'97 Civic isn't getting power to #4 connector...Help!
 

'97 Civic DX Hatch with a '98 D16Y5 (HX) swap. Complete changeover, engine harness, ECU, all stock. Ran fine for 5 years and then sold it to a friend who needed a car for work. He had it less than 24 hours before it threw a code for misfire.

- replaced fuel filter, no change.
- plugs and wires were recent.
- deduced that #4 wasn't getting fuel, pulled the injector and swapped it for #3, no change.

When I pulled the rail, #4 had no fuel in the manifold port (it looked dry) while the other three where wet. I confirmed the injector was not firing by using a flathead screwdriver against the injector body and not hearing the tale-tale tick*tick*tick that the others exhibited. I tested the injector itself by applying 12v on the bench and hearing the click as well as seeing liquid squirt out. The connector itself looks to be in good shape, no corrosion

Concluded it was #4 injector connector is not getting power. Would grounds do I need to check or what multimeter procedure do I follow to trace the culprit? Could it be the ECU? If so, why after running flawless when I owned it?

Thanks,

Mak

Check for power at the connector terminals to confirm, while it's running if possible. Then deduce if it's one wire or the other that's not getting continuity. You can test for continuity between said terminals and ground and between them and +12v. I'd assume they run on a ground-pulse like everything else out there does, so you should have continuous +12v on one terminal, and nothing or pulsing ground on the other. If you are not getting both, you then can tell which one you are trying to trace/fix.

Are you getting DTC P0300? the random misfire, or are you getting one of the P0301-P0304 codes? Fuel injectors are only one of the explanations for the latter bunch, and the P0300 is not a injector code.

EDIT: Also... have you checked wires to the ECM/PCM for an open? The Honda FSM indicates replacing the ECM/PCM if the injector is not the fault and if there is no open between the injector and the ECM/PCM.

Went back with a MM and a homemade Noid light. Yel/blk wire on #4 was getting 12v, the yel ground wasn't getting jack. Depinned A1 on the ECU and ran a long wire from injector to A1. She ran like a champ. It was getting dark so I packed it up and put everything back like stock so I'd have a clean slate for running a bypass another time and we cranked her again for shiggles. Runs fine. Test drove fine. Chalk it up to new owner luck? The ECU harness looked pristine for 20 years old, no corrosion.

Thanks for all who suggested things to try.

Now all I need to solve is the "slow response" O2 code (P1163? if I remember) that comes and goes.

Mak

So it was an open between the injector and the ECU. Thanks for sharing the result. The Honda Factory Service Manual called it... and you suspected an open ground from the beginning. The trouble shooting flow charts in the FSM are really good, man. If you don't have the Honda FSM, I recommend. Save a lot of time and frustration on the boards.