Good evening, I have 1994 Chrysler LHS that is a crank but no start. I pulled into a parking spot and was sitting idle for a 3 minutes and the car shut off, never restarted, only cranked. Dealership specified the PCM wasn't sending correct voltage to the starter. I found a PCM and replace it myself (company said, plug and play type) - crank only, no start. I replaced the starter - crank, no start. Replace ld the battery - crank, no start. I didn't have a fuel pressure gauge but I used my key to press in the insert and fuel shot out, I'm assuming meaning that the fuel pump works. What is another step/steps I can take to diagnose the problem? Thank you for your time.
What's confusing us is that you say the car will Crank but the dealer blamed the starter circuit.
If the vehicle cranks, there isn't a problem with the starter or the starter circuit.
You say the LHS will crank so let's assume that this is a Crank, No Start.
The 1st question to answer, "is the engine getting spark?"
Let's look at the ignition wiring diagram. I highlighted Red for Power and Green for Ground signals from the computer that fire the individual ignition coils. (it's a wasted spark ignition. 3 coils for 6 cylinders)
The 1st thing to notice is that the ignition coils get their Power from the ASD relay. ASD stands for Automatic Shutdown Relay and the computer controls it. (control side of the relay isn't shown in the diagram).
How it works is that the computer needs a signal that the engine is turning (from the crankshaft position sensor and camshaft position sensor) before it will energize that relay and provide Power to the ignition coils (and the fuel pump relay).
EXCEPT when you first turn the Key to ON.
When you first turn the Key to ON the computer energizes the ASD relay for a second or two to energize the Fuel Pump Relay and prime the fuel rail.
And you're saying that you stuck your key in the schrader valve on the fuel rail and gas shot out. That seems like the computer has control of the ASD relay (for at least the first second or two (like it should) when you turn the Key ON (When it isn't relying on crankshaft position sensor or the camshaft position sensor input voltages).
I'm going to post a link to a tutorial on how to start troubleshooting this from a website that assumes you know absolutely nothing about cars and walks you through it step by step.
But one thing. On Page 3, "Verifying Coil Pack Is Getting Power".
I need you to perform one more test.
Let's look at that page here.
1st. For this test you don't have to leave the wiring connector connected to the coil pack like it says in Step 2.
You don't have to "backprobe" the connector by sticking a pin or something into the backside of the connector.
Just disconnect the connector from the coil pack and probe that number 3 socket terminal.(it's easier).
So the "one more test" I'd like you to do is after you check for Power from the ASD relay to the coil pack while cranking (step 6), is to turn the car OFF, then with your test light alligator clip still on the battery negative post, and the test light probe in the "number 3" wiring connector socket, have a helper turn the Key to ON. (not start, just on).
The test light should light up for a second or two and then go out. That will confirm that the computer has control of the ASD relay and the wiring between the computer and the ASD relay and the coil pack are good.
AND IF you get power to the "number 3 terminal" for a second or two after Key ON, but you aren't getting power to it while cranking we need to start looking into the Crankshaft position sensor circuit and the Camshaft position sensor circuit.
Here's that link:
https://easyautodiagnostics.com/chrysler/3.3L-3.8L/coil-pack-tests-1
@jack62 to the rescue, again. Thanks.
Sir / ma'am this is amazing info. I'll have to take my time to understand/digest this. I'm diligent so I'll figure it out. Thank you very much.
Good evening. I'm not getting power @ the ignition coil plug. I am getting constant power @ the ASD relay but not sure how to test from the relay to the plug. I know there is an "activate power" (not sure what it's callled) when the ignition is turned on power is sent to said components. I unplugged the ignition coil and checked for power while cranking and nothing. Maybe I'm doing something wrong or missing a step. Thank you for your time
If you followed that tutorial I linked then I'm sure you're doing the tests right. (they make it pretty easy)
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I understand that you aren't getting any Power to that #3 wire on the coil pack connector in the above image while cranking the engine
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I'm not clear about the results from that "one more test" I asked you to perform in my original response
.
When you probed that #3 wire in the image above with your test light, and turned the Key to the ON position (not Start), did the test light come on for a second or two and then go out on its own?
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That's important because it will tell you that the ASD relay is working and that it has both of its Power inputs and its Ground input (from the computer to energize the relay) and that the wiring from the relay to the coil pack is good
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(The reason this has to happen is because the ASD Relay provides Power to the "Control Side" of the Fuel Pump Relay and the computer wants to "prime' the fuel rail when the key is turned to ON)
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Additionally, when the engine is cranking the computer needs voltage signals from the crankshaft position sensor and the camshaft position sensor to energize the ASD Relay. It doesn't need them when it's using the ASD Relay to energize the fuel pump relay to prime the fuel rail so you're taking the crank and cam sensors out of the equation doing it this way. Also a broken timing belt out of the equation
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However, if the test light didn't come on for a second or two when the key was turned to ON then the easiest thing to do is to recheck your fuses and then swap that ASD Relay with another (unimportant) relay to see if the problem is a faulty ASD relay
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You can probably use your AC clutch relay or the headlight relay for the test
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If that fixes the problem then go out and buy another relay
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If it doesn't fix the "no start" then the ASD Relay isn't the problem
.
It's time to test the ASD Relay sockets
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Here's how that ASD Relay is wired. These are the Pins on the Relay. You'll check their corresponding sockets in the fuse box
.
