fuel puzzle
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Elder User
Joined: Mar 2004
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From: mohave valley, arizona
fuel puzzle
1990 f150 4.9. started week ago. put $35.00 in each tank, i always run each equally. after i noticed that my front tank was 3/4 and rear was 1/2. should of each been at 1/2 full. any way i put about 70 miles on front and gauge doesnt seem to be moving much, switch to rear and its almost down to 1/8th. so i put some more in the rear tank bringing it back up to above 1/2. again i drive it, running on the front tank, again the rear goes down. then i drive in the rear, the front over flows. i know about the check valve getting a tear in it and letting gas go back into a tank your not running on. seeing as the front over flowed while running on the rear id think the front check valve has a tear, but how does running on the front enable the front to pull gas out of the rear tank. by the way i replaced both fuel pumps, and regulator, took the old pumps apart and i cant see any tear in the check valves. might be a pin hole ill check closer. problem is fixed but is a real puzzle. any one come across this ?
Thread Starter
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Elder User
Joined: Mar 2004
Posts: 759
Likes: 1
From: mohave valley, arizona
so take apart both fuel bump housings i removed from my tanks. both rubber diaphragms look to be in good shape, cant see any tears. so im thinking what other way could fuel from the rear tank get back into the front. so i connected a hose to the outlet of each pump, one i could blow though but the other i could. might be wrong but i dont think you should be able to blow though an electric fuels outlet. isnt there some kind of check valve in it ?
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