3.0 no spark problem...

Liberto · Mar 6, 2010

A little background...i bought this 98 ranger with a blown motor... i drove it on and off the trailer and into my garage... i decided to just completely rebuilt the 3.0... brand new everything CKS, CPS, pistons, rods, mains, rings... you name it it was replaced... even new heads.... i throw everything back in the truck and its cranking but not sparking... I have power going to the coil pack, but no spark. I took both wires off the crank signal sencor and unplugged the wiring harness at the firewall and checked to make sure there was no break in the wires (pin 21 and 22), i replaced the crank positioning sensor with another new one and still no start... i put the CPS in at TDC with the tooth in the window and on a 30* angle... this is the only thing holding me back and its been a month now..... can anyone shed light on this and help me. I've searched high and low on here, google and my home site (RangerPowerSports.com) and all i keep finding are problems with the old 3.0's with a bad distributor

1998 Ford Ranger 4X4 3.0 Automatic

Rearanger · Mar 6, 2010

Liberto said:
I have power going to the coil pack, but no spark.

Checked coil pack?

Liberto · Mar 6, 2010

Rearanger said:
Checked coil pack?

Yes the resistance is good, there's one power wireS and three signal wires... Well the three signal wires are 12 volt hot when key is on but while starting they don't pulse...

Rearanger · Mar 7, 2010

Power wire to ground should be greater than 10v, if not you'll need to trace that. To determine if possible PCM disable fuel pump, connect test light from power wire to each of the "signal" wires individually and crank the engine, light should show continuous pulse, if not possible PCM. Those signal wires are the primary side of the coil pack, each wire fires two cylinders, the PCM switches them on and off to create high voltage in coil pack secondary. If their not being switched then it may be your PCM as long as it's getting the timed firing signal input for each cylinder.

(You could disconnect the coil pack harness and induce an on/off 12v primary signal from battery with a sparkplug wire and sparkplug grounded. Apply 12v from battery to each signal wire on the coil pack harness and then pull 12v off, at that point you should get good spark at grounded sparkplug, if not then I'd replace the coil pack.)

On further thought, those signal wires may not see 12v, the switch for 12v could be in the coil pack and those signal wires may only see 5v from the PCM. I'd measure the voltage from those signal wires first. If 5v then it'll be hard to jump switch them directly unless you can do it with 5v and with 12volts attached to the power wire input. Sorry for the re-think.

Further Edit: I've looked at my manual and the PCM may ground the IGN Start/Run off/on to switch the primary on the coil pack. If this is so, then the 10v+ on the IGN Start/Run will not harm the PCM. We need someone more familiar with this to confirm before putting 10v through the harness connector at the coil pack so as not to overload the PCM.

Rearanger · Mar 7, 2010

A further look at my manual does confirm (at least for my year) that the PCM indeed does act as a switch to ground for the 10v+ power input to the coil pack. When the switch is closed 10v+ pwr flows through primary of coil, when switch is open that pwr is interrupted and the primary collapses inducing high voltage to the secondary in the coil pack. So using a test light from the 10v+ pwr connector to one of the coil connections of the PCM will flash as the PCM switches the ground off/on and will confirm that the PCM is functioning to switch the coils.

So if you wanted to test the coil pack independently of the PCM you would disconnect the harness, apply 10v+ to the PWR pin of the coil pack, then connect an off/on switch to ground from one of the coil connectors on the coil pack. With a sparkplug wire and plug attached to the corresponding coil pack connection and ground turn the ground switch on and off and you should get a bright blue spark at the sparkplug. Little to no spark will confirm a bad coil pack.

Liberto · Mar 7, 2010

awesome this is alot more help then ive gotten from RPS. tomorrow i'm gonna go back over the truck and figure this out, at this point i dont think it can be a ground so its looking like a ECU right?

masterbrenden · Mar 8, 2010

on a 98 the crank sensor controls spark and if it goes out or is unplugged it will not fire

Rearanger · Mar 8, 2010

Liberto said:
so its looking like a ECU right?

Not until you prove out the coil pack and connections. I had assumed from your first post that you had replaced the crank angle sensor, but masterbrenden is right, if CAS is not sending signal the PCM will not switch the coil pack. Don't assume the most expensive part first.

Liberto · Mar 9, 2010

masterbrenden said:
on a 98 the crank sensor controls spark and if it goes out or is unplugged it will not fire

"brand new everything CKS, CPS, ..." CKS crank positioning sensor lol it's brand new AND I double checked it with my multimeter

Liberto · Mar 10, 2010

SnapOn's MODIS tool confirmed the ECU is in proper working order and nothiong out of the ordinary... its communicating with the sensors etc etc... i'm so lost...

ADD: actually it told me the coolant temp sensor was out of range as the only problem...........

Rearanger · Mar 10, 2010

Liberto said:
SnapOn's MODIS tool confirmed the ECU is in proper working order and nothiong out of the ordinary... its communicating with the sensors etc etc... i'm so lost...

Let's go back. You confirm your CKS is working, including checking connections, you know you're getting 10v+ from PWR connection pin at harness with volt meter, you confirmed that the PCM is switching on/off for each pin that corresponds to cylinders by using test light on PWR pin and cylinder pins, even though MODIS confirms PCM OK - YES? Did you independently test coil pack to confirm no spark to spark plugs?

Did you confirm timing is set properly?

ADD: actually it told me the coolant temp sensor was out of range as the only problem...........

Side issue.

Liberto · Mar 10, 2010

Rearanger said:
Let's go back. You confirm your CKS is working, including checking connections, you know you're getting 10v+ from PWR connection pin at harness with volt meter, you confirmed that the PCM is switching on/off for each pin that corresponds to cylinders by using test light on PWR pin and cylinder pins, even though MODIS confirms PCM OK - YES? Did you independently test coil pack to confirm no spark to spark plugs?

Did you confirm timing is set properly?

-CKS is working and brand new.
-Connections are good and traced to be confirmed.
-We are getting the 12v to the main coil wire
-The PCM is not switching the signal wires on the coil pack... thats my ongoing problem
-Brand New coil pack

Rearanger · Mar 10, 2010

Liberto;663658The PCM is not switching the signal wires on the coil pack... thats my ongoing problem[/QUOTE said:
You'll need to disconnect the harness back to the PCM and do a continuity test to confirm no broken wires. It's strange all three cylinder pins do not switch pwr from PCM if you are getting the power to the pwr pin which leads me to think open circuit to PCM from CKS. Check that harness connection and wires as well. Your installation of CKS at crank is ok? Your timing is ok?

Liberto · Mar 10, 2010

Rearanger said:
You'll need to disconnect the harness back to the PCM and do a continuity test to confirm no broken wires. It's strange all three cylinder pins do not switch pwr from PCM if you are getting the power to the pwr pin which leads me to think open circuit to PCM from CKS. Check that harness connection and wires as well. Your installation of CKS at crank is ok? Your timing is ok?

yes in my first post i stated that i ohm'd out every single wire and no wires are broken... the CKS i just bolted on... i put the motor at TDC and installed the cam sensor at 30 degrees and with the tooth in the center of the opening... lol see my frustration with this truck

Rearanger · Mar 11, 2010

Check ground from PCM. The PCM switches to ground is about all I can add.

3.0 no spark problem...

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