The important thing here is to NOT have battery voltage there, and if you do have it at the wrong times, In DODGES ONLY, cutting that wire usually fixes the problem and the truck will run fine forever! It is not unusual and OK to see low voltage, like. This test is accurate 99% of the time in my experience. If there is battery voltage there at any other time, the engine is being told to not start or run, by a pissed off ECM. The ONLY time there should be battery voltage on pin 5, is for about three seconds after turning the key to the “off” position. On a Dodge find the light blue wire with a red tracer (pin #5 on other trucks) and verify that there is NOT battery voltage there during either the “run” or the “start” functions of the ignition switch, WITH THE PLUG PLUGGED IN. If you have battery voltage on pin #7 in both key positions, and a known good ground on pin 6, cut the black tape off the VP44 plug harness to access the wires going into the plug and reinstall plug. Hopefully you find your problem this easily, but if not, get out the schematic for this circuit. If they are both good, then try swapping the fuel system relay in the PDC with the one for the horn. If you don’t have power at the plug, check the fuse in the PDC (Power Distribution Center, aka fuse box under the hood) for the fuel system, and if that is good, check fuse #9 in the fuse box on the left side of the dash. If you see no voltage then, it means there is no ground! Use only pin positions, not wire color, when diagnosing a Ford or Freightliner. Then verify the ground on the bottom left pin (pin#6, which is a black wire with a tan tracer on a Dodge), by doing the voltage test again at pin 7 with the ground connector of your test instrument on pin 6 in the plug. Using a test light or voltmeter with its ground connection on the engine, verify battery voltage on the bottom right pin (pin #7, which is a red wire with a light green tracer on a Dodge), during both “run” and “start” key functions. When you have the plug in your hand, hold it so it looks like a smiley face, with six pins below the smile and three pins above. Remove the big plug on the back of the injection pump by wiggling the plug with your right hand pulling toward the firewall and the left hand pulling the indented locking tab toward the fender. Next test the electrical wiring and verify that there is battery voltage getting to the VP44 injection pump with the key in the “run” AND ”start” positions. NO START – TEST #2 FUEL SYSTEM ELECTRICAL TEST This explains why VP44 fueled engines don’t die on the side of the road when the electric one fails. The reason this strange scenario happens, is because there is a mechanical lift pump built into the VP44 which works fine UNTIL air gets into the system. If the lift pump doesn’t come on, or doesn’t pump fuel into the filter canister when you click the key to the “start” and release it to the “run” position, you can bleed the system to get fuel to the VP44 injection pump and get the engine to run again by pressurizing the fuel tank with air pressure, or diagnosing and replacing the electric lift pump. When the ECM sees the “start” signal from the ignition switch it runs the lift pump for 25 seconds, and when it sees idle RPM it runs continuously. Please remember when you are doing this diagnosis that the ECM turns on the electrical power to the lift pump only for 4 seconds when the key is in the “on” or “run” position. If the engine was running BEFORE you CHANGED THE FUEL FILTER or OPENED A FUEL LINE, and it HASN’T STARTED SINCE, or, it started and stalled after doing this, and it WON’T BLEED or restart, and you can hear the lift pump running, but won’t fill the filter canister, you most likely have a bad electric lift pump. You will be very glad you did this if your truck runs again and you don’t need an injection pump! In this situation air and fuel is what you are trying to start the engine with! Pressure indicators don’t know the difference between air and fuel pressure, so they make you falsely think everything is fine. Your gauge may have just failed and be out of calibration for the first time and the tank is actually empty. We say this because of the famous Dodge fuel tank sender problem. If the fuel gauge reads 1/8 – 1/4 of a tank, put a few gallons in the tank and bleed the fuel system. You only need 12 volt power, ground, and fuel to the VP44. To make the engine start and idle only, you don't need any sensors or computers or electric lift pump.
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