Hot Start Issues AGAIN??

[NC Scout]

Ok, I've read some of the other hot start issues that some have had and they seem different than what I have going on. I hope someone can help.

I have a 1971 Scout II with 49000 confirmed miles, 345/727, Holley 2 barrel w/ no spacer that I know of, stock engine other than pertronix. I run 93 octane with leaded additive.

Cold start is immediate with no smoke at all, I mean not even a complete rotation and its running fine and idles fine. No hesitation anywhere, no spark knock, idles perfect and runs great. New tune up all around and new carb rebuild.

If I drive somewhere, say the grocery store, and its off for 20 minutes or so, the truck doesnt want to start at all. It turns over easily, but doesnt fire. I have tried pumping the gas three times before cranking, I have tried pushing the gas to the floor while cranking and have tried no gas at all. Doesn't seem to make a difference, and when it finally starts, it smokes badly and sputters until revved and then runs fine.

I have read about fuel boil, fuel evaporation, fuel seepage back into the tank, carb spacers, oil passages clogged, etc.

Most all of these make no sense to me at all since cold start is perfect. All of these issues would effect cold start I would assume except maybe fuel boil.

Any ideas?? Or am I missing something.

 

[jauringer]

I had a post recently with pretty much this exact problem. It did turn out to be fuel boil. I now add 1/2 oz per gallon of ATF and it's gone.

a quick search should turn up some good information on that thread.

Jason

 

[NC Scout]

Jason, thank you for your reply.

So the fuel in the bowl is getting so hot that it is boiling, correct. Boiling fuel keeps the scout from starting how? And where does the smoke come from, unless its just rich fuel being spit out, it is more black than blue.

Seems that fuel boil would effect normal running, or does new fuel being introduced keep everything cool? Confused!

 

[250gibson]

Seems like it is running rich. Ratio is fine at cold start, then when engine hot, too much fuel, which will also explain the black smoke. Adjust your idle mixture screws, and use your choke if it is manual, or if it is electric, adjust it so it works as it should at cold start.

 

[timscout1]

The black smoke is due to flooding!!! I would check the float level since if high running it can boil out of the carb thru the vent when parked and flood h*ll out of the engine. Do you have the insulating spacer under the carb?? also what is your mileage when running?

 

[scoutboy74]

You really should have the thick base gasket with fuel bowl heat shield in place, specifically to combat this issue. It does make a difference. Its a Holley part number which I don't have, but Thomas and others have posted it numerous times here in the past.

And as a side note regarding octane, unless this engine is some hopped-up high compression mill, burning hi-test fuel is overkill. Unmodified SV8 engines are low compression beasts that gain no benefit from higher octane fuel. The lead additive is also unnecessary, but its your dough and your show to do with as you see fit.

 

[NC Scout]

You really should have the thick base gasket with fuel bowl heat shield in place, specifically to combat this issue. It does make a difference. Its a Holley part number which I don't have, but Thomas and others have posted it numerous times here in the past.

And as a side note regarding octane, unless this engine is some hopped-up high compression mill, burning hi-test fuel is overkill. Unmodified SV8 engines are low compression beasts that gain no benefit from higher octane fuel. The lead additive is also unnecessary, but its your dough and your show to do with as you see fit.

It looks as if I might have a 3/16" gasket/spacer under the carb, the rebuild was done by the PO. I have heard of spacers, but need to search and see where to purchase. Also, I may try the ATF to see of this helps the boil issue.

I'm actually used to 93 octane since I have a Subaru WRX as my DD, so sometimes even fill the minivan with 93 by habit. But if you are correct and it makes no difference as with the Lead additive, I'll stop adding this and go to 87.

 

[scoutboy74]

You don't need a carb spacer. That's a completely different animal and used for a different purpose. If you have the thicker gasket with a portion that extends underneath the fuel bowl, that's the ticket. In all the times that I've put fuel in my binders over the years, I've never put anything but regular in with my only regrets being that even it is way too damned expensive and doesn't last long enough. Some older engines do benefit from the lead additive, but that's not the case with our SV8's. They do just fine on the decaff.

 

[Jay Tabor]

next time you fill up add a half gallon of diesel#2, to the fuel tank. then drive park a few times to notice the change for the better.

