Possible PCM Failure??? No Spark!!
#1
12-01-2015, 01:47 AM
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Possible PCM Failure??? No Spark!!
I Have a 93 Dakota 5.2 MPI. I have searched for a couple days for this specific situation and have not found it.
It just wouldint start the other day. It cranks but no start. I can smell fuel after cranking on it several times as I test things. so I believe I have fuel. I definitely have fuel pressure the asd relay is working and I have full time 12v to the ecm on pin 3. And switched 12v w/ key in run and start position, on pin 9.
I have tested this voltage while cranking and it does not drop. The asd relay has 12v on port 30 and the fuse checks out (no corrosion).
I figure the cam sensor is working but I had a known good spare and swapped it out. Both tested good. Tested the crank sensor via a procedure I found on the web. It has 8.92 volts to the cps and triggers 5v when spinning the crank by hand slowly. Also when this happens the asd relay would kick on again for a second or so.
Now to the part that makes me think its the PCM. The green striped wire at the coil and at the PCM show full + voltage when cranking. But the gray wire at both the coil and PCM show full + voltage when cranking and no pulse, this is with the coil in line. When I unplug the coil, I get a pulse from negative to positive with my test light (one that you connect to both battery terminals and signals red or green).
I have changed the coil for good measure. still no spark...
Any help would be greatly appreciated. Thanks
It just wouldint start the other day. It cranks but no start. I can smell fuel after cranking on it several times as I test things. so I believe I have fuel. I definitely have fuel pressure the asd relay is working and I have full time 12v to the ecm on pin 3. And switched 12v w/ key in run and start position, on pin 9.
I have tested this voltage while cranking and it does not drop. The asd relay has 12v on port 30 and the fuse checks out (no corrosion).
I figure the cam sensor is working but I had a known good spare and swapped it out. Both tested good. Tested the crank sensor via a procedure I found on the web. It has 8.92 volts to the cps and triggers 5v when spinning the crank by hand slowly. Also when this happens the asd relay would kick on again for a second or so.
Now to the part that makes me think its the PCM. The green striped wire at the coil and at the PCM show full + voltage when cranking. But the gray wire at both the coil and PCM show full + voltage when cranking and no pulse, this is with the coil in line. When I unplug the coil, I get a pulse from negative to positive with my test light (one that you connect to both battery terminals and signals red or green).
I have changed the coil for good measure. still no spark...
Any help would be greatly appreciated. Thanks
#2
12-01-2015, 08:41 AM
Champion
With the battery disconnected, unplug and replug the PCM several times (I'd say six myself).
After that, and after you reconnect the battery, find out how much pressure you actually have on the fuel line.
Wouldn't hurt to borrow a NOID light set and see if the injectors are firing properly also.
Yes, I know you smell gas. I'm asking what PSI you actually have, and is it within spec?
My Malibu used to do this when the Airtex pumps would fail - about 30 to 35PSI on a system that required 50PSI IIRC.
RwP
After that, and after you reconnect the battery, find out how much pressure you actually have on the fuel line.
Wouldn't hurt to borrow a NOID light set and see if the injectors are firing properly also.
Yes, I know you smell gas. I'm asking what PSI you actually have, and is it within spec?
My Malibu used to do this when the Airtex pumps would fail - about 30 to 35PSI on a system that required 50PSI IIRC.
RwP
#3
12-01-2015, 10:06 AM
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With the battery disconnected, unplug and replug the PCM several times (I'd say six myself).
After that, and after you reconnect the battery, find out how much pressure you actually have on the fuel line.
Wouldn't hurt to borrow a NOID light set and see if the injectors are firing properly also.
Yes, I know you smell gas. I'm asking what PSI you actually have, and is it within spec?
My Malibu used to do this when the Airtex pumps would fail - about 30 to 35PSI on a system that required 50PSI IIRC.
RwP
After that, and after you reconnect the battery, find out how much pressure you actually have on the fuel line.
Wouldn't hurt to borrow a NOID light set and see if the injectors are firing properly also.
Yes, I know you smell gas. I'm asking what PSI you actually have, and is it within spec?
My Malibu used to do this when the Airtex pumps would fail - about 30 to 35PSI on a system that required 50PSI IIRC.
RwP
Do you know what the fuel pressure is on this truck? If memory serves me well its 32-35psi?
Also with the Noid light am I just checking each injector to make sure its getting signal or is there something more specific your looking for. Thanks Again
#4
12-01-2015, 11:08 PM
Champion
No, it's just that one of the problems may be no injector fire, or a hung injector.
Two different possibilities.
As to what it should be on a 1993, I dunno. For 1995, the FSM on page 14-6 states 35-45 PSI, I'd say that'd be good for you also.
And yes, I'd check to make sure the injectors are being fired, but not run wide open.
The ASD should be off after about 2 seconds until the motor starts cranking, at which time it should turn on again. Jumping across it, however, should be OK for a quick test.
RwP
Two different possibilities.
As to what it should be on a 1993, I dunno. For 1995, the FSM on page 14-6 states 35-45 PSI, I'd say that'd be good for you also.
And yes, I'd check to make sure the injectors are being fired, but not run wide open.
The ASD should be off after about 2 seconds until the motor starts cranking, at which time it should turn on again. Jumping across it, however, should be OK for a quick test.
RwP