2 injector failures, 4.9L

Tiny
STEVENTASINC
  • MEMBER
  • 1992 FORD F-150
  • 6 CYL
  • 2WD
  • MANUAL
  • 120,000 MILES
Have 92 F-150, 4.9L, w/sudden no injector pulse @ cylinders 1 & 3. Engine runs but only on the other 4 cylinders. When ground (via test light, for instance) is applied to ground wires @ injectors 1 or 3 for a few seconds, then removed, engine temporarily runs perfectly on all 6 cylinders for a few seconds, then fails again back to no pulse @ 1 & 3. So apparently there is a ground/pulse issue somewhere.A rebuilt distributor with new PIP has already been installed to no avail. EEC relay? EEC? What?
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Saturday, August 20th, 2011 AT 6:28 PM

7 Replies

Tiny
HMAC300
  • EXPERT
#1-3-5 all get their power from the same place which is from the eec. I wold try cleaning theground at teh top right of rad panel, that is for the eec relay and another at the bottom of the right cowl panel. The only thing I can think of offhand is the engienground to battery isn't clean and causing this or the one for the eec which is near the right front by the battery. I'd try cleaning those first. I t may be the wires are broken in the harness or the connection is bad at the eec. Especially if you pull the plug and you see corrosion.
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Saturday, August 20th, 2011 AT 8:06 PM
Tiny
STEVENTASINC
  • MEMBER
Is the location of EEC connector the one at the driver's side of the firewall about half way up from the bottom?
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Saturday, August 20th, 2011 AT 9:28 PM
Tiny
HMAC300
  • EXPERT
The right cowlpanel would be passenger side by right fender, but clean the one you are talking about as well, you might as well do all of the ones you can find.
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Saturday, August 20th, 2011 AT 11:18 PM
Tiny
STEVENTASINC
  • MEMBER
So here's what we've got so far: All the ground connections & EEC connections are clean, no change, same symptom. Ignition module swapped out for test with a new one, same symptom, original put back in place. Distributor & cap are new as are plugs & wires (needed a tune anyway). What do we look for next?
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Friday, August 26th, 2011 AT 8:01 PM
Tiny
WRENCHTECH
  • EXPERT
Have you determined whether it's power supply or pulsing ground that you are losing on those injectors?
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Friday, August 26th, 2011 AT 8:18 PM
Tiny
STEVENTASINC
  • MEMBER
Appears to be pulsing ground. When a good ground is directly supplied to injectors @ cylinders 1 & 3 for a few seconds and then removed, engine will run on all injectors for a few seconds when ground is removed. Then fail again. It's as though the introduction of the known good ground is manually creating a good pulse condition for a few seconds then it fails again.
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Friday, August 26th, 2011 AT 8:59 PM
Tiny
WRENCHTECH
  • EXPERT
You need to use a noid light to confirm that first and then you will have to test the circuit back to the ECM for those 2 injectors. If you find no problems with the connecting wires from the ECM, then you would be looking at a bad ECM
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Friday, August 26th, 2011 AT 9:49 PM

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