sr20 only runs on 3 cylinders, injector #1 not firing

[Firestorm]

hi guys,

i was just starting up my rebuilt SR but it was only running on 3 cylinders.

at first i had an ignition problem that caused #1 and #2 not to fire but i fixed that, but the #1 injector won't spray. i removed the spark plug and found the cylinder/piston bone dry.

i already checked the wiring, injector gets 12v and the wire from the injector to the ecu has continuity. i also swapped injectors but it still won't spray on #1.

i checked the wiring diagrams again and noticed that there are only 3 injector grounds going from the ecu to the chassis...does anyone know how the 4th (or maybe 1st) injector is grounded? i think my problem is that there is no connection from the ecu to ground (ecu worked fine till i pulled the motor).

are there any circuit diagrams floating around for an sr20 ecu?

if anyone has any suggestions or solutions, please let me know!

[ka4life87]

Have u tried a noid light to see if ur getting injector pulse?

[Firestorm]

no, but if i'd get a pulse i wouldn't have a problem, because i tried a working injector on the #1 injector plug.

so my problem seems to be a lack of a pulse from the ECU. i'm gonna check my ecu tomorrow, hopefully it's not fried.

[ultimateirving]

If u have amultimeter, u can also try to see if the first injector is shorted, Run Continuity tests on both injector plug leads. If its shorting out/ cracked or broken wire. This would be a good way to tell.

Vs fried ecu which would really be bad

[ShadowMan]

Sometimes when I know Im going to be leaving my car in a parking lot for a bit I'll pull the ignitor chip and unplug the ecu. When I plug them back in it only runs on 3 cylinders sometimes, so I unplug them and replug them back in making sure they are fully seated, and then it works just fine. Start with the simple stuff first, especially if its free.

[Firestorm]

okay, so i checked the wiring again, every wire to and from the ecu has continuity, i checked the plugs, checked my grounds, swapped injectors and...

...nothing. no matter what i do, the injector on the #1 plug won't fire. the other injectors work fine, and the engine runs considerably well for the fact that it's on 3 cyls.

i opened up the ecu to see if there are any indicators that it may be shot but visually it looks fine. (it's a #62 with a mines daughterboard). maybe it's time to get a replacement, but SRs aren't exactly common where i live. at least redtop ones.

[Firestorm]

okay, so just a quick follow-up: i checked the wiring again and noticed a bent connector in the big blue plug. so i fixed that and grounded the ecu (the housing itself) and now it works. i don't know which measure actually did the trick but i'm just glad that the engine runs now :)

[codyace]

Good news!


But to add to this thread, just because an injector has continuity between itself and the ECU does not eliminate there still being a fried driver inside the ECU