I have a 98 Plymouth Breeze Expresso 2.4L /AT with 315k miles and crank but no start situation. Timing is dead on and the cam shafts are rotating. I have measured 12 volts to the coil and have switching signals from the ECM on each coil bank during cranking but no spark to the spark plugs using a HEI plug tester. I have verified voltage and signals using a digital multi-meter and LED circuit tester I have replaced the crank sensor(3), cam sensor, coil pack (3), spark plug wires, ASD and Start relays, and the ECM and I also have 50 lbs of fuel pressure during cranking. What am I missing or is my car defying the laws of automotive science.
Sorry to take so long to reply. I was hoping someone else had an answer. When you're checking for spark, do you have the other spark plug wires attached to their spark plugs? If you do not, you may not get any spark even from a good coil. When you think of the older distributor systems, and you pulled off a plug wire, that was the only break in the circuit and it was the only place the spark had to jump. With your distributorless system, two spark plugs are in series and the spark jumps both gaps at the same time. If one wire is removed from the plug creating a gap that's too big for the spark to jump, there won't be any current flow so there won't be any spark at the other wire either where you might be testing.
Have you checked for diagnostic fault codes?
February, 5, 2013 AT 8:54 PM
I did have the other 3 plug wires attached when I checked the number one plug for fire.
I will redo the test again with the other wires unplugged. As for DFC's I've installed a new (re-flashed) ECM since the trouble started but before that I got a P340, loss cam signal /crank. I will have to buy one since I can't get to the auto parts store or know anyone that has one.
Also.I back pinned the coil plug (red to plug, black to ground) to check for voltage and signal and noticed that when I turn the ignition switch on I get 12 volts to the meter as long as the check engine light is on (about 3 sec.) And then when the check engine light goes out it goes out the voltage across the plug drops to zero. When I crank the engine the voltage goes up and down erratically. When I check for ECM signal across coils 2-3 and 1-4 with the LED circuit tester (black to plug and red to positive battery) the LED light is on and then flashes when I crank the engine. Is this normal?
February, 6, 2013 AT 12:12 AM
First of all, you checked for spark correctly by having the other three wires connected to the plugs, (as long as the plugs were installed).
12 volts at the coil for three seconds is longer than normal but is okay. One second is typical.
The erratic 12 volts during cranking has a very common cause on the single cam engines. You said, "Timing is dead on and the cam shafts are rotating", which I took to mean you have the dual overhead cam engine. If you have the single cam engine, remove the cam sprocket and check if the dowel pin is sheared off.
February, 6, 2013 AT 8:07 AM
I rechecked the coil spark with no spark plug wires attached to the coil and attached the HEI tester( grounded to the negative battery terminal) directly to the coil using a small piece of vacuum hose. No spark on either bank.
I do have the twin cam engine and verified that the cams are spinning by looking in the belt cover and removing the (new) cam sensor. All good.
I rechecked the voltage and signal to the (new) coil and (new) plug also installed a (new) ASD relay and checked all the fuses inside and out. The same as I mentioned before.
I have 50 PSI of fuel pressure and can hear the fuel pump running (switch on).
I have checked the wiring to the (new) crank sensor and the coil plug back to the (re-flashed) ECM connector pins for continuity. All good.
I will recheck the cam sensor and grounds today after work but at this point I'm scratching my head and thinking ignition switch or knock sensor. The only components I haven't changed yet!
(New car maybe, at this rate I'll have one except for a paint job!)
February, 6, 2013 AT 9:50 AM
You're getting wrapped around the axle with confusion and you missed some of my points. You can not remove all the spark plug wires and expect to have spark. Each coil feeds two spark plugs at the same time. If either one is disconnected, that break in the circuit will prevent both from firing.
My story about the camshaft dowel pin doesn't apply to your dual cam engine, just to the single cam engine. The timing belt and sprockets are lined up perfectly giving the false illusion that valve timing is perfect. When the dowel pin shears off, that lets the camshaft turn very slightly on the sprocket. You're looking at the timing mark on the sprocket but the camshaft position sensor is looking at the position of the camshaft on the other end. That's where it will be late in relation to the crankshaft position sensor. When the camshaft is off by the equivalent of one tooth, the Engine Computer will turn on the Check Engine light and set the fault code "cam and crank sync". At the equivalent of two teeth off, the computer will shut the engine down to protect the valves. It does that by turning off the automatic shutdown relay. The common clue there is that erratic 12 volts you had at the dark green / orange feed wire at the coil pack or any injector. You can't learn anything by observing the camshaft turning, and there's no way to visually tell the camshaft has turned on the sprocket except to pull the sprocket off and look at the dowel pin. In your case we can forget that. I have never heard of this problem occurring on the dual cam engines.
At this point the best thing to do is get your hands on a scanner that displays live data and look at the cam and crank sensors. During engine cranking they will be listed as "present" or "no". If both are present you will also see the ASD relay listed as "on".
February, 19, 2013 AT 7:26 PM
Sorry it took so long to answer back, but I actually found the problem for the crank but no start to be the wiring harness to the crank sensor. I splice in some new wire and a new crank sensor connector. She starts every time now. Now I'm back at the original problem which is the engine hesitates under acceleration at which point the RPM gauge either bounces upward or downward while driving at any speed ending in a P1391 code in the PCM. This also happen if I rev the engine above 3000 RPM. My Actron code scanner read idle @750-800 rpm's and spark advance moves around 13.5 14.5 degrees As I mentioned before, I have replaced the crank sensor, cam sensor, coil pack, spark plug wires, ASD and Start relays, and the PCM. Is it possible that the aftermarket cam and crank sensor can cause this problem?
February, 20, 2013 AT 12:41 AM
P1391 Intermittent Loss of CMP or CKP
On older engines they would stall if the signal from the crank or the cam position sensor dropped out, but on most newer ones a running engine will stay running when the cam signal disappears but a stopped engine will not start because the automatic shutdown relay won't turn on. I would look first at the cam sensor's connector to be sure there's no corrosion on the terminals and they aren't spread and making poor contact. I don't like throwing random parts at a problem but in this case you may need to try a new cam sensor to see what happens.