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float bowl empty overnight
#802346 March 20th 2023 3:45 pm
Joined: Feb 2018
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oldpar Offline OP
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Trying to figure out why the carb float bowl is empty overnight.
1979 Dodge b200 360 cid edelbrock 1905 4 barrel carb newly rebuilt and bench tested by reputable rebuilder, new mechanical fuel pump and new fuel filter.
California compliant 2 charcoal vapor cannisters, one has a paper filter and is essentially open to atmosphere.
Watching carb when cranking quite a while cold no fuel from accelerator pump. pour a little gas in carb fires up immediately and runs good. Shut off before chokes fully open and watch again fuel from accelerator pump fine.
can't find any leaks in carb or fuel lines. where to look next? is there any sort of check valve in the vapor or fuel return line that may not be working?

Last edited by oldpar; March 20th 2023 3:49 pm.

1979 Dodge B200 wrangler factory authorized van conversion.
360 cid 727 auto trans NP203 full time 4 wd
Re: float bowl empty overnight
oldpar #802360 March 20th 2023 11:40 pm
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Originally Posted by oldpar
Trying to figure out why the carb float bowl is empty overnight.
1979 Dodge b200 360 cid edelbrock 1905 4 barrel carb newly rebuilt and bench tested by reputable rebuilder, new mechanical fuel pump and new fuel filter.
California compliant 2 charcoal vapor cannisters, one has a paper filter and is essentially open to atmosphere.
Watching carb when cranking quite a while cold no fuel from accelerator pump. pour a little gas in carb fires up immediately and runs good. Shut off before chokes fully open and watch again fuel from accelerator pump fine.
can't find any leaks in carb or fuel lines. where to look next? is there any sort of check valve in the vapor or fuel return line that may not be working?

I might be able to help...
Are you driving it, then putting it in the garage over night, then come out the next morning to find it empty? If so, it may be heat from the engine evaporating the fuel. I say this, because my 383 in my El Camino did the same exact thing. Even if I went for a little ride and stopped to get a bite to eat....20 min or so, come back and carb was enpty and took a little while to refil before it would start again, It had a holley 670 avenger on it, and it would evaporate this cheap fuel we have now out of the carb over flow vent. Thats the only place the vapor can escape from. The charcoal canisters are for tank vapors, they have no effect on the carb overflow vent. You may need to do what i did, and that is, put a small electric pump on it and use it to prime the carb before you start it. Worked great for me.
Hope that helps.


87 G10 with a 92 G20 transplant
Re: float bowl empty overnight
Heavy Metal #802381 March 21st 2023 2:32 pm
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oldpar Offline OP
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Yep, exactly! Thank you
Do you put the electric fuel pump in line and still use the mechanical pump to run on, or replace/ bypass the mechanical pump?
I have seen a couple you tube videos where people put an electric fuel pump in line with a momentary contact switch to prime.
I assume the electric fuel pump has to let fuel run through when not in use. Would it then restrict flow to the mechanical fuel pump?


1979 Dodge B200 wrangler factory authorized van conversion.
360 cid 727 auto trans NP203 full time 4 wd
Re: float bowl empty overnight
oldpar #802384 March 21st 2023 5:02 pm
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oldpar Offline OP
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2 days ago:
cranking engine watching in carb. Accelerator pump moved, no fuel squirt.
Poured a little gas into carb. Fired immediatley, let it run for a couple hours.
1 day ago:
Cranking engine watching in carb. Accelerator pump moved, no fuel squirt.
Poured a little gas in carb fired immediately. Shut off before engine got warm.
Waited about 5 hours. Cranked engine watching in carb accelerator pump moved and a good squirt of gas. Shut off immediately without letting it warm up.
Today: cranked while watching in carb accelerator pump moved and good squirt of gas ran for about 5 minutes. Ran well.
Why now? Thought about it for a while.
We used to live at sea level with really mild weather. This year after retirement we moved away from city to the country at an elevation where it snows. Rather than having to put on required chains or 4wd with snow tires, I thought it would be more comfortable to use the van with 4wd.
In all the years of driving the van it never reached normal operating level always running cold. This never bothered me as the van ran well and could sit a week or 2 still starting on a short crank. Where we live now this cold running made the defroster and heat inadequate, so I changed the thermostat to get a hotter run for better defrost and heat. Could that be it?
I still like the idea of an electric fuel pump to prime the float bowl. Please detail what you have done.


1979 Dodge B200 wrangler factory authorized van conversion.
360 cid 727 auto trans NP203 full time 4 wd
Re: float bowl empty overnight
oldpar #802404 March 22nd 2023 9:27 am
Joined: Oct 2015
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old hand
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Originally Posted by oldpar
I assume the electric fuel pump has to let fuel run through when not in use. Would it then restrict flow to the mechanical fuel pump?

I have this same question, as my bowl will empty after a few days in my 79 and I have to use Ether to get it to reprime. I have a Holley/Mr Gasket pump that I bought YEARS ago and planned to put in just to reprime and never have installed it... I know my [to-be ex] Wife ordered an electric pump to put inline to cure the vapor lock issues she was having. I installed it and had not wired it yet and the van would not start without power to the pump. I took the pump back out of the line and it started right up, so obviously the one she had restricted flow when it wasnt energized.

Re: float bowl empty overnight
NEmery #802412 March 22nd 2023 10:50 am
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oldpar Offline OP
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That is one of the things I wondered about.
The other is if you place one in line that has a flow through design does it restrict the flow any noticeable amount.
There must be some that have that feature as people have done it and it seems to work.Looking at electric fuel pumps on line they never specify.
I would think that you would need one that has a higher flow rate than your current fuel pump and a flow through design.
I suppose if you went to a parts store and asked for the one with the highest flow rate and a low pressure then blew through it you could tell. But I don't know.
It was a lot easier before they started adding corn mash moonshine to the gas!


1979 Dodge B200 wrangler factory authorized van conversion.
360 cid 727 auto trans NP203 full time 4 wd
Re: float bowl empty overnight
oldpar #802432 March 23rd 2023 8:35 am
Joined: Oct 2015
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old hand
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Originally Posted by oldpar
That is one of the things I wondered about.
The other is if you place one in line that has a flow through design does it restrict the flow any noticeable amount.
There must be some that have that feature as people have done it and it seems to work.Looking at electric fuel pumps on line they never specify.
I would think that you would need one that has a higher flow rate than your current fuel pump and a flow through design.
I suppose if you went to a parts store and asked for the one with the highest flow rate and a low pressure then blew through it you could tell. But I don't know.
It was a lot easier before they started adding corn mash moonshine to the gas!


Funny that you SAY THIS, because I was in the garage last night and saw the pump that I have sitting on the cabinet. I took it out of the package and could indeed blow through it. it definitely wasnt a free feeling and took some pressure, but I am sure the mechanical pump would have no problem pulling through it.

Re: float bowl empty overnight
oldpar #802438 March 23rd 2023 11:02 am
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oldpar Offline OP
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For all the questions, effort, wiring and plumbing I now am thinking why not just pull the mechanical pump fabricate a cover plate for the block, run an electric fuel pump and be done with it forever.


1979 Dodge B200 wrangler factory authorized van conversion.
360 cid 727 auto trans NP203 full time 4 wd
Re: float bowl empty overnight
oldpar #802455 March 23rd 2023 11:34 pm
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I did that on a Corvair van I had back in 71. Did it on a 62 Impala in 66. Used clicker pumps.

1 member likes this: oldpar
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