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If you aren't getting Power to the coils then either the Power on pin sockets 30 or 86 is missing OR the Computer Ground signal on Pin socket 85 to energize the ASD Relay is missing
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As far as your concern about the wiring between the ASD relay and the coil connector you can test for continuity between ASD Relay Pin socket 87 and the #3 coil connector terminal
Okay my apologies. I didn't follow the directions exactly. When I reread it I see where I went wrong.
I'm getting power at the green (#3) wire, so I use the HEI spark tester (don't have the name in front of me and I forgot if that's the correct name) and had read about "pair cylinders, I think it's called" I am not getting sparks from any coil plugs @ the coil box. My next step I believe is the check something called "signal switching".... do I have you make the LED with resistor light as shown in the link you sent me or can I just use a test light?
You're better off using an LED test light for this just to protect the transistor in the computer
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These days you can just buy a LED Automotive test light at any auto parts store or from Amazon/ebay
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They make them with just an LED light bulb or with a digital display built into them. (You just need a cheap one with an LED bulb
.
.
Okay, cool. I have a test light that shows 12/24v so I'm good there. I haven't checked the crankshaft or camshaft sensors yet. Guess I'll do that to make sure I'm getting power to them. Is having the vehicle on (not cranking) okay to check them or should I crank the engine and check for power?
Thank you for your time on this
Make sure to read that tutorial carefully as you perform the voltage tests
.
IF you have Power on that #3 wire while cranking the engine it means that the computer IS getting a voltage signal from the Crankshaft Position Sensor (because it needs that voltage signal to energize the ASD Relay (and send power to that #3 wire on the coil connector)
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So go ahead and check for the Ground Switching Signals on the other wires like the tutorial explains
Okay, no problem, thank you. Only issue I'm having is how to use the test light instead of the led test tool. It's specifying "connect the black lead of the LED light to the wire identified with the number 1 in the image viewer." I understand how I'm preforming the tests just not how I'm supposed to use the test light.
Back probe the connector. Here's a video on how to do that
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You don't need a special back probe tool like in the video. You can use a straight pin from your wife's sewing basket
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You'll attach the alligator clip of your test light to the pin and the probe of your test light to battery positive
.
https://youtu.be/JfGa3hFSg7U?t=141
Good morning, I did tests 5 - 7 it didn't specify I had to do them all but I wanted to make sure I was getting voltage through all signal switching wires. I didn't read anywhere that said what "good or bad" voltage was. Each one hit around 7.4v. The battery I have connected is new but has been drain by my stupidity. Everything at this time is pointing to a bad ignition coil pack. I've already purchased it and hopefully will have time in the morning to put it on. I'll let you know what happens.
It didn't start up. I got the battery recharged. I made sure to marked the coil wires to.put them in the same place. I changed the coil box. Still crank but no start
The tutorial does specify that you have to do all three tests (5, 6, and 7) because you need to confirm that the computer is creating and feeding the Ground Switching Signal to each of the 3 individual coils
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And you would have gotten one of two test results for each of those 3 tests
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CASE 1: The LED light flashed ON and OFF the whole time the engine was cranking or running. This tells you that the PCM is providing the Switching signal and the circuit is OK. This result confirms that the ignition coil pack is bad, replace it.
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CASE 2: The LED light DID NOT flash ON and OFF the whole time the engine was cranking or running. This tells you that the Switching signal is not present
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So, did the test light flash on and off when you tested each of those 3 wires while cranking the engine or didn't it?
If you aren't getting those Ground Switching Signals from the computer, BUT you are getting Power to that #3 wire while cranking, then the likely suspect (since you've already replaced the computer and the "No Spark" persists), is the Camshaft Position Sensor
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While you have it out, look down the hole it goes into and have somebody crank the engine so you can confirm that the camshaft is spinning and the timing belt hasn't broken
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If it's turning then you can either test the sensor or just replace it (they're cheap)
Oh wow. It wasn't flashing, it was steady on. Okay so next step is the camshaft sensor. You're saying, I take the sensor out and as it's being cranked look inside and see if it's turning. If it's turning potentially it's the sensor and if not potentially it's the timing belt
Good evening. Just to verify, the camshaft sensor is in the front right of the engine? If that is correct, the camshaft turned while cranking. I'm waiting for the cam shaft sensor to arrive. If for what ever reason that doesn't work. Could it be possible that the aftermarket alarm could cause my car to do the same thing?
Thank you for the time you've spent. I wish something had worked. I know I most likely missed something somehow.
Thank you for the time you've spent. I wish something had worked. I know I most likely missed something somehow.
If the PCM wasn't sending the correct voltage to the starter, why did it crank? Please see FAQ section.
Why the down vote @twobsolo? Based on the info you gave, it's a legitimate question.
I'm not even sure how I did that. I was pressing the arrows not knowing what they were
I know nothing about how the electrical part works or how to diagnose it. I don't know what the PCM is for completely. I just know 2 other shops couldn't diagnose the problem and the one dealership they said something about the PCM was going to charge me $1200 to change a part that I could do myself
only cranked. Dealership specified the PCM wasn't sending correct voltage to the starter.
What a bunch of scumbags. They just wanted to sell you an expensive computer.
Steer clear of stealerships!