.
anyfuel/ any liquid has a volatility point- to where it gasses off at a certain temperaure F.
, turns from liquid to vapor. [grade school science class]
todays fuels have such a low volatility ratio that it will boil from engine heat. old days gas didnt do that.
its all part of the wonderful smog regulations brought to you..
that boiling fuel in the fuel lines or carb turns to vapor and that goes into the engine intake man and then into what ever cylinders valves are open.
this makes for a rich condition, and thats why the engine crank time is longer to evacuate the rich mixture from the manifold and cyls.
and thats why smoke is seen upon start up.
everything that burns produces smoke..
boiling fuel- vapor makes for a super rich fuel to air ratio which cant be ignited.
and high test gas does help in that regard because a higher octane is less volatile than low octane- ignites/burns slightly slower than super race octane 87..
thats why using that gas means less detonation compared to what happens in same engine using that super race fuel 87 with alcohol!

whats confusing about that?

as cool fuel goes into a running engines carb- it is consumed within seconds, its cooler than the carb, so heat is transfered to the cool incoming fuel,
then as it is sucked into the low pressure venturis it gets super cooled momentarily, before it gets into the intake manifold, where it gets heated up rather quickly on the way to the cylinders to be burnt.

 

[NC Scout]

Did some testing without adding Diesel or ATF just to see what was going on. I warmed up the engine in the driveway until the temp gauge got to normal operating temperature, then I cut the truck off.

About 15 minutes later I tried to start the truck and it took a bunch of rotations before it finally started, and it smoked bad.

The carb bowl was barely even warm to the touch so it definitely wasn't fuel boil, any other clue what the issue could be?

 

[Jay Tabor]

just what we stated.
you didnt get the engine hot enough, while idling in driveway. go drive the thing like you normally do...........................
now you can turn off the engine next time and immediately open throttle wide open and hold it there. and look into the carbs barrels and watch the show.

also feel the steel fuel tube between pump and carb. for high temp.
but its usually the fuel boiling/vaporizing in the carb.

you got the correct heat sheild carb base gasket on that race machine?

 

[NC Scout]

I understand what you are saying about the truck not heating up enough and needing to go drive it more. But the issue showed it self with the little bit of warming up in the driveway. I didn't have to completely warm it up by driving around, it still didn't want to start up.

Unless it is being super heated in the mechanical fuel pump, I don't see how it could be fuel boil in the carburetor. I'll post a picture of the gasket when I get a few minutes. It extends under the bowl some in one direction and is fairly thick.

 

[Houston]

sounds to me like a bad automatic choke. I wouldnt press the gas pedal before a hot start. Take the air cleaner off before you do a hot start, see if the choke is closed.

 

[scoutboy74]

I understand what you are saying about the truck not heating up enough and needing to go drive it more. But the issue showed it self with the little bit of warming up in the driveway. I didn't have to completely warm it up by driving around, it still didn't want to start up.

Unless it is being super heated in the mechanical fuel pump, I don't see how it could be fuel boil in the carburetor. I'll post a picture of the gasket when I get a few minutes. It extends under the bowl some in one direction and is fairly thick.

I agree. I think your luke-warm test proves that it is NOT fuel boil. No doubt the engine is getting flooded with fuel every time you shut it off regardless of engine temperature. I think your fuel float level is either too high or sticking. This carb hasn't been properly identified yet either and that needs to be remedied. If its a 2300 model it will have a brass site plug on the passenger side of the bowl.

 

[gmbarker78]

I've been chasing a hot start issue around for a while. I swapped the carb spacer to one of the wooded ones from Jeggs, it reduces the carb heat tremendouslly. I also re-routed the fuel line. Problem still existed. I found that I have an issue with the squirters letting off pressure and flooding when the engine is off. It took me forever to find it but by sheer chance I was looking around the carb and seen a little fuel drip out. I'm just going to do a good cleaning/rebuild and hope it fix's it. Maybe this little tid bit will help someone.

FWIW, float level has been properlly set.

 

[Houston]

also if you stomp the pedal 3 times prior to starting the engine hot, you are flooding the snot out of it. It should start at the turn of the key without any gas pedal action when hot.

Check your oil, if you are flooding the engine on a regular basis, chances are the oil is contaminated with gas.

 

[Jay Tabor]

a rich fuel condition all the time would show up as a bad running engine.
and that may be.
a simple sticking nose in carb after engine is shut off would SHOW WHATS HAPPENING IN THE CARB.
internet guessing wont . .

 

[scoutboy74]

Internet guessing and providing suggestions is all any of us can do. The only person who can do any more than that hasn't responded in over 8 hours. We still don't even know which carb model we're dealing with. Lack of specifics leads to even more guessing. LOOKY HERE. MY ALL CAPS WORK TOO! WHADDA YOU KNOW! I'M YELLING! I'M SPECIAL!

 

[Jay Tabor]

large type ISNT YELLING..ANOTHER OLD WIVES TAKE PUT TO REST..

 

[bull]

on a way out there like in master zen philosophy idea..how are your battery cables??..maybe go up a guage or 2 and buy some quality cables (not autozone ****)..heat is hell on circuits and if your cables are crap it may be worth replacing..heck may be even eliminate the fire hazard of which many times i have seen guys running around with exposed cables and the like..this takes in everything else on your rig is up to snuff like carb, proper tun-up--etc

ps: dont even think about paying for ofc wire (oxygen free copper)..thats a huge scam