Engine stalls going over speed bumps

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DartThis74

DartThis74

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I'm not sure if this is the proper thread to post in,but just as the title reads, my dart stalls when I slowly go over speed bumps. In order to keep my headers from dragging on the speed bump, I take it nice and slow over them. In doing so it causes the engine to die. Could it be that too much load trying to roll over the bump that it is dropping the rpm too low? I believe the idle is set near 750. I have a 360 with a 2k stall converter in a 727.
 
sounds like you are running lean at idle. IT should have plenty of oomf at idle. How high does your car idle in N? what drop in D....it shouldnt be more than about 100 rpm especially with a 2K stall. What carb, could your bowls be low?
 
I can check on that, I did take it to a mechanic that works on carbs and engines, as well as races himself and he set the carb up at least by ear anyway. It idles nicely and doesn't seem too low. I need to get a tach gauge to check the difference when switching from N to drive. I just moved the car to Houston where I live and I don't have any tools with me yet...
 
Unless you have a completely wrong rear end ratio, then it can only be one of a few things, one would be float level too high and sloshing fuel. two would be electrical connection. If it instantly restarts after speed bump, does it blow a cloud of black smoke like a overly rich condition? Does it restart but, loaded up? What happens if you hit a bump at speed?
does it seem like fuel or spark when it dies? If you keep your foot on brake but keep rpm up with throttle does it still die? Drive-ability issues require a lot of logic and elimination of components. Eliminate as many causes as you can and concentrate on symptoms and conditions. Change speed, rpm, etc. If you jack front end up and try to start car, does it run correctly? Have you checked float level? Holleys have level screws and should be even with bottom of hole, Edelbrocks/AFB's are checked by float drop. What happens when its running and you "bounce" suspension by shoving on fender?
 
It is a Holley 750 and the rear end gear is 3:23. Those are very good suggestions. I had to go over two speed bumps yesterday and it died on both. That was the first it had ever done that. In the past it seemed like it wanted to try and do something like die, but it never did. Once I got it to my garage I parked it.. I'll have to go out and check on those suggestions. Thanks for any thing !
 
If it dies instantly or almost instantly, I would tend to suspect an electrical connection. If it sputters and dies, I would more suspect a fuel issue or low idle issue.
 
Hmmm... I does seem to want to die almost instantly when I go slow over it. But I can drive the car all day long and hit bumps in the road and nothing happens. Maybe hitting bumps in the road is so fast that the car doesn't have time to react to any electrical disruption?
 
DartThis74 said:
Hmmm... I does seem to want to die almost instantly when I go slow over it. But I can drive the car all day long and hit bumps in the road and nothing happens. Maybe hitting bumps in the road is so fast that the car doesn't have time to react to any electrical disruption?
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The difference would be that a bump is a bump, the speed hump is an up and down motion. It's possible something (in the harness, something grounding out) is moving just enough at that particular moment to kill the ignition.

Certainly worth a look.
 
Bad Sport said:
Great minds think alike, lol.
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I guess that lets me out LOL..

OP, try jiggling the ignition switch while it is running. Seems like I knew a lady who had a similar issue; her key set was very large and heavy and it wore the ignition switch out eventually, and it would die wierdly. Just one of many possible electrical points to check. And the 'dies instantly' just makes it more likely that it is electrical; it could still be something else.
 
I don't know if it would be your problem. But a few months ago I was driving my dart and it randomly started driving funny, I was driving home so I was going to take a look when I got home. The idle changed and it ran funny in traffic. Before it did that the oil pressure dummy light started blinking. So I freaked out for a bit then remembered it wasn't hooked up and my mechanical gauge was showing good pressure. Then it died. I pulled over and looked under the hood, the wire for the oil pressure sender was grounding out the coil! So I wasn't getting good spark.

It happened after I hit a few bumps in the road that must have wiggled things around. Was a 1 minute fix and it fired right back up. I'm sure your problem is something simple too.
 
If its fuel level related, driving at speed with higher rpm, the engine would be much more able to swallow a big gulp of raw fuel than at idle. It would also depend on how your jetting is, if its already super rich, fuel will defiantly kill the engine. while idling, dump a tablespoon of fuel down carb. That will eliminate or illuminate it being fuel related.

Many older vehicles electrical problems start at the bulkhead connector, where loom passes through the firewall. Pull the connection apart and clean up contacts, then coat thin film of dielectric grease on the contacts. You can also wiggle connector while idling.
 
DartVader - I do not have a regular coil on this car anymore. I upgraded the electrical to an GM HEI kit. The "coil" is now up on the inner fender near the windshield washer reservoir.
 
Everyone I finally got to take a video of the occurrence happening when driving over the speed hump. This really kinda seems like a fuel issue instead of electrical now. What are your thoughts. Please check out the video. [ame="https://youtu.be/5m4BsILbAlM"]https://youtu.be/5m4BsILbAlM[/ame]
 
Sounds like it's reacting to coming back down to idle and nothing to do with the speed bump to me.
Can you recreate that by holding the brakes in gear and giving it a little gas and let off suddenly?
 
TrailBeast said:
Sounds like it's reacting to coming back down to idle and nothing to do with the speed bump to me.
Can you recreate that by holding the brakes in gear and giving it a little gas and let off suddenly?
Click to expand...
x2... sounds like a sudden lean condition with the quick throttle closure.
 
TrailBeast said:
Sounds like it's reacting to coming back down to idle and nothing to do with the speed bump to me.
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Agreed.
DartThis74,
If I may impose, how about another vid ?--- say up to 15 MPH, bump is coming up,
YOU LIFT OFF throttle , & roll over bump & lets see if inertia kills the car.
 
TrailBeast said:
Sounds like it's reacting to coming back down to idle and nothing to do with the speed bump to me.
Can you recreate that by holding the brakes in gear and giving it a little gas and let off suddenly?
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That is what I'll plan on doing tomorrow. I was thinking on this, if the idle is a little too low to begin with, it would stubble when trying to bring itself naturally to idle rpm right after going over would it ?
 
DartThis74 said:
That is what I'll plan on doing tomorrow. I was thinking on this, if the idle is a little too low to begin with, it would stubble when trying to bring itself naturally to idle rpm right after going over would it ?
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You might get the same results by just holding the brakes and giving the throttle a quick stab.
Or buy holding the brakes, give it a little throttle for a few seconds and let off quick.
I'd bet it does the same thing without the car even moving.
 
mech1nxh said:
Agreed.
DartThis74,
If I may impose, how about another vid ?--- say up to 15 MPH, bump is coming up,
YOU LIFT OFF throttle , & roll over bump & lets see if inertia kills the car.
Click to expand...

I don't think I could do that lol. The speed bump is pretty high and my headers are about an inch away from hitting just slowly going over it. I'll try the foot on the brake and a quick throttle response instead.
 
DartThis74 said:
I don't think I could do that lol. The speed bump is pretty high and my headers are about an inch away from hitting just slowly going over it. I'll try the foot on the brake and a quick throttle response instead.
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Lol, really ? My thoughts were predicated on taking YOU out of the 'inertia failure'
equation.
Try a smaller bump at say 20 mph !!! D=RxT. pretty sure the distance traveled @
20 mph is 29 feet ( rounded down ). ??? Headers ??? .

Apologies Honored Posters, I am out of this one.
 
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