Rb25 start trouble, please view, detailed info

[accel junky]

What vehicle/motor?

-------------------

1990 Nissan 240sx 180k miles on chassis

-Series I RB25DET motor (Inline-6 turbo) 121,000 kms on motor.

-Rb20det/Rb25de transmission

-infiniti q45 MAF

-550cc injectors

-adj. fuel press regulator

-Walbro 255lph fuel pump

-tons of aftermarket parts

Whats the problem?

------------------

When I turn the key to start (with a new battery), the engine turns over a few times, then I

try cranking again and the engine jolts once and thats it. Battery is now dead.

So basically as I try to start the car, all of the battery power is drained instantly.

This occurs with and without the fuel pump fuse installed. So with and without fuel.

What have I tried?

------------------

-Flywheel is not missing teeth.

-Motor has been turned over by hand successfully

-Motor has been compression checked 3 times with no problems turning over engine. (no fuel,

or spark involved).

-Checked battery main ground, 0 ohm.

-Checked battery main power to starter, 0 ohm.

-Checked starter, works fine when applied direct to battery, have a spare, both same

problem.

-This is the second new Battery, its an Everstart , 800 cranking amps, brand new, suitable

for Toyota Supra.

-Also tried a battery from a working nissan truck, same result.

-Tried an extra grounding wire (fat wire) from the starter body to block.

-Car rolls in neutral.

-Checked ecu codes, throwing a 55 for all normal with maf unplugged.

-Checked ecu codes, throwing a 12 for "MAF" with maf plugged in. (q45 maf, different voltage

readouts, but maf not required for start...i dont think)

-Tried cranking with maf plugged and unplugged, same result.

-Fuel pump primes

-fuel is getting into motor, so injectors working in some way.

What can I rule out?

--------------------

-Starter is not bad.

-Flywheel is not seizing with starter.

-Main battery cables have no resistance.

-Transmission is not siezed.

What are my own suspicions?

--------------------------

-Possibly a short somewhere is causing all battery power to be immediately drained?

-Possible bad Igniter chip

-Possible bad coils

-Possible bad CAS (Crank angle sensor)

-Possible bad connection from coils to spark plugs.

Please let me know if you have any ideas. I've searched and searched, and asked and asked

but have not found anyone that has had a similar problem. R33 service manual doesn't give me

any conlusions about this problem and is vague and contracdictory in testing some items.

Thanks,

Daniel

[email protected]

[Paulc]

I have a 98 Stagea (all of 3 weeks) with an RB25DE (Neo) motor that was showing similar if not identical symptoms.

In my case the motor would fire up fine when cold, however if the motor was hot eg 5 minute run or longer it would spin freely for a few seconds, then suddenly almost completely seize up, as in the starter sounded as if the battery had suddenly died. - Leave the bonnet open for 5 to 10 minutes and it would start reasonably normally.

(Battery new! everything else about the vehicle mint or near mint)

The answer was the Crank Angle Sensor mounted on the end of the exhaust cam was all chewed up.

Seems some Dick Head 'Professional' mechanic at a local garage had not put it back on properly when the Cam Belt was changed 2 years ago. The slotted disk had been slowly chewing through the LED Sensor ever since.

'My' Professionals tried to find a second hand one without success, so they had a go at Repairing it. I've only just got the car back tonight and they are saying to see how it goes. Methinks I'll be on the lookout for a new/used 'unchewed one, even though it appears to be starting just fine now.

BTW it took 2 years to get to the critical stage because the previous owner (very fussy careful owner I might add) only did 3000 Km in that time.

Paul.

PS (next day)

My garage guys rang to say one of their contacts had found a used CAS and sent it overnight, would I like it installed, you bet. Took literally all of 5 minutes to install.

I don't know if I'm imagining it but it seems to both start and run much sweeter now.

I've also found out that the original botched job was 20 months ago and the car had only travelled '1700' Km since, 1000 KM of which I had done.

Cheers

Paul.