MS3 Basic FUEL DUMP
 

I have an MS3 basic that I've been using for about 2 months. Just curious if it’s something in the MegaSquirt or if it's an electrical issue with the car. 2nd time this has happened. On a cold engine when the key is on, the cooling fan turns on and cylinder 3 injector dumps fuel into the intake and cylinder. Tried switching injectors around and it still was only 3rd injector. Fuel pump relay under dash also buzzes loudly when key is on and then the fuel pump stays on until key is turned to off. When it doesn’t do this the car drives great when warmed up but start up both warm and cold sucks. MegaSquirt won’t connect to TunerStudio either when this is going on so I can’t even get a catalog of this happening. Really lost as we’ve been battling this issue for a month. Changed FPR, changed fuel pump relay, cleaned grounds, all to no avail. Posted my tune below incase its a setting in there. For reference the car is a 96 with a 04 bottom end & 99 head.

I've found that if a relay is buzzing, it's usually because it's caught between on/off states, ie the coil voltage is greater than zero but less than necessary to turn the relay "on".

Is this buzzing associated with the cooling fan coming on and injector #3 dumping fuel, or is it a separate issue you observed?

Sounds to me like you have an intermittent wiring fault somewhere. I don't know what the cooling fan (which one?) and injector #3 have in common, but I'd probably check those wires in detail.

The buzzing happens on its own in the on position. The pump relay buzzes and keeps the fuel pump on but the car will start up and run.

The cooling fan and injector #3 staying on is a separate issue that occurs together in the on position when the buzzing doesn’t occur.

If it makes any difference I deleted my A/C and only have 1 fan.

Also tried plugging in stock ecu and it didn’t buzz or have any of the issues that the MS had when the key was in the ON position

It sounds like a power problem I had previously. One of the relays, the main one I think, had carbon on the points and the MS wouldn't connect and the fuel relay would buzz. It comes from the MS receiving power through some but not all of the circuits necessary. It gave me some really strange symptoms. Main relay underhood solved it. I kept the old one and cleaned the points as a spare in my glovebox.

Ok I’ll give that a try. Thanks guys!

Cleaned the contacts on both the fuel pump relay and main relay and no change. Nothing happens when stock ecu is plugged in, only when MS is plugged in.

FIXED THE PROBLEM!!There was a wiring issue in the CAS that happened to connect to the fans, injectors & fuel pump. When I first did the Engine swap, someone told me I needed an NB crank sensor with my NA CAS, but I actually didn’t. When I removed the sensor, I left the harness in the car and it caused it to give the injectors and fans a false signal.

Everything now works as it should with no hassle.

False alarm...

Went to start it today and the fans turned on a fuel dumped again... Emailed Rev a couple days ago so just waiting on a response to send it back for repair.