Help! fuel injector prob

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Jul 14, 2012 | 09:08 AM

countryboy40380

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Help! fuel injector prob

I have a 1994 f150 300 6 cyl started running bad was told I had a injector problem so I took the fuel rail out and number 2 4 6 are spraying 1 3 5 ain't if i switch the ones that ain't spraying with the ones that are they spray so none are clogged. I checked each plug with a multimeter am getting 12 volts to each injector plug all at the same time I may be wrong but shouldn't the current go in firing order any help would be appreciated

Jul 14, 2012 | 09:20 AM

rla2005

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Your truck is using the older style Speed Density "batch-fire" fuel injection. You probably have an open wire between the PCM and the 1/3/5 injectors. The PCM grounds injectors 2/4/6 then 1/3/5 to complete the electrical path to turn them on.

Ohm out the Tan wire that leads to pin 58 of the PCM.

Jul 14, 2012 | 09:27 AM

countryboy40380

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thank you I will do that today

Jul 14, 2012 | 10:01 AM

rla2005

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The White wire runs to pin 59 of the PCM. That one is for injectors 2/4/6. Red, as you have already found out, is the supply voltage for all of them.

Jul 16, 2012 | 08:10 AM

countryboy40380

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I ohm the tan wire pin 58 it ohm at 0.02 on my fluke

Jul 16, 2012 | 08:49 AM

bashby

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From: Charles Town, W bygod Va

probably a bad injector driver in the pcm.

Jul 16, 2012 | 08:55 AM

rla2005

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Quote:

Originally Posted by bashby

probably a bad injector driver in the pcm.

If the results you got with the meter are correct, then I would have to agree with bashby. It's rare to have this failure mode, but not impossible.

Another test to confirm our suspicions is to place the meter on the Tan wire, on one of the injectors, then crank the engine over. Verify you get some type of AC voltage, it's actually pulsing DC. Do the same to the White wire, compare the results. If one is significantly different from the other then you have more proof your PCM is toast.