Cranks but doesn't start

Hello,

It sounds like you lost power somewhere here is a guide and the fuel pump wiring diagrams to help you see what the problem is.

https://www.2carpros.com/articles/how-to-check-wiring

If you need to troubleshoot the circuit to the fuel pump, you can bypass the fuel pump relay to power the circuit without having to crank the engine. The easiest way to do that is to pop its cover off, then squeeze the contact. Normally I show people how to use a paper clip or piece of wire instead, but I don't know what your relay looks like. If it comes to that, I'll try to find the information online.

Please let us know what happens.

Cheers

Probably the fastest way to start is with a test light. Remove the relay, then probe all the terminals. One should have 12 volts all the time. A second one should have 12 volts only while you're cranking the engine, and possibly for one second after turning on the ignition switch.

If you have those two voltages, move the test light's ground clip to the battery positive post, then probe the remaining two terminals in the socket. It should light up on one of them indicating there's a good circuit through the fuel pump motor.

In the meantime I'm going to try to find a wiring diagram for your car.

I found the diagram and I see I told you wrong. You should have 12 volts on two terminals in the relay socket, but only when the ignition switch is on. Then, those voltages should stay there steady. The relay is turned on by the Engine Computer by grounding the second terminal for the relay's coil.

I'm not familiar with your anti-theft system, but when there's a chip in the key, you're tied to the dealer. You may get a replacement from a locksmith, but they often buy them from the dealers too, then cut them for your car as needed. If that is the only problem, the second key should have worked.

Let me tell you more than I know. On older Chrysler engines, there is a crankshaft position sensor and a camshaft position sensor. Both have to send signals to the Engine Computer for it to turn on the fuel pump relay. That means the engine has to be rotating, (cranking or running). If either signal is lost, the engine will stall and not restart. On newer models the same thing happens, however, if the fuel pump relay is bypassed, like you're doing, the engine will run on just one sensor. That sensor is providing the timing signal for the injectors and the ignition coil(s), but the computer isn't turning on the fuel pump relay. Typically the crankshaft position sensor provides the timing information for the ignition coils and the camshaft position sensor provides timing pulses to synchronize the injectors, but when the camshaft position sensor signal is lost, the crankshaft signal is used as a backup strategy. The injectors will fire in the right order, just not at precisely the right time.

On older GM engines, if the camshaft position sensor fails on a V-6 engine while you're driving, you'll never notice it until you stop the engine and try to restart it. Then, there is a 33 percent chance the computer will fire the correct ignition coil at the right time. If it does, it will just continue to fire all three in order each time it gets the right timing pulses from the crankshaft position sensor. There's a 66 percent chance it will guess wrong and the engine won't start. It will continue firing the coils in the wrong order until you turn the ignition switch all the way off, then back on and try to restart it, then it will guess again and have another 33 percent chance of being right. For this reason, you can have multiple failures to start, then unexpectedly it will start and run.

You likely have some similar situation. Be sure to check your fuel pump relay. Two terminals must have 12 volts with the ignition switch on. You don't have to be cranking the engine for those to appear. If those are there but the computer isn't turning that relay on during cranking, I would suspect the camshaft position sensor or the crankshaft position sensor. You'll need a scanner or code reader to see if the computer detected a missing signal from one of them. If no diagnostic fault code was set, you'll need the scanner to view live data to see if those sensors are listed as "yes" or "no" while cranking the engine.

If there was a short you'd be blowing a fuse. An open circuit, meaning a break in a wire, will cause what you're describing. Regardless, I never allowed my students to run a different wire except temporarily as a test. A cut wire, corroded splice, or a wire rubbed through and shorted to ground occurred for a reason, and it's just a matter of time before another wire in that harness will do the same thing. THAT wire cold be to something equally important and it lets you sitting on the side of the road, ... On a dark Saturday night, ... After midnight, ... In a freezing blizzard, ... With hungry wolves surrounding your car!

The only proper repair is to find the location of the defect, repair it, and do something to prevent it from happening again. As an example, in one older popular minivan, it was not uncommon to find a wire rubbed through in the harness under the battery tray. By the time it caused a problem and was located, there were a half dozen other wires just ready to do the same thing. It was caused by that harness sliding back and forth each time the engine rocked from accelerating and decelerating.

The black / yellow wire goes from the relay socket to the fuel pump connector. If you can determine which wire that is, run a jumper wire from the positive battery terminal to that wire at the relay socket. If the pump runs, the cause of the problem is the relay isn't being turned on by the computer. If it doesn't run, check for 12 volts on that black / yellow wire at the pump. If it's missing there, we have to figure out where the break is. If you DO have 12 volts, check for voltage on the black ground wire at the pump. If you have that, the ground wire is broken or corroded.

Dandy. Happy to hear it's solved.