318 Runs Like Sh*t When Warm

[NHCharger]

Coming off the highway on to another road she started to sputter, we made it a mile before she quit. It wouldn’t restart. I waited 5 minutes, it started. We drove home (7miles), it started acting up again close to home. Figured I had some junk in the carb.

Cleaned the carb, changed the fuel filter, took it for a 4 mile ride-all good. The other day couldn’t make it a mile. Last summer I replaced the old smogger intake with an Edelbrock, and replaced the fuel pump since I was still running the original from the looks of it, put 1,000 miles on it after the swap. The engine was rebuilt 37k miles ago. Has always run like a champ. I converted to electronic ignition a few years ago.

When I cold start it she runs smooth for 5-7 minutes. As soon as she warms up she bogs down and quits when I give it any gas. She doesn’t blow any smoke, I have a ½” carb spacer.

This is what I’ve done so far, with no results.

I have a spare carb, so I swapped out the carb.

Pulled the fuel line off the pump and ran the engine off a 2 gallon can.

Replaced coil and ballast resistor. Coil was a used unit but was working when I removed it a few years ago.

Checked for any vacuum leaks.

Radiator is full. Used a heat sensor gun and checked the temps on the hoses, heads, intake and exhaust manifolds- all good.



Any input would be appreciated.

 

[Kern Dog]

I've had cars that ran great when they were first started but then were slower once they were up to temp.
My 2007 Dodge truck with a 5.7 is like that. It is more responsive in cold weather than it is even on an 80 degree day. The engine likes the cooler temperatures.
I had a 76 Dodge Dart Sport that was the same way. For the first start of the day, it was really snappy but once warm, it was like the edges were rounded off. That engine was a 100% stock 318.
The 440/495 in my red car seems to run about the same no matter the temperature. I have an air fuel gauge in it and it usually runs within the target spec of high 13s at idle and cruise and high 11s to low 12s at WOT. The ethanol infused gasoline changes the target number from the old standard of 14.7 parts air to one part fuel to the high 13s.
To your issue though...
What if it isn't fuel related but an overheating coil that is failing? I'm not claiming this is absolutely the issue but this can happen. A bad coil can run fine when it is cold but misfire when underhood temperatures rise. Once it cools back down, it can work fine again.
Report back what you find...

 

[3sloppydogs]

Sounds kinda like vapor lock. I had that happen in a w150 with a 360. Once hot no start ran terrible with no pulling power. After trying the obvious thing like a new pump I rerouted the fuel line to the carb and secured it better.
Problem solved it never did it again

 

[Unkle Krusty]

My 318 after sitting for quite a few years, got a new fuel pump, plugs and carb. I had fired the engine with the original carb, but bought a new one anyway. It ran awful, so I took the carb back,and got another one. It ran fine. But I do not think that is your problem. As well as the coil, I would change the ballast resistor thing, and maybe the ignition module, and or the plug wyres.

 

[Charles Cook]

Like KD said, coil.

 

[PurpleBeeper]

Sounds like vapor lock…. But it could be your ignition box. I had a 318 Charger act like that. The back of the ignition box was “gooey” (heat I guess). Replaced the box and problem gone

 

[NHCharger]

Thanks for the quick replies. I installed new plugs and wires when I installed the new intake last year. I did check 4 of the plugs this morning, they looked good. Doubt that it's vapor lock. Car has ran fine for years in the heat, we haven't hit 70 yet this year.
KD. i've pretty much ruled out fuel. I removed the tank last year and cleaned it. Tried two carbs, changed the filter. Like I said I even ran the fuel pump off a 2 gallon tank of ethanol free gas, no change.
I suppose it could be my orange box on the firewall, or maybe my used coil that I swapped in was N/G. I'll try these two tomorrow and report back.

 

[Kern Dog]

Thanks for the quick replies. I installed new plugs and wires when I installed the new intake last year. I did check 4 of the plugs this morning, they looked good. Doubt that it's vapor lock. Car has ran fine for years in the heat, we haven't hit 70 yet this year.
KD. i've pretty much ruled out fuel. I removed the tank last year and cleaned it. Tried two carbs, changed the filter. Like I said I even ran the fuel pump off a 2 gallon tank of ethanol free gas, no change.
I suppose it could be my orange box on the firewall, or maybe my used coil that I swapped in was N/G. I'll try these two tomorrow and report back.

That idiot "B-5" at the Charger forum suggested an alternator or battery?

 

[Rusty knuckles]

Sounds liksquirms even though you changed it. I have had a similar symptom that turned out to be a worn fuel pump push rod. It acted like a vapor lock because the fuel pump wasn't getting full squirts.