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]

[crxcess]

Instant drain of all battery power? sounds like you are shorting the + and - directly together. check your wire routing.



I would undo all the wires you modified for the swap and redo it from the start

[accel junky]

Looks like thats what its coming down to.

[xjon]

Sorry, not really helping but, I wish you Good Luck!

[accel junky]

^^^ Thats cool. All goog luck is welcome.

[goofynick6]

Your buddy posted this on the virginia tech car club forum, I saw it last night...kinda funny.

Yeah, sounds like a short...keep checking..

[accel junky]

^^ Yeah, I'm desperately seeking things to try. Got it posted on all the forums I'm a member of and then Michael posted for me on CCVT.

[BKdaMoRoN]

Sounds like a short.

[accel junky]

So I solved the starter problem. It was definitely that the positive terminal on the battery wasnt tight enough around the post.

Thanks for all of the help.

[Nameless EJ6]

Sweeeet! Let us know how it drives~

[BoostFab]

So I solved the starter problem. It was definitely that the positive terminal on the battery wasnt tight enough around the post.Thanks for all of the help.

it's great to know it's that simple issue.

[accel junky]

....well I was wrong. Apparently there's still a problem because now its back to the usual problem...

I think I'm going to replace the lower harness with a new one and then go from there.

I guess if it comes down to it I can send my harness to mckinney and have them figure it out but thats $350-400....

[Joe]

there could be a break inside the insulation on your main positive or ground cables. ive seen it happen before because if a battery post starts to leak the cables act like a wick and suck it down the cable. id replace those cables before you do anything drastic like buying new harness' or going to mckinney.