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Injector won't stop spraying

L

Laurent Wagoneer

NAXJA Forum User
Location
Boyle Heights,CA
New injectors.
One of them won't stop spraying even if I unplug the connection off it!
It's the same side where the oter old one was doing the same thing.
It's the first one by the fuel pressure regulator. 1993 cherokee 4.0
 
If the pressure regulator is fubar'd, all the injectors would most likely be running. Sounds like it gummed up. I would try filling the rail with BG44k and the rest in the tank. Start it up and see if that will clear the injector. I have seem quite a few injectors like this and it has always handled it. Don't bother with any other cleaner other than possibly Lucas.

I might also try taking the injector off and taking some carb cleaner with a nozzle and stick the nozzle in the inlet and flushing the injector.

You might just pull the injector and take it to a shop that has an injector cleaning setup. If it is out and ready to go, they probably won't charge you that much.
 
If the injector is open with no electrical power, that injector is stuck open. If you want to satisy your curiosity, you can swap the position of this one with another injector, the stuck injector should move to the new position.
 
Old man-
I changed the fuel filter, cleaned out the rail, new injectors and still spraying like the old one. Same spot. By the regulator. So imagining that the regulator is crapped out and not doing it's job causing too much pressure build up?
 
Prove it to yourself. Take the faulty injector and move it to cylinder 6.
 
Ok... Took the rail out and placed bottles to see if there's a leak... No leak.... It's the pump that won't shut off.... The relay is fine... Swapped it with a spare that I had laying there and still stays on. This is with the key on.
My Renix shuts off after about 5 seconds. Is it different for the HO?
 
The pump should always be running. No way to maintain pressure otherwise. Renix has the little ballast resistor, it probably changes to low-current mode and you can't hear it running.

I think it's time to start looking at the wiring harness. The PCM operates the fuel injectors by grounding each one when it's time to make some boom. Note that power is always applied to the positive side of the coil via the ASD relay. If something has chaffed or damage the wiring between the injector and the PCM and grounded it out to the manifold, body, valve cover, or another wire, then exactly what you're describing will happen. My bet is that with the key in RUN you'll see 0 resistance between the battery ground and the negative pin of that injector's plug.
 
Maybe I'm mistaken. I thought the old fuel systems would keep running the pump and let the vacuum FPR keep things in order. I have a '99 so I haven't messed with the old guys much.
 
Laurent Wagoneer said:
Old man-
I changed the fuel filter, cleaned out the rail, new injectors and still spraying like the old one. Same spot. By the regulator. So imagining that the regulator is crapped out and not doing it's job causing too much pressure build up?
Click to expand...

The pressure will be the same on all the injectors, no matter what position, within maybe a half pound even when they are all running flat out.

Swap the injector around and check the results. If the same position is still failing, you most likely have a blown/shorted drive transistor in the ECU. Check that by pulling the connector on that injector. If it stops spraying, it is the ECU, if not, it is the injector. You can also test it with a noid light.
 
Laurent Wagoneer said:
Old man-
I changed the fuel filter, cleaned out the rail, new injectors and still spraying like the old one. Same spot. By the regulator. So imagining that the regulator is crapped out and not doing it's job causing too much pressure build up?
Click to expand...
 
Laurent Wagoneer said:
Old man-
I changed the fuel filter, cleaned out the rail, new injectors and still spraying like the old one. Same spot. By the regulator. So imagining that the regulator is crapped out and not doing it's job causing too much pressure build up?
Click to expand...

The pressure will be the same across all the injectors unless they are running wide open, and even then the pressure difference is maybe 1 psi.

If you pull the connector and the injector is still flowing, it is the injector. If it stops, you have a short in the wiring or more likely a blown/shorted channel driver in the ECU.
 
Ruled out the injectors.
Did a spray test with water bottles on tem.
No spraying. The sound is the rail not building pressure to stay shut I guess.
The pump stays running. But the injectors don't spray.
 
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