FETs are a high power transistor, designed
to ground the injector and make it fire.

Wild

Have you checked that 5V is present at the MAP sensor? I have heard of the regulators failing on some ECUs. The problem could also be that FET that Wildgoody mentioned. The FETS are marked 2422 IIRC but I haven't been able to find any data for them (or much else thats inside the stock ECU  ). I did see something on the net that said that someone had replaced one with a TIP3055, but that is a conventional bipolar transistor and I wouldn't expect it to last very long driving an injector. Any general purpose FET in the correct case should do the job but it would have to be of the type that includes a freewheeling diode. I am plannning on using an Infineon BTS 133 which is an automotive quality part and has (to all intents and purposes) the same pinout as a TIP3055

Some of the FET's are green and some are black are they the same? or which one should I change?

Or how do you test them???

Hay Rhinoman anyideas where to get the fet's???

Any GOOD electronics supply can help, or
you could order from Digi-Key.com part #
IRFIZ34N-ND  this is the part in the MegaSquirt
EFI computer I built, I don't know if it is
compatable with the Zuke Computer but
it does have the capacity for the Amps.

Good Luck,
Wild

Hay Rhinoman anyideas where to get the fet's???

My ECU has 4 black devices which are marked 2422? and one green device. I haven't investigated the green one yet. I have no idea where to get the stock FETS. Giving it some more thought I was probably wrong about using any general purpose FET. The reason I don't use the IRFIZ34N-ND that Megasquirt use is because it needs additional circuitry to cope with the back emf from the injector (I think they call it the flyback board) when used with low impedance injectors like the ones on the Zuk. I think the Infineon device will be OK but I haven't done any endurance testing yet. The Infineon device is available from Farnell in the UK, they are also in the US so try them:
 http://www.farnell.com

That is true, however the IRFIZ34N-ND
will handle 1 low Ohm injector (called lowZ)
so it would work with the TBI in this case,
it will actually take 2 lowZ injectors, but
it needs serious cooling so it won't fry

Wild

Guy's would this workhttp://www.irf.com/product-info/datasheets/data/irfiz44g.pdf in place of the IRFIZ44G-ND as that part is back-ordered about three mth's. I taked to diyi-key tech and they said ok
As for the heat problem what if I mounted a fan (ie computer fan) to blow in the case and cool it I know I would have to vent the case too.

Sounds Good

It just needs to be mounted to the case to keep
it cool, fan and venting is not needed, and yes
I think the replacement would be fine.

Wild

Its been a while since I looked at the MS stuff, if it can handle one injector OK then go for it. In the stock case it is mounted on a heatsink bar so it should be OK

I've dragged this thread up from the grave cos I found some more information while I was doing something else, it may be of some help to someone else if they're doing a search for info.

The stock transistor is a 2SD2422 this is a High Power Darlington Transistor Pair. I wonder if the IRF FET worked as MS uses a FET driver to operate the IRFIZ34N-ND (FETs are Voltage driven, Darlingtons are current driven). The datasheet for the IRF device shows that it may not get enough volts from a stock TTL output to drive it. I did find an equivalent device listed as a 2SD1415, a datasheet for this is available so it might be possible to locate a more readily available device, alternatively the BTS133 FET I suggested originally may well work as it needs a much lower drive voltage. The 2SB1335A device used for the 5V is a PNP power transistor.

Edit: I just noticed the original date, time flies eh?

did anyone find out what it was cause last night i let my buddy drive my sammie and he sunk it up the the top of the steering wheel and not the injector isnt opening i checked the pump all the way up to the throtle body and its getting fuel o this is a 1994 suzuki samurai by the way but the injector is not letting the fuel in but i was wondering if the tracker 8v ecu would work on it because i heard about the resistor taking a crap if it got hot then wet or something like that

You should start by drying out the ECU and see if it will work,
you can bake it at low heat in the oven, about 200* should
do for a few hours

You'll probably need to pull the ECU apart and clean the PCB. I had one come to me that was flooded, the tin on the component legs rusted and shorted the pins out. That was the only ECU I've not been able to repair. The 5V regulator blew and dumped 12V on all the 5V components.
In the pic you can see the  areas that are really badly affected:




For those with long memories, this was the ECU from Dave Jones' SuperZuki

well this is my daily driver right now and i have to use it everyday so i was going to just put a new ecm in it but i dont know if the tracker is the same or not