It really looks like you have excessive resistance in the circuit some where. You said you manually ran 12v to the pump & it worked fine so that would indicate the pump is ok. If you have a volt meter you can do a voltage drop test on the circuit to find the problem. One key to this test is to remember the voltage drop will always equal system voltage... i.e you have 7.6 volts @ the pump so you are probably going to find a 4.4 voltage drop somewhere if the system voltage is exactly 12.0 volts...
I'm sure if you googled "voltage drop testing" there would be some good info if you aren't familiar with this type of testing.... The flow chart HT posted is a good flow chart but covers the ground circuit in a different way and for the rest of the testing you are going to need an IDS (factory scan tool). The only problem I have with checking the circuit with an ohm meter as opposed to a voltmeter is, in resistance testing the circuit isn't loaded where as when you are doing a voltage drop test it is. Also with voltage drop testing you just need a volt meter & wiring diagram.......
That's the great thing about automotive repair, there is usually more than one way to get there. It's whatever works best for you........
One last thing you mention you found a post but the person never end it with a fix...... That a big problem a lot of folks do.... Once they find the fix they never come back & post it where it might help someone else with the same problem.. Maybe when you find your problem you'll let us know
Even if we were all way off base & completely missed the target.......
(This post was edited by Sidom on Aug 2, 2009, 10:59 AM)
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