Crank no start, backfires on crank

MALLYBOY

MEMBER
2002 DODGE CARAVAN
3.3L
2WD
AUTOMATIC
124,567 MILES

This vehicle started backfires every morning when you first start it and after which it will started. It continues the same way until when it was driven at highway along the line the engine turnoff. Crank and crank and crank, it could not start. Towed it down to workshop. Diagnosed it using Bluedriver and obdlink MX+ scan tool, it didn't record any fault code. I first check the timing and it was okay, I check spark and it was continuous but on the injectors, that is where the problem lies, I used a test lamp and probe the injector connector, I noticed that the test lamp illuminate twice and stopped, if it blink the first time, the second time: it will back fires and stopped, I used the ECM on another vehicle and it started but I bring it and it could not start, I change the coil pack, was still doing the same, what's the problem?

9 Replies

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

Hi,

Does this happen on one or all fuel injectors? Have you checked the ASD relay also?

I ask because the PCM provides battery voltage to each injector through the ASD relay. Injector operation is controlled by a ground path provided for each injector by the PCM. Here is where I would start. Switch the ASD relay with one having the same part number in the fuse/relay box. If there isn't one, here is a link that explains how to test a relay.

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

If you look at pic 1 below, it shows the location of the ASD in the power distribution box under the hood.

Check this and let me know what you find.

Take care,

Joe

See pic below.

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Wednesday, October 13th, 2021 AT 6:55 PM

MALLYBOY

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Does this happen on one or all fuel injectors? Have you checked the ASD relay also?
I don't know if it is injectors, but I do see flame coming out of intake manifold. I have also checked all other things and they tested okay. What's is the problem?

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Friday, October 15th, 2021 AT 1:55 PM

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

The idea that you lose the injector pulse should shut the engine down. Often times, backfiring is caused by too much fuel getting into the engine. Do me a favor and take a look through this link. It describes how to identify and repair a backfire. See if anything helps.

https://www.2carpros.com/articles/engine-backfires-while-running

Also, I need for you to check the ASD relay. It's located in the under-hood power distribution box. I attached a picture above identifying its location.

Switch it with another relay having the same part number or you could follow the link I attached above.

Let me know the results.

Joe

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Friday, October 15th, 2021 AT 5:39 PM

MALLYBOY

MEMBER
309 POSTS

Have you checked the ASD relay also? Yes! That was the first thing I checked, I using test lamp and probe it on the control side of the relay and I ground it on the engine body and turn ignition on, the lamp illuminated and off after 3-seconds, then I hold the key on the start position, it remains on and as I return the key, it turns off. I was thinking maybe it was the ECM, I removed it and put in another vehicle, it started and I put the one for the vehicle on this vehicle and it didn't start, also I probe the test lamp on the injector connector to see if it illuminates on steady crank, it will blink once and ceased, sometimes it will blink twice and backfires. If it blinks at first crank and backfires, it will not blink again until another cycle. I had checked all the ignition circuitry for short to voltage or power, but none was seen. What actually should be the problem? Should I replace the set of the injectors?

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Friday, October 15th, 2021 AT 11:35 PM

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

Hi,

Does the Blue-driver have a live data setting? If it does, check to see if there is an RPM signal being generated by the crankshaft position sensor. The PCM uses crankshaft position reference to determine injector sequence, ignition timing, and the presence of misfire. Once the PCM determines the crankshaft position, it begins energizing the injectors in sequence. Something could be failing there. The only thing that confuses me is the idea that it has spark.

When the key is in the ON position and the engine is not running (zero rpm), the Auto Shutdown (ASD) and fuel pump relays de-energize after approximately 1 second. Therefore, battery voltage is not supplied to the fuel pump, ignition coil, fuel injectors, and heated oxygen sensors. So, if you have spark, the sensors should be working. That leaves a wiring problem or a PCM problem.

If you can check for an RPM signal, let me know. If not, we need to start at the injectors and work backward. I would really like to know if all the injectors are doing the same thing. That could help eliminate possibilities.

I attached the wiring schematic below for the entire powertrain management system. I need you to locate the brown wire with a white tracer at each injector. There is a wire splice near the breakout for injectors 5 and 6. Inspect that splice for corrosion or damage.

If it is good, we need to work back to another wire splice which is large. See the schematic. I circled both splices to check. Make sure the same thing is there, no corrosion, and in good condition.

Let me know what you find.

Let me know.

Joe

See pics below. Note: I had to cut each page of the schematic in half to make them readable for you. I did overlap them so you can follow from one to the next. I highlighted and wiring involved. Note that the splice sends power to several different components (S112) which is near the IPD module under the hood.

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Saturday, October 16th, 2021 AT 7:40 PM

MALLYBOY

MEMBER
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Thank you and thanks once again.
I had unplugged the splice and plug it. No corrosion and it is still on its factory standard, and there is power source to it.
Is there another wire harness that can make the vehicle to ceased Injector-Pulse?

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Monday, October 18th, 2021 AT 7:32 AM

JACOBANDNICKOLAS

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Hi,

If you have power to each injector, then either there is a bad connection at the PCM, a wiring issue (unlikely if they all lose pulse), or a possible PCM issue.

Before we jump to that, have you inspected the camshaft position sensor? If not, check that connector. See pic 1 for location.

If that appears good, I need you to disconnect the battery. Then, disconnect the connector at the PCM and check for corrosion, damaged pins, or anything that could cause a problem. See pic 2 for location.

Let me know what you find.

Joe

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Monday, October 18th, 2021 AT 5:20 PM

MALLYBOY

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I have checked all these and didn't find any fault, except on the injectors that when I crank the vehicle, spark on plugs will be continuous, but injector pulse can only blink twice, first time. Second time it backfires and cease the pulse.

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Wednesday, October 20th, 2021 AT 12:11 PM

JACOBANDNICKOLAS

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Hi,

If everything is good, then the problem must be the PCM itself. Have you checked for an injector pulse right at the PCM? If you lose it there, then chances are the PCM is the issue.

Remember, the PCM provides power to the injectors via the ASD. Then, based on input from the CKP and CMP sensors, along with other sensors, the PCM provides a ground path. So, make sure the ground (where the PCM mounts) is in good condition.

Let me know.

Joe

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Wednesday, October 20th, 2021 AT 7:17 PM