losttheplot

Hello.
I have a 1991 Chevy 2500 pick up with a 350 V8.

Only the drivers side fuel injector is spraying fuel so the truck is running on 4 cylinders.

If I un clip the 2 wires from each injector and switch them to the opposite injectors, the passenger side injector fires and the drivers side does not.
The truck again runs on (the other) 4 cylinders.

This makes me assume there is no problem with the fuel delivery system or injectors?

A test light shows 12 volts to the hot side of both injectors.

If I hook the test light to the other side of the injector wires,
and to a + battery terminal,
The test light flashes as I crank the engine. (same strength pulse rate each injector)

If I run the engine with only the 12 volt terminal of the non working injector connected and ground the other terminal (of the same injector) I get a constant spray from the (previously) non working injector.

I hope you can understand my description and hopefully tell me what is causing one of my injectors to not fire?

I am leaning towards changing the ignition control module in the distributor, but dont want to change parts to try and find the problem.

UnderCover89TBI

iTrader: (25)

almost wanna say that the injector connector is faulty.

losttheplot

I took the plastic connectors off the injectors and put the wires straight to the injectors. still no better.

when I put 12 volts to the purple/ white wire from the ignition sensor one injector fires the other just wines a little like it wants too but dosent have enough power.

while I had the engine running i jumped the downstream (ground side) terminal of the no working injector from the ground side of the working injector.
This dumped fuel from both injectors and stalled the motor.

I took the jumper wire off and fired it up again and both injectors are working fine



This problem has been intermitant for a few months, then yesterday the problem stayed.
hopefully it does not come back.

UnderCover89TBI

iTrader: (25)

faulty connection somewhere then, I almost wanna say bad ground but I dont see how that'd only effect one injector. weird.

Schurkey

Doesn't the ECM control the injectors by switching the ground on and off?

Faulty ECM or broken wire/bad connection on the ground wire to the non-functioning injector.

losttheplot

Yes your right.
I found a wiring diagram on line and the problem is in the blue wire that goes from the injector to the ECM.
The problem has been intermittent, so I now carry a multi meter on the dash in anticipation of the problem re occurring.

When it comes back I will test the blue wire, from the injector to the ECM, for continuity.

If the wire is good, a neighbor has the same truck and I will temporarily put my ECU into his truck to see if it gives the same symptoms.

Thanks.
Colin.

Cam_RS

"losttheplot" did you fix it? I have the same issue as yours. My driver side injector does nothing, no power on red wire and no ground on ecm.

RBob

iTrader: (1)

Fix the no power to the injector first, as that has no bearing on the ECM. There is a fuse for each injector: INJ1 & INJ2, best place to start.

RBob.

Cam_RS

Checked the fuse wires (pink/black) for continuity and both wires were good. Then checked resistance, INJ 1 and INJ 2 both ohmed out 0.9 or 1.0.

No signs of broken wire on injector wire (red) and (white) both have good continuity. I still get no power on injectors and no pulsing at all? how do i fix this?..

Schurkey

Keep tracing the power wires back until you find power, then fix the break. If this was me, I'd want a GM factory service manual with the wiring diagram(s) as a visual aid. I have bought these service manual sets on eBay for between $20 and $85; the most expensive one is for my '77 Nova and the thing is in shipment to me--I just bought it a few days ago.

It might be that the ECM is providing the ground, but with no power on those wires, the system still doesn't work. It's good advice to fix the power first.