97 TJ no spark no injector Pulse but fuelpump primes

Tiny
97HEEPTJ
  • MEMBER
  • 1997 JEEP TJ
  • 2.5L
  • 4 CYL
  • 4WD
  • AUTOMATIC
  • 267,000 MILES
I parked the jeep for 2 days and when I tried to start it, it ran for a second and died. No codes stored in computer and gauges/check engine light all function. I have no spark, no power at the coil, no injector pulse but the fuel pump is priming. Battery is fully charged.
I replaced the crank sensor, cam sensor, tested the coil (in specs), the asd relay is good, getting power to engage the asd but no voltage for the circuit it makes. Cleaned ecm ground and checked all applicable fuses.
I jumped the asd and introduced 12volt to the circuit, nothing.
I jumped 12v to the green coil wire, nothing.
I eliminated the aftermarket alarm, nothing.
I checked for burnt or broken O2 wires, nothing.
So in conclusion there is no voltage passing through the asd circuit, there is no voltage at the coil or injectors, not even for a second. I followed the test procedures I've found on here and other sites. It all seems to point in one direction.
Am I missing something? Or am I correct in assuming the Ecm is toast even though there's no codes and the dash powers up.
Thanks for any input.
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Sunday, March 26th, 2017 AT 5:49 PM

8 Replies

Tiny
97HEEPTJ
  • MEMBER
So update.
I jumped 12v to #5 slot for ASD relay and it fired.
I tried it once already but must have had a bad connection.
Anyway. I believe this confirms ECM?
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Monday, March 27th, 2017 AT 12:25 PM
Tiny
CARADIODOC
  • EXPERT
It sounds like you don't have 12 volts feeding the ASD relay. I'm not familiar with a terminal #5. Most Chrysler products use a 1" cube relay, and terminal 30 has constant 12 volts. If that is missing, a fuse is blown due to something being shorted on that line. If you can jump 12 volts onto that line and the engine runs, that eliminates the Engine Computer as the cause of the problem. They don't cause many problems anyway.

Some Chrysler products use a separate fuel pump relay that is turned on by the same circuit, at the same time, as the ASD relay. If you hear the fuel pump run for one second when the ignition switch is turned on, the ASD relay is turning on too.

Check for that 12 volts in the ASD relay socket. That will tell us where to go next.
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Monday, March 27th, 2017 AT 2:32 PM
Tiny
97HEEPTJ
  • MEMBER
Thanks for the response. Fuel pump primes, asd relay clicks. No 12v coming into the relay on 30.
If I put a jumper from 12v to 87 it starts.
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Monday, March 27th, 2017 AT 2:54 PM
Tiny
97HEEPTJ
  • MEMBER
Also where does A22 on the ECM/PCM get its voltage?
Thanks
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Monday, March 27th, 2017 AT 3:00 PM
Tiny
97HEEPTJ
  • MEMBER
I'm chasing the wire now.
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Monday, March 27th, 2017 AT 3:32 PM
Tiny
CARADIODOC
  • EXPERT
I looked at a wiring diagram, and your vehicle does indeed use a separate fuel pump relay, so that hum of the fuel pump can't be used for a clue. The clicking of the ASD relay does prove the Engine Computer has control of it.

If there's no 12 volts on one terminal in the ASD relay socket, fuse 6, a 30-amp is blown. That is in the under-hood fuse box on the right side of the engine compartment. That circuit also feeds terminal A22 at the Engine Computer.
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Monday, March 27th, 2017 AT 4:36 PM
Tiny
97HEEPTJ
  • MEMBER
I ended up finding the battery power to the asd (that forks off from the Ecm) had worn thru and corroded. I repaired the wire and it fired right up!
Thanks for you info, it got me headed in the right direction.
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Monday, March 27th, 2017 AT 9:08 PM
Tiny
CARADIODOC
  • EXPERT
Dandy. Happy to hear it's solved.
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Tuesday, March 28th, 2017 AT 2:17 PM

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