I'm working through some stalling issues on my 71'. The fuel level in my fuel filter varies from about the halfway level in the filter to about 1/2" from the bottom. Does anyone know if the varying fuel levels in the filter are typical for this car? I'm running an original mechanical pump and it's pumping out the fuel just fine. Just going through the process of elimination and this seemed kind of strange. Thanks!

 Over 20 years of daily driving my 71 (mechanical pump), I never once saw my firewall-mounted filter anywhere near full. It drove me nuts for a few years but I never had any fuel starvation problems with a half-full filter, so I gave up worrying about it. Describe the stalling issue.

The car starts fine with choke, idles fine, but is sluggish upon initial acceleration and sounds like it's missing. After it gets going, it runs fine and the power is good. I accumulated a good collection of spares and have shotgunned the coil, condenser, plugs, wires, and ballast. The distributer is original but the timing looks good and advances with increased throttle. I have a second set of SUs and the issue did not change when these were installed. Found a few minor vacuum leaks, fixed them, and they had little effect although it did idle smoother. The spark looked good via the Colortune, but the plugs seem to be a little more sooty than I had expected. Thanks for the feedback, one less thing to think about.

Having a spare set of carbs helps eliminate a lot!

Fuel: weak or sporadic pump, bad tank or lines, too rich?

Ignition: bad coil, bad cap, bad dizzy

More vacuum leaks

Sorry, forgot to mention the problem occurs with a replacement mechanical pump. Didn't exactly measure the flow but it seemed to be pumping out fuel (into a large water bottle) just fine. I'm guessing there isn't a fuel blockage problem if I'm getting a good flow out of the pump? Can the sight-line fuel test be performed if the SUs are still on the car? The dizzy seems to be ok, but it is original. Is there something more I can check on it other than timing/advance? Did have to previously remove the dizzy for some clean-up work. Hope to hell I didn't re-install it a notch off. Thanks!

Forgot to mention that the coil, cap, and condenser have already been shotgunned.

My float chamber lids had loosened over time and caused me some problems. Make sure those screws are snug and the gaskets are complete, no wrinkles.

My filter was low of fuel but after I got the float levels right it stays pretty full at idle. I have '72 carbs though, they're a little different than your's and @Mark Maras

My favorite pic I "borrow" from @zKars (I think) shows it done on the car.

 

Edited January 26, 20241 yr by siteunseen

If the problem started with a new pump I'd run a fuel pump pressure and volume test. Last year there was quite a bit of discussion about new mechanical pumps not working properly.

Thanks, people. Will try these things this weekend. The second pump I tried was an original Nikki. Have purchased two new brand-new mechanical pumps over the years and neither of them had the volume of the Nikki. They are both taking up space on the garage shelf.

How much timing are you running? BTW, you can’t be a tooth off unless you drop the oil pump. Timing is important in these cars. What are you running at idle?

Edited January 27, 20241 yr by Diseazd

I'll check the timing this weekend, set it months ago per recommendations on this forum, don't remember the numbers, though. Didn't drop the oil pump, so the timing should be ok.

Confirmed fuel level in carbs are good, car wouldn't start, dead as a doorknob. Put the colortune on a plug to confirm no spark. Replaced the ignition capacitor and voila, got a nice, bright spark, the car started and idled just fine. Set the timing to 20 degrees and everything looked good. After about 5 minutes the car just stopped. No warning, no rumbling, just stopped. Checked the colortune and confirmed that once again, there is no spark. I had previously changed out the ballast resistor, the coil, points, and ignition cap just because they were very, very, old. I put back on the old coil and ballast resistor, which were working fine when they were removed, to no effect. Not sure what happened to my spark. Going to take a break from the devil car for a while, lest I do some harm to it. Any ideas are appreciated. Thanks.