1988 Ranger 2.9 bad ICM?

PowerRanger · Feb 20, 2018

Ignition Coil seems to be firing in a strange way. Hooked up a spark plug test light thing and it only flashes when I first turn the key to crank it over and once or twice when I let off the key. List of things I've replaced trying to solve this
-new plugs
-new wires
-new ignition coil
-new ICM (Have not installed it yet, want to make sure I need it just incase I can take this expensive thing back to napa)
Any help would be appreciated guys, really trying to get this truck back on the road so I can stop bumming rides. Thanks!

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adsm08 · Feb 20, 2018

Try hooking up your light again, turn the key to run, and crank the engine with a screw-driver across the starter relay terminals.

The TFI module gets power from two different pins at the ignition switch. One for start, one for run. If the splice starts to fail it will do more or less what you describe. The test I gave will show if power is not getting to it in start, but is getting there in run. If power is getting there in run it will probably also start the engine, so be ready for that.

If said test shows the same results I would at least take the TFI to get tested, if not just replace it outright.

PowerRanger · Feb 20, 2018

Thank you, I will do this test when I get off work.

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PowerRanger · Feb 20, 2018

adsm08 said:
Try hooking up your light again, turn the key to run, and crank the engine with a screw-driver across the starter relay terminals.

The TFI module gets power from two different pins at the ignition switch. One for start, one for run. If the splice starts to fail it will do more or less what you describe. The test I gave will show if power is not getting to it in start, but is getting there in run. If power is getting there in run it will probably also start the engine, so be ready for that.

If said test shows the same results I would at least take the TFI to get tested, if not just replace it outright.

Is the tfi module the same as the ignition module? Or are they two different things?

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adsm08 · Feb 20, 2018

ICM is the generic abbreviation for ignition control module.

TFI (Thick Film Ignition) is Ford specific abbreviation for the type of module used on most Fords with distributors between about 1986 and 1996.

So its more of an "all thumbs are fingers, but not all fingers are thumbs" kind of deal.

PowerRanger · Feb 20, 2018

This is what I bought, not this exact one, but I got it from Napa and it looks just like this. Is this the right part? I also picked up an ignition switch because incase this doesn't work. I get off work around 11pm and will be back out in the shop with updates for everyone.

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adsm08 · Feb 20, 2018

Yup, that piece of shit looks just like the OE piece of shit.

FWIW I don't think very highly of the TFI systems. Actually, the system itself is great. It's the placement of the heat-sensitive module that was shit.

PowerRanger · Feb 20, 2018

adsm08 said:
Yup, that piece of shit looks just like the OE piece of shit.

FWIW I don't think very highly of the TFI systems. Actually, the system itself is great. It's the placement of the heat-sensitive module that was shit.

Any idea of a better way to mount it then? I've heard that they go bad as soon as they heat up and I also read somewhere that ford once recalled them for the same reason. I've got the ICM and the ignition switch brand new sitting here but if there's a better (or less likely to fail) way to install them let me know. Really hoping it'll start after I get these on there. If not I'm all out of ideas, damn near the entire tru k is brand new at this point and it all started over a leaking injector.

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adsm08 · Feb 20, 2018

As far as better mounting goes starting in 93 most of the vehicles that still had TFI systems had the module remote mounted on a huge heat sync that was mounted to the fender, rather than bolted directly to the distributor. If you can get your hands on the heat sync and the remote mounting pigtail off a 3.0 Ranger or a 3.8 T-bird you should be able to just throw that in there, more or less.

PowerRanger · Feb 21, 2018

Update, I replaced the TFI (ignition control module) and it still won't start. And I don't think I am getting power at the coil anymore or at least I couldn't see my light flash when I connected it between the post and the plug wire. This truck is driving me insane. I am at my wits end and im all out of ideas. What else could it be?? Again, it ran when I parked it. I have replaced the following:
-Ignition coil
-Ignition control module
-Ignition switch (not the lock)
-Fuel injectors
-Throttle position sensor
-o2 sensor
-Idle air control valve
-MAP sensor
-Spark plugs and wires
-Fuel filter
-Disassembled the upper intake and completely cleaned it
-Cleaned all ground wires I could find
-Cleaned all wire connections and relays
-discovered eec relay does not have the black cap thing and was likely bypassed to stay on by P.O. ( I think this because the truck ran fine before I parked it)
Again, this all started when I parked the truck a week ago because an injector o-ring had busted and was spraying gas everywhere. Started fine with new injectors but ran really rough, bad hesitation, jerking back and forth driving down the road, parked it to look at it in the morning, battery dead when I got up in the A.M. haven't got it to start since.

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adsm08 · Feb 21, 2018

Check power at the coil, check pulsing ground at the coil.

Check power at the TFI module.

Did you ever test spark while bypassing the run post of the ignition switch?

PowerRanger · Feb 21, 2018

adsm08 said:
Check power at the coil, check pulsing ground at the coil.

Check power at the TFI module.

Did you ever test spark while bypassing the run post of the ignition switch?

I did not, I'm not really sure how to do that, I am still learning. But I will look it up and check that tomorrow

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adsm08 · Feb 21, 2018

Ok, I'll see if I can simplify the instructions for you a bit. Have your timing light hooked up like you have the last few times. Have the key turned to the run position.

Find your starter relay, frequently but incorrectly also called a starter solenoid. It is large, has two big posts coming off the top and a third much smaller one. It is bolted to the inner fender just to the rear of the battery. If you are really lost looking for it just follow the positive battery cable away from the battery and it will take you right there. It looks like this:

https://www.cjponyparts.com/85-93-efi-starter-solenoid-1985-1993/p/SS7/?year=1992&gclid=Cj0KCQiAzrTUBRCnARIsAL0mqcz2IRtpudOP_oh7rU6R6_No9VXv_VQiTRIvYbRs6ZHB4YeIKIq1sucaArA1EALw_wcB

Take a screw driver and touch it to both of the large posts at the same time. This is going to crank the engine. It's supposed to crank the engine. Also, if the issue is at the wiring splice that I am starting to suspect the engine is going to start. If it catches and starts running you need to be ready and get the screw driver out of there quick so you don't chew up your starter, so maybe bump it a few times just to get the feel before turning the key on.

PowerRanger · Feb 22, 2018

Thank you very much, I also thought it was called a starter solenoid. It's been raining the past three days so I haven't made much progress on testing and checking everything. As soon as the rain let's up, or I can get a spot in the shop, I'll be back with an update for you. Thank you for the help!!

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PowerRanger · Feb 26, 2018

Update: I tried the screwdriver bypass you mentioned. The engine did not start but it did crank.
Checked power at the TFI by poking a small hole in the power wire (i think it's the third wire from the bottom of the harness if the website I read is right) and it's getting 11.6v. About to try and test for TFI ground and pip signal. Hopefully this will shed some light on my issue. Thanks for the help!!

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1988 Ranger 2.9 bad ICM?

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