I think you are confusing the issue with your terminology. "Crank" means the starter spins the engine. If the engine runs when you pour gas into it, that means it runs. The next concern is you said you have spark. If that is correct, we are way past looking at the crankshaft position sensor and the camshaft position sensor. Those have to work for the Engine Computer to turn on the automatic shutdown, (ASD) relay. That relay sends current to the ignition coil, injectors, alternator field, and fuel pump or pump relay. The fact you have spark proves the ASD relay is turning on, and it proves there should be twelve volts at the injectors. What a lot of people overlook though is the ASD relay only turns on for one second when you turn on the ignition switch. It turns on again during engine rotation, cranking or running, and the computer knows that by the signal pulses it gets from the two sensors. If you are testing for twelve volts at the injectors, it is best to use a test light because digital voltmeters do not respond fast enough to see that initial one-second pulse. After that, you must be cranking the engine when testing for voltage on that circuit.
Your crankshaft position sensor is in the transmission bell housing, right behind the right cylinder head, but as I mentioned, it has to be working if you have spark. The first thing you must be aware of is if the battery is disconnected or run dead, the Engine Computer loses its memory. Same is true when you disconnected the computer. Chrysler Engine Computers have an extremely low failure rate, so that should be the last thing on your list of suspects. Fuel trim data will be rebuilt as soon as you start driving, but you have to perform a procedure to relearn "minimum throttle". Until you do that, you may need to hold the accelerator pedal down 1/4" for the engine to start. You will not get the nice 'idle flare-up" to 1500 rpm at start-up, and it will tend to stall at stop signs. To meet the conditions for the relearn to take place, drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the pedals.
You are also right that the people at auto parts stores that will read fault codes for you can usually only do that on 1996 and newer models with the on-board diagnostics version 2, (OBD2), emissions system. I am surprised your mechanic does not know that Chrysler makes reading fault codes yourself much easier than any other manufacturer. Cycle the ignition switch from "off" to "run" three times within five seconds, without cranking the engine. Leave it in "run", then count the flashes of the Check Engine light. You will get a single flash for the digit "1", a short pause, then two flashes. That is code 12 and just means the power to the Engine Computer was lost recently. That's because it was unplugged. If there are other codes, they will flash the same way after a longer pause. The last code will be "55" which means "end of message".
Any codes that were in the computer were erased when you unplugged it, so that valuable information was lost. Some codes will not set easily just from cranking the engine. If I had to guess, based on your description of the symptoms, I would be looking at a failing MAP sensor or a cracked vacuum hose going to it. That sensor has the biggest say on fuel metering calculations on Chrysler products. Most other manufacturers have not figured out how to do that. They use the mass air flow sensor instead.
Also, be aware the Chrysler dealer's parts department has repair kits for the fuel filter. You get four fittings, two straight and two curved, four fuel injection hose clamps, and two pieces of hose. You use only the two fittings needed on your truck. If I understand that you moved the filter to under the hood, that is likely to make the hose too short to flex properly when the engine rocks. Heat could be an issue too as it can turn hot fuel to a vapor that cannot be pumped. That is not an issue on your truck because the fuel is constantly flowing through the regulator and back to the tank. The bigger concern is the rubber o-rings in those fittings. When they get cold, they do not flex and stretch well to accommodate the flexing. It is real likely you will find fuel leaking from them until they warm up. Throttle body injection systems run at a pretty low pressure, typically around fourteen pounds, but that is more than enough to spray fuel onto hot exhaust parts.
Check if you have fuel pressure. If you hear the hum of the fuel pump for that first one second, but you do not have any fuel pressure, suspect the two hoses are switched at the tank. I had so many miles on my 1988 Grand Caravan that I had to replace the pick-up screen in the tank twice. Both times I ended up with a crank/no-start because I switched the hoses, and I am supposed to be the expert! If the hoses are switched, you will find fuel spraying from the return hose when you loosen the clamp.
Wednesday, January 11th, 2017 AT 7:36 PM