Cant figure it out: Voltage drop when trying to start on AEM

[2_Liter_Turbo]

My new motor is having some electrical issues. S13 Redtop with AEM EMS (MAP), when running the starter, voltage drops to 9-10V area from about 13-14V when starter is not engaged. I tested the starter out of the car at a few auto parts stores (on their starter test benches), and I get about 14V @ 75amps. All grounds looks to be good, and tested all the grounds on the ECU itself. Hoping someone has ran into this before, and has some insight. Before new setup, car started on a flashed factory ECU, but did take a little work to get it to start. The AEM ECU wont start the car at 9-10V.

[2_Liter_Turbo]

We tried about 3 different batteries (one being brand new). The grounds that I can think of is the battery ground to the engine (with chassis in the middle), the small ones on the intake manifold, the one on the back of the cylinder head to firewall, and the one from the starter solenoid to the chassis. Am I forgetting any? All grounds in the ecu tested good as well.

[compactfean]

This may be a stupid question, but did you enter in your base settings in the aem and make sure it saved? I've had issues with stand alones and even piggy backs where rather the wrong base settings were entered for the setup or it didn't save properly causing a no start.

[compactfean]

Also, did you do the cas disc swap?

[2_Liter_Turbo]

This may be a stupid question, but did you enter in your base settings in the aem and make sure it saved? I've had issues with stand alones and even piggy backs where rather the wrong base settings were entered for the setup or it didn't save properly causing a no start.

I am not doing the tuning (I'm not an ECU guy, lol), but the shop that is doing it has done hundreds of AEM setups, so I'm pretty sure it's good there. Thanks for the response! They said that the ecu wont start with a large voltage drop that the car is doing when the starting circuit is engaged (its fine otherwise).

[2_Liter_Turbo]

Also, did you do the cas disc swap?

Not yet, but it will be here on Monday. They said that it would start without it, but that I still need it.

[compactfean]

Well unfortunately the aem unit has a faster more ”thirsty” processor that may need that higher voltage like the shop says. E-prom tunes still run off of the slower oem processor which is probably the reason you can start the car. those stupid testing machines are incorrect alot of the times (your car being a perfect example) according to many fsm's (for all sorts of cars) when testing a starter, on older cars if voltage drop is 10 v or higher you're ok. That's been a rule of thumb for a while until recently (past 5 years.... Maybe longer) many vehicles now require the vehicle to be at 11v or higher!!! (not much room for leeway) id say that the starter is drawing a bit too much, robbing the ecu the power it needs (even though those stupid machines say its good) does the starter seam weak or slow? Either way though, I point to the starter for the problem.

[2_Liter_Turbo]

The starter is the same one that I've had since 2005, and it's never given me issues. It's smooth, quiet, and isn't slow IMO when starting (except when the battery is low, lol). Know of a good way to test the starter myself? Also, I tested a couple different test benches because I know they can be fairly unreliable, and they were all within the 13.5-14.5V range.

[compactfean]

That is how you test a starter when on the car is voltage drop when cranking. Also you can check amps on the starter cable when cranking. Check the fsm, it should have all the info you need to diag the starter. Those bench test machines don't put a realistic load on a starter to get true results. Other than that I'm out of ideas but a large voltage drop during cranking always points back to starter or Starting system (corroded cables, poor terminal connection).

[moso]

I would also look into the starter. at 7 years old its probably time for a new one. the problem with bench testing the starter is most of them dont load the starter when they test them. if the bearings are bad the armature will sit slightly crooked when loaded, the bearings will bind, and the starter will not efficiently make use of the supplied current due to being offset in its housing.

[2_Liter_Turbo]

OK, went over to a buddy's house and tested the starter on his SR car (tested his starter as well), and there was only about a .5V drop (normal) max between the three different tests I did on both starters (ground, power, and solenoid). So it's not the starter at all. I get the AEM trigger wheel on Monday, so after I get that installed, I'll see if we can get it started. I'm still out of ideas.

[compactfean]

Did you perform these tests while cranking?

[2_Liter_Turbo]

Did you perform these tests while cranking?

Yes sir.

[2_Liter_Turbo]

We got the car started today. The fuse for the ignition switch was corroded and basically fell apart when removed, and the car needed the AEM CAS disc. Couple small bugs to work out now, and hoping to drive it home on Friday!