No spark, no codes

[metalmole]

99 ranger, spins over, but wont start, fuel pressure is at 60 psi, not getting spark out of the coil bank, checked for fault codes, no codes, anyone that could point me in the right direction ??? ....... Thanks

 

[442fanatic]

test the coil pack for a dead short maybe.

 

[matt0248]

Well, do you have a test light or a multi-meter to check for voltagtes and a wiring diagram? I suspect that you will find that you do not have pulses for you fuel injectors also. You could simply have a bad coil pack. To check it you would need to unplug the connector and crank it over to see if there are any firing pulses on the wires from the PCM. IF there are no pulses than you probably have a failed cam or crank position sensor.

 

[metalmole]

Yea have a couple meters, I guess I will have to buy a repair manual to get the wiring diagram and test points for the coil, have you done these tests.............

 

[matt0248]

Yea have a couple meters, I guess I will have to buy a repair manual to get the wiring diagram and test points for the coil, have you done these tests.............

Yes. Testing the primary side of the coil should be pretty simple. Althogh it helps to a a second person to crank the engine over. Basically you need to check for a constant 12 V on one of the wires for the coil, you will be able to tell this from the diagram. The PCM grounds another wire to turn the coil on. So what you are looking for is this switching of the ground. If you take one lead of you meter to a 12V source and the other to the wire that the PCM grounds you should see the meter switch between 12 and 0 volts as the engine is cranking. Depending on if you have a 4 or 6 cylinder you will have multiple PCM grounding wires, one for each coil pair.

If there are no pulses present at the input of the coil, you need to move on to check the cam and crank sensors. These are best tested with a graphing meter or a scope. But a test light and regular meter can be used in a pinch. Similar to the coil the output of these sensors should be pulses from high to low (probably 5 and 0 volts, but could be 12 to 0 volts). With the sensor plugged in you need to check for output from both sensors.

If you have a scan tool that can display data you can also check to see if it shows RPM's while cranking. If it does not, this could be another indication of a crank sensor failure.

Another thought popped into my head. Check all sensors for shorted 5 volt reference. IF any one of the sensors that share "reference voltage" from the PCM is shorted, it can cause all the other sensors to not work also.

Sorry to be so long winded.

 

[metalmole]

Thanks, I like long winded people, they have like to share there knowledge. I will get back after I do some checks............
So your saying I should have three wires ( its a 4.0 v6 ) that plug into the coil pack that will switch ground as the engine cranks over to signal the coil packs to fire ??

 

[metalmole]

Ok, just done some checks, there is one wire which is swithced 12 volts with the ing. switch the other three wires have a constant ground, I couldnt get them to switch, with my positive clamp on the positive battery terminal and negitive on one of the three wires on the coil plug I get a constant 12 volts. I am using a didital meter, do I need an antilog meter to see the needle sweeping ??

 

[Turdle]

Check the crank sensor. Sometimes the act of unplugging or tapping on it will make it work again.

 

[matt0248]

Ok, just done some checks, there is one wire which is swithced 12 volts with the ing. switch the other three wires have a constant ground, I couldnt get them to switch, with my positive clamp on the positive battery terminal and negitive on one of the three wires on the coil plug I get a constant 12 volts. I am using a didital meter, do I need an antilog meter to see the needle sweeping ??

No you should not need an analog meter. IF you think you are missing the switches you can set the meter to read frequency. 0 Hz = no change in voltage. Anything other than 0 Hz means it is switching.

P.S. I forgot to mention. if the crank sensor craps out the PCM will not get an RPM input, therefore it does not even know that you are trying to start the engine, so to speak. So you do not get any codes set.

 

[metalmole]

Big thanks to you guys !!

You were both right

Turdle you hit it on the head, unpluged the crank sensor and pluged it back in, started right up.

Matt0248 your right also, the ECM not seeing the engine cranking over so no codes and no coil pulsing.

Also it looks like the crank sensor is just barley rubbing the cogs on the crank gear, I know thats not good, can it be adjusted, is there a cretain air gap ??

 

[matt0248]

It should not normally rub. make sure there is no dirt crammed on to the end of the sensor. The air gap should be pretty small, but I do not konw exactly what it should be. THere is unually no adjustment for the air gap.

 

[metalmole]

Hey thanks for your help!

I have another small issue with my ranger, it has the fuel leak back problem when it sets turned off for a little while, all I do is cycle the key a couple times, but would like to fix it. I know the check valve is in the tank with the regulator and pump, I was thinking of putting a check valve in the line just after the fuel tank, that should keep the fuel from leaking back to the tank. What do you think ??

 

[matt0248]

Probably not worth it. IMHO. The time and $$ and headache (not install with out leaking) is much greater than cycling the key a second time before cranking.