pin 37 not grounding fuel pump relay

[84rabbitgti]

ok to start v2.2 ms1 pcb msnse code
My car has been sporadically shutting off while running trouble shot some misc stuff, ended up rewiring my 2 relays to get rid of all the crimp connectors and spade plugs. Everything is soldered together now and much nicer with relay sockets etc.

Pin 37 on the ecu currently isn't grounding the second fuel pump relay (pin 85), when measured with a multimeter that pin on the relay(85) gets 12v at ignition on and the pin on the ecu (37) gets no voltage ever.

I have everything wired the same as before and I am baffled. I tried re flashing the firmware and manually jumping the relay and everything seems to work fine. I even temp used the f-idle pin which primed the fuel pump like the other circuit should. The car runs normally when the fuel pump relay is manually grounded.

I suspect my sporadic shutdown issues were caused by the fuel pump turning off, what would be the best way to fix this?

my relays are set up like in this diagram

[Matt Cramer]

Pin 37 should be at zero volts when grounding the relay. Does the fuel pump LED work on the Stimulator?

[84rabbitgti]

I don't have a working stim unfortunately and pin 37 reads 0 volts but isn't grounding the relay if I connect the wire from pin 37 to the relay it just reads 12v like the relay.


I just came across this but not sure if that is my problem?

"If you have reversed the stimulator (or in-vehicle) polarity, even momentarily, for MegaSquirt® EFI Controller, you may find the Fast Idle Led on the stimulator appears to be reversed, i.e. it is off when it should be on and vice-versa. The Warm Up LED on the case should work okay. Also the fuel pump LED may not come on anymore. This behavior is caused by damage from the reversed polarity, and can usually be fixed by replacing Q3 and Q5 (the ZTX450/PN2222AD26ZCT transistors)."

[Matt Cramer]

It does sound like it may need a new Q3.

[84rabbitgti]

Yeah thanks for the quick reply on the vortex too Im gonna try to pick one up today from radioshack and swap it out. My mom is bitter I stole her volvo to get to work

[84rabbitgti]

replacing the q3 transistor fixed the problem!! thanks for the help

[efims]

"If you have reversed the stimulator (or in-vehicle) polarity, even momentarily, for MegaSquirt® EFI Controller, you may find the Fast Idle Led on the stimulator appears to be reversed, i.e. it is off when it should be on and vice-versa. The Warm Up LED on the case should work okay. Also the fuel pump LED may not come on anymore. This behavior is caused by damage from the reversed polarity, and can usually be fixed by replacing Q3 and Q5 (the ZTX450/PN2222AD26ZCT transistors)."\


Can we add a diode to the Source(Power) to the ECU to avoid damage due to reversed polarity?

[SymTech Laboratories]

Can we add a diode to the Source(Power) to the ECU to avoid damage due to reversed polarity?

The v2.2 board already has a diode for this purpose, but the fuel pump and idle air control outputs are connected to the 12V rail before the reverse polarity diode. One thing you could do is remove D7 and D9 and install 22V/1W Zener diodes from the outputs to ground (anode to ground). The v3.0 board uses this scheme.

[efims]

If use Zener 1N4748A to replace D7 and D9, is the band orientation still same as Diode(normal D7 and D9)?

[SymTech Laboratories]

If use Zener 1N4748A to replace D7 and D9, is the band orientation still same as Diode(normal D7 and D9)?

No. If you use Zener diodes to replace D7 and D9, you cannot fit them in place of the original diodes since the original diodes were connected to +12V. The cathode of the Zener diode (the "banded" end) needs to be connected to the output, and the anode (the "non-banded" end) needs to be connected to ground.