The Stovebolt Site Forums The Shop Area Engine Shop Engine bogs/stalls when braking.

Use a wire to by pass the ignition switch and go straight from the + side of the battery to the + side of the coil and see if you still have the stall. This will by pass the electrical circuit under the dash. You can run it for a few minutes this way to see if the stall continues. If the stall continues then go back to your regular wiring.

If there is a wire bad under the dash, it may be losing contact under hard braking conditions. Might be rare, and may not be that at all.


Make sure distributor advance vacuum source is ported vacuum. You may have to adjust the timing to compensate if you have the advance hooked up to full time vacuum source. This will tend to advance the timing at idle, yet when vacuum drops will retard the timing until the mechanical advance can do its job.

Roy Rodgers, I see what you mean. I will put that on my list if the carb and tranny do not solve the issue. Seems to me though, that that wire would act up not just when I am in Drive/Reverse. She starts real nice, idles and drives nice.

The power glide does not have a torque converter clutch so it won't cause the stall. If your stall is still happening in neutral then you can rule out the tranny since no clutches will be involved.

If you have capped all your vacuum sources and still have the stall I would certainly look closer at an electrical problem causing it under heavy braking.

Good luck. Hope you find it soon. And get the vacuum advance hooked up to ported vacuum.

Roy Rodgers, the vac adv is hooked up to the base of the carb. I do not know if I can call that 'ported' since my understanding is that the base of the carb always has vacuum in it. But the I6 250 has no other hook up for the dizzy. It has been that way for 50 years.

I prefer to have a carb issue than a tranny issue, so I like your post. If it turn out to be the carb, I have to keep this core and find out exactly what was bad with it. If it be electrical, that will take some real doing to find.

Some easy Tranny checks.
Make sure the vacuum line from manifold to modulator valve on the tranny is good w/no leaks.

Pull vacuum line off of modulator valve and check for trans fluid. It should be dry, if fluid is present the valve is bad.

Make sure the modulator valve is tight in tranny.

What fluid are you running in the tranny?

Make sure linkage is properly connected at tranny.

Does the tranny have the kick-down linkage connected?

Good luck
Dave

Volfandt, can I get to that modulator valve without lifting the truck? The fluid is DOT 3 if I recall. Linkage is good. The I6-250 PowerGlide has no kickdown linkage that I am familiar with, but I would have to hit the books. The only linkage I see is the choke and throttle. But I would not know a kick-down linkage if it kicked me in the buttt.

I'm no expert and haven't worked on a PowerGlide in decades so bear w/me.

Trace the vacuum line down to the tranny, it will lead you straight to the modulator valve.

Have you changed the tranny fluid recently or add any? Did the previous owner tell you what fluid was in it? i.e. Type F or Dexron, Dexron II etc.? Sometimes mixing fluids can cause problems.

Since you can manually shift to neutral and not stall the engine, the tranny "may" be all or part of the stalling issue.

On these older auto tranny's, the kickdown linkage is used to shift the tranny from high to low when you floor the throttle pedal giving you increased rpm and power. Again I'm no expert and it could be possible if not probable that the tranny works fine without it connected. I do know from past experiences that it needed to be properly adjusted for the tranny to shift properly in "stock OEM" applications.

The problem could still be engine related, the easy checks I recommended are just some troubleshooting tips to try and isolate the problem.
Good luck
Dave

Volfandt, well what you say makes sense to me. I will check that modulator valve shortly. As for the kickdown linkage, I will have a look at the throttle linkage and see if there is some additional linkage going to the tranny from it. My gut also tells me I have a tranny issue. I am using Dextron III and no mixing has occurred.

I may have misread a post. Does shifting to neutral end the stalling?

Roy Rodgers, when I am driving and I come to a stop sign or red light, I put her into Neutral and then brake. She does not stall.

Roy, he has tried the stop in neutral, without getting a stall. I'm wondering if a loose motor mount is letting the engine shift under hard braking in gear and possibly causing a momentary open or short circuit in the primary ignition wiring.

I'd suggest running a temporary jumper wire directly to the coil + terminal and see if the stall goes away with the ignition switch circuit bypassed. If the engine is running a HEI distributor with a remote-mounted coil, some of that wiring could be compromised and responding to engine torque shifting from bad motor mounts also.
Jerry

Hotrod Lincoln, I HAVE A BROKEN MOTOR MOUNT ON THE DRIVER'S SIDE! SHOOT! But please elaborate as to how that might give the symptom we speak of here.

When I look at new mounts, I find for a few dollars and I find for over a hundred dollars. What is that all about?
http://www.summitracing.com/search/...et/model/c10-pickup/engine-size/4-1l-250

Go to the local parts store to get the mounts. They don't cost much there and they may even have them in stock.

Having a bad motor mount will allow the engine to move or tip to one side more than it should. The movement over time can break a wire inside the insulation where you can't see it.

So try the jumper wire for grins and giggles.

If I were a betting man you have a bad wire that provides power to the coil.

Roy Rodgers, Ok I will try that one. For the grins and giggles. It is no worse than changing all the bulbs in the truck.

Or because of the bad mount its moving enough that the float is way out of spec causing the stall, but I do agree that its probably a fatigued wire.

Roy nailed it- - - -it's possible the movement of the engine on a bad mount is causing a loose connection to break contact, or a wire to short out. Try this - - - -Hold the brakes with the transmission in gear, forward and reverse, and give the throttle a little goose while watching the engine for movement. I think you'll be surprised at how much it moves around. Now look for a piece of the engine wiring harness that might be stretched or pinched as the engine moves. Hard braking while in gear will also allow the engine to move around wits similar results.
Jerry

Yes, I did that. That is how I saw the engine jumping clockwise, almost an inch. But she stalls even with gentle gas, as when I travel just an inch or so. But I am going to check this out real good. And she does not stall if I am in Park or Neutral and I give the hard gas that lifts the engine.

Be interesting to see what you finally figure out. Wish I was closer to look.

I can't see the torque converter in the transmission being a problem since it does not have a clutch inside to lock up. Even with a clutch (forward or reverse ) applied inside the torque converter would still slip.

If something happened inside the torque convert it would destroy the inside and metal filings would be every where.