Listen this is a carb issue and your jets are not going to effect your idle circuit, and you have an idle circuit issue. If someone got to tweaking your back linkage your back butterflies could be hanging open and this will cause a fuel bleed. With your idle screw removed if you go to idle the engine should die because it is starved of AIR. Without air going through the carb it can not pull fuel into the engine.
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Re: I need help with 454 pre-ignition problem

Post by HOLOTYPE » Wed Oct 24, 2012 6:13 am

crowhater wrote:Listen to me I know Allen at S&S very well and the solenoid is a band-aid for a carb that is not set up right. Do this!!!!!! Take the air cleaner off and run the engine, when you shut it down if it does not turn off " put a towel over the carb" . I bet you money it shuts off. Your butterflies are not closing all the way and you are dribbling fuel into the intake. Do you have a blown power valve? This will cause excess fuel to get by.

With the engine off look down your carb and make sure it is shutting all the way! I have seen butterflies get caught on a carb gasket and this keeps them from closing all the way. Your bottom butterflies should be 100% shut.

Listen this is a carb issue and your jets are not going to effect your idle circuit, and you have an idle circuit issue. If someone got to tweaking your back linkage your back butterflies could be hanging open and this will cause a fuel bleed. With your idle screw removed if you go to idle the engine should die because it is starved of AIR. Without air going through the carb it can not pull fuel into the engine.
Could not have said it any better myself!!!!!!!
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Re: I need help with 454 pre-ignition problem

Post by air-roberts » Wed Oct 24, 2012 6:28 am

yes carbon build up can cause it if thats the cause try running a high idle and start pour water slowly down the carb and that will clean that up but however i have a feeling that you head combustion chamber was not ground smoothly if thats the case each little burr can cause a diesel effect and the heads would have to be removed. i assume your timing is right and you using min 93 oct,
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Re: I need help with 454 pre-ignition problem

Post by jinotown » Wed Oct 24, 2012 5:51 pm

Try the basics first. Too hot of a spark plug will cause high CHT's and are an easy change. Many people think that a hot or cold plug is the power of the spark. Hot or cold is how fast the plug transfers heat away from the combustion chamber. Try some plugs several steps colder. Don't assume your degree marker is correct in zero or degrees. Use a piston stop to find true top dead center and check your zero mark. Then use a dial back light to check your max advance. After that, I would guess a very rich air/fuel mixture or a weak spark. Too large of a carb, idle or jet settings, throttle linkage problems, restrictive intake, or a weak spark will all cause overly rich conditions. As already stated, have the mix checked with a wide band meter so there is no guessing. If everything is right, there is no need for a solenoid.
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Re: I need help with 454 pre-ignition problem

Post by oldairboater » Thu Oct 25, 2012 7:42 pm

My 454 will diesel if I try to kill it hot and rich. My engine is rich on purpose and I refuse to lean it out or change the timing. If I let it idle for five minutes or so it shuts down right. Try that first if you haven't already before you start changing things and adding parts.

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Re: I need help with 454 pre-ignition problem

Post by TobyZ » Fri Oct 26, 2012 5:47 pm

Thanks guys! I think I'm going to look at the carburator a little closer.

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Re: I need help with 454 pre-ignition problem

Post by STAFFER » Sat Feb 07, 2015 12:59 pm

sounds like you have the white wire from alternator connected to your ign. Eather put a dio in line or disconnect white wire from alt.

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Re: I need help with 454 pre-ignition problem

Post by airjohn81 » Sat Feb 07, 2015 1:32 pm

crowhater wrote:Listen to me I know Allen at S&S very well and the solenoid is a band-aid for a carb that is not set up right. Do this!!!!!! Take the air cleaner off and run the engine, when you shut it down if it does not turn off " put a towel over the carb" . I bet you money it shuts off. Your butterflies are not closing all the way and you are dribbling fuel into the intake. Do you have a blown power valve? This will cause excess fuel to get by.

With the engine off look down your carb and make sure it is shutting all the way! I have seen butterflies get caught on a carb gasket and this keeps them from closing all the way. Your bottom butterflies should be 100% shut.

Listen this is a carb issue and your jets are not going to effect your idle circuit, and you have an idle circuit issue. If someone got to tweaking your back linkage your back butterflies could be hanging open and this will cause a fuel bleed. With your idle screw removed if you go to idle the engine should die because it is starved of AIR. Without air going through the carb it can not pull fuel into the engine.
went through this on the same exact motor... an mr. crowhater is absolutely correct !!!! be sure to check timing as well.. but every one ive seen do this was exactly what he said.. CARB problem
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Re: I need help with 454 pre-ignition problem

Post by Deano » Sat Feb 07, 2015 6:53 pm

This post is over two years old, and all 4 of the poster's total posts are in this thread.

Evidently, one way or the other, he is beyond this problem. :?
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but it is not the path to knowledge; it has no place in the endeavor of science."
- Carl Sagan

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