Hard starting when sits overnight
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Elder User
Joined: Mar 2006
Posts: 670
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From: Western, PA
Hard starting when sits overnight
So my truck that has always been great at starting right up even on the coldest days is starting to develop an issue. When you let it sit over night it's been extremely hard to start. Have to do a lot of cranking and peddle pumping. When it Has just been run within a few hours it starts right up. Ignition has just been tuned up. Almost like it's loosing it's fuel prime overnight. The carb doesn't appear to be leaking, is there any other way for fuel to escape the float bowl? I'm wondering if maybe a pin hole in the line could cause this or it's just time for a carb rebuild. Any ideas and input would be appreciated, thanks.
Lead Driver
Joined: Oct 2018
Posts: 7,871
Likes: 2,360
I've had this problem with lots of AFB's ( Edelbrock's ) and I cannot figure out why. even newer ones. they absolutely do drain out and I can't explain it, you have to crank them back up. . I have pulled them apart to verify it.
As if one needed another reason to run a Holley anyway.
As if one needed another reason to run a Holley anyway.
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Elder User
Joined: Mar 2006
Posts: 670
Likes: 0
From: Western, PA
Stock 2100 style carb. Yes the choke seems to be working. It's actually been the best operating choke I've ever had on one of these trucks. All last winter three pumps of the pedal it would fire right up and run on fast idle until I kicked it down. I should also add when I try to start it now in the morning it fires for a second or two right away then stalls, then it takes a minute or so of cranking after that.
Laughing Gas
Joined: Apr 2018
Posts: 1,244
Likes: 12
A few things come to mind....
The carb is draining out, but there is some fuel in the accelerator pump giving you enough for a few seconds of running.
Maybe there is a small hole or leak in the fuel line causing it to drain out. You have enough fuel in the carb to start, but then the line is empty.
Has it been particularly hot in your area lately? Maybe your fuel is evaporating/boiling out? You could try taking the air cleaner off and putting plastic wrap over the carb the next night you park it, take it off in the morning and see if it starts as normal. If it does then you know the problem is the fuel evaporating over night.
Do you get fuel at the same place regularly? Is that place pretty busy, meaning they go through their tanks quickly? If somehow you are getting a winter mix, it will definitely boil off in the summer heat.
Do you have fuel with no ethanol available in your area? If so, try a tank and see if it resolves the issue. If it does, then this also points to your fuel boiling out of the carb.
The carb is draining out, but there is some fuel in the accelerator pump giving you enough for a few seconds of running.
Maybe there is a small hole or leak in the fuel line causing it to drain out. You have enough fuel in the carb to start, but then the line is empty.
Has it been particularly hot in your area lately? Maybe your fuel is evaporating/boiling out? You could try taking the air cleaner off and putting plastic wrap over the carb the next night you park it, take it off in the morning and see if it starts as normal. If it does then you know the problem is the fuel evaporating over night.
Do you get fuel at the same place regularly? Is that place pretty busy, meaning they go through their tanks quickly? If somehow you are getting a winter mix, it will definitely boil off in the summer heat.
Do you have fuel with no ethanol available in your area? If so, try a tank and see if it resolves the issue. If it does, then this also points to your fuel boiling out of the carb.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
First, with the engine OFF ensure that the accelerator pump discharge nozzles are squirting fuel. With a good light look down the carb and move the throttle a few times, should see two steady streams or squirts of gas immediately each time throttle is goosed. The pump diaphragm may be torn, modern gas eats the cheap stuff up. But that's what provides the juice when pumping for a cold start.
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Tuned
Joined: Jan 2006
Posts: 356
Likes: 78
Gentlemen,
Is it possible that the fuel pump is allowing the fuel to drain back towards the tank. (In addition to the carb possibly draining out.) If I remember correctly, the fuel pumps are supposed to have a "check valve" of some sort to hold the fuel between the pump and the carb. (I know to have a defect in the pump and the carb at the same time is a little unlikely, but can happen)
Is it possible that the fuel pump is allowing the fuel to drain back towards the tank. (In addition to the carb possibly draining out.) If I remember correctly, the fuel pumps are supposed to have a "check valve" of some sort to hold the fuel between the pump and the carb. (I know to have a defect in the pump and the carb at the same time is a little unlikely, but can happen)
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Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
A failed fuel pump check valve would not empty the carb, nor would a leaking fuel line.
There are only 2 ways for the bowl on a 2100/2150 to empty its self.
Evaporation which is possible but seems unlikely given your symptoms. If the carb was getting hot enough to cook the fuel out of it, it would happen within a couple of hours when the engine was still hot. So since you are not having starting issues after the truck sits for a couple/few hours, but only overnight then it probably is not that.
Second is a failed power valve. If the diaphragm has ruptured or is leaking it would take several hours for the carb to empty. Given your symptoms, the first place I would look and the most likely cause of the problem is the power valve.
This is provided you have no external leaks (accel pump) Even if the accel pump diaphragm failed, the bowl still be near half full of fuel. But you may not get a pump shot when starting.
There are only 2 ways for the bowl on a 2100/2150 to empty its self.
Evaporation which is possible but seems unlikely given your symptoms. If the carb was getting hot enough to cook the fuel out of it, it would happen within a couple of hours when the engine was still hot. So since you are not having starting issues after the truck sits for a couple/few hours, but only overnight then it probably is not that.
Second is a failed power valve. If the diaphragm has ruptured or is leaking it would take several hours for the carb to empty. Given your symptoms, the first place I would look and the most likely cause of the problem is the power valve.
This is provided you have no external leaks (accel pump) Even if the accel pump diaphragm failed, the bowl still be near half full of fuel. But you may not get a pump shot when starting.
Lead Driver
Joined: Jun 2006
Posts: 5,654
Likes: 979
From: Near Yosemite CA
X2 on the power valve, had a small hole in one I had just rebuilt carb on a few months previous, it would leak out and evaporate off from the heat of the engine.. 4 screws and 7 or 8 bucks to NAPA and all was good.
FTE Legend
Joined: Nov 2015
Posts: 30,904
Likes: 4,122
From: Angier, NC
The carb needs venting.
When putting fuel in to the bowl the air has to go somewhere and then when the fuel is taken out if air did not go in you would have a vacuum and no fuel would go into the carb to run.
Its just like the vented gas cap. If it sits out when it gets hot it wants to expand and if it had no where to go then what?
Pulling fuel out if it was not vented it would be in a vacuum and the pump could not pull fuel.
That is why when having fuel issues like running out of gas the first thing to do is remove the gas cap and do test runs.
Dave ----
When putting fuel in to the bowl the air has to go somewhere and then when the fuel is taken out if air did not go in you would have a vacuum and no fuel would go into the carb to run.
Its just like the vented gas cap. If it sits out when it gets hot it wants to expand and if it had no where to go then what?
Pulling fuel out if it was not vented it would be in a vacuum and the pump could not pull fuel.
That is why when having fuel issues like running out of gas the first thing to do is remove the gas cap and do test runs.
Dave ----