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Old July 26th, 2015, 05:19 PM
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Joe Manzi
94 NAS D90
Join Date: Jul 2015
Location: Cranston, RI, USA
Posts: 1
Unhappy Fuel Injectors Inoperative!


I am brand new to this forum and am desperate for some advice. I have a 1994 NAS D90 fuel injected 3.9. The truck has been sitting for at-least 10 years and I am working to get it running.

I was able to get everything working electronically under the hood. My fuel pump and ignition system are working fine. The last hurtle that is giving me a lot of trouble is getting the fuel injectors to fire. I can get the engine to fire with starting fluid momentarily to prove that fuel is in fact my issue.

Having been idle for 10 years my next thought was the fuel injectors are all seized and unable to spray even though they are being commanded to. So, I removed the upper intake plenum and trumpet housing to remove the fuel injection rail. I removed the fuel rail as an assembly with the injectors still attached to see what the nozzles looked like. They all looked brand new.

I then started digging into the electronics using my factory repair manual and other diagnostic software I have available. I have traced every wire more than once directly to the ECU and there are no breaks. For some reason the ECU is not commanding the fuel injectors to fire. The injectors are being supplied with voltage but are not being grounded to spray. I know the injectors work because I manually grounded that particular side of the electrical harness while they were still removed; and they sprayed just fine.

Does anybody have any hint as to which direction I should go next? I even purchased a "good used" ECU just for testing purchases and nothing changed.

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Old July 26th, 2015, 09:57 PM
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Robert F
1995 Discovery
Join Date: Feb 2012
Location: Dallas, TX USA
Posts: 138
sounds like the white and black wire on the - post of the coil is the problem. It tells the ECU the RPM. Check continuity on it back to the ECU. It will have a small black plastic resistor inline marked lucas.

A quick check to see would also be to loosen the distributor and twist it and listen if the fuel pump re-energizes for 2 seconds, or get a noid light and put it in place of an injector while cranking.

And when you say the ignition is working fine I assume you have spark, right?
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