Tough to start warm
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Mountain Pass
Joined: Feb 2023
Posts: 112
Likes: 47
From: NY
Tough to start warm
I have the 351m and am having a hard time starting it after its been running.
Tonight I drove it for 20 minutes, turned it off and 3 minutes later she wouldn’t go without pushing the pedal all the way down to get it to start. Cold starts I just pump it a few times and she fires right up.
I’m no mechanic but id guess something with the carb?
Just threw in a new set of plugs last week.
Tonight I drove it for 20 minutes, turned it off and 3 minutes later she wouldn’t go without pushing the pedal all the way down to get it to start. Cold starts I just pump it a few times and she fires right up.
I’m no mechanic but id guess something with the carb?
Just threw in a new set of plugs last week.
Tuned
Joined: Jan 2006
Posts: 356
Likes: 78
Zag78F150,
You may be getting a "heat soak" condition where the carb gets warm enough to not supply enough fuel after sitting warm. Now I know the first thing that comes to mind- Why did it not do this from 1978 to now ? One change is that the ethanol in our fuel these days can magnify this problem, the other change could be that your engine is running a little hotter ? The temp gauges in our dents are not very accurate so you could be running a little hotter than you used to and not realize it. An overall check of your cooling system and/or the installation of good temp gauge may be in order. (Of course with fall and winter coming on you may see less of this issue in the short term but it would return again when it gets hot. ) A good way to reduce/eliminate heat soak problems is a phenolic spacer between the carb and intake manifold. Easy to find, Summit Racing has a wide variety.
When you say it is hard to start, I assumed it was turning over good, just not starting. More suggestions will be coming along, a wealth of knowledge on this website !
You may be getting a "heat soak" condition where the carb gets warm enough to not supply enough fuel after sitting warm. Now I know the first thing that comes to mind- Why did it not do this from 1978 to now ? One change is that the ethanol in our fuel these days can magnify this problem, the other change could be that your engine is running a little hotter ? The temp gauges in our dents are not very accurate so you could be running a little hotter than you used to and not realize it. An overall check of your cooling system and/or the installation of good temp gauge may be in order. (Of course with fall and winter coming on you may see less of this issue in the short term but it would return again when it gets hot. ) A good way to reduce/eliminate heat soak problems is a phenolic spacer between the carb and intake manifold. Easy to find, Summit Racing has a wide variety.
When you say it is hard to start, I assumed it was turning over good, just not starting. More suggestions will be coming along, a wealth of knowledge on this website !
Tuned
Joined: Jan 2006
Posts: 356
Likes: 78
Oh, I forgot about Duraspark issues ! Your ignition module can be very subject to acting up when it is warm. The units go bad over time. This is more likely than the carb heat soak I talked about above. Rather than fight with the original Duraspark system, I switched all of my ignition system over an aftermarket system. (MSD) Consequently, I am not the best to advise you as to making changes to your ignition. Plenty of knowledgeable people will be along to advise. This is extremely common with our trucks !
Lead Driver
Joined: Oct 2018
Posts: 7,876
Likes: 2,364
Almost certainly carburation. advancing your timing a little might help.
I'm assuming you're all stock. If you don't need the EGR plug the hole in the intake with a screw and toss it in the trash. put a thick phenolic spacer in it's place, that will help a lot. if you still have problems your carb is probably getting tired and may need help.
This is why you should always block the crossover in your intake unless you run in cold weather a lot. and toss the EGR if equipped. I do this on everything then install a new 4160 and my rigs start hot or cold like they have fuel injection.
I'm assuming you're all stock. If you don't need the EGR plug the hole in the intake with a screw and toss it in the trash. put a thick phenolic spacer in it's place, that will help a lot. if you still have problems your carb is probably getting tired and may need help.
This is why you should always block the crossover in your intake unless you run in cold weather a lot. and toss the EGR if equipped. I do this on everything then install a new 4160 and my rigs start hot or cold like they have fuel injection.
Logistics Pro
Joined: Jun 2018
Posts: 3,553
Likes: 442
X2 on block the cross-over. A phenolic spacer will also help. The wood ones are better than the plastic or aluminum for low profile.
wood carb spacer for sale | eBay
wood carb spacer for sale | eBay
Cargo Master
Joined: Oct 2011
Posts: 2,245
Likes: 302
From: Kenner,La.
No hot start
Another check to do is the “I” terminal on the starter solenoid. With a volt meter you want full battery voltage at that point during cranking. A weak or dead “by pass” circuit shows up more on a hot start than a cold start.
FTE Legend
Joined: Nov 2015
Posts: 30,912
Likes: 4,123
From: Angier, NC
With a clue like "she wouldn’t go without pushing the pedal all the way down to get it to start."
It is a hot carb issue.
Another clue when it fired up did it acted like it was flooded then clear out?
Hot carb.
My take on this, the fuel in the bowl boils from the heat and the fumes get pushed out and out the bowl vent.
Being heavier than air the fumes fill the intake manifold and "flood" the motor.
This is why for you to get it to fire up you have to floor it like it was flooded.
Now that it is getting cooler the gas blend is changed to help EFI cars start faster when cold.
This dose not help us with carbs and even more so it the temp goes up for a few days.
Most of the time you see this as winter breaks and have a few warm / hot days before the blend is changed to summer blend.
