Engine Stalling when Braking

[Rob_M]

Hey Guys,
I have a 68 427 Biscayne w/original power 4 piston disk brakes that has an issue when braking. After the car is fully warmed up, when I brake the engine stalls. As an example I will put it in neutral going 30 mph hit the brakes, and it stalls. If I take my foot off the brakes quick enough the engine will resume. It's as if I turn the key off and on quickly. It will even do this when in gear. Of course it dumps raw gas in the exhaust and I get a *very* loud pop out the back when I let up on the brakes.
I have checked for vaccuum leaks, blocked the vaccuum booster, adjusted the floats, (has a Holly), checked for loose wiring near my brake pedal and engine bay, etc - Nothing.
I am at a total loss on what is happening. I plan to replace the check valve that is on the front of the brake booster but like I mentioned earlier it still does it when the booster is unplugged & vaccuum is blocked. I have noticed it doesn't do it when the car is cold and when I go backwards.
Any ideas or thoughts would be greatly appreciated.

Thanks,
Rob Mansfield

[TDW]

Air cleaner cover just touching the coil wire when braking? Coil wire loose? The 12 volt wires, not the center coil wire? Bad connection at the horn relay? Ignition switch wire loose?

[PeteLeathersac]

Could the wiring be mixed up where the ignition feed is somehow connected via the under-dash brake light switch?.
The hot/cold difference is perhaps it's own problem but it's possible someone's wired things up so the reverse lights are supplying ignition power while backing up?.
Run a hot-wire + battery to + coil and see if it still happens when you step on the brakes?.

Goodluck!.
[img]<<GRAEMLIN_URL>>/beers.gif[/img]
~ Pete

[SS427]

What about parked, running and the brakes applied. If it still does it then it is likely related to electrical. If not, likely fuel related or like Tony mentioned. I would also experiment with driving down the road and VERY gently applying the brakes though enough to slow the car over time. If it stalls, I would again look at electrical. If it does not, look for fuel related.

[Rob_M]

Well..... I'm a little embarrassed. After checking all the wiring, a friend suggested checking the floats again. Sure enough I had the springs in backwards!
[img]<<GRAEMLIN_URL>>/smile.gif[/img]
Thanks for all of the assistance!

Rob M

[mockingbird812]

Looks like Rick gets the prize. Glad you got it figured out. Nothing to be ashamed about, most of us have been there before! There seems to be a healthy dose of folks 'round here willing to help out a fella when he's havin' issues! [img]<<GRAEMLIN_URL>>/beers.gif[/img]

[TDW]

Glad ya got it fixed Rob. Are any of you Kazoo guys heading to Flint for the &quot;Back To The Bricks&quot; next month? Should be a real good show again.

[Rob_M]

Hey Tony - Probably not this year but I have heard good things about it. I will be at the Grand Rapids cruise though. I've been there every year since it started and it gets bigger every year. I usually park my car at Berger Chevrolet.... I've been to the Woodward cruise and I think the Grand Rapids one is bigger!

[Rob_M]

Well I was/am a little premature on the success of my repairs. The car is really doing it now - Every time I hit the brakes the engine dies. I bypassed the ignition switch in the dash but no luck. I went around the whole car while it was running and shook wires including under the dash but nothing.

I also installed another carb that I had, and the car still died while braking.

I have a MSD box and distributor so I'm wondering if I need to find another distributer to test that out.....

[njsteve]

Did you disconnect the brake light switch to see if the car still dies when the brakes are applied? Could be a 12v wire crimped against the firewall by the brake bracketry - when you apply the brakes, the bracketry shifts and grounds the wire and backfeeds the car into a 12v positive ground system.

When I pulled my 69 Z11 pace car apart I found a main power lead wire from the dash harness clamped between the brake/clutch pedal assembly and the firewall. It would have eventually caused one helluva electrical fire.

Also, one of the brake light bulb assemblies themselves could be internally shorting to ground when the power goes to the bulb. From experience I know the Mopars are extremely sensitive to a bad ground on the tail lights - so bad that they backfeed all the other lights in the car when the brakes are applied, if the ground is not good enough.