Dies on speed bumps/sudden spots

[mistaake]

I'm pretty sure it is that carb issue where it dumps fuel in since when it restarts there is a huge cloud of black smoke. When it happens am I better of putting gas pedal all the way down while cranking, or doing nothing and just cranking it until it starts again? I know on newer cars putting gas pedal all the way down puts in in "clear flood mode" but IDK if that applies on 70s carbed stuff like this.

The fuel gauge does actually seem to work. After completely filling it, at about half on the gauge I had to put in like 19 gallons to fill it.

I don't think it's an electrical issue because it always starts up like normal if I crank long enough.

I'm thinking of changing fuel filters as well because who knows when they were last changed. Not sure what to do about carb because I sure can't fix it myself.

 

[highdesertrange]

what kind of carb? highdesertranger

 

[Quadrajet Power]

Float can get hung up, or set a little high, or low.
Drain down after shut off may be causing the excess fuel when starting up after sitting.
I can fix your carb better than new for much less than any replacement. It probably needs a complete refresh.
Changing filters also good idea. I do include new filter in fuel inlet in all my builds.

 

[mistaake]

Float can get hung up, or set a little high, or low.
Drain down after shut off may be causing the excess fuel when starting up after sitting.
I can fix your carb better than new for much less than any replacement. It probably needs a complete refresh.
Changing filters also good idea. I do include new filter in fuel inlet in all my builds.

hi, it only releases a big puff of black smoke when trying to get it to restart after dying from a bump. on a normal start the exhaust is clean.

 

[mistaake]

ok so new carb from mark should be here in the near future i'll report back if it solves the problem. if not, i will at least know i have a nice refreshed carburetor that will give me the best driveability and fuel "economy" possible for a 1977 suburban

 

[mistaake]

well **** - yesterday on the way home from work the truck left me stranded.

basically what happened is i was accelerating when some ass in a tesla cut me off and i had to brake moderately hard. the truck didn't seem to die completely but started vibrating and running really rough, and there was a major loss of power. i floored it in order to keep going, and it just kept slowing down, until it just died completely.

i kind of drifted off the road into a safe spot but then subsequently trying to restart the truck it sounded different than usual and smoke started coming out from under the hood. everything under the hood visibly looked ok.

of course, over half an hour later when the tow truck showed up it started up perfectly and ran fine and we drove it onto the tow truck. and then at the shop we were able to start it right up and drive it.

my theory is that i was having the same float stuck issue and that i simply cranked it too much and maybe the wire to the starter was smoking, but i've had to crank the truck for a while before and it never did that. any ideas appreciated.

 

[yevgenievich]

any loose power cables(battery/ground/etc..) can arc and create smoke when cranking. Also could be vapor coming back through carb if it was trying to fire but too rich.

 

[da_raabi]

Call me crazy, but does this always happen while braking?

What kind of brakes do you have - vacuum or hydro?

 

[mistaake]

Call me crazy, but does this always happen while braking?

What kind of brakes do you have - vacuum or hydro?

Hey there, honestly it's hard for me to tell whether it starts to die after I've already started braking. I will be driving it home from the shop later today, so next time it happens I'll try to pay closer attention.

The shop found nothing wrong with it besides being a quart low on oil (not a big deal) and while they were unable to replicate it driving, there is a dip in their parking lot that I took way too fast (to test), and it did die there. After two cranking sessions it started again.

They're pretty sure the issue is fuel related. They are confident that the new carb I ordered will solve that, but also said to change the fuel pump and be sure to change any fuel filters while I'm at it since that's cheap. They also told me to dump two things of Seafoam into the gas tank in the mean time. Once/if I get it home, I'm probably not going to move the truck until the new carb shows up.

 

[highdesertrange]

from your description it sounds like it's flooding. I am 99% sure of this. Sea Foam and fuel filters are not going to help. if you described it to the shop the way you did here it should have been obvious to them and they should have been able to replicate it. highdesertranger

 

[Ivan_Drago]

My ‘81 did this exact very thing today. Hit a sharp speed bump and died. Smelled like fuel under the hood. Let it sit for a bit and it fired up. I did check all the batt wires and distributer wires. All were good. Gonna throw a Holley on it.

 

[K201979]

Mine does this on steep, bumpy inclines. Im guessing the float level is too high. Doesnt do it often enough for me to tear into it. Just hold it wide open, clear it out, n it starts right up.
Edit: steep, downhill inclines. Never has done it going up

 

[dvdswan]

Bumps, moderate to hard stops... sounds more of an electrical (loose connection) rather than a fuel issue. Shifting cables. If the float level in the carb is off this can happen, but it wouldn't be instantaneous.

I would start with the battery connection to the starter for loose or corroded connections, then start checking you grounds. Just because the connection is tight doesn't mean its good also.

 

[theblindchicken]

Happened to me going over a pretty harsh speed bump. Ended up being that the float got stuck in the bowl after it reached a certain point.

Swapped out the float for a new one and never had the issue again.