fuel pump back flow
Thread Starter
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Tuned
Joined: Feb 2013
Posts: 418
Likes: 37
fuel pump back flow
Hello All,
1978 400, mechanical pump.
almost done with the new motor and notice the fuel in the clear filter is always empty after the truck sits. It is a one year old stock mechanical pump. Should these has some form of a black flow preventer or check valve built into the pump or is this a symptom of a failing diaphragm?
Prior to the rebuild i did not have a clear filter and if it sat too long i had to dump a little gas in the carb. no amount of cranking would primp the pump. I am using the same pump on the rebuild. It was only a year old but i guess it has always had problem.
Thanks,
1978 400, mechanical pump.
almost done with the new motor and notice the fuel in the clear filter is always empty after the truck sits. It is a one year old stock mechanical pump. Should these has some form of a black flow preventer or check valve built into the pump or is this a symptom of a failing diaphragm?
Prior to the rebuild i did not have a clear filter and if it sat too long i had to dump a little gas in the carb. no amount of cranking would primp the pump. I am using the same pump on the rebuild. It was only a year old but i guess it has always had problem.
Thanks,
Grumpy goat
Joined: May 2017
Posts: 3,058
Likes: 594
When my truck sits for a day, I notice the clear filter is nearly empty. That's normal for the fuel to slowly seep back down. But if you're having to pour fuel in the carburetor, that means your float bowls are draining into the intake manifold. Mine will do that if the truck sits more than a couple of weeks.
Thread Starter
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Tuned
Joined: Feb 2013
Posts: 418
Likes: 37
When my truck sits for a day, I notice the clear filter is nearly empty. That's normal for the fuel to slowly seep back down. But if you're having to pour fuel in the carburetor, that means your float bowls are draining into the intake manifold. Mine will do that if the truck sits more than a couple of weeks.
Grumpy goat
Joined: May 2017
Posts: 3,058
Likes: 594
If you know it's vapor lock, put a phenolic spacer under the carburetor.
Are you sure it's vapor lock? I once thought I was having vapor lock issues. Turns out my fuel tank wasn't venting. The pump would pull a vacuum on the tank until it equalized and no fuel was coming. Turned out to be a non-vented aftermarket fuel cap I bought.
Are you sure it's vapor lock? I once thought I was having vapor lock issues. Turns out my fuel tank wasn't venting. The pump would pull a vacuum on the tank until it equalized and no fuel was coming. Turned out to be a non-vented aftermarket fuel cap I bought.
Thread Starter
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Tuned
Joined: Feb 2013
Posts: 418
Likes: 37
I made a piece of black walnut for under the carb, It lasted 10 years. When it goes over 100 i had to be careful with the VL. With ethanol in the fuel it boils so easy. I now have a better carb, intake and routed my fuel lines a little better.
We will see with the new set up.
Chris
We will see with the new set up.
Chris
Grumpy goat
Joined: May 2017
Posts: 3,058
Likes: 594
I made a piece of black walnut for under the carb, It lasted 10 years. When it goes over 100 i had to be careful with the VL. With ethanol in the fuel it boils so easy. I now have a better carb, intake and routed my fuel lines a little better.
We will see with the new set up.
Chris
We will see with the new set up.
Chris
Thread Starter
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Tuned
Joined: Feb 2013
Posts: 418
Likes: 37
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Grumpy goat
Joined: May 2017
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You're an evil genius. I'm keeping my eye on you. Note I said, "eye". Only got one that works.
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From: S/W Missouri, Polk county
As I understand it, the clear filter will not stay full when the vehicle is not running, at least it will not on my Bronco. Here is what FTE member put on his fuel line.
Aluminum One-Way Check Valve 8mm Barbed
X2 heat soak/vapor lock install a phenolic spacer.
Aluminum One-Way Check Valve 8mm Barbed
X2 heat soak/vapor lock install a phenolic spacer.
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