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Brian
Brian, Auto Service Technician
Category: Ford
Satisfied Customers: 1227
Experience:  5 years Ford Technical Hotline/Service Engineer. 2005 Ford Master Cert. Automotive Technology degree
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94 ford ranger. No spark. Changed coil packs, crank sensor, ...

Customer Question

94 ford ranger. No spark. Changed coil packs, crank sensor, icm, Computer and fuel filter. Alternater checked out good. Fuses are good. Turns over but will not fire. On my timing. it looks to be where it should be. There is a white paint mark on the cam pulley that lines up when it's at TDC. Cannot find cam sensor. Is it under the valve cover? All relays are good also. Out of options except for taking it to mechanic. Don't wanna do that since I already have put alot into this unit.
Submitted: 8 years ago.
Category: Ford
Expert:  Brian replied 8 years ago.
There is no cam sensor. Since you have replaced all the components (except EEC-IV module), then there is probably a wiring problem somewhere. You will have to prove out the wiring to make sure there are no shorts, opens, or poor connections. If there are no wiring problems, then the EEC may be at fault. The crank sensor produces an AC voltage signal that may be getting corrupted by the time it reaches the ignition module, due to bad wiring. Make sure to verify whether the ignition module is receiving a clean strong signal by using an oscilloscope or at least measure the signal with an AC voltmeter at the ICM connector while cranking the engine. The voltage will vary with speed, you are looking for a steady signal that doesn't drop out or become erratic. You can run new wires, and make sure they are not connected to possibly shorted sections of the old wiring, by cutting the old wires off at the connectors and connecting new wires to the cut ends. Or replace the connectors and wiring if you suspect that the connections are bad. Inspect carefully for damaged terminals that won't make a good tight connection with their mating pins when connected.

Here is a basic diagram of the entire system, it is common to all the distributorless units even though this one shows a 6-pack coil.
graphic

Here is a diagram that may help as well:
graphic
Customer: replied 8 years ago.
now I've been reading some today and it's being said that on the ICM. The lower left bolt hole is mainly the ground. This is a must to have that bolt in. My bolt is broke off in that hole and cannot get out.
how do I ground? Drill the hole out?
Expert:  Brian replied 8 years ago.
If you can get the bolt out with a bolt extractor, that would be ideal, but it may be very difficult since it is a steel bolt into the aluminum intake, and it is probably corroded in there tightly. On the ICM, there would be a metal sleeve inside that bolt hole that the bolt makes contact with to get good ground. You could take the ICM to the work bench and solder a wire to that metal sleeve inside the ICM, and then run the wire to a suitable ground somewhere nearby. Put an eyelet terminal on the wire so it can be bolted down well. You want to ensure good contact for the long run, so make sure to clean the metal and use good soldering technique. Weatherseal the exposed solder joint with some paint, or some of that liquid electrical tape stuff that you paint on and it dries.
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Customer: replied 8 years ago.
1 last ? whats the percentage that this could be my problem after changing all this? I know this is 1 of my cheapest fixes.
Expert:  Brian replied 8 years ago.
If it does indeed ground through the bolt hole, it is very likely that the broken bolt is causing a lack of ground for the ignition module. The module cannot turn on without power and ground, so I'd say your chances are good.

Customer: replied 8 years ago.
Reply to Brian's Post: The power to coil packs come through the ICM does it not? All 3 wires on coil packs are hot. So ground should be there also. How many wires on packs should be hot? I have 3 and all are hot.
Expert:  Brian replied 8 years ago.
No, the ground for the coil packs is not constant, it is pulsed on and off by the ICM. When the ground is taken away, current flow through the coil windings stops, and the collapse of the magnetic field makes the coil fire a spark.

When the truck is off, there is no ground to the coil pack, so voltage will show up on all the wires. When you start the truck, one wire at the coil packs is constant power, and the other two are pulsed ground. The voltage on the pulsed ground will be zero when pulsed to ground, but 12 volts when ground is taken away.

The ICM needs ground so it can pulse it to the coils. In other words, the ICM briefly connects the coils to ground, then disconnects the ground when it wants a coil to fire.
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Customer: replied 8 years ago.
Reply to Brian's Post: Good answer
Expert:  Brian replied 8 years ago.
I hope you get it runnin' good again soon.

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