I recently posted an issue with the fuel gauge on my 1969 Camaro and got the problem solved very quickly by a couple of great board members. Thanks Vette-Freak and 69-Pace! I’m back again with another puzzler—at least for me—that I’ve been battling for a couple of months now. As usual, thanks in advance for your thoughts.
After I drive the car normally and then let it sit for a few hours, I can start the engine but then really struggle to keep it running. For about 20 seconds, it stumbles like it’s running on only half of the cylinders and then smooths out and is fine. Of course, this only happens when everyone’s watching. It’s a real crowd pleaser among anti-Camaro crowd at the local drive-in on Saturday night. Supremely embarrassing.
In many other situations, especially ones that don’t involve Camaro haters, like in the morning after sitting in the garage, after stopping at the drug store for a few minutes, etc., the car starts and runs fine.
Also, there is a raw fuel smell very often when driving. Prior to the installation of the phenolic spacer (see below), I noticed the fuel boiling off in the primary and secondary bowls.
The general setup:
What I’ve done so far:
- 1969 Camaro purchased about 4 months ago (We’re still in the wooing phase and getting to know each other.)
- 427cid, stock heads, cam
- Road Demon 750 (vacuum secondary), electric choke
- Stock cowl induction air cleaner assembly
- HEI ignition
- Mechanical fuel pump, no return line
- 92 octane Chevron with “up to 10% ethanol” (With my luck, it’s right at 10%.)
What I HAVE NOT done:
- Double-, triple-, quadruple-checked for fuel leaks; none detected
- Checked that choke linkage was not obstructed by air cleaner assembly
- Inspected distributor cap, spark plug wires; look new
- Installed new spark plugs
- I thoroughly disassembled, cleaned and rebuilt the carburetor with the usual new bits
- Bowl floats set so fuel is near the bottom of the sight glasses
- Installed ľ” phenolic plastic spacer between carb & intake
- Measured spark timing, 12 (initial), 38 (all-in)
- Set idle mix screws as per Demon, then adjusted for maximum manifold vacuum at a constant rpm
- Set primary fast idle when warm to approx. 850 rpm
- Replaced plug wires, distributor cap or coil—because it’s all looks fairly new, but I don’t know for sure.
- Measured fuel pressure—because I wouldn’t expect pressure above 7 psi from this mech. pump, but I don’t know for sure.
- Constantly monitored for fuel boiling in the bowl after each drive--because I think it's not boiling off now and I don't know where to go from here regarding heat soak
My gut feeling is that the problem is carb-related. Unfortunately, I don’t have another carb laying around, and can’t justify (yet) purchasing another one simply for testing. If this persists, I might just break down and get one. (Any suggestions which one?)
Also, I noticed that there was still pressure in the fuel bowls after the car sat for a while and when I loosened the float set screws and fuel spurted out. This is normal, right?
The main question:
What might be happening immediately after starting after sitting for a few hours? Do fouled plugs cause the rough running? If so, do they stay fouled? How do I check for this condition prior to starting?
I really don’t want to have to start parking in the dark back corner of the drive-in parking lot so no one notices me. Thanks for your input.