It came home yesterday, and this morning it refused to start. Even though I can hear the fuel pump engage, I tried a shot of starting fluid into a vacuum port on the intake. It made no difference. I pulled all six plugs and did a compression test. All were between 120 and 130 PSI except one that showed 150. That shouldn’t keep it from starting. So I laid all the plugs atop the intake with their wires connected and checked for spark. None of them sparked. The check engine light is not on. What is the most likely cause for this situation?
Start by finding out whether or not 12V is making it to your coil pack. If not, then your next stop should be relays and fuses.
I should also have mentioned that it was a little hard to start a few weeks ago, but that had largely straightened itself out. I thought it was a dirty injector and ran some BG-44K through it. That may have nothing to do with the current situation as spark didn’t seem to be an issue.
The coil pack has white numbers painted on it, leaving me to believe that it was replaced by a salvage yard unit at some point. I’ve only had the car three months.
The first step still doesn’t change. If 12V is making it to the coil, then worry about the coil. Think about it - a very simple way to narrow your search by eliminating whole problem areas.
It’s possible that the ASD relay is at fault. Here is some information from ALLDATA about it that may aid you in checking it out.
The PCM energizes Auto Shutdown (ASD) relay by supplying relay ground, when ignition switch is in START or RUN position and PCM is receiving a reference signal from distributor.
When the ground is applied, the relay is energized, and voltage is allowed to flow to fuel pump, fuel injectors, ignition coil, generator field winding, and O2 sensor heating element.
When PCM does not receive reference signal from ignition system, (indicating engine is not running), then the PCM interrupts relay ground circuit and no voltage is supplied to fuel pump, fuel injectors, ignition coil, generator field winding, and O2 sensor heating element.
The PCM controls fuel pump relay and ASD relay simultaneously, through same ground circuit.
CIRCUIT OPERATION
The Automatic Shut Down (ASD) relay is located in he Power Distribution Center (PDC). Power for the coil side of the relay is provided by circuit F12. This circuit is HOT in the START and RUN position, and is protected by a 10 Amp fuse in cavity 18 of the junction block.
Power for the fuse is supplied on circuit A21 from the ignition switch. The A21 circuit receives power from the A1 circuit. The A1 circuit is protected by a 20 Amp fuse located in cavity A of the PDC.
The Powertrain Control Module (PCM) controls the ground path for the coil side of the relay on circuit K51. This circuit connects to cavity 51 of the Powertrain Control Module (PCM) connector. It is also spliced and connects with the coil side of the fuel pump relay
When the ASD relay is energized, the contacts internal to the relay close connecting circuits A14 and A142. The A142 circuit is spliced and provides power to the fuel injectors, generator, and the PCM.
Circuit A14 is protected by a 20 Amp fuse located in cavity B of the PDC.
In his post he said he casn hear the fuel pump and has no spark at the plugs. That would rule out the ASD relay.
That’s what I thought too.
Here is some more info. I checked for voltage at the four pin connector at the coil pack by checking each recepticle to ground and each to each of the other recepticles in turn. None showed voltage. Yes the key was on. Then I ohmed three fuses that had to do with ignition even though they looked good from the outside. They checked OK too. So I tried to start it. It fired up on the first try, but missed and ran at 2200 RPM. AS it settled down it seemed to run OK. Then it started to pop through the intake. I shut it off and restared it. It ran ok part of the time and popped part of the time. I do not hear any vacuum leaks hissing. Unless someone has a good theory about this thing, I’ll probably tow it to a pro tomorrow. I should have mentioned that it is the 3.5L OHC V6.
Go to Autozone’s website, register an email address, plug in the car’s info, and go to the Repair Guides section. Find the ignition section. It should tell you which wires are which on the harness for the coil pack and how to check for voltage so that you can double-check. It may also tell you how to check the resistance on the coil pack - that’s not a full check but you can at least tell if its definitely bad.
I’d do that before jumping into the expenses of a tow truck and paying a shop for both diagnostics and then parts. If the coil pack is bad, you’re probably just looking at something like $60 for a new one, and as you can see it is a breeze to install.
A failed crankshaft sensor will prevent your car from starting and will not necessarily set a code depending on the ‘failure mode’, or how it has malfunctioned. Basically the computer cannot tell if the engine is turning and will not energize the ignition system. This may not be your problem, but it’s one thing to check.
His plug spark test was FAULTY…you need an assistant or use a creative clamp method to ground out the body of the plug in order to see arcing at the plugs… I suspect that you do have a spark issue but at least test them properly to see first if you actually have no spark. You need to ground the body of the plug somewhere on the engine would be nice…
No it doesn’t.
It has a separate fuel pump relay so it’s possible for the pump to energize. The ASD relay powers the ignition system and the injectors so I would be checking the ASD relay circuit and fuse.
I attached the wiring diagram but I’m not sure how well it will show up. Here is the description of operation as well…
OPERATION
PCM controls the fuel pump through the fuel pump relay ground.
When the key is in START or RUN position and the PCM is receiving an ignition reference signal, the PCM grounds the fuel pump relay, activating pump.
If no ignition signal is sensed by the PCM, the PCM interrupts relay ground, turning pump off.
CIRCUIT OPERATION
The fuel pump motor, located in the fuel tank, is controlled by the fuel pump relay located in the Power Distribution Center (PDC) . Power for the coil side of the relay is provided by circuit F12. The F12 circuit is HOT in the START and RUN position only and protected by a 10 Amp fuse located in cavity 10 of the PDC.
Circuit A21 is used to power the fuse and is connected between the ignition switch and the PDC. Power for the A21 circuit is provided by circuit A1. This circuit originates in the PDC and is protected by a 20 Amp fuse located in cavity A.
The F12 circuit is spliced and provides voltage to the Powertrain Control Module (PCM) and the Automatic Shutdown (ASD) relay.
The ground for the coil side of the relay is controlled by the PCM through circuit K51. The K51 circuit connects to cavity 51 of the PCM. Logic internal to the PCM determines when the coil side of the relay should be grounded.
When the PCM grounds circuit K51, contacts internal to the fuel pump relay close connecting circuits A1 and A141. Circuit A1 is connected to the BUS bar in the PDC, HOT at all times, and protected by a 20 Amp fuse located in cavity A. Circuit A141 is connected from the relay to the fuel pump motor. Ground for the fuel pump motor is provided on circuit Z1. This ground terminates at the body ground, located on the left rear wheel well.
It turned out to be a faulty ignition switch. Apparently it worked intermittantly or I suppose we would not have heard the pump. If it was held “just right” it would start for an instant, but die when it was released. A new switch fixed it
Don’t worry, I did the spark plug test correctly. The base of each plug was grounded on the metal intake manifold.