Electric Fuel Pump Issues

[ndutton]

Guys here will measure the coil and then accept that as the absolute fact. There is always some error.

. . . . but doesn't measurement give us the best information possible? If not by actual measurement then what??

[romantic comedy]

Neil, it depends on the instrument.

I have an expensive fluke multi meter that I trust. We never get the exact answer. That may sound weird, but that is the way it is. Things are designed with tolerences. There is always a plus and a minus.

There is a lot of discussion about coil voltage and resistance. Sure we can measure the coil and calculate the required resistor to add to the system. There again is an error present. But the coil also has a working tolerance. it may be a variation of several volts.

I also have a few cheap multi meters. i have measured a battery charging at 15.5 to 16 volts with the cheap meter. I go and check with my fluke and it measures 14.4 volts.

[ndutton]

Please keep in mind we aren't taking the calculations to the razor's edge. We factored in a 15% margin of safety in the ballast resistor calculator and thus far the solution has been successful regardless of who measures what with whatever test instrument.

[romantic comedy]

I have wondered what measurement is more accurate with our meters, resistance or amperage.

For the ignition sysytem some are adding a resistor to control the current. 4 amps is the max. The coil resistance is measured and a current is calculated. A resistor is added and the current is assumed to be what the calculation found.

I would prefer to measure current to find the proper resistor to add. Then measure the curent after it is added.

Then again, we have plenty of wiggle room. The resistor can vary quite a bit.

The answer is that Yes measurement is the best way for us to find the resistance.

[HalcyonS]

regarding tolerance and precision

yes, I'd wondered about the tolerance in coil resistance readings. Most electronics components have a tolerance range - they're mass produced after all. Resistors and eletrolytic capacitors are usually +-10% or 5%. That is why resistors come in those odd values 2.1, 3.3, 4.7 etc...That is the bounds of their precision. And certainly, heat etc will change values. The coil is a power element, and inductive - the rules for induction are different from resistance - inductance is a bit arcane. just my two cents.