94 q45 wont start

[Rokketarm]

Hi all,

I'm having trouble getting my q to start. It ran fine yesterday, I got home went to start it up and it said "low battery charge" on the display screen inside. At this point it just clicked when I turned it over, so I took the battery out had it checked and found it to be bad. So I put the new battery in last night, turned over just fine, but now it wont start. have no clue where to start on this one, as it was running just fine earlier in the day. Any help, or suggestions would be greatly appreciated.....Thanks

[Q45tech]

Make sure alternator is supplying as speced current vs rpm [graph in FSM] make sure alternator does not have a high off pararsitic drain...............same with all other circuits.

Usually bad alternator destroys 3 year old battery or 3 year battery destroys alternator.

[Rokketarm]

Thanks, is it possible that the bad battery fried my ignition coil? The alternator is a year old, also was wondering if it damaged the ecu??

[Rokketarm]

Update....I checked the coils and the spark plugs, all worked fine. had a spark emitted from each coil, and no fouled plugs. Any suggestions on where to look next would be greatly appreciated.....this is driving me nuts.....Thanks

[maxnix]

Test alternator and battery in the manner Q45tech has suggested in many posts.

If they are good, proceed to starter relay, ignition switch, etc.

[goody90q45]

Update....I checked the coils and the spark plugs, all worked fine. had a spark emitted from each coil, and no fouled plugs. Any suggestions on where to look next would be greatly appreciated.....this is driving me nuts.....Thanks

From your descriptions it sounds like the engine is cranking but not starting. You've got spark to the plugs so the next step would be fuel. What's the fuel pressure past the filter? How many miles on your Q? Have you changed the fuel pump or FPCU? Have you had what sounds like a swarm of bees in your trunk lately?

The summer heat seems to be bringing out the worst in the Q's fuel delivery system. Seems to be a lot of fuel pump and FPCU problems as the heat rises. It might be time to jumper the fuel pump to ground and see if the FPCU has taken a dump.

[Rokketarm]

Update.....I called a local mechanic at Infiniti, and he said to check the ECU, which I did....turns out my ECU was fried. I replaced the ECU today and it started right up and purred beautifully. Thanks for all your suggestions and help. I have a quick question on a sensor.....I'm trying tor replace the oil pressure sensor, but it's so inaccesible. Any suggestions on the best way to tackle this problem, and install it without taking half the car apart would be greatly appreciated...Thanks

[texasoil]

Put a jack -and wood block to protect pan from dents- under the oil pan and lift the engie a bitt (1"). THen there is enough room to snake a ratchet and socket into the space. I used stubby pliers to R&R th electrical connection. Not easy access, but possible. Done it 3 times once on each Q45 I service. Seems to be endemic.