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No start, no spark

Tiny
NEGGEN
  • MEMBER
  • 1991 FORD F-150
  • 5.0L
  • V8
  • 4WD
  • AUTOMATIC
  • 200,000 MILES
Drove this truck yesterday about twenty miles and it ran fine. Got home and left idling to check the cows, got back in a few minutes later and it shut off when trying to accelerate. Started back up fine but would shut off under load. Today it would not start at all. Fuel pressure is okay, but no spark. Tested it using a timing light. Had a pre-existing check engine light (just bought this truck a few weeks ago) so I checked the codes. The codes showed 113 (ACT), 116 (ECT) and 636 (Transmission oil temperature out of range). Not sure where to go next. ICM maybe? ECM maybe? I checked the inline fuses by the starter relay and they're fine, but I'm not sure if they are the right ones. Thanks!
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Saturday, April 9th, 2022 AT 8:08 PM

24 Replies

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
There are a number of things that can cause this, so we need to track the spark back to the TFI module.

The way we do this is check the voltage going to the coil from the TFI module and find out if it is commanding it on.

I suspect it is not which means we will need to take the next steps.

Here is a guide that will help with this:

https://www.2carpros.com/articles/how-to-check-wiring

I am attaching the wiring diagrams that will help with this but the last is a good diagram that is going to show what we need. Basically, the hall sensor is the crank sensor that we need to get a signal from and then find out if the TFI module is sending the signal.

That will tell us what we need to know so let's start with this and go from there.

Thanks
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Sunday, April 10th, 2022 AT 7:56 PM
Tiny
NEGGEN
  • MEMBER
  • 16 POSTS
Okay. So, I confirmed that the TFI and the coil are getting power (red/light green wire). I took the connection off the coil and checked the power from the TFI to the coil (tan/yellow wire) and nothing. I read up on the TFI in those Fords and due to their proximity to the engine block they get hot and fail often. Could this be the issue here?
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Monday, April 11th, 2022 AT 10:49 AM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
That is exactly what I was going to reference as well. Have seen numerous times where they get hot and fail. Based on this info, I would suggest replacing it.
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Wednesday, April 13th, 2022 AT 8:33 AM
Tiny
NEGGEN
  • MEMBER
  • 16 POSTS
Well, I jumped the gun and replaced it along with cleaning all the grounds that I could find. Still no start. There was one point where it tried to fire once but then nothing. There is 0.4 volts coming into the coil from the TFI with the key on now. When I replaced the module, I did so by marking the position and then turning the distributor enough to access the screws. I didn't remove it completely. Is there a chance I screwed something up when doing that?
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Wednesday, April 13th, 2022 AT 2:52 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Okay. Let's step back and let me know what voltage you have on the red and light green wire when trying to start the engine.

I assume you have.4 volts on the wire from the coil to the TFI module? If that is the case, then we are missing voltage somewhere else so let's check this and go from there.

Thanks
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Thursday, April 14th, 2022 AT 4:09 PM
Tiny
NEGGEN
  • MEMBER
  • 16 POSTS
Yes, it’s.4 volts from the TFI to the coil with no change when I’m cranking on it. The red and light green has 12 volts when the key is on and drops to 9.5 when cranking on it.
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Friday, April 15th, 2022 AT 11:45 AM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Okay. The dropping to 9.5 volts is expected as the starter is pulling a large load and pulls the voltage down. However, that is a lot so it may be worth trying to put a charger on the battery while cranking.

There is a chance that the coil is not firing due to not having close to 12 volts. However, this is unlikely.

Have you replaced the coil? If not check the resistance from the terminal of the red/light green wire and the wire to the TFI.

Let me know what the resistance is, and we can go from there.

Thanks
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Friday, April 15th, 2022 AT 7:29 PM
Tiny
NEGGEN
  • MEMBER
  • 16 POSTS
The coil has not been replaced that I am aware of. The resistance across those 2 terminals reads 00.4 ohms.
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Saturday, April 16th, 2022 AT 10:21 AM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
That resistance appears correct, and it shows the coil is not an open circuit.

