Bronco Injector and fuel pump problems

[deano9006]

Hey guys,
New here and new to megasquirt. I did have the sense to run some searches regarding my problem but didn't really find a definite answer because.....well it could probably be a couple of different things. Ok, so what I installed is as follows:

- Megasquirt 1 v2.2
-Relay Board w/connection cable (yes the end labeled ecu is hooked to the ecu)
-holley 670 cfm tbi unit with low impedance injectors
-corresponding fuel pump and sensors

I installed this over christmas break on my cousin's bronco.......everything was running awesome when I left, good acceleration, tuning was fairly close, the bronco started up easy enough. He called me about a week after the fact and tells me that when you just turn the key on that it just starts spewing fuel into the engine. (just in the "on" position, not in crank) He hydrolocked it once already. Claims he never messed with the settings or anything. What could this be? I have read that a resistor might have burnt out or the code could have gotten corrupted. I know that I did leave the PWM setting at 75% because I don't have the flyback board installed......could that be it? Thank you for the input!

[Matt Cramer]

Holley TBI injectors are pretty noisy - there's a good chance an unmodified V2.2 board may have had a flyback failure. Does he have a Stim to test this with?

[deano9006]

No he doesn't have a stim to test with. We can get one if it's needed though. I actually just got off the phone with him trying to do some troubleshooting on it and here are the results:

- all guages are operational in megatune: clt, mat, tps, pw, etc.
- even when megatune shows no pw output, the injectors are still staying open and the fuel pump works properly
- the relay board did get some moisture on it, I have a feeling that has something to do with this failure
- All the values were still saved correctly within the ecu

So if there are any suggestions, please let me know. I plan on going back there this weekend to see if i can get something figured out. I noticed that the injectors may have been leaking a little when i first installed the tbi unit (from ebay), is there a better chance that the injectors stuck open and there is nothing wrong with the ecu?

[Matt Cramer]

Try unplugging the injectors from the ECU and turn the key on - that'll show if they are stuck open.

[deano9006]

Ok, the injectors are not stuck open. Tried a whole different TBI unit and it does the same thing. The injectors are grounded out all the time. I'm wondering if a resistor got burnt out. I'm thinking about trying to reflash the ecu but i'm not sure if it would help. Please let me know of any ideas.

Thanks,

Kyle

[Matt Cramer]

I strongly suspect this is a flyback failure - many TBI injectors are pretty low impedance. Usually it's the output transistors that burn.

[deano9006]

Ok, I was a little afraid of that. Now I realize that I could just go in and fix the problem and it would run again. No problems there, but should I upgrade the flyback circuit to prevent this from happening again? Could this have been my fault from inputting the wrong PWM settings? Sorry if these questions are kinda dumb. Thanks for the input!

Kyle

[Matt Cramer]

I would add the Flyback Board when you're making the repairs.

[deano9006]

Ok thanks a bunch matt. I think I have found everything I needed.........which of course was in the megamanual if i would have looked a little harder. Thank you again for your help! I'm pretty sure I'll be able to get it up and running now, but if I run into anymore problems I'll let you know!

Kyle

[deano9006]

Just in case you were wondering, I have an update on the bronco. The board indeed had a flyback failure, so i installed the upgraded flyback circuit. The bronco has been running great ever since! Thanks soo much for all the help and advice!