Engine turns over, no spark

Hello,

This ADS relay in these trucks had big problems.Here is a guide and a diagram (below) and a guide to help you confirm the relay failure:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

and

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Please run this test and get back to us we are interested to see what it is.

Cheers, Ken

Assuming that you checked for a spark at oneof the spark plug wires, you now need to check for a spark at the coil tower. You can do this by disconnecting the coil wire from the distributor and checking for a spark at the end of that wire. If you don't get a spark there it could be a bad coil wire, so check a second time using a different coil wire [if you have or can get one].

If you still don't get a spark: use a voltmeter to probe the GRY/BLK (gray with a black stripe) wire in the ignition coil wiring harness. The meter should read 12v. If not, check for an open in the GRY/BLK wire.
(I am assuming the Auto Shutdown Relay is good since you get fuel when the engine cuts off and the Auto Shutdown Relay also sends power to the ignition coil).

If you got 12v, we have to check to see if the coil is getting a switching signal from the pcm. Use a voltmeter or testlight to probe the BLK/GRY (black with a gray stripe) wire in the ignition coil wiring harness. The BLACK terminal of the voltmeter should be used to probe the connector and the RED terminal connected to the POS of the battery. Crank the engine over as if you're trying to start it, the 12v display should flash on and off the whole time your partner is cranking the engine.
The Test Light flashed On and Off: This is means that the Power Control Module (Fuel Injection Computer) is activating the Ignition Coil and since the Ignition Coil is not Sparking. The Ignition Coil is BAD. Replace the Ignition Coil.

The Test Light DID NOT flash On and Off: The most likely cause of this missing Switching Signal is either an Open Short in the wiring between the PCM and the Ignition Coil's connector or the PCM (Powertrain Control Module = Fuel Injection Computer) is BAD (although this is a rare thing).

When the engine will not start up, please repeat the following test Using a voltmeter this time.

THIS TEST IS FOR THE FIRST WIRE IN THE IGNITION COIL CONNECTOR:
use a voltmeter to probe the GRY/BLK (gray with a black stripe) wire in the ignition coil wiring harness. The meter should read 12v with the ignition switch ON. If not, check for an open in the GRY/BLK wire.

THIS TEST IS FOR THE SECOND WIRE IN THE IGNITION COIL CONNECTOR: Use a voltmeter to probe the BLK/GRY (black with a gray stripe) wire in the ignition coil wiring harness. The BLACK terminal of the voltmeter should be used to probe the connector and the RED terminal connected to the POS of the battery. Crank the engine over as if you're trying to start it, the 12v display should flash on and off the whole time your partner is cranking the engine.

Post your results please

Inspect and test the auto shutdown relay it powers the fuel pump and the coil

Hi dirtrider501. Welcome to the forum. First of all, understanding how the circuit works will help in diagnosing it. When you first turn on the ignition switch, the Engine Computer turns on the automatic shutdown relay (ASD) for one second to insure fuel pressure is up and ready for starting. Besides the fuel pump or pump relay, the ASD relay also sends voltage to the ignition coil, injectors, oxygen sensor heaters, and alternator field. If you hear the hum of the fuel pump for that first second, you know the ASD circuit is working.

The Engine Computer turns the ASD relay on again when it sees engine rotation, either cranking or running. It knows that by the pulses coming from the crankshaft position sensor and on some engines, the camshaft position sensor. Both of those sensors run on 5.0 volts or 8.0 volts supplied by the Engine Computer.

The fuel pressure you measured could be from the one second initial burst. The missing voltage at the coil can be explained if you measured it when the engine wasn't rotating. If the fuel pump is running and the coil has no voltage, there has to be a break in a wire or splice since both are on the same circuit. To double-check, measure the voltage to the coil for that first second and again during engine cranking. If it's there only for that first second, suspect the crankshaft position sensor.

The rest of the system operation has to do with a crash that ruptures a fuel line. The engine can't run without fuel pressure so it stalls. Loss of pulses from the crankshaft position sensor tells the Engine Computer to turn off the ASD relay. That removes voltage to the fuel pump so it also turns off to prevent dumping raw fuel onto the ground. The circuit is very reliable but often misunderstood. A lot of people try to diagnose the first thing they find missing, spark or fuel pressure, but it's important to check for both. The most common failure is the crankshaft position sensor. The individual coil and pump circuits account for very few problems.

Caradiodoc

Dandy observation on the fuel pump. If it was running during cranking, the crankshaft position sensor is working. Check for voltage at the ignition coil. One wire, possibly a dark green with orange stripe, (that's from memory) should have battery voltage during cranking. It is on the same circuit as the fuel pump. If voltage is missing and you have no spark, that could be the splice you're referring to. In that case, I'll have to find a Chrysler service manual to determine where that splice is located.

Caradiodoc

Well, if you read the system operation description in the service manual, they say one sensor turns on the ASD relay and the other one is for injector timing. All I've ever found is when either sensor is defective, the ASD relay doesn't turn on and there is no power to the coil(s) OR the fuel pump. Complicating the issue is some vehicles have a separate fuel pump relay that is in parallel with the ASD relay so they both turn on together but they feed different circuits. Complicating that even more, there are a few vehicles that use two different pins from the Engine Computer to run each relay.

If you have no voltage to the coil during cranking, the first thing to do is determine if the ASD relay is turning on. If you had Chrysler's DRB3 scanner, it will tell when the relay is commanded on. I don't know if aftermarket scanners will show that. An easier way is to pop the cover off the relay, reinstall it, and watch the flipper while a helper cranks the engine. If the contact flips on but there is no voltage to the coil, it becomes a simple matter of finding the break in the circuit. If the ASD relay is not turning on, head back to the cam and crank sensors.

As an alternative, you can try measuring for the same voltage on the two small nuts on the back of the alternator. One of them should also have battery voltage during cranking.

Caradiodoc

Think this might be the issue?

see my answer in this link

https://www.2carpros.com/questions/1997-jeep-grand-cherokee-car-kept-cutting-off-while-driving-had-fuel-pump

return back here with a grin!.....or any other questions....i'll do what i can

the medic