Ignition or ........?

Justin Plant

Member
Joined
Nov 11, 2021
Messages
142
Reaction score
136
Location
Moneta, VA
This past Sunday I was going to visit a friend and show him my Royal Monaco. I had to leave a stop light in a bit of a hurry, I should have been in the right lane, but found myself in the left.
I hit the gas and about 60 ft in the car died. The left turn signal light popped on to let me know my key was where I left it. Then, as fast as it died it came right back on and took off. Its never done this. Granted I've only put about 2500 miles on it since Oct. of last year. But, I ran the hell out of it on my trip home from Indiana. As usual, when I buy an old car I go through it, and hit the high spots and some low if needed. Here's what's been done. Cap, Rotor, plugs, wires, coil, ignition module, voltage regulator, all new rubber fuel lines, new gas tank, valve cover gaskets, Weiand intake, Edlebrock AVS2 650. My thought is a loose connection, but where should I start? Occasionally it'll stumble at idle. Otherwise, I can't ask for a better running car. Please advise..... Thanks all!
Oh, just in case 1975, 400 cu, 46k miles. With exception of intake and carb, it's totally stock
 

CBODY67

Old Man with a Hat
Joined
Mar 27, 2011
Messages
7,450
Reaction score
4,577
That lh front fender-mounted turn signal lamp coming on was probably the Fuel Pacer in action? But the engine faltering is not part of that activity, though. Might check the vacuum lines going to the sensor that turns on the light, for good measure.

Otherwise, it might be that, for some reason, the metering rods didn't move and stayed in their "eco" position, so that as soon as the pump shot was consumed, a lean spot happened and the engine faltered, but when you suddenly closed the throttle, all was fine again, momentarily. Then the rods moved and things happened as they should have.

IF it had been a purely ignition issue, it most probably would have repeated itself, I suspect.

Have you been able to make it do something similar again, since then? Might try firmly applying the foot brake with the car idling in "D", then jabbing the throttle to see if it falters again. Or slowly throttling into it. Then, driving it on a vacant parking lot, nail the brakes to see if it will falter then, too.

For general principles and just to see where things are, you might get a carb kit and take the top off the carb to check the float levels. Might not find anything but then you'll know where things are at.

How much fuel was in the tank when it faltered?

Just some thoughts,
CBODY67
 

Justin Plant

Member
Joined
Nov 11, 2021
Messages
142
Reaction score
136
Location
Moneta, VA
Just shy of 1\2 tank. I never considered the metering rods. Good call. The Fuel Pacer will light up the left unit when the key is in the ignition and turned on but engine off, that's why my mind hung on electrical. But, there again if it was electrical I probably would've had to start the car back up. I'll try to replicate it this weekend.
 
Joined
May 30, 2019
Messages
79
Reaction score
102
Location
Portland Oregon
The dumbest reason my 300 ever gave me intermittent trouble was the time the wire to the ballast resister was disconnected... but the terminal was resting on the spade connector so when you looked at it it seemed fine, and they were touching so the current was flowing...

But when I stepped on the gas or brakes a little hard occasionally the connection would open as the wire lifted off of the resistor and she would die. Once she died, the wire would flop back down on top of the resistor and it would work fine. It took me a while to notice that the two parts were separated. Reconnected it and problem solved.
 

Big_John

Illegitimi non carborundum
FCBO Gold Member
Joined
May 21, 2013
Messages
15,714
Reaction score
21,057
Location
Marcellus, NY
The fuel pacer light threw me... I had no idea what you were talking about...

So, was the car still cold? Or not completely warmed up? Since it sounds like it really didn't stall (you didn't say you had to restart it), I'd say it's some sort of carb issue, but if the car was still cold, the choke may have been just coming off and it went lean for a second when the secondaries opened and then once it had fuel (accel pump shot), everything fired and it was good. If it was warm, it still seems like a lean condition and possibly an accel pump adjustment is needed.

I would try to get the car to do the same thing before getting too crazy. A look at the wiring, coil, distributor etc. is all good and not a bad idea, but unless you see something bad, I wouldn't touch it until it does it again.
 

Justin Plant

Member
Joined
Nov 11, 2021
Messages
142
Reaction score
136
Location
Moneta, VA
The car was at operating temp. Although checking the choke is not a bad idea. The carb is new, I put it on in January. I will try to get it to happen again this weekend. Thanks for the pointers.
 

Big_John

Illegitimi non carborundum
FCBO Gold Member
Joined
May 21, 2013
Messages
15,714
Reaction score
21,057
Location
Marcellus, NY
The car was at operating temp. Although checking the choke is not a bad idea. The carb is new, I put it on in January. I will try to get it to happen again this weekend. Thanks for the pointers.
If at operating temp, then think about adjusting the accel pump... If you can get it to do it again that is...
 

CBODY67

Old Man with a Hat
Joined
Mar 27, 2011
Messages
7,450
Reaction score
4,577
The thing to remember is that most of the popular replacement carbs are more universal than not. Meaning they might work decently well out of the box, BUT they can need a certain amount of tuning to match the engine/vehicle where they are installed. Other than getting the hot base idle speed pretty much to OEM specs for the vehicle, optimizing the idle mixture to "lean best idle", AND then adjusting the electric choke (or existing divorced choke thermostat) so that the choke comes off quickly and cleanly, while still allowing good start-up drivability until at operating temp. "Operating temp" which takes about 5+ miles of highway driving (depending upon ambient air temp) for EVERYTHING to get to a stabilized temp, rather than just watching the temp gauge or feeling the heat from the heater.

When we got one of the 1980s "flip front" Corvettes, which had an engine oil temp gauge available in the cluster, I never realized that when the coolant temp is at "operating temperature", that the engine oil is still quite a bit colder. Which also tends to explain the "Severs Use" criteria for 3000 mile oil changes (mostly trips less than 10 miles) rather than the "normal use" 7500 mile oil changes, too. So, just because "the water's hot" does not mean everything else is too, after a full-cooled down start.

Check everything and please advise of what you found.

Enjoy!
CBODY67
 
Top