Will not start

Hey; my daily driver is a 1994 Grand Voyager!

How and when are you finding twelve volts to the fuel pump? Chrysler fuel pumps almost always fail by failing to start up. It is extremely rare for one to stop running while you are driving.

You need to list which engine you have in case I need to refer to a wiring diagram.

Have you checked the actual fuel pressure with a gauge?

There should only be twelve volts to the fuel pump for one second when the ignition switch is turned on. That twelve volts comes back during engine rotation, (cranking or running). If you are finding twelve volts with the engine not cranking, I suspect you are on the wire for the sending unit. Or, you have the voltmeter grounded to the battery's positive post. Or, you have an auto-ranging meter and you overlooked that it is reading millivolts. (I have over a dozen digital meters for TV repair and I never use auto-ranging meters for that reason. Get tricked too many times).

Not the computer. It turns on the automatic shutdown, (ASD) relay during engine rotation. That relay sends twelve volts to the ignition coil pack, injectors, alternator field, oxygen sensor heaters, and the fuel pump or pump relay. You have spark, so the ASD relay is working.

Double-check the voltage to the fuel pump. A test light works best because most digital meters do not respond fast enough. The light should light up for one second when you turn the ignition switch on, then again during cranking.

That should be the dark green/black wire at the pump.

The circuit has changed a little from what I have memorized. There is a separate fuse and relay for the fuel pump, but the relay is in parallel with the ASD relay. That means they both turn on at the same time and by the same circuit. Check the "fuel pump" fuse in the under-hood fuse box. It is a blue fifteen amp.

If the fuse is good, swap the fuel pump relay with another one like it. The AC compressor relay is a good one to use. If the engine starts now, pop the cover off the relay, and I will bet you find the contacts are blocked with a gob of rust.

Feel if that relay clicks when a helper turns the ignition switch on. If it does, that half of the circuit is working. Remove the relay, then check for twelve volts in the socket. You should have twelve volts on two terminals.

I don't approve of splicing a new wire to run parallel to the old one unless the old one is cut out on both ends. I taught my students to always find the break or short, and fix it, because you don't know what caused it otherwise. If it got cut laying across the sharp edge of a metal bracket, you want to correct that before the same thing happens to another wire in that harness.

Which wire color has the problem?

I got confused when you asked "which wire". What did you do to get the engine running?

The difference I was referring to is the oxygen sensor heater is also powered from this circuit. The diagram shows two individual wires leaving the fuel pump rely in the fuse box. If I had an original service manual, that would show all the connectors and splices in the circuit. It is possible there is only a single wire leaving the relay, and it goes to the O2 sensor at the rear, center of the engine compartment, then there's a splice there and the rest of the wire goes to the fuel pump. On some cars, the wiring harness can break off its plastic mounting clip and fall down onto hot exhaust parts and melt. If you have an intermittently-blowing fuel pump fuse, that would be a good place to look.

Splices are also good places to find a break due to corrosion. Those can cause part of the circuit to be totally dead, or, if it's a low-current circuit like for a light bulb, that bulb might just be dim.

If you can dig down to the O2 sensor, see if you get 12 volts there.

There has to be a break in the wire going to the fuel pump. The only experience I've had with that on a friend's Caravan years ago was the terminal in the connector right at the pump was stretched after he struggled to reconnect it. It made a poor contact, so heat built up, and eventually the terminal overheated and burned the rubber cap. It took a couple of months to cause an intermittent stalling problem after the pump had been replaced.

There is no other common history of this circuit causing problems. When you check for 12 volts at the pump's connector, don't forget to check the ground circuit. The ground is okay if the fuel gauge is reading correctly. It shares the same ground wire.