Determining The Fuel Injector and Fuel Pump Size For Your Car 

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Great content, keep it coming guys. Is there going to be a part two? The fuel system has other pieces to the puzzle

This guy seems nice and all but has he held a digital multi meter in his hands? Was it turned on? I started with carburetors but in 1976, other than a mechanical or CIS injection system, there were only two mass produced cars with EFI, the Cadillac Seville and the Datsun 280Z. This was it! Alternators produce less electrical potential at low speeds to idle, yet far better that a generator. At 1,200 RPM you would see a voltage of 13.2 - 14.3 at the alternator based upon ambient temperature. The colder a battery, the higher the voltage needs to be. Hot batteries have less internal resistance and are charged at a lower rate, perhaps 13.2Vdc. It always needs to be roughly 20% more for the battery to charge. This brings us to the battery. A fully charged battery at 100% state of health requires about 0.20Vdc to maintain a charge. Today, even with more electronics than ever, it falls on the alternator to power the vehicle. I would never suggest this on any vehicle made the last 30 years, but, I could start a vehicle, remove the battery and drive it into the shop. Most everything has to be oversized but I have seen a careless trend to smaller gauge wire for everything. I the exact distance is known, and the max amperage passing thru it was 1 amp, engineers may select a 28 gauge wire. Copper is expensive, wiring harnesses are hand built and expensive plus the can weigh several hundred pounds. Voltage drop increases with higher amperage circuits, snow plows, lift gates, certain amps or electric heater circuits. The fuel pump in a normal vehicle runs at 7amps. 7.5amp for many, less for others. A terminal of 1.5mm will carry 22 amps, but is ran with 18 AWG wire. So in any condition short of stock with power adders included, get an amp clamp to use with a good digital multi meter and know how electrical circuit work. Voltage drop works only when this circuit is turned on. Since this is a series circuit, the component is supposed to consume all of the voltage in the circuit. If measuring across the component, it will show how much potential for electrons to flow. The closer to battery/alternator system voltage, the better. In a perfect circuit, you have small losses at each component including terminals inside each plastic connector, the switch, each wire and even a fuse. Don’t forget the negative side. This completes the circuit for the return of electrons. Amperage is the measure of force. The force in a fuel pump system should be measured to establish a baseline. If the amps go up, the pump is working harder, so a pinched line, clogged filter will change this measurement. If lower than normal, perhaps the the brushes are worn, spring tension is low or the copper on the commutator plates have worn severely and plastic insulated material is showing thru. Always know your circuit and it’s parts. Voltage drop is very quick, it is accurate and never lyes. Some ask “What if the meter leads are backwards?” The digital readout will simply show a (-) negative sign in front of this value. It is still correct. Starters, bulbs, fans all contain copper or elements that when cold, allow a surge of current. This is known as In-Rush current and is gone very quick. To check this, use a DMM with a Min-Max feature that records this event when first turn on. The DMM & Amp Clamp shows you happens in a circuit, but for decades, the big engine analyzer that rolled on wheels, set to Primary, will show electrical activity in the circuit, just like an oscilloscope. DK. ASE Master Tech since 78, retired.