My fuel pump is not working, why?

I bought this truck 6 months ago and the sending unit in the front fuel tank stopped working. The rear tank was removed due to a hole in it, so the truck would not run as it only had one tank. The sending unit was replaced, but I went ahead and replaced the inline high pressure pump at the same time. Life was good then. However, the other day, the truck sputtered like it did when the sending unit stopped working. I hauled the truck home and immediately noticed that the inline high pressure pump wasn't heard running. I climbed under and saw that the hot wire was disconnected. I was thankful to find that, thinking this would solve the issue. I rewired it and nothing, so I got my voltage tested and learned I had no power at the pump. I proactively replaced both the relays in the left side of the engine compartment, with no change. I ran a wire from the battery to the pump to test the pump and that caused it to run, and subsequently, the truck did as well. What on God's green earth is keeping the fuel pump from getting power? I don't want to purchase a new EEC-IV and that not be the solution, but I am at a loss in trying to determine why the fuel pump isn't getting power.

Thank you for taking the time to read this and ponder the issue.

Yes, the truck has been running during testing. I will check the inertia switch in that manner and return tomorrow with my results. Thank you

The culprit was determined to be a bad wire feeding the inertia switch from the relay. It has been rewired and now works. The truck is all fixed

I can't get power to the fuel pump. I have changed the fuses and the relays and checked the inertia switch. I can use the test harness at the relay and ground it out and have power that way so I know there is no problem with the wiring from my fuel pump to the front of the truck. Can someone please help?

Hi, we have a problem with the truck listed above Custom 5-spd, with dual fuel tanks. When we try to start it, it won't start, no clicks. We figured it out and it was a fuel pump problem. There is no power to the fuel pump. When we turn on the ignition, the fuel pumps won't come on, even with clutch to the floor. Tried checking the fuses, but no luck. What could be the reasons we have no fuel pump power?

Truck has two tanks, no power to fuel pump. Can the switch on dash that controls tanks cause the power not to go to pump. I can spray gas into air holes on plyem and truck will fire.I tried to straight wire pump, but truck wont fire like that. When I take off straight wire to pump and spray gas into intake it will fire. Will bad switches cause computer to give wrong single and cause it not to crank. What switches can cause the power not to go to pump. I know it has fuel cut off switch, and front and rear tank switch, and fuel pump relay on fender well. Need help please.

When I cut the key on there is no power going to the fuel pump. I also checked for power on the fuel cut off switch under the glove box, and the front and rear tank switch on the dash, and I have no power on either one when the key is turned on. I would think they would have power on them when I turn on the key. Does the fuel pump relay on the fender well suppose to have a hot wire to it that feeds everything.

Hi,
I want to thank you for your help first. This has been a real headack. I want to fix it right. First let me explain everything. The truck was running butthe enginehad a knock, so I had the motor changed. We put a 302 motor out of a 86 linclon, but the guys had to change the fuel injection because the linclon had only 1 air hose on it to the air filter, and the truck motor had 2, and maybe the fuel linage was different. After the mechanic changed over everything he couldn't get it cranked. He said the fuel pumps wouldn't work, but if you spray gas into the air hole's on the plyemn the truck will fire. He told me he didn't think the injectors were letting gas in. I checked the wire on one of the injectors with the switch on and it had power to it, so I figured the injectors were ok. I put a new fuel relay on and had no effect. I checked the relay for power and it has five wires on the plug-in and one has power. I have the dash out so I can see all the wires and they look good. I have the back fuel tank unhooked, could this cause a problem. Could the computer cause the fuel relay not to work, and how do I check the injectors to make sure they are working right. I just checked the fuel pump to see if it come on for 3 seconds when the switch was turn on, and it did not come on, so what would cause it not to work like you said for 3 seconds.
Again I appreicate your help

The motor came out of 86 Linclon, same 302 motor but the intake had to be changed. The origonal motor in the truck was also 302. It was running until the motor swap. I checked the fuel pump relay plug-in wires for juice, and only 1 wire has power. It is the wire going to the coil. Another mechanic told me that there was suppose to be 2 hot wires going to the fuel pump relay. He said it was suppose to have hot wires on the points side, and the coil side on the relay. The hot that is going to the relay is going to the points terminal on the relay. I checked all of the wires on the relay and where they were going and this is how the wires go-- 1 red wire comes from the computer, 1 striped wire goes to the fuel cut off switch, 1 striped wire goes to a switch beside the battery, which I think is a timer, and 1 striped wire goes to a plug-in on the fender welll that splits and goes to the fuel pump on the frame, and the other wire in the plug in that splits off, that wire goes to the tank switck on the dash.
The truch has the computer from the origonal motor.
What gets me is, that if I straight wire the fuel pump the gas is getting to the injectors but the truck won't fire. But I sprayed a shot of eather in the intake, and it fired. It just don't make any sense unless both fule pumps have to be running before there is enough pressure to get through the injectors. Is there any way I can rig the truck to run without fixing it back oragional? Thanks for any help

The Linclon pleym says ford 5.0 Liter The truck plyem says Ford ELECTRONIC FUEL INJECTION. Neither says HO

The inertia switch wires are 1 wire going to fuel relay and 1 wire going to fuel pump which is pink with black stripe. The red wire on the relay goes to the computer. Yellow wire is hot and goes to switch or coil. It has a brown and blue stripe wire that goes to a red-plug in beside the battey that is not pluged up. It is a wide plug-in and I don't see a place for it to go.
I think I need to check the input wire on the inertia switch to find out why it dont have any juice because you said the inertia wire going to the relay needs power.