Tracing power feeds?

[trbojo]

OK.. New battery.. New ignition switch... Checked bulkhead, fuse links, grounds, tightened up all terminals, connectors, etc... STILL losing almost 3 volts at the alky pump... Started checking in the car at the controller... With the pump commanded full duty it looks like I'm losing 1 volt through the GROUND circuit of the controller: I checked voltage on the red wire, pump output side of the controller with the ground lead of my meter attached to the dash where the controller is grounded.. I measure 13.4 with the car running.. I moved my meter ground lead to the same side as the positive lead, on the output side of the controller and it drops to 12.4 volts.. So there's 1 volt loss.. Still need to find the other 2...

 

[trbojo]

Another thing I checked was resistance across the pump motor black and red terminals.... Measurement on the pump I'm using is .8 ohms... To compare I checked my old pump which probably was good but leaked, probably from sitting dry when I swapped it the other day and I measured 1.5 ohms.. Don't know what the reading it's supposed to be...

 

[garyk1970]

Ohm out ground from pump to battery should be close to zero....if you were closer, we would have you fixed up in no time.

 

[trbojo]

Ohm out ground from pump to battery should be close to zero....if you were closer, we would have you fixed up in no time.

I don't think that will tell me anything... The controller applies power and ground to the pump?

 

[garyk1970]

The question is pump speed controlled with ground, positive or both....?
This is a good question for Julio...alky system not performing? Sorry if already stated.

 

[trbojo]

From what I've checked I think it's controlled by the ground side... I have some of this posted over in the alky forum so I'm waiting on Julio for that....

 

[trbojo]

But at least I know for a fact at this point that it is NOT a supply voltage or supply ground issue....

 

[garyk1970]

You mentioned the ohms were lower on this pump.....more of a load (lower ohms) will drop volts as controller works harder

 

[trbojo]

You mentioned the ohms were lower on this pump.....more of a load (lower ohms) will drop volts as controller works harder

BINGO!!! that's kinda where I'm leaning..... We'll see..... I hope.... Like I said... This car is just a downright f#$%cking nightmare sometimes... Like all of them...

 

[trbojo]

I have full voltage at the pump connector with the pump disconnected.... Bad connections can cause a voltage drop, but do can bad components (motor) correct??? Like you said.. Resistance... Kinda like putting a carbon pile load tester across a battery... As you DECREASE resistance, the voltage drops...

 

[earlbrown]

Oh yeah, and the resistance reading gets numerically lower, you're getting closer and closer to a direct short.

 

[trbojo]

HOLY SHIT HOUSTON I THINK WE HAVE SUCCESS!!! So I did one more thing... Again, remember in all of this I still never really found the "smoking gun" per se.... I've known for awhile that there was corrosion under the cover for the pos battery cable.... I found a neat little repair end today and replaced it... It still did not change my voltage readings at all... I'm thinking it's a possibility that by the battery being weak, the alternator just wasn't able to keep up with demand under load causing everything in the system to be marginal at best.. I'm still only able to get a max of 150 psi on the alky pump but apparently it is enough.. On to the show.... Went for a couple of test hits and my IDC is down from 105-107% to 88-90% !!!! I'll post some logs in a bit..

 

[trbojo]

And before someone says it, I did NOT have drop across the pos cable, believe it or not....

 

[trbojo]

Logs....