Q45 will turn over but won't start

macanudo

Hi all -- My car has new fuel pump, air filter, 2 new ignition modules. I really think it is some type of an electrical problem.
Car was running great. One day, I parked it for about 45 min and when I returned, it wouldn't start I had to get it towed home. I'm clueless
PLEASE HELP!?!

Thanks in advance for any help -- I really appreciate it.

bretfraz

Type in "Q45" in the Board Search and find "Q45 troubles". Ask your question there. Q45Man aka Dennis Evans will answer eventually. He is the Lord King Guru of the Infiniti Q45.

Or, even better, go to Yahoo Clubs and find the Infiniti Owners Club. It's pretty much dedicated to the 1st generation Q45.

jgmilberg

Try shooting some starting fluid down the intake, if it starts you have either a bad replacement fuel pump or maybe a faulty fuel pump relay. I would start there first.

When was your last tune up, I don't know if your car has one but check the cap rotor and ignition coil, if you are not getting spark to the plug it won't start. Be careful when testing for spark 45,000 volt ain't fun!

q45man

The Q has 8 individual spark coils [what cap what rotor? What plug wires?] and it takes 4 hours to get to all of them plus they almost never fail [like 1 in 1000 in 10 years]!

Measure the fuel pressure after filter [34-44 psi].

When the pump was changed was the electronic pump control module checked [common failure is burned ground contact from leaving the loud worn pump in too long...eventual open circuit in module......take wire with 2 alligator clips jump pump ground to ground temporarily bypassing module. Can't leave it this way for more than 10 minutes new pump will over heat and fail.

Other things like hydrolocked from bad injectors start with pump circuit. Measure current at pump fuse [inside fuse panel] 3-6 amps depending.

The pump shuts off 10-15 seconds after key is turned on ----if no start! or engine dies.

http://clubs.yahoo.com/clubs/infinitiownersclub

q45man

The 90-93 Q had the most advance engine technolgy available until 1994-98 when BMW, Lexus, MB finally caught up via varible valve timing and coil on plug systems.
All owners should have the 1000 page shop manual as the systems are very different and complex compared to run of the mill old style designs.
The 32 valve 4 cam engine is built to racing standards [interfearence valves, 6 bolt mains and bearing girdle, stainless steel exhaust headers, sodium cooled exhaust valves, etc.] and as such you have to be patience and very careful dealing with it. Most tolerances are 10 times more severe [0.0001"] beyond most shops ability to work on correctly.
After 12 years of refinement the 2002 engine barely produces 10% more torque than the orginal design with much more complexity! The 96-2001 engines were real dogs [low power].

macanudo

This is great to know! Thank you so much for you knowledge, I really appreciate it.

jgmilberg

I did not know that the Q had coil on plug design. I was shooting from the hip with standard trouble shooting procedure. I was at least partially correct on the fuel pump "relay" or as Infinity calls it controller. Anyway I will put that in my mental data base for future reference. Thanks for the info.

Mr_Shiftright

Yikes! What does it cost to replace 8 coils I wonder? I know on the Saab V-6 with only 3 it's quite expensive.

q45man

The controller [$500] is in addition to the more common relay it provides a varible resistance ground to the fuel pump. Three different speeds for pump depending on demand: Crank and WOT, cruise, and idle as requested by ECU [Rpm and load based].
We have over 400 old Q customers [400x 8 coils] only 1 out of 3,200 has failed in 6 years [on up to 11 year old cars] and that was caused by an oil filled spark plug well.
90-93 0wners must change chain drive tensioners and chain guides at +100k [depending on luck] or engine destruction as guides break, chain jumps time allowing valves to hit. pistons!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Knock sensors harness and sensor failure [due to overheats] are common due to sloppy maintenance...$450 worth of parts takes 6 hours to get to and change.
A 1990 design with 278 HP and 300 lb/ft from 274 cubic inches requires a little special care.

jgmilberg

That seems a bit excessive to have a controller to run the fuel pump. Three speeds, WOW! Why not just use a regulator to control the pressure instead of the pump itself? It sound pretty neat though. How reliable is the system though, it seems over complicated.

q45man

The idle injection time is 2.0 millsecs at 34 psi with 370 cc injectors. Max power is 11.0 millsecs at 44 psi....that's a 18x increase in fuel [the first 1.5 millsecs doesn't flow much] from idle to WOT.
The pump has a max capacity of 33 gallons per hour while maintaining a 44 psi pressure.
The trispeed is necessary to minimize pump noise [lux car] at low speeds and extend pump life while still being able to deliver 320 HP on demand....the injector duty cycle never exceeds 60%.
Just one of the things necessary to get 100-150k out of a pump.
The system never fails unless you fail to change fuel filter every 30k and ignore the sound when the pump gets noisey from dirty gasoline!
Many expensive High Power cars used an extra cold crank injector to start the engine; Q just supplies WOT pressure and volume, much simplier and less injectors to break.

q45man

There is also a regulator to finely control rail pressure based on engine vacuum [34 psi at 18" ...increasing to 44 psi at 1-2"] this translates to a 14% flow increase with a constant injector opening time....acts like the accelerator pump on a carb on sudden tip in acceleration before the WOT switch tells the ecu to tell the pump controller more volume is needed....there is a time lag and this covers the 1/2-1.0 second.