yup, on my way to the MOM meet last weekend the alternator quit charging completely. just bought a new S5 alt with warranty... but it seems like it might actually be a FD one - it has a 17mm shaft instead of 15mm, which i think all FCs should be?

made it over 100 kms, likely closer to 200 kms with battery power only!

 

Easy way to tell on the FD alternator is that it has a large weather tight connector on the periphery, as opposed to the FC which has a two connector non-sealed port on the rear.

 

I thought S5 and FD are the same connector, and S4 was different?

Attached pics of it:

 

i have charging again with the new alt, but it doesn't seem to have made much of a difference in the megasquirt logs... still lots of voltage fluctuation at high rpm/load

no resets since though, but i've only had the car out a couple times since installing the alt

 

Then there is either a ground or supply line problem.

Also check for damage to the DB37 pins.

 

I checked the DB37 when I re-did the MS ground and everything looked OK. I'm planning to re-do the main alt power wire since that's about the only one that isn't new at this point.

Anyways, I haven't had any resets at all since I installed the new alternator, but the fluctuations are still worrisome.

 

Is it possibly something incredibly simple like a battery terminal vibrating? An interesting one I saw years ago was an intercooler pipe very close to the fuse panel. When the engine moved, it would knock against the + terminal. Caused resets.

 

Car is back on the road, back to troubleshooting!

I moved the Megasquirt panel ground directly to the battery negative terminal (which apparently is the new recommendation?) And re-did the alternator wiring, both the 'B' and 'S' terminals. New, larger gauge cable for 'B' and the 'S' now goes to the bulkhead connector which connects directly to the battery.

So far it seems a lot better. No more of the steady voltage drop under load. I do seem to have more random dips and peaks in voltage now though! Did i trade one voltage problem for another?!?

 

Subscribed...I'm having a very similar issue!



I tried a different alternator and ended up buying a new FD alt. No improvement.

Re-did all my grounds, added an alternator ground, no improvement.

I re-wired both B and S wires end to end from the alternator. This fixed the wandering voltage problems I was having before (pretty solid at 14.0 now), but still get random spikes...mostly down to 9v or so, a few up in the 16v range.

I replaced the main circuit breaker because I've heard those can have weird problems and I'm running out of things to throw money at. No improvement.

Either one of these wires is EXTREMELY fussy or maybe we both got a batch of "chinese quality" alternators?

 

Shaolin, have you had any actual Resets where the car cuts out? Or just the fluctuations in the logs

 

I've definitely had the problem exactly as you describe it...car just dies completely and then comes back to life a second later like nothing happened.

This happened a handful of times back when I was first tuning the car. I seem to have lessened the problem because the car hasn't died on me in quite some time, but the fluctuations in the logs are still there.

 

Also subscribing. Having the same issue with my Haltech Sprint RE. Does this battery Voltage look normal?

 

Cancel

 

ms2? what injectors are you using? do you use the PWM injector current limiting or resistors or high-impedance injectors?

 

MS2 3.57 with Zeal
1000cc unknown brand/1600cc

I always confuse myself with low/high impedance. I believe these are high Z injectors...my settings are:

35% PWM limit
1.0 PWM threshold
66us PWM Period

 

if they are high impedance, i believe your PWM limiting should be turned off (set to 100%). It seems that the PWM limiting is what's causing my fluctuations.

If I set it to 100% I get voltage drops under load though, since I have low imp. injectors currently, it's damn near a short circuit when the injectors fire

 

PWM limiting has always been problematic, especially since the flyback damping is dumped onto the board. Generally I recommend injector resistors instead of PWM.

But, with high impedance injectors you don't need either. Just set the PWM settings to disable.

 

Well, I was totally wrong. Primary injectors ohm at 2.3 each, secondaries at 4.3.

I'm not entirely convinced this isn't part of the voltage problem, sounds like I should pick up some resistors and disable PWM. 1 resistor per injector...do I want them near the injectors or near the ECU?

 

i think anywhere in the circuit is OK, they probably throw off some heat so you'd want them in the engine bay somewhere with some room to breathe.

I just bought some new high impedance injectors instead (shinny new ID1000s )

 

Hah, I've been shopping ID850's and ID1000's for the last hour! I'm going to give my current injectors ONE MORE SHOT with resistors.

 

I usually place resistors at the ECU so they are protected inside the car, but they can go anywhere.

I don't think it is the cause of your problem, but as mentioned the flyback circuit HAS been problematic in the past. Without being there it's a guess.

Now it could also be a bad pin in the DB37. Seen that, drove me crazy.

 

Don't meant to revive an old thread but I've been having the exact same issue with my MS1 Supercharged Mazda Miata (na). Did OP every figure out the issue? I've been scratching my head on this for too long and unable to find a solution. Found this thread as I was searching Google.

 

This probably wont help you, but my issue ended up being a broken solder joint on my main power wire at the fuse block.

 

IIRC this was resolved by changing to high-impedance injectors.