Long crank time when hot.
Moderator
Joined: Jan 2001
Posts: 57,027
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From: Virginia
With my truck, when fighting with a hot restart, I've noticed the starter cranking speed actually increases after a few seconds. Seems kinda odd at first, but I believe this is caused by hot fuel bubbling/foaming out of the carb and getting into the cylinders. All this extra unburnt fuel washes the oil from the cylinder walls. No oil = reduced compression = less load on the starter = faster cranking speed. However, unlike the previous example of a compression release on a motorcycle, even though the engine is spinning more quickly, that hot foamy fuel is hard to ignite and might even foul the spark plugs. Therefore, the cranking time increases.
Cargo Master
Joined: Oct 2016
Posts: 2,738
Likes: 217
From: Northern VA
I'm not sure this problem is not caused by an improper tune. I would triple check timing, A/F ratio mixture adjustments, choke, and vacuum before resigning to the scourge of modern fuel.
Perhaps you could visit a private air field next time you are almost empty and sample some Low-Lead 110 octane aviation gasoline? If that cures all, then you know it's our fuel. If not, then we have some tuning to do.
Perhaps you could visit a private air field next time you are almost empty and sample some Low-Lead 110 octane aviation gasoline? If that cures all, then you know it's our fuel. If not, then we have some tuning to do.
FTE Legend
Joined: Nov 2015
Posts: 30,986
Likes: 4,137
From: Angier, NC
I'm not sure this problem is not caused by an improper tune. I would triple check timing, A/F ratio mixture adjustments, choke, and vacuum before resigning to the scourge of modern fuel.
Perhaps you could visit a private air field next time you are almost empty and sample some Low-Lead 110 octane aviation gasoline? If that cures all, then you know it's our fuel. If not, then we have some tuning to do.
Perhaps you could visit a private air field next time you are almost empty and sample some Low-Lead 110 octane aviation gasoline? If that cures all, then you know it's our fuel. If not, then we have some tuning to do.
Dave ----
Cargo Master
Joined: Oct 2016
Posts: 2,738
Likes: 217
From: Northern VA
I know of a private air field not to far from here that supposedly will sell you av gas.
"At older small airports that sell fuel, there is often a fuel pump location that planes can taxi up to. More often then not today there is simply a fuel truck. Go into the FBO and ask to purchase fuel. He will ask where your aircraft is so he can send the truck to that location. You will tell him that you have cans or a barrel in your vehicle. Generally, that is the entire discussion and he will tell you to pull around to the hanger taxiway entrance and he will send the truck to meet you. People will often drive their car to their hanger space, so there is generally an auto gate. After you are fueled up, you go back in with your fuel slip and pay your bill."
"At older small airports that sell fuel, there is often a fuel pump location that planes can taxi up to. More often then not today there is simply a fuel truck. Go into the FBO and ask to purchase fuel. He will ask where your aircraft is so he can send the truck to that location. You will tell him that you have cans or a barrel in your vehicle. Generally, that is the entire discussion and he will tell you to pull around to the hanger taxiway entrance and he will send the truck to meet you. People will often drive their car to their hanger space, so there is generally an auto gate. After you are fueled up, you go back in with your fuel slip and pay your bill."
Lead Driver
Joined: Apr 2002
Posts: 5,390
Likes: 1,264
+1 on that.
For the moment, I’d hold off on mixing your own fuel blend, etc. Maybe try a different brand of fuel, as previously suggested, but I wouldn’t go much deeper than that for now.
With my truck, a big factor with a hot restart is how I position the gas pedal. I’ve found it works best if I slowly open the throttle about one third of the way. Definitely don’t pump the pedal, as that causes the accel pump to spray extra fuel (and/or foam) into the intake manifold, which makes things worse.
If the first start attempt fails, don’t release the gas pedal until after trying again. Otherwise, the accel pump sprays again, and you want to avoid that.
For the moment, I’d hold off on mixing your own fuel blend, etc. Maybe try a different brand of fuel, as previously suggested, but I wouldn’t go much deeper than that for now.
With my truck, a big factor with a hot restart is how I position the gas pedal. I’ve found it works best if I slowly open the throttle about one third of the way. Definitely don’t pump the pedal, as that causes the accel pump to spray extra fuel (and/or foam) into the intake manifold, which makes things worse.
If the first start attempt fails, don’t release the gas pedal until after trying again. Otherwise, the accel pump sprays again, and you want to avoid that.
Another thing to check is that the choke is wide open when hot. Adjust as necessary.
Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
You should never have to touch the pedal on a hot start.... that may be the issue if the OP is doing that
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Senior User
Joined: May 2014
Posts: 463
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From: Ashton, MD.
I don't touch the pedal when restarting shortly after shutting it down. Usually fires right up if its less than 10-15 min or so (guessing). But if it's longer than that i usually use some pedal. Seems to crank longer if i dont. I was going to experiment next time with not giving it a press before cranking and maybe holding it down a couple inches while cranking.
Cargo Master
Joined: Oct 2016
Posts: 2,738
Likes: 217
From: Northern VA
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Senior User
Joined: May 2014
Posts: 463
Likes: 2
From: Ashton, MD.
650-700 rpm.
When i replaced the carb last summer i got it dialed in pretty decently.
When i replaced the carb last summer i got it dialed in pretty decently.
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