4.9 fuel injection

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Dec 15, 1999 | 09:55 PM

red

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4.9 fuel injection

Fuel injectors will not fire. Replaced my 90 F-150 4.9 with 300,000 miles with a 96 4.9. Used ignition and harness from the 90 to minimize connector problems. Got spark and it passes the Key on Engine Off test but no fuel flow. Do have pressure in the fuel rail. Anyone have any suggestions.

Dec 15, 1999 | 10:37 PM

PAUL_2

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4.9 fuel injection

Red ,
Did you use the also get the computer w your new engine ? It needs the brain it came with . I suspect it will need the 96 computer that was calibrated for the 96 engine ? Only 300,000 miles on the old engine ? You must have abused it ? Good luck
Paul

Dec 16, 1999 | 08:16 AM

Phillip Guidry

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4.9 fuel injection

Red,i guess you have voltage at the injectors but no pulse while cranking,right? If so,you probably don't have spark at the plugs either.This could be from a bad module/pick-up, or, something that is not plugged in, or a ground wire that isn't screwed down from the swap of the engine.Double check the fuses,double check the harness,rework the ground wires at the battery,and, double check the frame/cab to engine ground straps.This problem is something very small and almost ridiculous,I can feel it.
Phillip

Dec 16, 1999 | 08:19 AM

Phillip Guidry

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4.9 fuel injection

Sorry, I re-read your post Red and I see you stated you DO have spark, so forget what I said about module/pick-up. But I did remember something about a Fuel Inj. Relay,seperate from the EEC & Fuel Pump relays. Check that also.
Phillip

Dec 19, 1999 | 10:20 PM

red

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4.9 fuel injection

Thanks for the suggestion. At least it was on the right track. Turns out we used the 96 injectors which will not work with the 90 electronics. We sure learned a lot about the electronics and wiring. Once we swapped the injectors it started right up and runs great. Thanks again for your effort.

Dec 20, 1999 | 08:12 AM

Phillip Guidry

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4.9 fuel injection

I'm glad you found your problem,and, it seems to make sense to me,but the injectors for the 96 must have plugged up to the harness after the swap? I'm thinking it has something to do with the difference between injectors for MAF vs. MAP sytems.More than likely,the injectors have different resitance values as well as duty cycles,so the "driver" in the processor couldn't "fire" the injectors because the electrical values were way out of range. What is your theory on this ? This makes me wonder how come you can change to MAF system on an older truck that has MAF, and not change the injectors out(at least I've never read you had to)?
Phillip

Dec 23, 1999 | 02:44 PM

86fordguy

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4.9 fuel injection

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Dec 23, 1999 | 07:22 PM

red

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4.9 fuel injection

Pretty close once again. The sequentional injectors, used on the 96, are a totally different design from the bank type used on the 90. I realized that from reading about them but I seem to have misunderstood something. The moving parts are lighter so they would be easier to fire. Right no wrong. Because they are easier to fire Ford changed the electromagnetic part, inside the injector, because they were easier to fire and did not need the conventional coil to open the injector. Since they either eliminated the coil or changed it dramatically the new injectors actually require a higher voltage to move the lighter parts. I am not absolutly postive about all of this but I think it is close. I do know, now, that we should use the same color code. One set was grey and the other was black. My son has been driving this a few days now and it is running great. Next we try swapping the rear axle.