trouble restarting after driving and then sitting for short cool down

[synner88tc]

I have a 71 Jimmy with a stock 350. Mechanical fuel pump. I have a new Edelbrock 600 with adaptor for the stock intake. I bolted the carb on and it ran great out of the box so I haven't messed with anything on it other than idle adjustment. I installed it at the end of the summer when temps were in the 10-15 deg Celsius and now we are in the 0-6 deg Celsius area.

I drive the truck once or twice a week right now and with one press of the gas pedal it will usually fire right up with a few revolutions.

It takes about 10-15 min to get it warm and then it drives fine no issues. If I stop somewhere for a brief cool down 15-30 min it will fire right back up but if I stop for an hour plus it will turn over and over (I stop after 10-15 revolutions to cool starter in-between) and not fire at all and when it finally does it runs very rough for the first 10 seconds or so and requires a lot of gas pedal work to keep it going. Yesterday it took 2-3 min of messing around to get it to fire up.

One area of concern I have is my aluminum fuel filter is pretty close to the heater hose where it connects to the block. I thought perhaps the fuel was getting hot and evaporating from the float bowl but that wouldn't explain why it has issues after one hour but not after one week of sitting.

[sick472]

Soulds like a flooding issue. I wonder if you carb bowl is draining into the intake. I little bit of draining (like 15 minutes) may not cause the flooding, but an hour of draining could be enough to soak the plugs when you try to fire it up...let it sit even longer (all day) and the gas has time to disapate so it's not an issue. I had that trouble with a Quadra Jet once, not sure if the Edelbrock is prone to it though.

Warm it up, shut if off, wait for an hour plus, try to start it once, if it does not start...pull a plug and see if it is wet with gas.

OR, Vapor lock could be the issue, but I doubt it...It would likey give you trouble within that 15 minutes after shut of and after an hour. If the fuel is vaporizing from the line and the carb...it would take some time of cranking before it filled the line and carb back up regardless of how long it sat.

[synner88tc]

Thanks! I will give that a try.

Originally Posted by sick472

Soulds like a flooding issue. I wonder if you carb bowl is draining into the intake. I little bit of draining (like 15 minutes) may not cause the flooding, but an hour of draining could be enough to soak the plugs when you try to fire it up...let it sit even longer (all day) and the gas has time to disapate so it's not an issue. I had that trouble with a Quadra Jet once, not sure if the Edelbrock is prone to it though.

Warm it up, shut if off, wait for an hour plus, try to start it once, if it does not start...pull a plug and see if it is wet with gas.

OR, Vapor lock could be the issue, but I doubt it...It would likey give you trouble within that 15 minutes after shut of and after an hour. If the fuel is vaporizing from the line and the carb...it would take some time of cranking before it filled the line and carb back up regardless of how long it sat.

[57rookie]

I think I can solve this one for you but let me know. Go get a carb spacer - a metal or thick paper one that goes between the intake manifold and the carb. I really like the Edelbrock 4 BBL carter style setup but they usually like some space between the intake and the 4BBl... Cheap and simple.

[synner88tc]

I have the aluminum square bore to spread bore adaptor in there I think that is about an inch think. Are you thinking another one in addition to that?

Originally Posted by 57rookie

I think I can solve this one for you but let me know. Go get a carb spacer - a metal or thick paper one that goes between the intake manifold and the carb. I really like the Edelbrock 4 BBL carter style setup but they usually like some space between the intake and the 4BBl... Cheap and simple.

[57rookie]

That should be suffice.....
Pull the fuel filter and see if when you shake/drain it if rust contamination comes out. Could be as simple as a plugging fuel supply from the filter....

[synner88tc]

Ok sounds good. I will look at that as well. FYI I replaced the fuel line from pump to carb along with fuel filter when I installed the carb and the tank was replaced by the previous owner a year ago. I also installed a pressure gauge and it reads 5-5.5 PSI (bounces back and forth while running. I assume this is a mechanical pump thing?) I have a regulator in a box that I opted to leave out as the pressure seemed good.

Originally Posted by 57rookie

That should be suffice.....
Pull the fuel filter and see if when you shake/drain it if rust contamination comes out. Could be as simple as a plugging fuel supply from the filter....

[Sparky dave]

Yea flooding past the float bowl. Does it start easier if you hold your foot to the floor on the gas pedal ( to clear the flooded engine). Also could choke not be dropping back to closed position for cold start? You removed the air filter to look?

[Sparky dave]

Ps regulator shouldn't bounce me don't think. Does it hold pressure when you turn engine off for a while if not that could be telling you it is leaking past the float bowl

[Sparky dave]

Sorry guys me again I can't sleep so have nothing better to do than try and help. One last maybe and it is a big one. If your fuel line is not air tight between the tank and the pump ( like a loose clamp or a split in the pipe) all the fuel will drain back in to the tank and you will have to crank the fuel all the way back from the tank again. That is if you have a relocated tank at the back of the truck and not in its origional position where it's higher up.

[synner88tc]

Jimmy's and blazers have the tank at the rear of the truck between the frame rails from the factory. So it is in it's typical location. Pickups have the tank behind the seat in the cab.