EFI systems dont have this issue as it is a sealed system.
I would not say it is the DSII box or the volts from the solenoid "I" post but a easy way to check is look for spark.
Also on the DSII box and the "I" post this dose not supply a full 12 volts to the box like it did for points.
It is a trigger to retard the timing on start up so you dont have kick back when hot if you are pushing the timing advance a lot.
Not all boxes do this but it is the white wire into the box.
Dave ----
ps I have a 300 six and have the same issue on hot restarts.
Thing is I run hot water to the intake manifold to heat it, EFI exh manifolds, as I drive the truck in the winter, 20*f or lower at times.
I believe this is my cause of heating the carb at this time.
It is a hot carb issue.
Another clue when it fired up did it acted like it was flooded then clear out?
Hot carb.
My take on this, the fuel in the bowl boils from the heat and the fumes get pushed out and out the bowl vent.
Being heavier than air the fumes fill the intake manifold and "flood" the motor.
This is why for you to get it to fire up you have to floor it like it was flooded.
Now that it is getting cooler the gas blend is changed to help EFI cars start faster when cold.
This dose not help us with carbs and even more so it the temp goes up for a few days.
Most of the time you see this as winter breaks and have a few warm / hot days before the blend is changed to summer blend.
EFI systems dont have this issue as it is a sealed system.
I would not say it is the DSII box or the volts from the solenoid "I" post but a easy way to check is look for spark.
Also on the DSII box and the "I" post this dose not supply a full 12 volts to the box like it did for points.
It is a trigger to retard the timing on start up so you dont have kick back when hot if you are pushing the timing advance a lot.
Not all boxes do this but it is the white wire into the box.
Dave ----
ps I have a 300 six and have the same issue on hot restarts.
Thing is I run hot water to the intake manifold to heat it, EFI exh manifolds, as I drive the truck in the winter, 20*f or lower at times.
I believe this is my cause of heating the carb at this time.
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Tuned
Joined: Jun 2018
Posts: 458
Likes: 123
From: Arkansas
Some people will disagree, but with modern e10-15 fuel on an old carbureted vehicle: having to depress the pedal and crank an extra second to me is basically normal. Depending on how long a "long" crank time is it may be an issue. Like others have said you can improve it by running a phenolic spacer/trying to insulate your carburetor and fuel lines from the heat. The ultimate fix is to run an electric pump or even a mechanical pump with enough flow to run a return line to the tank so you can clear out vaporized fuel when it heat soaks after you shut it off.
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Mountain Pass
Joined: Feb 2023
Posts: 112
Likes: 47
From: NY
I think you’re right on Dave.
I mostly run no-ethanol but lately I’ve been driving nearly every day as my daily driver trucks in the shop. So I’ve been rotating both non ethanol and reg gas. Deff a difference imo. I will give the spacer a try.
Appreciate everyone’s input!! Thank you!
I mostly run no-ethanol but lately I’ve been driving nearly every day as my daily driver trucks in the shop. So I’ve been rotating both non ethanol and reg gas. Deff a difference imo. I will give the spacer a try.
Appreciate everyone’s input!! Thank you!
Tuned
Joined: Apr 2023
Posts: 363
Likes: 108
i've been over 100*f for well over 100 days this year and this doesn't happen to me... 1/2 choke 1 pump on cold start, 0 choke zero pedal on hot starts, the only time it acts different is when i ask my 8 year old son to start it and he messes around and floods it and then i send my 11 year old daughter out there to start it holding the pedal to the floor.
the only thing i do have is one of those phenolic under my holley.
the only thing i do have is one of those phenolic under my holley.
Hotshot
Joined: Feb 2004
Posts: 10,805
Likes: 2,604
From: The Shenandoah Valley
I currently have the Edelbrock on a 1" aluminum spacer with two gaskets over top of a Performer 400 intake (AFAIK the exh. crossover is open), & manual choke. Plugs are near new. Lately towards the end of the hotter weather and as of yesterday, I have been paying closer attention to "my" starting techniques .... 2 pumps and about half choke, it fires off almost immediately (but 3 pumps and / or more choke seem to push it towards flooding and while just 1 pump and the half choke will just often get it fired off, to keep it running I need to pump again or pull the choke out to about 3/4 which cams in high idle too before it dies).
On a hot restart after a heat soke period, I can stand beside the truck and reach under the wheel and turn the key to start, & it starts at a normal idle, with no pumps & no choking.
I almost hesitate to say it ... I do think it got better about starts after several days or a week unused since I put a "bowl" shape top over the air filter that seems to lessen evaporation.
On a hot restart after a heat soke period, I can stand beside the truck and reach under the wheel and turn the key to start, & it starts at a normal idle, with no pumps & no choking.
I almost hesitate to say it ... I do think it got better about starts after several days or a week unused since I put a "bowl" shape top over the air filter that seems to lessen evaporation.
FTE Legend
Joined: Nov 2015
Posts: 30,912
Likes: 4,123
From: Angier, NC
It seams from the last few posts that if the carb is kept as cool as you can it helps with hot restarts.
When I get the time I need to look into trying to keep my carb cooler as I do have some hot restart issues.
Dave ----
When I get the time I need to look into trying to keep my carb cooler as I do have some hot restart issues.
Dave ----
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