Any Way to Test a Coil Pack on a 1992 4.0?

rangerenthiusiast · Feb 22, 2018

Hey, guys. Does anyone know if places like Advance or AutoZone can test a coil pack on the ’92 Ranger Custom I just bought (equipped with a 4.0)? I have a handheld voltmeter, but I’ve always been lousy at trying to use it (too many options on the dial for my weak brain to figure out).

Thanks!

adsm08 · Feb 22, 2018

No, the parts stores have no machine that can bench test a coil.

The easiest way, if you suspect it is bad, is to just hook a timing light to each wire and see if one is not firing.

rangerenthiusiast · Feb 22, 2018

adsm08 said:
No, the parts stores have no machine that can bench test a coil.

The easiest way, if you suspect it is bad, is to just hook a timing light to each wire and see if one is not firing.

Thanks, ADSM. Don’t actually own a timing light (not sure how that would work with wires), but I just watched a video on how to test a coil pack using an Ohm/volt meter. I’ll give it a shot tomorrow.

adsm08 · Feb 22, 2018

rangerenthiusiast said:
(not sure how that would work with wires)

Uh, the same way it works with any other wires? You hook the clamp to the spark plug wire and when the coil fires the pickup in the clamp detects the surge going down the wire and triggers the strobe light in the gun...

You know you can't use a timing light on an engine that doesn't have plug wires, right?

rangerenthiusiast · Feb 22, 2018

adsm08 said:
Uh, the same way it works with any other wires? You hook the clamp to the spark plug wire and when the coil fires the pickup in the clamp detects the surge going down the wire and triggers the strobe light in the gun...

You know you can't use a timing light on an engine that doesn't have plug wires, right?

Sorry, it’s been decades since I saw someone use a timing light. Thought it was just used to turn the old fashioned distributors in order to set the timing. Didn’t realize they could be used to test ignition coil function.

adsm08 · Feb 22, 2018

rangerenthiusiast said:
Sorry, it’s been decades since I saw someone use a timing light. Thought it was just used to turn the old fashioned distributors in order to set the timing. Didn’t realize they could be used to test ignition coil function.

Well the light doesn't turn the distributor, you do.

And no, that test wasn't an intended function, but it works for it.

If you don't have a timing light just buy a spark tester. It does mostly the same thing as far as testing for a bad tower on the coil, but costs a lot less than a timing light.

rangerenthiusiast · Feb 23, 2018

adsm08 said:
Well the light doesn't turn the distributor, you do.

And no, that test wasn't an intended function, but it works for it.

If you don't have a timing light just buy a spark tester. It does mostly the same thing as far as testing for a bad tower on the coil, but costs a lot less than a timing light.

Good advice. I didn’t know that such a tool existed. I’ll see if I can pick one up at my local parts store. :icon_thumby:

catfish · Feb 28, 2018

hey im new and not sure im in the appropriate spot. that being said, i have a 97 ranger with a 4.0 and an m5odr1 its 4x4 also. so the truck will turn over a couple times then will not do anything but still has power all the lights are on the interior and exterior. i checked the signal terminal on the starter selinoid and it has no power after the initial start. ive checked all fuses and relays they are all good nothing was blown. ive replaces the starter, starter solenoid, cpps, and the ignition switch and still nothing. im at a loss any help would be much appriciated

rangerenthiusiast · Mar 3, 2018

Just a quick update for everyone that was kind enough to chime in on the thread and those that come after. Turns out that the coil pack was just fine (despite being ancient). The problem was my fuel injectors. They were absolutely disgusting. 67 bucks for a rebuilt set of Bosch injectors and I’m up and running with no more vibration. HUZZAH!

adsm08 · Mar 4, 2018

Awesome.

I have actually started just replacing the injectors any time I pick up a 4.0. With those inexpensive Bosch remans on ebay and how nice they run after new injectors it just makes sense.

rangerenthiusiast · Mar 4, 2018

adsm08 said:
Awesome.

I have actually started just replacing the injectors any time I pick up a 4.0. With those inexpensive Bosch remans on ebay and how nice they run after new injectors it just makes sense.

Definitely. With new ones running around $70 a piece for parts store ones, those babies were worth every penny and then some. It’s great to be able to go bombing down the road without that godawful vibration anymore, and now I can feel confident enough that the engine’s not toast to start on all of the other maintenance that the previous owner neglected to do. Good times. :icon_bounceblue:

Any Way to Test a Coil Pack on a 1992 4.0?

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