Seems to me this kind of issue would cause my truck to also not start after sitting a week. If fuel was draining back to the tank wouldn't it also take some time to pump fuel back after a week? thus making my weekly start take multiple revolutions? but after a week it starts up no problem.

Originally Posted by Sparky dave

Sorry guys me again I can't sleep so have nothing better to do than try and help. One last maybe and it is a big one. If your fuel line is not air tight between the tank and the pump ( like a loose clamp or a split in the pipe) all the fuel will drain back in to the tank and you will have to crank the fuel all the way back from the tank again. That is if you have a relocated tank at the back of the truck and not in its origional position where it's higher up.

[synner88tc]

Should it hold pressure after the engine is off? I have never checked. I will check on this as well and report back.

Originally Posted by Sparky dave

Ps regulator shouldn't bounce me don't think. Does it hold pressure when you turn engine off for a while if not that could be telling you it is leaking past the float bowl

[Sparky dave]

Yes it will creep down after a while but as long as it stays up for a little while it shows your float is working

[synner88tc]

Ok. Added to the list of things to check. Thanks!

Originally Posted by Sparky dave

Yes it will creep down after a while but as long as it stays up for a little while it shows your float is working

[Sparky dave]

Originally Posted by synner88tc

Jimmy's and blazers have the tank at the rear of the truck between the frame rails from the factory. So it is in it's typical location. Pickups have the tank behind the seat in the cab.

Seems to me this kind of issue would cause my truck to also not start after sitting a week. If fuel was draining back to the tank wouldn't it also take some time to pump fuel back after a week? thus making my weekly start take multiple revolutions? but after a week it starts up no problem.

Yes rule that one out then.

[El Dorado Jim]

sub'd

[68 P.O.S.]

Edelbrock carbs are known for being finicky with flooding and fuel percolation until they are tuned right. Once tuned right they are a great carb and you won’t have to do anything to it very often.

2 things to cure flooding. 1, fuel pressure needs to be restricted to 5.5 psi per Edelbrock (which you’ve done), or else the high pressure will push the fuel past the needle & seats and flood. 2, the floats need to be adjusted to the specs in the carb manual. Float drop is between 15/16” to 1” and float rise is 7/16”. If the floats are off, which is common right out of the box due to shipping & handling, it will flood too.

For fuel percolation, you have to install a heat insulating gasket between the carb and intake. Otherwise the heat from the intake will get transferred to the carb and start percolating the fuel, resulting in hard starting issues and stalling at idle. The heat insulating gasket should not be metal as it easily transfers the heat to the carb. Obviously a square bore to spread bore adapter is made to install an Edelbrock carb on a stock intake (which is metal), but that is not a heat insulating gasket and will not solve the percolation issue. Now the problem is, I don’t know that a square bore to spread bore heat insulating gasket is made. Hopefully someone knows for sure and will chime in on this. If not, you’ll either have to deal with the percolation, or install a square bore intake manifold on it with a heat insulating gasket.

[synner88tc]

Looks like I can get one of these black phenolic plastic spacers. https://www.edelbrock.com/carburetor...stic-8710.html

I will have to check if I have the height clearance to add another inch as I already have an air cleaner riser. I plan to change over to an edelbrock intake at some point but not right now.

I will get a gasket kit and check the floats.

Could the percolation also be caused by my the fuel heating up to much in the fuel line by being too close to that heater hose?

I may ditch the chrome edelbrock hard fuel line that I have on the carb so I can relocate the fuel line away from it.

Thanks!

Originally Posted by 68 P.O.S.

Edelbrock carbs are known for being finicky with flooding and fuel percolation until they are tuned right. Once tuned right they are a great carb and you won’t have to do anything to it very often.

2 things to cure flooding. 1, fuel pressure needs to be restricted to 5.5 psi per Edelbrock (which you’ve done), or else the high pressure will push the fuel past the needle & seats and flood. 2, the floats need to be adjusted to the specs in the carb manual. Float drop is between 15/16” to 1” and float rise is 7/16”. If the floats are off, which is common right out of the box due to shipping & handling, it will flood too.

For fuel percolation, you have to install a heat insulating gasket between the carb and intake. Otherwise the heat from the intake will get transferred to the carb and start percolating the fuel, resulting in hard starting issues and stalling at idle. The heat insulating gasket should not be metal as it easily transfers the heat to the carb. Obviously a square bore to spread bore adapter is made to install an Edelbrock carb on a stock intake (which is metal), but that is not a heat insulating gasket and will not solve the percolation issue. Now the problem is, I don’t know that a square bore to spread bore heat insulating gasket is made. Hopefully someone knows for sure and will chime in on this. If not, you’ll either have to deal with the percolation, or install a square bore intake manifold on it with a heat insulating gasket.

[synner88tc]

Or maybe this is even better.

https://www.amazon.ca/Edelbrock-9265...GX3FHKSRX3GQHJ

[garyd1961]

My truck with a Holley and electric fuel pump does this also but not as bad as yours. Mine will do it every once in a while and only takes a few revolutions to start up. I've added a heat spacer and changed the filters but it still does it every so often. I'm thinking it's the carburetor but it runs good otherwise, may try a new carb someday just to see if that is what doing it.