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Alot of tank Vacuum

D

duramaxdude

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Carberry, Manitoa, Canada
My Trucks runs perfectly fine but when I go to open the tank after it runs for a bit there is alot of vacuum. If I even let it sit for a few days there is still alot of vacuum. Is this normal. Is it supposed to put air in through the fuel cap or some were else.
 
Your fuel cap will release pressure as defined by the spring pressure in the cap. Vacuum in the tank is a design feature to control foaming of fuel. This is particularly helpful at low fuel levels. Only if you're having problems with stuttering under an extended run at full throttle should you need to worry about excessive vacuum from a malfunctioning fuel cap.
 
Dan Hunter said:
Your fuel cap will release pressure as defined by the spring pressure in the cap. Vacuum in the tank is a design feature to control foaming of fuel. This is particularly helpful at low fuel levels. Only if you're having problems with stuttering under an extended run at full throttle should you need to worry about excessive vacuum from a malfunctioning fuel cap.
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Oh ok. As long as its nothing to be worried about. Thanks for the reply.
 
I just replaced my sending unit and tank on a count the fuel cap. The cap snaps apart , clean the screan and if you feel like poke a couple of small holes in it
 
I gut the caps on my trucks. Read about it a couple years ago. Sounded like the right thing to do at the time. Something about too much vacuum in tank makes the lift pump work harder and possibly the IP work harder. If i remember correctly.
 
Well could it make the lift pump work harder. I put 2 lift pumps a year on and have no idea why. Maybe thats why they go. could it be to much vacuum. I no for a fact i cant have any leaks because my truck sat for a month cause I couldnt afford to drive it and it still had alot of vacuum when I poped the cap to dump fuel in.
 
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