whats the cause?
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Senior User
Joined: Feb 2010
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From: Colorado
whats the cause?
every morning when i cold start my truck it makes like a knock type noise after start up seems like the cylinder isnt fireing? its goes for about 20 seconds and then it runs fine after that. any one know whats wrong?
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Joined: Jun 2010
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From: Tennessee
Well everyones noises are interpreted differently... but.. If your hearing a Piston slap type noise sounding hollow and bell-like during cold engine operation and louder at acceleration, you could have worn piston rings, worn cylinder walls, collpased piston skirts, misaligned connecting rods, worn bearings, excessive piston to wall clearance, or poor lubrication...
An imporant point to keep in mind is that insufficient lubrication is the most common cause of engine noise.. So check the fluid levels.
Some noises are more pronounced on a cold engine because clearances are greater when parts are not expanded by heat. Aluminum and iron expand at different rates as temperature rises. For example, a knock that dissappears as the engine warms up, is probably piston slap/knock. An aluminum piston expands more than the iron block, allowing the piston to fit more closely as engine temp. rises.
An imporant point to keep in mind is that insufficient lubrication is the most common cause of engine noise.. So check the fluid levels.
Some noises are more pronounced on a cold engine because clearances are greater when parts are not expanded by heat. Aluminum and iron expand at different rates as temperature rises. For example, a knock that dissappears as the engine warms up, is probably piston slap/knock. An aluminum piston expands more than the iron block, allowing the piston to fit more closely as engine temp. rises.
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Joined: Aug 2010
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From: Denver, CO
Knocking at start-up
Zakk,
I believe these trucks have a cold start timing compensator which causes the knocking. I believe it is set when the pedal is depressed to the floor after the key is turned on and before starting. Mine does the same thing. I think that is what you are hearing. My understanding is that this is normal. I am sure someone else will elaborate, who knows much more about it than I.
I believe these trucks have a cold start timing compensator which causes the knocking. I believe it is set when the pedal is depressed to the floor after the key is turned on and before starting. Mine does the same thing. I think that is what you are hearing. My understanding is that this is normal. I am sure someone else will elaborate, who knows much more about it than I.
Last edited by akamacgyver; Mar 25, 2011 at 07:57 PM. Reason: added info
Thread Starter
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Senior User
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From: Colorado
Zakk,
I believe these trucks have a cold start timing compensator which causes the knocking. I believe it is set when the pedal is depressed to the floor after the key is turned on and before starting. Mine does the same thing. I think that is what you are hearing. My understanding is that this is normal. I am sure someone else will elaborate, who knows much more about it than I.
I believe these trucks have a cold start timing compensator which causes the knocking. I believe it is set when the pedal is depressed to the floor after the key is turned on and before starting. Mine does the same thing. I think that is what you are hearing. My understanding is that this is normal. I am sure someone else will elaborate, who knows much more about it than I.
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Joined: Aug 2008
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From: 50450 IOWA
how about its not running on all 8? mine will do this i need to check all glow plugs again i think its just one cylinder not fireing till it warms up enough to
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From: Colorado
thats what i was guessing
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From: Tennessee
yea i don't know sounds real distorted over the camera.. almost sounds exactly like my truck on a real cold start.. I don't know I think your best option is to have a well experienced diesel tech listen to it as well.
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Senior User
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From: Colorado
these people know everything just start a new thread asking your question
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From: Massachusetts
Josh, welcome to the IDI forum.
You'll have much better luck getting an answer is you start a new thread with a good title
Do you have a decent oil pressure gauge? Have you checked your oil level?
Seems like it's either taking a while to build oil pressure...
Or...it's taking a while to fire on all 8...
What temperature is it outside when you do this?
I don't think that's long enough for the cold timing advance...definetly not long enough for high idle. This week, my high idle has been taking 3 minutes or so to get up to temp and kick off. Colder weather, can be up to 5 or 6 minutes.
Mine sounds good instantly at start-up, but my fuel system only has 25k miles on it. Engine gets beaten daily though...
Mileage on the engine? Mileage on the fuel system?
You'll have much better luck getting an answer is you start a new thread with a good title
Do you have a decent oil pressure gauge? Have you checked your oil level?
Seems like it's either taking a while to build oil pressure...
Or...it's taking a while to fire on all 8...
What temperature is it outside when you do this?
I don't think that's long enough for the cold timing advance...definetly not long enough for high idle. This week, my high idle has been taking 3 minutes or so to get up to temp and kick off. Colder weather, can be up to 5 or 6 minutes.
Mine sounds good instantly at start-up, but my fuel system only has 25k miles on it. Engine gets beaten daily though...
Mileage on the engine? Mileage on the fuel system?