Engine 97 Gt Cranks But No Spark 5.4l Swap

[terryhowellus]

My 97 GT with a 5.4L decided not to produce spark last week while driving home from work. I've gone through a list of items to check and replace but the common stuff seems ok. All electronics in the car are the original 4.6 electronics. I've got the torque app hooked up to it but not anything is obvious from the app.

Here is what I've done so far
1. Verified no spark from either coil
2. Fuel pressure 40psi
3. Replaced crank sensor
4. Measured crank and cam sensor voltage at 0.07 volts while cranking (seems low but is the same for both sensors even after replacing them).
5. Coils are getting 12 volts power.
6. Cleaned cam and crank sensor plugs
7. Removed tuner chip from PCM
8. Tried disconnecting MAF sensor
9. Theft light come on then goes off in 2 seconds after key on.
10. No codes stored in computer
11. Verified tps sensor is working.
12. Replaced relays in main fuse panel
13. Check all fuses under the hood and in the car
14. Connected the torque app but need PIDs for all sensors.

No sure what else to try other than PCM. Any additional ideas before I replace parts?

Also, how can i perform a PCM pinout test to see if the circuits are good...I.e. pinout diagrambor list of PIDs for car.

Thanks.

 

[wmburns]

Does the RPM meter "work" on the app?

Confirm there is +12 volts key on voltage at the O2 sensor Red wire (O2 heater circuit). Use a known good ground. If not +12 volts STOP and find out why.

Measure the key on voltage between the GY/R and BR/W wire of the TPS.

 

[terryhowellus]

Thanks wmburns. The torque app is connected to the ecu but when cranking no RPMs are displayed.

Tests Results
1. O2 red heater wire has 12 volts
2. The TPS has 5 volts between Grey/R and Brown/W wires

I'm certain I tested the correct wires.

Other test I've run
1. 12 volts on R/G wire of coils
2. Disconnected the radio capacitors on the coil
3. Tested all circuits on the PCM for shorts. Used ohm meter to make sure resistance was on all circuits that aren't switches.
4. Tried another key thinking the key chip might be bad.

Any next steps?

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[terryhowellus]

One additional test I ran. This one confused me.

1. Key On I get 12 volts at the pcm input wires on the coils.
2. Cranking I get around 10 volts DC at the pcm input wires on the coil.

If this is really the case then shouldn't I get spark on the plugs? My plugs aren't sparking? This is true for all 8 cylinders.

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[wmburns]

The torque app is connected to the ecu but when cranking no RPMs are displayed.

IMO this symptom that should not be ignored and may point the real problem. IE that the PCM is not getting a good CKP sensor signal.

To double check the no spark condition use a "noid" style test light to confirm spark.

 

[terryhowellus]

I'm throwing in the towel for now and having the car towed to Extreme Mustangs in Monroe NC. I'll post the final cause once I know. Thanks for your response....really appreciate the feedback.

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[terryhowellus]

Problem solved!!!!

The issue ended up being a failed crank trigger wheel. The wheel center actually came apart from the outer portion of the wheel. This caused all kinds of weird results. Many on the web claim these never fail and there is no need for hipo versions of this part....to that I say neigh!!!

When testing ckp voltage I got a reading of 0.04 volts ac when cranking. Also, I got injector pulse but not consistently.

For 3 months I've chased possible bad pcms, bad ckp sensors, bad harness wires only to learn after each test nothing was wrong. I kept coming back to the low ckp voltage was telling me something was wrong. 1 thing threw me off was a Haynes manual stated the cranking ckp voltage should be 0.04 ac volts....I don't feel this is correct based on what I saw. It should be 0.40 ac volts..an increase of x10.

How did I figure out the trigger wheel was bad?
1. Bought a cheap scope for my phone on Amazon. I stuck this in the ckp bore hole but the images weren't conclusive.
2. Purchased an old STEEDA timing wheel kit that basically externally mounts the trigger wheel and sensor on the outside of the timing cover. The car started immediately proving the trigger wheel was bad.
3. Removed the timing cover to find the broken trigger wheel.

Moral of the story...wmburns is correct to follow the data. The data was telling the truth....low voltage from the ckp!!!! I should have checked the trigger wheel....better yet the pros I sent it to should have checked the trigger wheel. I spent 2k in tow trucks, rental cars, and a shop bill only to fix it myself.

See photos below of what my scope showed versus what the actual broken parts looked like.

Note: the scope pics show the trigger teeth aren't aligned with the bore hole. They also show some weird metallic sheen coming from the broken metal but it's not clear what's actually happening. Hopefully this can help someone else.

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[terryhowellus]

Some more photos from when I pulled the timing chain.

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[trinity_gt]

Good find. Question for you: What damper are you running? OE Ford or aftermarket?

If it's aftermarket, the failure of the trigger wheel may be attributable to that, either because the crankshaft bolt was incorrectly/insufficiently tightened or because the damper is not tuned (mass, durometer etc, related to torsional vibration damping) properly. It's also worth noting that there are instances of oil pump failures on record having been attributed to swapping out the OE damper for an aftermarket piece...

 

[terryhowellus]

What I pulled from the crank shaft looks like a normal crank pulley. Its very light and feels like aluminum. It does not appear to be a dampener. I'll take a photo tomorrow.

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