somehow My megasquirt is cycling my starter solenoid 3 or 4 times a second when the key is in the "ON" possition. When the key is turned to start the starter works normally but the car does not crank.
When I unplug the DB-37 connector from the MS the starter functions normally, so I don't think it's in my harness. When I plug the stock ECU back in the starter functions normally and car will crank and run well after I unflood it.

I've Ohm'd out a couple pins on the DB-37 and found some weirdness. I don't have my test sheet right now, but I can remember that the Fuel Pump relay wire (DB-37, # 37) makes contact with ground with not a lot of resistance. Also Inj #2 wires make contact with each other with near-0 resistance while the Inj #1 wires don't contact.

Has anyone heard of this issue? I've searched for it both here and on the MS forums. How is it possible that something can short out and cycle the starter?

 

also when I get home tonight I'll use my computers powersupply to run MS and look at what its doing with megatune on my laptop. So I'll know if anything weird is happening with it off the car, and then off the car with the harness plugged in. Maybe I can round up an extension cord and try it all plugged in with the car off

 

Something is very wrong...But I can guess at two things that are happening.

1. There is a wiring error somehow connecting the fuel pump relay's contacts to the starter solenoid. Never heard of this happening.

2. One side of the fuel pump relays coil is connected directly to a constant 12V source and not a switched 12V source. This will cause the fuel pump relay to blink about once a second and momentarily energize the relay. Not sure why this happens as I don't have the circuit handy. Connect the fuel pump relay coil to switched 12V.

 

The thing is, I don't have the fuel pump wire connected to anything. I have a lead running from the pin on the MS side and the other end is taped to keep it from shorting. I didn't go home last night so I didn't get a chance to bench test it.

edit: I should also say that the MS is connected via an adapter to the stock harness, nothing of the stock harness has been changed.

 

Where did you get the adapter?

I've never heard of anything like this happening before. It really sounds like there must be a short somewhere.

 

I built it out of a gutted ECU. I've quadripple checked the pin out on the adapter. I've been out of town since my first post and haven't had a time to double check the adapter with the multimeter. I know the thread is kind of worthless without that, but my main question is why and how a short can cause these symptoms. I've never heard of a short causing the starter solenoid to rapidly cycle or cycle at all. With the frequency that it's going it seems like it'd be some kind of spark or injector output. but I still don't see how those shorting against anything would cause this. but those shouldn't be firing when the car is off

 

Yeah, honestly to accurately debug this problem, I'd have to be sitting there when it happens as I've never seen anything like this happen before.

 

D'oh. Found it. Went to plug it into a test harness and realized that I had lettered the pins starting from the wrong end so what I thought was 1A was actually 1W... Maybe this thread will be helpfull to someone else who has suffers from temporary retardation