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Discussion Starter · #1 ·
Mild 454 build installed in September 2013. Car spent the next couple years in paint jail and being put back together. After working through some carb and ignition tuning, car ran like a champ for years until now. I’m struggling to determine what’s wrong.
Car does not want to idle and makes poor power. Basically undrivable. Seems like it is lean.
MSD 6 box, pro billet distributor, MSD wires, MSD coil, all 9 years old. Autolite plugs new winter before last. Just ohm checked the wires and checked cap and rotor. Found nothing wrong.
Checked battery voltage and charging system found nothing wrong. Thought MSD maybe running in an under volt condition.
Checked for vacuum leaks, found nothing. Now running with all manifold vacuum supply lines disconnected and plugged.
Fuel supplied by an Edelbrock 1722 mechanical pump, through a Holley 40 micron filter to a Holley 4779 DP.
Installed a fuel pressure gauge in the feed line last night. Only read 2 psi while running. ( not sure I trust the gauge)
Header tubes all measured about 220 degrees however I didn’t have the engine running long.
Pulled the filter and pump off tonight. Filter is clean. Pulled the pump apart, saw nothing out of place. Put the pump back together, installed the same gauge previously used and bench tested pump with water. Once full, pump dead heads against the gauge at 4 psi. Maintains pressure.
So last night I was sure the pump was bad. Now I’m not so sure. I hate to spend $175 for a new Edelbrock pump if that’s not the problem.
Thinking about putting the old pump back on and checking again.
Problem does not seem to be mechanical. Car starts and runs, no odd noise, etc. Has not been idling well this spring, like air bleeds needed to be cleaned but ran fine otherwise. Been a few years since I rebuilt the carb. I have a Holley kit but have never seen a carb failure causing something like this. Any other thoughts?
 

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Buy a cheap HEI distributor/wires and swap it in to bypass all the MSD stuff. just use a jumper to the battery for power. Good to have as a troubleshooting tool or spare in the trunk on road trips.
 

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Check your float levels on the carb.
Fuel air & spark.....just start going through these basics. The reason I suggested the HEI swap in was because it eliminates a weak coil, electronic spark box, distributor and all of the associated wiring so its a big swing at the problem. @nd step for me would be to pull the carb and remove the fuel bowls and metering blocks. The reason for pulling it off s to check the transfer slots that way when you put it back on you know that important part is correct. Spray every circuit out with carb cleaner and put it back on the car. Install fresh plugs, start the car and start with the mixture screws...I start with 2 turns out and adjust in until max vacuum, adjust idle and repeat. If its still not running right then I'd run a compression test.
This is what I do and the order I do it in but not set in stone - to each his own. The important thing is to look at each system.
 

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Discussion Starter · #9 ·
Not very old. Drove the car quite a bit in May and beginning of June. Ran out 2-3 tank fulls. Ran out half of current tank out before problem started.
I was driving to a local cruise night about 20
minutes away. Just about there and car stalled at a light, like it ran out of gas. Fired right back up but has not run right since. Car has never stalled once warmed up. Manual chock wired open so cold starts take throttle feathering.

I appreciate the replies. I’m dealing with elderly parent issues so little time to work on it. Won’t get back to looking at it until next week.
 

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Swap the coil. I previously said to swap in an HEI to rule out everything in the existing ignition system but based on your last post just go to Napa and get a cheap canister coil and swap the MSD coil out. I've had MSDs fail in the past with the exact same symptoms. They are not like a light bulb where they either work or do not.
 

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Discussion Starter · #11 ·
Thank you! That’s the kind of experience I’m looking for. I assumed a coil would completely fail. I’ve run MSD stuff for years but never had one fail.
 
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Discussion Starter · #12 ·
Update:
MSD 8207 Blaster ohm checked bad. Replaced with an MSD 8252. Reinstalled the fuel pump and a fresh set of Autolite plugs. She starts and runs but still doesn’t want to idle. Like she’s lean. I can get her to idle by turning the idle adjustment screw in a turn, exposing more transfer slot. Almost like there is a vacuum leak. If there is,
I can’t find it.
I’ve never seen a Holley go lean at idle. Intend to pull carb apart the next couple days see if anything jumps out.
Thinking back on all of this, car didn’t want to idle right since back in the spring. Now I’m thinking that is a separate problem from the coil.

Changing the coil made a huge change. Thank you so much Travisch, I would not have researched and tested the coil without your recommendation. I’ve never seen a coil fail like that.
 
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