No power at fuel pump

[Sunk]

I checked last night, but i'll check again. i had the TFI unplugged for a little while, I dunno if I checked it with it unplugged.

 

[Sunk]

Ok, I just checked it again. With the key on, there is no power at the little plug for the Inertia Switch. Should I be looking at the TFI? I know they're known to fail from heat, but its dead cold since its been sitting for 2 days.

 

[Psychopete]

I think it's the relay with the green plug.

I had my timing 180 off, flooded the engine, unplugged that relay and the truck popped a couple times - it was still making spark.

On the dianostic plug you can jumper to run the fuel pump all of the time. I am not sure of the wiring on the relay itself, but that might get you a little closer. I'm just not sure which wire it is that actually runs back to the fuel pump.

PCM getting powered? The ground on the switch side of the relay is controlled by the PCM...

Pete

 

[Jorley]

If there is no power at the interia switch the problem is with the relay. It has yel, org/Lt. blu, tan/Lt.grn, and red wires running to it. It should click when you turn key on . Check continuty between the tan/Lt grn and red wires. should read low ohms. The power to the inertia switch comes thru the relay so it's probaly bad.

 

[Sunk]

Alrighty, I'll go check the relay.

 

[Sunk]

Ok, on the green relay, testing the tan/light green wire to the red wire, I have 4.72 volts steady. So, I take it that the relay is the problem.

 

[Jorley]

That would be my guess, unless the computer isn't energizing the ralay and I think if that was the case there would be other problems. Try jumping the yel to org/Lt. blu wires, the pump should run.

 

[Sunk]

Ok, time to take a step back. I actually tested the light blue/orange and the red before... This time I checked the colors again and tested the tan/light green to the red and got 1.8v. The yellow to tan/light green gets me nothing.

 

[Jorley]

The yel and org/Lt. blu are the power for the pump. The red and tan/Lt. grn are to energize the relay. they are 2 different circuits.

The yel(all the time) and red(key on) to ground should read 12v. The tan/Lt. grn goes to the EEC. The org/Lt. blu goes to the inertia switch and fuel pump.

Since you have voltage on the red, tan/Lt. grn wires the relay should energize.

Put a jumper between the yel and org/Lt. blu and the pump should run.

Connect the relay back up and have someone turn the key on, you should hear or feel it click. If it does click and the pump doesn't run, or if it doesn't click, the relay is bad.

I know this seems pretty complcated, but just remember that a relay is like a remote control. What I mean is that it uses one circuit to control another.

 

[Sunk]

Ok, I put a jumper between the yellow and orange/light blue wires, and the pump didn't go.

 

[Sunk]

I pulled out the jumper, hooked the relay back up and turned the key on/off multiple times. No clicky. Bad relay.

 

[Jorley]

I pulled out the jumper, hooked the relay back up and turned the key on/off multiple times. No clicky. Bad relay.

Most likely, but the pump should have ran when you jumped the yel and org/Lt blu wires. Let's try one more thing.

Jump the yel and org/Lt. blu wire at the relay and jump the 2 wires at the inertia switch. I know this sounds silly, but make sure you get a good connection with your jumpers. Pump should run.

By doing this it is like running a wire straight from the bat. to the pump, and from an earlier post you said the pump run with power to it.

I know this is all kinda of aggrevating. Welcome to the world of troubleshooting. It takes some time, but can end up saving you money in the long run.

 

[Sunk]

Ugh, i just got home from my friends house where the truck is. Earlier I had a jumper from orange/light blue to yellow and had a multi-meter on the leads to the inertia swithch, and had nothing.

 

[viperfangs2]

Whats A Drive Line

 

[Jorley]

Ugh, i just got home from my friends house where the truck is. Earlier I had a jumper from orange/light blue to yellow and had a multi-meter on the leads to the inertia swithch, and had nothing.

No problem we can start again tomorrow. I enjoy fixing things even if it is second hand.

With those 2 wires jumped the org/Lt blu wire(at the inertia switch) to ground should read 12v.
Reading between the 2 wires at the inertia you wouldn't read any voltage. Always check for voltage to ground.