Jeep GC troubleshooting cranks but won't start
Cranks but won't start. WHY? ECM bad. CPS bad. Fuel pump bad.
Cranks strong, battery 18 months old and trickle charged - OK.
ASD and Fuel pump relay click in. Voltage test shows relay is activated.
Spraying starter fluid into intake manifold and engine runs fine.
Therefore no fuel or fuel injectors not opening.
No fuel? - is pump getting enuf amps (shud be 8 amps). Fuel pump relay shud be
activated for @2 secs before ASD relay will shut it down if CPS is bad. (I don't know if
CMS will shutdown via ASD or simply run rough.) Do any other sensors input into ASD
which can cause Fuel pump relay to switch off. BTW put in new No. 6 and No. 15 fuses.
I don't see amperage on Orange wire output from Fuel pump relay and don't hear fuel
pump priming or smell fuel (yes tank is 3/4 full). Also installed new FP and ASD relays
as cheap fix, assuming new relays are not defective. Has anyone built a causal mapping
to aid in troubleshooting a "crank but won't start" condition? BTW2 dealer had this for 2
days and didn't find a any codes but I had CPS replaced just in case and it ran for 4
weeks but not running for last 2 weeks after my son took it 4WD- it ran fine all day then
wouldn't start after returning home and hosing mud off undercarriage.
I would double check all the fuses. Also with some relays they are making and breaking the negative side of the circuit. Just a thought.
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