Fuel injector not injecting fuel, 2.8L Trooper

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Fuel injector not injecting fuel, 2.8L Trooper

Postby m_force » Mon May 08, 2017 5:11 pm

Hi guys,

I'll cut right to the chase- 1991 Trooper 2.8 V6 5 speed driving down the highway the other day and I felt a loss of power, and could not slug back to highway speeds without flooring the accelerator. Went through thinking it was a vacuum leak, and while looking for leaks with the air filter lid off I suddenly notice that one fuel injector is delivering fuel to the engine. I took off the connector to the working injector, switched it to the non-working injector, and BAM it's delivering fuel. Is the connector bad, ecm bad, something else? Added new fuel filter thinking that could be gumming it up.

Thanks guys.
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Re: Fuel injector not injecting fuel, 2.8L Trooper

Postby Ed Mc. » Mon May 08, 2017 5:55 pm

The injectors have a constant 12VDC supplied to them via the black wire with blue stripe, coming from the Main Relay.

Each injector is grounded by the ECM when it's time to spray. So one thing you could do is check for power to ground on the blk/blu wire to the injector connector that doesn't work.

If you do have power, then far as I can tell by the diagram, the only thing that stops it from working would be an open wire (blue or green depending on which injector) between the injector connector and the ECM. Or an ECM fault which you could test by swapping injector wires at the ECM.

See the attached diagram, it shows all the ECM connections. If you need to wirecheck, you can unplug the wiring harness at the ECM and check for continuity on the injector wires.

Hopefully it's just a bad wire or issue with the connector itself, but ya never know.

HTH & let us know what you find; this is an odd one, never heard of a failure like that..........ed
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Re: Fuel injector not injecting fuel, 2.8L Trooper

Postby steve mortillaro » Tue May 09, 2017 8:40 am

I had something similar after at the end of a 1600 mile trip. Power loss, slugging it to get up to speed, hesitation. Thought it was a plugged cat because I couldn't feel much at the tailpipe , so I bought one and no difference. Then I got som new injectors (probably needed them as these were the originals with over 225k on them). That didn't solve it. Bought a TBI rebuild kit. Turned out the screws on the fuel pressure regulator were loose and leaking fuel a little. I took it all apart and put in the new gaskets and I used blue thread long lock when I reinstalled the screws. That solved it.
Don't know if that's your condition, but check those screws. Also may want to check fuel pressure if you can. I think it wants to be about 14 psi, but LOOK THAT UP to be sure.
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Re: Fuel injector not injecting fuel, 2.8L Trooper

Postby m_force » Tue May 09, 2017 1:22 pm

Ed,

I went ahead and checked the ground on the ECM, made sure there was no corrosion on the connectors, and plugged them back in. Sure enough, it fired back up and had been good for the 40 miles since. Thanks for the heads up on the grounding at the ECM, that'll be good to know for the future. I know older VW and Audis are Bosch-built computers, who built the trooper ones?

When you are in Portland, I owe you a cold one.
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Re: Fuel injector not injecting fuel, 2.8L Trooper

Postby Ed Mc. » Tue May 09, 2017 2:50 pm

The ECM's are GM-built and that opens up a whole world of tuning if you're into that, as a new chip can be burned to tune for a larger motor, etc.

There are free diagnostic programs such as WINALDL that allow you to interface with the OBD-I computer, via a laptop with serial-port connector and an interface cable that you could build yourself really cheap. Or more expensive USB cables available as well.

Early Rodeo's used a GM ECM with the 3.1 and that unit is supposed to work very well with larger engines such as the 3.4 in my Trooper. Perhaps a 3.4 is in your future, you never know!! :twisted:

Glad yours was a simple fix. I may take you up on that Cold One, one of these days!

Cheers......ed
'90 3.4 Troop LS;
'89 Troop RS (Exhaust Valve Challenged), now gone to a Good Home!
Yes, I am a Trooper-Holic!!!
Keep On Troopin' !
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