| Short circuit, left side fuel '90 Speed Density |
Subject: Short circuit, left side fuel '90 Speed Density by whalepirot on 2013/1/17 19:07:55 Pulled the PITA Lingenfelter intake to check for pinched wires to the FIs. Maybe relieved it, but I started checking resistance to ground in a number of places, with my digital VOM. I NEED to ensure of a fix before reassembling it. (FelPro should make Velcro gaskets for this unit.) I'd just driven the car after having this intake off/apart for another issue, parked it -- No start after about an hour; code showing the short, as above. Comparing the L/R side ohmages, ( no tech detail of that sort is available to me) the L side was near zero.Pulled only #1 & 3 inj plugs (only ones accessible, w/o further disassembly); both checked around 15 ohms, as did #7 & 8. Those plug lead's resistances matched also, UNTIL I checked with #3 plugged to its injector, whereupon it dropped from the 5.4 ohms, to 4. That would tell me the injector is shorted, IF it hadn't checked at 15 ohms! With four (each side) injectors connected in parallel, as they are, the theoretical resistance would be 3.75, reasonably close to the observed, given the unknowns in the remainder of each (L/R) circuit. I must be missing something here; comparable readings everywhere and the 'problem' injector testing okay as does its plug,... Are there resistance specs or procedures that differ from what I have tried? thanks for any support. MORE: I felt I was doing a poor job of explaining. The fuses are out, disconnecting the power, but the ECM is connected. I was hoping to find the short an easier way. I took comparative measurements with all injectors plugged in, one off, and two off. The odd thing is how all comparisons matched, until the #3 injector was plugged in; again, that injector's resistance was about 15. I did not check any resistance at or of #2,4,5 or 7, as I'd found an anomaly at #3 and b/c they'd require pulling the runners for access, due to the design of this manifold. As expected, disconnecting one injector on the 'good' side, increased the measurement, to a value identical to the 'bad' side. That seems to indicate that the problem is not with the ECM, the wiring to it, or with the other injectors and their connections. With the injectors wired in parallel, isolating the short may be a visual task. I guess it's possible that the ECM connection may alter the comparison readings, but I bumped the starter as a check, with no change in the readings. |