The last thing is to check the voltage on the Dark green and yellow wire.

This is the wire that will interrupt the signal and create your voltage spike. If you have voltage there, then I would replace the coil. Unless we missed something with these checks, that appears to be the issue.

However, let's check that and go from there. Thanks
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Saturday, April 16th, 2022 AT 4:44 PM
Tiny
NEGGEN
  • MEMBER
  • 16 POSTS
Okay, so, the diagrams you sent showed a tan/yellow wire at the coil and the other diagram showed a dark green/yellow wire. Mine has the tan/yellow so I'm assuming that's the one you're referring to? There doesn't appear to be a dark green/yellow wire in play here anywhere else unless I'm missing something. If so, the voltage on that wire shows.4 at the coil connection and 12 at the TFI connection with the key on.
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Saturday, April 16th, 2022 AT 8:00 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Okay. Just want to make sure we are at the correct points that you are seeing this voltage.

Take a look at the diagram below. If you have the tan/yellow wire, then this is the correct diagram.

If this is correct, then we need to measure the resistance across the suppression resistor. It should be 22,000 ohms.
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Sunday, April 17th, 2022 AT 10:13 AM
Tiny
NEGGEN
  • MEMBER
  • 16 POSTS
What you added to that chart is correct. I measured the resistance between those two points, and it bounced around a bit and ended back at zero. It never showed a value anywhere near 22,000.
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Sunday, April 17th, 2022 AT 11:38 AM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Okay. That is interesting. I think we are narrowing in on it but when you checked the resistance where you on just the resistor?

Meaning did you unhook the connectors from the resistor and measure just the resistor? If the connectors were still hooked up, then you are going to get resistance through the entire circuit and that will cause it to bounce around like that.

Also, if it settled on 0 ohms that is different than an open circuit. Can you get a picture of what the circuit does when it settles out like this?

Thanks
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Sunday, April 17th, 2022 AT 7:28 PM
Tiny
NEGGEN
  • MEMBER
  • 16 POSTS
I might have misunderstood. I checked the resistance on the yellow/tan wire between the TFI connection and the Coil connection. Where is the resistor? Is that the connection that looks like it’s pigtailed off the TFI wiring harness?
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Monday, April 18th, 2022 AT 4:23 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Sorry, that may have been my fault. The resistor is in the suppression resistor which is part of the wiring harness.

I am attaching the picture of the harness that contains this resistor.
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Tuesday, April 19th, 2022 AT 2:51 PM
Tiny
NEGGEN
  • MEMBER
  • 16 POSTS
Okay, I found the resistor in the wiring harness and it showed 21.9 when I had the meter set at 200,000. I’m assuming that means 21,900 Ohms.
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Tuesday, April 19th, 2022 AT 4:29 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Perfect. So based on all this info, I think the coil is the issue. However, just to confirm you were getting.4 volts on the coil wire when you were cranking the engine or just with the key on?

If you are then this may be a TFI module issue.

Basically, the EEC module gets the PIP signal from the TFI and then sends the signal to the coil to interrupt the signal to create the high voltage spike.

Here is a chart that helps with this and a couple tests for the coil which you may have already done but this will confirm the coil issue.
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Tuesday, April 19th, 2022 AT 6:21 PM
Tiny
NEGGEN
  • MEMBER
  • 16 POSTS
Yes, the tan/yellow wire had.4 volts with the key on and no change when cranking. I’ll check out these other tests and report back. Thank you for everything up to this point.
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Tuesday, April 19th, 2022 AT 8:13 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Not a problem. Sounds good. We will wait to hear back. Thanks for the update.
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Wednesday, April 20th, 2022 AT 4:59 AM
Tiny
NEGGEN
  • MEMBER
  • 16 POSTS
Okay, the voltage seems good. I don’t have a spark tester, but I put a timing light on the coil wire. It fires pretty intermittently (maybe twice in 20 seconds of cranking) and the engine will not fire properly when it does.
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Wednesday, April 20th, 2022 AT 4:53 PM

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