Inner fuel pump not coming on all the time

K. My truck is pressure fed switch valve. It has a switch on dash to change the pump over by pressure. Now let me tell you the whole story about the truck. I bought the truck in January. After two week both of the fuel pumps went out. Well But now I dont think it was the fuel pump. So I only put the fuel pump that went in my front tank jn. So I have no back tank pump. It ran but it had a very high idle so I park it n started to work on that promble. I change the fuel pressure regulator, MAP sensor, and throttle body sensor out. It seem to run better for a couple day than it quit. So I checked things out and come back to my fuel pump comes on and off. Last night I checked relays out, the electrical switch valve out and power n ground going to fuel pump. My fuel pump in tank worked ever time by I'm not get good fuel pressure any more. So I thank it in the switch or the high pressure pump going out. I don't know what to do?

The in tank pump is only a lift pump so it’s pressure is around 4 to 6 pounds to the main pressure pump then that pump makes the high pressures for the injection system, check the fuel filter or just replace it then try blocking the return line off the fuel rail and see what the main pressure pump can make, it may be the regulator.

I put a new fuel filter and a fuel regulator on it all ready. Let me also tell u what I did on the switch valve that is located behind the high pressure pump. I did away with it. I thought the valve was miss up on it so I just run straight line from high pressure pump to the pump in the tank. Did that be giving me? Do u know how much a fuel pressure tester cost. I running low on funds. Thanks

Harbor freight has one for twenty bucks that should work.

K thanks. I thinking that high pressure pump needs be replace.?? But im not going to be able to work on it again till some time next week. Got some business with family till next week. What do u think?

Just put it out of your mind until your done with family, it’s not going anywhere and by the time you get back you can have a fresh perspective

Thanks you. I will be posting next week when I start back up on it. Ttyl.

Okay I should be here.

Hey my uncle come get me to go out of town and he was asking what my truck was doing? He said let's do a little test with digital multimeter to test that electronic switch valve. It has the switch on dish. We ran a wire to the - battery post n tested the switch for volts. When it was turn on at the front tank it readied 1.47 v. He switch it to the back tank it readed 8 something v. So I just took the wire harness from the back tank n plugged in my front tank n test it at the switch again and with the switch flip on the back tank it readied 1.47 v and I switch the switch to the front tank it read 8 something v. It didn't make sense. So I decided to test the plugs under the truck. I still had a wire running the the - battery post and tested the plug. It readied 8 something v with the switch on than my uncle switch it to the father plug it reads 0 and the other plug readied 8 something v. So My switch is working? Right? Does that mean even though I hear my in tank pump come on can it still be missing up that the was the 2nd pump in put in the truck. I just don't know. What you think. Or did we test that wrong?