fuel Pump voltage?

[KCsurfer420]

I am having problems with a fuel pump that i just installed in my 88 comanche 4.o now my question is if i disconnect the plug from the fuel pump what kind of voltage should i be seeing feeding the fuel pump. After testing it with volt meter i am only seeing 6 1/2 volts to the pump is this correct? I am going to replace the relay tomorrow and check the ballast on the fender but can some one give me a heads up to what the voltage should be? :???:

[KCsurfer420]

Any one...

[KCsurfer420]

any one? :???: aw come on mj gods... i know your here some where....

[Pete M]

ya know, we aren't staring at a computer screen 24/7. it just seems that way. :D

 

In theory the voltage should be 12 at startup, but in reality it's more like 10 on an old truck due to corrosion and other voltage drop. 6.5 is still really low.

 

I would clean up the ground behind the drivers side taillight. the pump in my 88 grounds there.

[HOrnbrod]

You sure your are reading the power pin at the 3-pin plug to ground and not the sender output wire? Also check the power pin to a closeby good chassis ground, then to the ground pin in the plug. The voltages should be the same IF the ground behind the left tail lamp is okay. Also check the voltage on both sides of the ballast resistor on the left side fender well in the engine compartment. Let us know what these readings are.

[Pete M]

good point. forgot to ask when you were checking it. The pump only gets voltage for about a second after the key is turned to run, and then anytime the engine is either cranking or running. If none of those things are going on and you're reading a voltage, then it's the sending unit's voltage, not the pump's.