|
Hi all,
It is a rainy Sunday, so I figured I'd start looking in the easiest places I could from inside the warm garage, without actually running the motor.
For me, the easiest check of them all was to measure and scope the current drawn by the pumps. The scope is only 10 feet away, and I already had a remote switch rigged to the fuse panel.
Made from fog light switches found on the floor of any 240 left more than a day in a pnp.
Measuring current just needed the addition of a shunt resistor. I had 0.1 ohm 7 watt in the junkbox.
The main pump has an interesting signature. It would draw 3.1A, and certainly more if I had 13.6 instead of 12.6 at the battery terminals. The current would go up slightly when I turned on the tank pump, but any cavitating noises, if that's what they are, did not affect the waveform or introduce electrical noise.
The new tank pump is flatter through a revolution, but surprisingly draws more than the positive displacement main pump, 3.6A.
Since I didn't feel like pulling the car out and running the wife's 89 wagon in for comparison scope readings, I did the next easiest thing - pulled the tank pump, to see if the little hose was still intact, the sock gummed up, or the pump wired backward. The pump was wired backward, just as Afton discovered before me. If the photo is any good, you can just make out the + on the round post next to where the yellow (ground) wire is connected.
I switched it around and repeated the current measurements. Three distinct changes came about. I figured a centrifugal pump would not really suck if wired backward, but apparently it does more sucking than I predicted. The tank pump was much less noisy and smoother sounding. The main pump current went down instead of up, when I turned on the tank pump. And the main pump no longer makes any raucous noise as a result of turning on the tank pump.
The filter sock looks a bit browner than it was last month, but still very porous, and I took another, more critical gander at the bottom of the well. I might have wiped it out some if it didn't have 10 gallons of fuel in there, but for practical purposes, it was clean.
Thanks again all. I will post back if the mis-wired tank pump turns out to be not the whole story, but for now, I'm fairly confident, and grateful for the suggestions.
--
Art Benstein near Baltimore
"Freedom is not worth having if it does not include the freedom to make mistakes." -Mahatma Gandhi
|
