1.5jz cranking slowing with no start

[b3n_rix]

hey guys, Im sure some of you have seen my build of my s14 with a 1.5jz in it.

Now I am at the stage where it's time to try to start it, bolted the factory throttle body onto my manifold, plugged what needs to be in new plugs and filled the tank.

it's cranking but extremely slowly.

I have
12.8volts at the battery
12.8volts at the battery side of the kill switch
12.79volts at the engine side of the kill switch
12.7volts at the power side of the start button
12.65volts at the ignition side of the start button
12.5 at the starter.

here's a paint shop of how I have it wired up.



I can't understand why I am not getting it to crank better I'm down to the starter being faulty which I am hoping to god it's not because it's not easy to get at.

[b3n_rix]

I have plenty of fuel pressure, and 0.7volts at the injectors I have spark at the plugs as well.

[sc400]

whats the volts when cranking?

[Daddio]

Battery voltage is a little low (would expect 13+ volts at a fully charged battery)
Make sure earths are good (run an earth from battery to engine block if not present)
Also, almost 0.5v drop from battery to starter is a little higher than expected, but obviously enough to kick in the solenoid as it cranks.
Slow cranking usually a sign of either: battery insufficient, poor earth, poor starter, high resistance/insufficient capacity for isolator.

[b3n_rix]

So I made a few mistakes. I wasn't paying attention when I was writing. They should all be 13.??volts.

What point should I check when cranking??

[b3n_rix]

Just checked it again going off the volts meter on my turbo timer and it reads 12.94 and cracking 12.72

[midnight_purple_GA70]

what is the CCA rating of the battery
What gauge and amp rating is the power cable running from the battery to the starter
did you connect up the thick (4 gauge from memory) ground cable from the block behind the air con compressor to the chasis/battery

[b3n_rix]

Just checked it again going off the volts meter on my turbo timer and it reads 12.94 and cracking 12.72

scrap that, I have just taking a video, it's worse than that.. I will upload shortly

[b3n_rix]

what is the CCA rating of the battery
What gauge and amp rating is the power cable running from the battery to the starter
did you connect up the thick (4 gauge from memory) ground cable from the block behind the air con compressor to the chasis/battery

400cca battery
4 gauge gauge wiring all the way through
there are 3 earth cable from the engine to the chassis then 4 gauge from the chassis to the battery.

I have had this setup running my old sr20 and never had a problem. I do however, understand that the 1.5jz will need a bit more bump due to the high compression and 6 cylinders, however, I have had a 650cca battery jumper cabled to mine to try and get it to crank faster from a running car. still no difference

[lexsmaz]

As long as your battery rest voltage is above 12 volts thats good enough, but its important to see what the voltage is reading when cranking, you should normally read around the 10 volt mark when cranking, either at the battery or starter etc, if you are readiing 12.72 whilst cranking that is way to high a reading, need to recheck your meters, turning on headlights will drop it more than that ..

As has been said, i would be running additional heavy earth leads to isolate if there is an issue there & try that .. If that doesnt work i would personally use another good battery & hook up some Heavy duty jumper leads to it & run a power wire direct to the starter motor main Battery power wire & run the earth to the engine block, leave all the other leads on the car battery & connected to the car & try that, that way you are cutting out any voltage drop issues through the car wiring & if it still cranks slow the starter motor is no good or your engine is very tight ( have you seen this motor run ?? if not pull out the plugs & try turning it over by hand from the crank pulley, it should turn over fairly easily ) ..

Just read your reply then to the other guy, i should know but cant really picture it, what diameter in mm is 4 gauge wiring ..

[b3n_rix]

[b3n_rix]

this is what is happening, watch the turbo timer (set on voltage) the wires I am putting together are just a hot wire to bypass the button

[midnight_purple_GA70]

4 gauge is reasonable about 10mm but for cables going back to a battery in the boot ide be using a minimum 2 gauge or 1 gauge

[lexsmaz]

The voltage you have reading there is way to low, around 10.0 volts is a minimum you should ideally ever see, you are getting around 7.5 ...

[b3n_rix]

I know, but I can't figure out where the voltage drop is. because up to there is all 12+ any ideas?