1966 cranks, but dies after 10 seconds | Ford Thunderbird club group 1955-2005 T-Bird models

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1966 cranks, but dies after 10 seconds

maxval775

maxval775

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Thunderbird Year
1966
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Hello everyone,


I’m having trouble with my 1966 Thunderbird (390 FE). The car will crank, and sometimes it does start up, but it only stays running for about 10 seconds before it bogs down and shuts off. After that, it just cranks without catching.


Here’s what I’ve replaced so far:


  • Gas tank
  • Fuel lines
  • Mechanical fuel pump (the old pump tested at ~2 PSI before replacement)
  • Carburetor (Edelbrock 1405, manual choke, square-bore intake)
  • Carburetor spacer
  • Spark plugs
  • Entire cooling system

The car did run fine right after I installed the new carburetor, but one day it simply stopped staying on. The engine itself ran strong and was very responsive to throttle during those brief moments it stayed on.


I’ve checked for leaks and played with the distributor timing — it’ll kick a little more with adjustments, but still won’t hold idle.


Since the pump is new, I’m trying to figure out if this points more toward timing/ignition, a vacuum leak, or something else I might be overlooking.


Has anyone run into something similar? Any troubleshooting steps or advice would be greatly appreciated.

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How is anyone going to know what your post is about when you title it "1966 390 landeau".

Title revised. Follow the posting directions moving forward.

model-year.jpg
 
74 Harley said:
So, what actual diagnostics have you done? Does the carburetor have fuel? Does it have spark?
Click to expand...
It has spark, I opened the carburetor it has fuel inside the bowls themselves

lcboyer said:
Did you check fuel pressure on new pump? Could you have a kink in the gas line?
Click to expand...
I checked the entire gas line from the tank to the carburetor there doesn't seem to be any kinks, plus I know fuel is getting into the carburetor because there's a clear fuel filter right before the carb I attached to the line and I can see fuel filled it up.
 
Does it die abruptly or stumble and then die?
If it were me, if it starts to die, I’d try some carb cleaner spray down the throttle and see if it try’s to continue to run. If so, it may be fuel related. Have you checked for any vacuum leaks?
If it runs and stops abruptly, then maybe an electrical issue.
 
It stumbles when it dies down, the thing is afterwards it'll crank and fire but not start completely if that makes sense? Now its starting to ping sometimes during crank so im pretty stumped Im leaning more towards timing issue
 
Timotbird said:
Does it die abruptly or stumble and then die?
If it were me, if it starts to die, I’d try some carb cleaner spray down the throttle and see if it try’s to continue to run. If so, it may be fuel related. Have you checked for any vacuum leaks?
If it runs and stops abruptly, then maybe an electrical issue.
Click to expand...
Also im thinking it could be the float level, or needle and seat in the carburetor, im wondering should I just clean and put the old holley carburetor that came on the car?
 
Spark, fuel or timing are generally the only issues that can prevent the engine from starting to run. Once running, any issues with those three can prevent the engine from running smoothly. A significant vacuum leak may make it difficult to start. I once had the vacuum hose running between the carb spacer and pcv valve unknowingly come off the spacer and it wouldn’t start.
Sounds like your trying to get it to just run. It’s a process of elimination.
On the electric side check the points, cap, rotor and coil for spark issues. You can due a rough check of timing by removing the #1 plug for top dead center and making sure the rotor points to the right plug wire.
If spraying carb cleaner down the throttle doesn’t pick up rpms as it starts to stumble then maybe it’s not fuel.
Double check your cold choke setting to make sure it’s shut to start and slightly open when on cold fast idle.
If you can get it to run briefly, put a vacuum gauge on to see where it’s reading. It needs to be in the vacuum range that would be acceptable at idle. I think approx 18 inches
 
Sounds like it's starving for fuel. Measure the fuel pressure or do a pump test to verify the new fuel pump is working like it should. If not, check and make sure the input and output fuel lines on the pump aren't reversed. If that's correct, then the pump might be defective.
 
Ballast resistor? I had a car that did what your is doing and it was a failed ballast resistor. Just a shot in the dark from someone thinking about buying an old bird. Good luck.
 
maxval775 said:
Hello everyone,


I’m having trouble with my 1966 Thunderbird (390 FE). The car will crank, and sometimes it does start up, but it only stays running for about 10 seconds before it bogs down and shuts off. After that, it just cranks without catching.


Here’s what I’ve replaced so far:


  • Gas tank
  • Fuel lines
  • Mechanical fuel pump (the old pump tested at ~2 PSI before replacement)
  • Carburetor (Edelbrock 1405, manual choke, square-bore intake)
  • Carburetor spacer
  • Spark plugs
  • Entire cooling system

The car did run fine right after I installed the new carburetor, but one day it simply stopped staying on. The engine itself ran strong and was very responsive to throttle during those brief moments it stayed on.


I’ve checked for leaks and played with the distributor timing — it’ll kick a little more with adjustments, but still won’t hold idle.


Since the pump is new, I’m trying to figure out if this points more toward timing/ignition, a vacuum leak, or something else I might be overlooking.


Has anyone run into something similar? Any troubleshooting steps or advice would be greatly appreciated.
Click to expand...
Had a similar issue on my 65. Ended up being the ignition switch. Good luck!
 
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