Truck died. Need efi troubleshooting help.

hammer said:

Got it running. Coil wasn't producing a strong enough spark anymore. Picked up a spark strength tester. Read that our efi systems should produce a spark strong enough to travel 1/2". Mine was barely able to travel 1/4". New coil and it fired right up. Lesson learned. Having spark is not good enough.

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glad you got it fixed. didn't know that about the spark strength, thanks for the info

Glad you got it fixed!

Got to ask about the spark strength tester. I didn't know there was such a thing. Where did you get it?

My dad had it. But here it is;

http://www.thexton.com/mobile/ignition-spark-tester-mp-34.html?redirectCancelled=true

I didn't know there was such a thing either.

Good to see you figured it out and posted the result on this thread. Always cool to follow up your repair question with the successful repair.

hammer said:

Got it running. Coil wasn't producing a strong enough spark anymore. Picked up a spark strength tester. Read that our efi systems should produce a spark strong enough to travel 1/2". Mine was barely able to travel 1/4". New coil and it fired right up. Lesson learned. Having spark is not good enough.

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Where did you read that data?

Used those for years myself tracking down problem ignition issues. Haven't had to use it in recent years though, with the relatively robust sparks that usually emanate from these modern setups. Hate to even think what kind of gap my distributorless Explorer setup would jump.

When you don't have a tester though, another way to visually tell if a spark is decent or not is it's color and, well, "sound" and speed.
A yellow or red spark might seem good based on color, but that color is usually associated with the bottom end of power. What you're really looking for are whiteish/bluish sparks with a real snap to their sound. You might not be able to tell when you've seen a weak spark at first. But you'll certainly know when you've seen a good healthy spark!
It fairly screams "keep your hands away from me!" and in plain English too!

If you ever have a chance to play with one of those old MSD spark comparison machines that all the speed shops used to have on their counter you'll see as well.
Our old stock systems were halfway decent when working up to expectations. Modern electronic ones with good coils however are a league above.
Test sparks/arcs from my old combination Duraspark and Jacobs ignition was a sight to behold for sure. You'd almost have thought it was the business end of a MIG welder!
It would jump almost to the limit of the testers.
I still like telling the story%) about how I started my engine one time and it was running kind of rough for some reason. Also some snapping/hissing/buzzing noises were coming from under the hood. Popped it open and realized I'd left the distributor cap all the way off!
It was laying at an angle off to the carburetor side of the distributor and the rotor was out in the real world spinning merrily away, while sparks were jumping the gap from the rotor tip to the upended cap's contacts!
Reason it was running rough was simply because it naturally wasn't able to always hit the correct plug contact point. Duh...

Anyway, gave me a good healthy respect for a good ignition and I never touched a plug wire of a running engine again. That was about 25 years ago now and I still cringe when I get near a plug wire.:-[

Paul

chuzie said:

Where did you read that data?

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My dad's a mechanic by trade. He had access to a website called identifix. Basically we ran codes and then the website is pretty good for real world fixes not just manufacturer remedies. Read it on there.