I have read at least a dozen posts, just like the problem I have and there seems to be no simple answer. I live in the middle of nowhere in Montana and if you have no other choice but going to a mechanic, it's over 100 miles for the tow. I do have some help, but we are all stumped. I bought a 1989 F-150 XLT Lariat with only 79,000 original miles. It has always run like new, since I bought it over 2 years ago. Has the 302, manual transmission and "manual" everything else, as well. This past summer, it started bucking and jumping a bit when in a higher gear and low RPM... say 4th gear and slowing down to 25 MPH and then hitting the gas again... it would act like it was missing and sputtered. Before winter hit with dozens of feet of snow and -30 degree nights, (no, I do not have a garage), I was slowly replacing the basics... new spark plugs, wires, cap and rotor, but no luck on the issues. Two weeks ago, I was turning around in a pullout and it simply died, with no warning. It sure seemed to be ignition related the way that it shut down. Since then, we have replaced and tested a new coil, a new ICM, a different cap and rotor and still, no spark to the plugs. Seemed like a week spark from both the old and new coil when tested So, we put in a new re-manufactured distributor with yet another new ICM, thinking this had to be it, since about the only thing missing was the pick-up coil in the distributor. Nothing! How much more is linked into this ignition system, other than the ECU??? What other components are even a possibility? I pulled the ECU this afternoon and having a friend pick up a new one, tomorrow. I did open the top and check to see if anything was obviously burned up inside and saw nothing that looked bad. I really don't mind buying a couple hundred bucks in parts... we have no mechanics or garages up here and newer parts for a truck that is 28 years old, isn't all that bad... plus I now have spares. Could it be something as stupid as the inertia switch or a wire to that? Could that shut down the ignition? I had thought that was more for fuel shutting off from an accident, but maybe not. We've checked as many wires as we could, like to the coil and from the ICM harness. Seriously at a loss of what other components are left to check. Please throw me some ideas of what I may have missed. Maybe the new ECU will bring it back to life? Thank you!

 

The inertia switch has nothing to do with the spark.
If you think it is the ECM just unplug it and see if the spark returns. It will not start with the ECU unplugged as it will not be getting injector grounding so no fuel into the engine.

But sounds more like fuel issue to me.

 

Could be a lot of things; When was this truck tuned up last?

 

I don't know the difference between dying from spark and dying from fuel failure.

Spray ether, or something else combustible like carb cleaner, I to the throttle body and see if it starts. If it does, it's a fuel problem.

 

Seriously? I have no spark to the plugs and I see comments about fuel issues? When I am cranking over the engine, we all smell fuel. How does spraying starting fluid into the throttle body bring back the spark to the plugs? I have no spark to the plugs after all the above mentioned has been done. Tune up? Other than the slight bucking that I also mentioned, this truck has run fine and even started at -30 degrees, many mornings.

 

Sub, why would you call out a fuel issue if I have no spark at the plugs. Please explain.

 

Week spark could be from a low battery and slow cranking.
The bucking could be low fuel pressure. The fuel pressure has to about 28psi or above to start the engine.
If you have good spark at the ignition coil and a full battery voltage at the coil while cranking then you have either a bad ignition wires, distributor cap or rotor.

 

Tune up; Timing checked ? not mentioned...

Did you replace your EECM like you said you were going to ?
If so what was the result ?

Voltage to the coil ? vdc?

Check fusible links ?

Check inline resistors?

Voltage to the TFI module ?

Radio Noise Capacitor shorted ?

Voltage to the EECM ?

Key switch failing?

 

You're going to have to forgive us for dumbing down the process.....we aren't here to get our trucks diagnosed, and we can walk you through diagnosing anything on your truck, provided with accurate information in a logical order. We constantly deal with descriptions of "no spark" diagnosis from "it doesn't start", and "it's getting fuel because we can smell it". We aren't patronizing you, but we aren't going to assume that you have narrowed the problem to a particular running function just because you say so.

So. how did you confirm no spark?

Also...Have you pulled codes?

 

"We've checked as many wires as we could"

What did you check? What was the result? Wire color? vdc? Resistance?

Your wiring harness has a few junction points that may have wires no longer or barley attached.

Bucking, low rpm? Could be Fuel/Air mixture, intermittent wire connections.

 

Do you have a dash mounted Tachometer?
If so; Is it working?
Is it shorting out Wire #11 DG/Y ?

 

Tune up; Cleaning the Throttle Body? Cleaning the Ar Bypass Valve?

Sounded like you may have had a Fuel/Air Mixture issue before you had a Spark issue.

You may very well have 2 issues at this point.

 

Part 1 -How to Test the Ford Ignition Control Module (Fender Mounted)

 

I do thank ALL of you for your replies and advice. If you read my original post slowly and accurately, you will have to trust me with what I said I replaced, tested and checked on. It had nothing to do with fuel and everything to do with ignition and not getting spark to the plugs. After replacing everything that I did, (which I m not disappointed in), my last shot was the ECM. I found one in Billings at a salvage yard and had it shipped to me last week. As soon as I plugged it in and turned over the ignition, it fired right up! A quick adjustment of the new distributor and it was running better than ever. Yes, I am sure with the right knowledge and test equipment, this diagnosis could have been MUCH quicker, but under my circumstances, I followed the basics from my past experiences... and I have NEVER had to replace an ECM. That would have been my last guess. Again, I thank you all for the advice and patience with me. Keep on truckin'!

 

LuckyLobo59: I am trying to rep you, but it is not going through.

Regardless, reps to you brother for coming back and posting your results and success. You thread will help others. And yes, it is good to keep on truckin!