1985 f150 ignition control module/won't start

[jka]

I have been having problems with my 85 f150 for about 5 months now and the problem was that it would start then I could drive to somewhere, shut it off and then get back in a couple of minutes later and it wouldn't start so I would have to wait a couple of hours or even a day and then it would start. Everybody including the auto parts store said it was the ICM so I replaced it.By the way before I replaced it the truck quit starting period. It turns over but doesn't start now. I have also replaced the coil and still nothing. I did notice today that the icm I just bought and put on only has 2 pins on one of the connectors compared to 3 slots on the end that is on the truck. I took my old part to the store and forgot it there so I can't compare the two. But the color (blue) of the specific piece on the icm did match the one I took out. They said that was the main thing. So does anybody know if I need to have 3 pins on the one side or do I just have another problem altogether. thanks for reading my babble

[SteveZ]

Originally Posted by jka

I have been having problems with my 85 f150 for about 5 months now and the problem was that it would start then I could drive to somewhere, shut it off and then get back in a couple of minutes later and it wouldn't start so I would have to wait a couple of hours or even a day and then it would start. Everybody including the auto parts store said it was the ICM so I replaced it.By the way before I replaced it the truck quit starting period. It turns over but doesn't start now. I have also replaced the coil and still nothing. I did notice today that the icm I just bought and put on only has 2 pins on one of the connectors compared to 3 slots on the end that is on the truck. I took my old part to the store and forgot it there so I can't compare the two. But the color (blue) of the specific piece on the icm did match the one I took out. They said that was the main thing. So does anybody know if I need to have 3 pins on the one side or do I just have another problem altogether. thanks for reading my babble

Part pinout should match exactly. You have 3 wires into the module?

The common problem with this vintage is heat and its long-term effect on the ignition coil and module. The Ignition coil and TFI are relatively inexpensive, usually come with at least a 12-month warranty, but either one fails slowly. Slow failure means engine becomes hard to start on hot days esp. The quits while moving sporadically. Then quits altogether and refuses to start even though it turns over strong and you can hear the fuel pump engage. Otherwise 99% of the time it runs just fine.

If you have the TFI-IV -not the ICM - "ICM" would be mounted in the fender, and your year model typically did not have one. Ford renamed the TFI to ICM and moved it to the fender mount later. Your year model would normally have the TFI-IV mounted on the distributor, facing you standing from the front. 1986 or after may have the fender mount ICM, and an added heat sink (some pattern here?)

There is a good reason they moved it - the TFI modules fail in high heat conditions. If the TFI module gets too hot, it stops working, the truck will stall and then start only after sitting for awhile - hours or even a day - no consistent pattern. When you install a new one there is a heat/conductive barrier that you want to be very careful of keeping very clean until mounted. Obviously you want to ensure your cooling system is working optimally, this vintage seems to run hot and be under-capacity for radiator sizing, etc.

Two tests - Primary/Secondary resistance on the Ignition coil, primary is across the connector pins, secondary is from on pin to the part where the coil to distributor wire connects. Coil primary resistance varies by model, likely is 0.3-1.0 ohms. Secondary is likely 8,500-11,000 ohms. If either of these are out of spec, replace the coil. You can do the same tests on the TFI module, I do not recall the specs for ohms. You will also want a test light (12V) to check the coil if it passes the resistance checks, one with long leads as you need to crank the motor and still be able to see it. Resistance will be on the low side when bad.

Also check: grounding wire, negative terminal battery wire, all connections, contributing problems are lack of quality grounding, corroded and oxidized wires leading to the harnesss, and a resistor upstream of the coil. Fuel is not usually the problem here.

IMHO the F-150 84-86 did not make the transition well to modern electronics for engine control, it changed every single model year until 87-88, Ford seemed to be trying various approaches to get it right, and problems don't show up until the wiring and ignition components are very old, then the gremlins start showing up. Looking under the hood you typically see some portion of the ignition circuit has been replaced by now, included seeing partial replacement of wires in the harness, new coil and TFI modules, etc. No surprise here, the ignition system is the weak link in 85-86 for high failure rates as they hit high mileage and/or age. I hit the same kind of problems with an '84 non-EFI Brono II. By 1986 they sorted out of host of problems from the year-one design.

The good news is the parts are relatively cheap, if you do the labor, it's not outrageously expensive.

The Haynes Consumer Manual is very good in this area, pick one up when you go back to get your part.

[SteveZ]

Sorry - forgot to add often the reason both of these components fail is poor condition of the wiring upstream, including possible bad connectors and or intermittent short-circuiting of wires with ancient insulation, oxided ends, etc.

[jwooden]

Originally Posted by SteveZ

Sorry - forgot to add often the reason both of these components fail is poor condition of the wiring upstream, including possible bad connectors and or intermittent short-circuiting of wires with ancient insulation, oxided ends, etc.

Hi Steve / others - If you have a second?

I have similar problem with 1978 E150 van (which I bought new ;-) The module is located on fender well of this vehicle. I have the intermit. start problem when hot. On first pass at resolving the problem I notice that the plug connectors on both the module and the inductive pickup have almost not strength left, the plastic is all crumbly. Fortunately most of the damage is on the female plugs which are the ones that are attached to the components and not to the harness - If I had to replace the connectors on the harness side, any idea where I might find suitable parts? :-(

In your experience is the inductive pickup in the distributor something that is worth replacing? Seems like this item has a pretty simple job so other than the connector issues might not commonly cause any problems?

THANKS,
Jim

[jwooden]

Originally Posted by jka

I did notice today that the icm I just bought and put on only has 2 pins on one of the connectors compared to 3 slots on the end that is on the truck.

Interestingly, my E150 van has same layout. The original Ford factory MODULE has only two pins on one of the connectors (the other is a 4-to-4 match up), while the factory HARNESS has three pin sockets in the mating connector.... I know that at least in my case it came from the factory that way ;-)

Jim

[ervinj]

Just for giggles, Check to make sure that the rotor actually turns when you crank the engine over, I thought I had your problem only to find that the gear on the distributor shaft had sheared not allowing the rotor to turn.

ervinj

[jwooden]

ervinj:
Ouch... that's a wierd one ... In my case rotor is turning , it is intermit. problem only occurs on warmer days after driving and parking for a while.

Advance Auto has new control module from GP Sorenson for $22 so I'm going to slap one in and see if life gets better ... I hope!

THANKS!
Jim

[nomanlikethetowman]

From my experiences, the blue connector ecu, only has 2 pins, red & white wire, the other should be 4 wires, orange, blue, purple and green? If it came with a blue one, then put a blue one back in. see other post s, check to see if you can grab on to your rotor and turn it.

[jwooden]

My rotor still appears firmly engaged with the rest of the engine - which I like ;-)

Since a new ECM was only $20 I have replaced it, mine was the original and after 26 years the plastic on the connectors was turning to crumbly crud anyway....

Now we have a cold spell and I guess I'll have to wait and see if problem re-occurs. I have put a can of "freeze-spray" in the van so that if it does happen again I can start cooling things off under the hood (inductive pickup and ....) and see if I can identify the problem. I remember hearing that the "high powered" ignitions took a toll on the coil, mine still reads good with the ohm meter (proper primary & secondary resistance and no short to ground) but I wonder if any "damage" to the coil would show up in the resistance readings?

Thanks all for the helpful hints!
Jim