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454 Big Block stalling when hot

4

454 blazer

1/2 ton status
Joined
Feb 27, 2008
Posts
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Location
bahrain
Gentlemen,
My 454 starts poping and misfiring and then totally dies when it begins to get hot ? (When i say hot i mean temp gage is on half )
I seems like its electrical as a about 5 mins later it will start again if i completely floor the gas peddle ? What do you guys think ? I changed the ignition module in the HEI with no effect.Spark plugs ?
Anyway really hope you guys have few ideas as ive just got it street legal and want to drive it :doah:.
Thanks in advance :bow:
 
Do you have spark and/or fuel when it dies? No point in replacing perfectly good parts.

Year? Injection? Carb?
 
You have to determine if it loses spark or not,or if its starving for fuel,or flooding..if it has a carb,it could be flooding or vapor locking,if its hot where you are,the fuel may even boil in the bowl under those conditions,and cause stalling,then start again once it cools down some...seeing you have to floor it to get it to start tends to point towards a flooded condition..if it has fuel injection it could be a lot of things..a failed fuel pressure regulator will flood the engine at idle speeds and stall it,for example..(not every truck with EFI uses one however)..

If you have a HEI distributor ,it could be the pickup coil failing,they often do as you described when they get hot..
We need more info on what year you have,if its carbed or EFI,and what kind of distributor it has to give a better idea of what might be wrong..
 
diesel4me said:
You have to determine if it loses spark or not,or if its starving for fuel,or flooding..if it has a carb,it could be flooding or vapor locking,if its hot where you are,the fuel may even boil in the bowl under those conditions,and cause stalling,then start again once it cools down some...seeing you have to floor it to get it to start tends to point towards a flooded condition..if it has fuel injection it could be a lot of things..a failed fuel pressure regulator will flood the engine at idle speeds and stall it,for example..(not every truck with EFI uses one however)..

If you have a HEI distributor ,it could be the pickup coil failing,they often do as you described when they get hot..
We need more info on what year you have,if its carbed or EFI,and what kind of distributor it has to give a better idea of what might be wrong..
Click to expand...

Sorry I didnt give you guys more info.It really does seem to be electrical though as it runs perfectly up until its getting a little hot.Its acarbed motor with a 750 Dp holley.
Its like the electrics just shut down.The spark plugs are trying to fire but cant.When it does finally fire it shoots out all the un burnt fuel and runs fine for maybe another half mile or so then bam....of again.This used to happen a while back but never this bad.
 
I have changed the coil and the ignition module.What is the small part the plugs into the ignition module ? Its kind of flat c shape with four male connectors on it ? As that is what I call the ignition module.Am I right thinking that our is it the part that plugs into that ?
 
The ignition module looks like the first thing pictured--the pick up coil is pictured under it..

There is another plug that goes on the module that has a condensor in it,thats only to supress radio interference,it doesn't affect the ignition at all..

F14603515.jpg

300px-HEI_pick_up_coil_assy.jpg
 
Thanks diesel for me.....but I cant see the pictures as im not a full member (YET).When I changed the module it did exactly the same thing.Is the pick up coil in the hei cap ?
 
Pick up coil sits in the bottom of the distributor...has a two wire plug on it,and its round,has gear looking teeth on it...if you type in "HEI ignition parts" on google and click "images" you'll see pictures of what a module and pick up coil look like...or look one up on a parts store website like Autozone or Napa,Summit Racing,etc..
 
You can test all this stuff by typing "test GM HEI" into google BTW, cheaper than throwing parts at it.
 
Thanks guys for the replies,I have googled it and will be testing the pick up coil tonight.
Cheers :bow:
 
I would suggest the next time it stalls you pull a spark plug and lay it on the engine block while someone cranks it over. See if you actually lose spark or not.
 
Ok so i tested the pick up coil last night and its fine, so i threw in a new module and a new rotor for good measure.So i will be taking it out for a spin tonight when its a bit cooler,lets see how it goes.As you suggested i will take a buddy along and if it does cut out again i will check for spark.Thanks again for your help :bow:
 
454 blazer said:
Ok so i tested the pick up coil last night and its fine, so i threw in a new module and a new rotor for good measure.So i will be taking it out for a spin tonight when its a bit cooler,lets see how it goes.As you suggested i will take a buddy along and if it does cut out again i will check for spark.Thanks again for your help :bow:
Click to expand...
Hey Guys! I know it's an old thread but curious how this ended! Having same issues with same engine. Please share the knowledge! :)
 
He was last on in 2019. Chances are it ran OK or he would have posted back?
 
Welcome @Andrasmarton

If you are experiencing a similar symptom, go ahead and start your own thread it will get more action
 
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