Re: Helen in Dillon, CO (1978 VW bus)
Helen had 2 problems, and I doubt the Car Guys did much to help either one.
a. Her momentary loss of power on hills and while accelerating sounds like a partially plugged fuel filter. When the mechanical fuel pump can’t get the required amount of fuel to the carburetor float chamber the engine will lose power. Within a few seconds, if some fuel is still getting thru, the pump catches up with demand, fills the float chamber and the engine runs OK for a while. The same thing happens if the carburetor itself is defective – float gets stuck in closed position. So my diagnosis: clogged up fuel filter or defective carburetor. Suggestion: replace the fuel filter(s) first; if that doesn’t solve the problem, rebuild the carburetor(s).
b. Helen has installed an auxilliary battery to run propane heater during the night, set up with relay to charge when engine is running. Fine, but I suspect her auxilliary is a normal car battery or maybe a “deep cycle” marine/RV battery, but not adequate in aH (amp-hour) capacity to do what she needs. Normal car batteries are not designed for slow drain, deep discharge (<12v. at rest) and doing so will destroy them by sulfation. Her present battery is most likely badly sufated already and can’t accept or deliver nearly the amp-hours she needs. Keep in mind also that at low temperature, a battery’s aH capacity is greatly diminished, so when it’s cold out, the battery is least able to do its job.
What capacity deep cycle battery would work? Measure the current required by the propane heater running on full 12 v. input. Let’s say it’s 5 amps. Multiply this by 20 – even though you may only run heater 7 hours/night, capacity will be impaired by low temperature AND you only want to draw battery down to 50% of capacity before recharging. To get 100 aH capacity (even more would be better) you need a really substantial battery – at least one, maybe 2 big “golf-cart, fork-lift” deep cycle batts in parallel. Helen needs to study in depth about lead acid batteries, and get a hydrometer. Voltage is not an adequate indicator of charge state.