RPM signal cutting in and out while cranking
 

Car is a 1990 with '99 BP4W using 1.6 CAS and harness and controlled by a DIYPNP. Finished up rebuilding my steering rack the other day, started up the car and pulled out of the garage, got to the bottom of the driveway and it shut off. After that would just crank while the relays under the dash clicked on and off. I did some diag and found that my rpm signal is cutting in and out rhythmically while cranking. In the high speed logger I see rpm jump from ~250 to zero about twice a second. Tried updating my firmware first, nothing changed. Tried changing the skipped pulses value which only makes the crank signal pulse faster or slower. I even tried rigging up the cam and crank sensors that the BP4W came with, but this setup I see no rpm while cranking except sometimes a tiny pulse as I let go of the key. I took the ecu out over night and after reinstalling it the car started, idled for about 10 min. I tried to rev it a bit and it stalled, after that it went back to crank no start. It also will start and run on the stock 1.6 ecu (much to my surprise) so I'm guessing the CAS is still ok? While working on the car I had the radio playing music, is it possible that running the battery down screwed up the MS? Although it had enough juice to fire up right after this before it died. I'm reaching my wits end here and I'm supposed to go to the track this Saturday! :vash:

Post a tune too.
Do you have a log of it running for the first few minutes?
My first thought is battery not charging and then it just dies and won't start up again. Your battery shows 11.8v at 0 rpm and it drops to 10v when cranking.
Charge it up, get it idling, check voltage, capture log. Confirm charging voltage.
Are you using an NB alternator and if so is your ECU telling it to turn on? NB alt are controlled by ECU.
NA alternator should just work as it did on your old car motor, if a 1.6 alt fits a 1.8 block. If it doesn't and you want an easy alt install, get a NA8 alt.
Good luck

Will post tune when I get home. I have charged the battery and it still behaves the same, also tried starting it with jumpers hooked up to my truck with the truck running, same thing. And I am running an NA8 alternator. Weird thing is twice I have taken the ecu out the car, let it sit for a while and after reinstalling it will start and run, but only once. If it is shut off or stalls it will go back to having intermittent crank signal.

I am having a similar issue. I have "determined" that it has something to do with the main relay and wiring. I am going to replace what's left of the engine mounted fuse box with a Amplink PDM.

Basically the injector relay, cooling fan relay, and fuel pump relay will be eliminated and replaced with the PDM. While cranking, I can feel my stand alone fuel pump relay clicking on and off. If I have someone put pressure and/or wiggle the main relay while cranking it will not click.

However, once started, the car runs fine but will have an intermittent "miss" which I think is the main relay and/or fuel pump relay turning on and off.

However, the fuel pump relay will not receive an on input if their is no rpm. So I may just be throwing parts at this with no solution to the root cause.

Ok, here's my tune file along with a fresh log of crank no start. This is after the battery was on a trickle charger all morning.

So the problem is definitely my ecu. I stole the MSPNP2 out of my brother's car and now my car will start every time. Put my ecu in his car and it does the same shit, crank no start with relays clicking. So I guess my next move is to start re-soldering my board in hopes I can bring it back to life.