The no spark mystery continues

[Kmcbride3956]

Okay one more thing... I just decided to test my coil wire for continuity and got nothing, so I tested another one I had laying around and got nothing. All I’m doing is touching the ends of the probes to the metal shaft of the coil wire that around the top of the coil and the distributor cap. I know my meter is working as I also tested other things to make sure. What’s up with that? Is there something to plug wires I don’t know about?

 

[RonD]

Spark plug wires have high resistance, so continuity tester may not work

You test them with an OHM meter, set to 100,000(100k)
Generally Ford uses about 5,000-7,000 ohms per FOOT of wire, so a 2 ft wire would be 10-14k

 

[Kmcbride3956]

I’m learning all kinds of stuff. Well here’s where I’m at.
Start had 10v while cranking; nothing with just the key turned on.
Run has 10 volts while cranking and 12 volts with key in run position.
TFI ground is good
Coil and TFI both have 12 volts with key on
Still no spark.

 

[RonD]

You can "make spark" with jumper wire

Key on
Use a GROUND wire to coils "-" terminal, then pull it off, coil should spark EACH time you remove the Ground wire from the coil's "-" terminal.

Thats what the TFI module should be doing when you crank the engine, grounding and ungrounding the "-" terminal to "make spark"

TFI gets the "timing" of the grounding and ungrounding from the hall effect sensor inside the distributor

So its not a complicated system but it all has to be working, and yes it is a pain to track do problems

 

[Kmcbride3956]

Well here’s the glorious ending to this stupid problem. I wanted to run through the tests ONE MORE TIME to make sure I didn’t miss anything. Only problem was, I was by myself and didn’t have anyone here to crank the truck while I watched the meter. So I rigged me up a way to hold the probe from the meter to one of the wires going into the TCM. This way I could sit in the truck and crank it, had my phone recording the meter, and had the probe held in place. Well something touched something else and you can probably guess what happened next. I turned the key to run position and got a nice little electrical fire under the hood. So now the wire harness that plugs into the TCM is melted and burned. I’m so irritated with myself and this little truck that I’m giving up. Everything had been checking out okay but still no spark. I’d love to know what the problem is but I’m done messing with it. I will either part out the thing or swap a 302 into it. That’s what I wanted to do from the start, but it looked like a little more work than I had initially thought. The body of the truck is 3 different colors and beat up, the inside is in surprisingly good shape but even if I put a V-8 in it it would still look like a beat up little POS. I certainly appreciate all the help and advice I got here. But I think I am done trying.

 

[RonD]

Bummer

Not sure how that fire would happen everything is fuse power

 

[Kmcbride3956]

Yeah I’m not sure how it happened either. It was when I was trying to test the RUN lead and my contraption that I had rigged up touched something else in that wire harness that had an exposed wire and it didn’t just melt, there was actually a little flame for a second. Now that makes me want to go look at the fuses because I want to see if it blew or not. Certainly should have. Which fuse would control the TCM?

 

[RonD]

In 1988 it would be a Fusible Link in the engine bay on the starter relay post with the battery Positive cable

Its for the ignition switch, if you turn on the ignition no lights should come on if that fusible link is blown

 

[Kmcbride3956]

Huh, everything still works and lights up. Okay I know i said I was giving up, but it’s really just driving me crazy at this point. I went and looked all around the engine bay and the wire harness for the TCM isn’t melted TO bad... lol. I’m pretty sure that this can’t be related to the no spark issue in any way, but I did find that the wire going to the oil pressure sensor is cut. I don’t suppose it would have a failsafe mode where if it didn’t think it had oil pressure it would cut the ignition??? Long shot, but it would be nice.

 

[RonD]

No, no fail safe
But back in the day when electric fuel pumps were first being used with carbs there was a fail safe that used an oil pressure switch to activate fuel pump power, no oil pressure no power to pump, but it was a safety issue not to save an engine
Didn't want an electric fuel pump continuing to pump out gasoline in an accident

 

[Kmcbride3956]

Well today I went out and inspected the damage from my electrical mishap. It looks like i mostly burnt up the little thing i had rigged up. I also inspected the fuseable links at the starter relay and they look good. So i plugged the TCM back in and turned the key to the and turned the key to the run position and noticed that the fuel pump isn’t coming on now! I cut the wires to the inertia switch and spliced them together just to rule out that component. Still the same thing though, fuel pump not coming on. I checked fuse #18 and it had continuity so I don’t know what I did to cause the fuel pump to not come on now. So now I got no spark and no fuel! I say I’m done messing with it, but every time I walk past it, it calls to me to come mess with it.

 

[Kmcbride3956]

Oh one other thought. If it was getting fuel again, do you think it would be worth trying to roll start the thing? I’m just wondering if there’s a wire near the ignition switch that’s messed up and when you turn the ignition to crank maybe it comes loose or something? Cause in the run position, everything seemed to check out. Another reason I’m suspicious of this is because the cover that goes around the steering column is kind of popped off a little like someone was messing with something in there. Like i said, all I know about this truck is that it used to run, it broke down like 3 years ago, wasn’t getting spark, and they “tried to mess with it some”.

 

[RonD]

Just run a 12volt wire to the Coil "+", in the old days this was called "hot wiring" an engine, prior to locking steering columns thats all you need to do to get engine running, lol, and jump starter motor

But yes you can try push/bump start, that bypasses one pathway from ignition switch, under the dash, out of the picture, same as 12v jumper to coil does