There is no signal to coil

Tiny
BILLY C
  • 2002 CHRYSLER SEBRING
  • 186,666 MILES

02 chrysler sebring; therefore no spark to spark plugs replaced cam sensor, crank sensor, ignition switch (new parts) installed used ecm have fuel pressure no signal to coil have replaced cam sensor, crank sensor, ignition switch (new parts) installed used computer, have fuel pressure?

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Wednesday, January 4th, 2012 AT 9:35 PM

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Tiny
CARADIODOC
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When you have an engine problem, please list the engine size. How are you checking for a signal to the coil? How did you check fuel pressure? Have you monitored the operation of the automatic shutdown relay?

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Wednesday, January 4th, 2012 AT 10:42 PM
Tiny
BILLY C
  • MEMBER

2.4 dohc checked fuel pressure with a fuel guage checked signal to coil with dovm meter & test light swaped relays in under hood fuse box

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Thursday, January 5th, 2012 AT 3:13 PM
Tiny
CARADIODOC
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The fuel pump may fail to run during engine cranking, but it WILL run for one second every time you turn on the ignition switch. That pressure will make it look like the pump is running all the time. If the injectors aren't firing, that pressure won't bleed off so it will look like the pump is working when it is not.

You can check for 12 volts to the ignition coil or coil pack but no test light or voltmeter is going to be able to show what's happening on the switched ground side. There won't be any voltage or pulses to the ground side if there isn't voltage to the feed side.

The first thing to do is measure the voltage to the ignition coil, any injector, or either small wire on the back of the alternator. On older models that was the dark green / orange wire. If yours is different, just look for the wire that's the same color to the injectors and coil. You should see 12 volts there for one second after turning on the ignition switch. You should be able to hear the fuel pump run at the same time. That voltage must return during engine rotation, (cranking or running). If you never see voltage there, you'll need to determine if there is 12 volts getting to the automatic shutdown (ASD) relay and whether the Engine Computer is turning it on.

If there is 12 volts during that one second, the computer has control over the ASD relay and the circuit is working. If it doesn't turn on again during cranking, it is not receiving pulses from the cam or crank sensor or they are out of sync. Those sensors share common 5.0 volt feed and ground wires. A corroded splice, a shorted sensor, or a grounded wire can stop the signal from one or both sensors. A scanner that displays live data will list both sensors as "no" or "present" to show whether their signals are being received at the computer.

A failed camshaft position sensor is the most common problem. The next would be a jumped timing belt. If it had jumped one tooth, the Check Engine light should have turned on and a diagnostic fault code, "cam and crank sync" would be set in memory. At two teeth off, the Engine Computer will shut the engine down to protect the valves. It does that by turning off the ASD relay. That removes power to the ignition coil(s), injectors, alternator field, oxygen sensor heaters, and fuel pump or pump relay. At three teeth off, or if the belt breaks, open valves will be hit and bent by the pistons as they coast to a stop. The clue will be found by checking those fault codes.

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Thursday, January 5th, 2012 AT 9:22 PM
Tiny
BILLY C
  • MEMBER

Caradiodoc your information was helpful found bad tensioner on timing belt. Timing had jumped, Replaced timing belt kit. Still no spark to plugs, or signal to injectors, alternator fieldor or coil

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Monday, January 9th, 2012 AT 7:06 PM
Tiny
CARADIODOC
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Do you see 12 volts going to the coil and injectors for that first one second? If you do not, check the fuses. If you do, but it doesn't come back during cranking, check the 5.0 volt feed to the cam and crank sensors. That should be there any time the ignition switch is on. Next, check their ground wires. Expect to find 0.2 volts. The voltage at the signal wires will vary from close to 0 volts to close to 5 volts when you turn the engine slowly by hand. If both signals change properly, you'll need a scanner that displays live data to see what the computer sees. Those two sensors will be listed as "no" or "present" during cranking. If they are listed as "present" but they are out-of-sync, the ASD relay will be listed as "low" or "off".

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Monday, January 9th, 2012 AT 9:41 PM

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