Thats what we want, one socket with voltage and the others read zero volts or thereabouts. but I need to understand 13.4V. An automotive battery fully charged at rest is 12.6V. The only way for that voltage is the truck running which should not be with the fuel pump relay pulled, the battery is on a charger while your measuring, or the meter is defective which can matter when diagnosing wiring faults and marginal voltage issues. Also, what are the two possible pin #'s for that always on voltage (look on the relay, both insertion directions).

George

 

Also, if you are jumpering/hotwiring things always use fused power.


George

 

So the relay says 85 87.
86 30

 

Yes those are the std pin number of a 4 pin automotive relay. Which pin number goes in the relay socket with always on power? Both ways, we need two numbers. Again, was the truck running or are you hooked up to a charger? If the answer is no to both of those questions then your digital meter is unreliable.

George

 

So it would be 87,the top right wich is the one with the power, and if I flip it around and insert the relay ot would be 86, but this is only with a 4 prong relay, a 5 pronged relay can only insert one way. So do you think my relay is bad, I need to replace with a good relay?

 

The insertion direction needs to be with pin 87 in the always on socket. Since you won't answer my questions regarding your voltage readings this is going to be a struggle and I don't know how much longer I am going to stay with this thread. I don't mind teaching you how to do this and saving you money but you have to answer my questions or I can't help you properly.

The way this circuit works is that the PCM sends a voltage to the relay coil to energize for a couple of seconds to charge the fuel rail for starting. After the truck starts an oil pressure switch then supplies fuel pump power. Since you never get fuel pump voltage at key on I am ignoring the oil pressure circuit for now. The next question is does the energizing voltage appear at the relay socket pin for 2 seconds at key on and is the voltage adequate (hard to answer if your meter is jacked up). The relay coil is on 85 and 86. One pin is permanently tied to ground and the other pin gets 12v at key on for 2 seconds from the PCM to energize the relay and route the power at pin 87 to the fuel pump on pin 30. Usually the ground is on 85 and power switching occurs on 86 but that can be reversed. Measure both sockets with the meter negative lead on battery ground and see if the socket is getting the PCM signal.

George

 

Sorry about that, the voltage reading could have been because my battery is low and the multimeter was incorrect.

 

Measure you battery at the posts with the truck off.

George

 

I will.make.sure my battery is fully charged, then I will measure the sockets again, I do believe the multimeter was incorrect. When you say relay coil? Do you mean just the relay?

 

I measured the battery and it's at 12.5 volts, then I measured the 87 pin with positive lead, and negative lead at battery, it reads 12.4 volts.