1996 Dodge Dakota Fuel Pump Power Issue

I know better than to leave things..... Not that I have thought much more about it.... I just drew an "equivalence" diagram to "simplify" understanding of the connections & voltages... IE - the thingemebobs are suspended between +12V and 0V (GND = zero Volts). (thingemebobs are whatevers - in this case electrical gizmos like fuel pumps, connections, bad connections, fuses, gremlins etc.) I often sketch such "simple" figs so I can imagine various situations - like shorts, opens, cross connects etc. Or so I can pencil in measured voltages etc and then brainstrain. FYI - I drew the PowerTrain Control Module C19 Fuel Pump relay Control as an "Open Collector" (grounded) transistor which is a common implementation. It is turned on by via its dashed line (somehow - eg CPU/EMS). In reality the transistor might be a grounded relay. It's like old car ignition points - either open else shorted to GND (else if faulty, maybe a resistance to GND). And I didn't know if the Fuel Tank's #4 or #6 is GND for the internal Fuel Pump.      Now, where was that ~7V reported....?

the 7v comes between connector 207 and connector 327. sorry I havn't posted back lately, again with the busy schedule. I hope to get back at this tomorrow as it starts my "weekend". today is my "friday" so things are all weird. Remember the other post you left about being here with no coffee? thats how I am right now, lol. I'm going to get myself some of that delicious awesomeness and try and wake up. Thanks Oldspark!

You druggie you! You are driving (bad pun?) the schedule so no need to apologise for delays. I'm used to anxiously awaiting the latest outcome... (LOL!) 7V b/w 207 & 327??? They should both be the same voltage (less maybe some drop - but not 7V - maybe up to a volt or 2?).... The voltage being ~12V when the relay is on, else GND with relay off because of Fuel-Tank GND #4 or #6 thru the unpowered fuel pump (ie, pulls "south of relay 5D/#87" to chassis/GND). Paraphrasing.... With 5D/#87 jumpered to +12V - preferably (read: SHOULD be) via fuse - eg, say to fuse-D 8W-11-9.... Then 5D/#87 is ~12V. And Fuel-Tank #1 C327 should also be ~12V (and the pump pumping). So C327 in that circumstance is ~7V? And C120 & C116 & C207 are ~12V? Hence ~5V drop between C207 & C327? (Or 7V drop, whatever - ie, a BIG drop.) If so, bad/thin cable else bad connection/s. If mere corrosion, the "standard" pull-apart & reconnect all connectors should fix it. Else maybe some cleaning is required (friction rub, or contact cleaner, etc). If contacts have been bad and hence heated, annealing and oxidisation may have ruined the contacts - replace else solder or a good joiner... If I have misunderstood... my next coffee is due in about 9 hours... FYI - remember that "finding heat" is a good way of finding bad or undersized contacts, connections, wires etc. The catches are (1) it assumes enough current gets through to cause heating, & (2) you have ice or burn cream handy - just in case...

Oldspark, Just thought I'd tell you the good news. I got the truck rewired and running today. I need to button the wire back up and everything so i have some finishing work to do. but Its running. I cut the a61 wire and soldered a new wire in its place. the only thing i need to do is double check and make sure that wire didnt supply power to anything else beyond the fuel pump :-O this came as an after thought but if it does won't be a big issue, I will just spice the wire into the new wire. Thank you SO MUCH for all your help, I am glad we got this figured out and fixed. Thanks again my friend!

GREAT! So a bad wire or connection.... (Not a "component" like a relay etc.) But hopefully you can do a similar fault find in the future... It's sort of simple once you understand a few basics. And have a DMM. I recall some idiot saying it was (likely to be?) a faulty relay contact... But both faults have the same "output" result, hence the need to drill down.... Well done issakar!!