Mark Phillips in TN
Joined: 10 Jan 2006
Posts: 431
Location: Columbia, TN
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 Posted: Mon Oct 06, 2008 8:34 pm Post subject: HAPPY Instrumentation on Jabiru 3300 (so far) |
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-ain't breakin' out the Champagne yet, but here is current synopsis:
Further analysis determines that due to FWF packaging considerations the VDO fuel pressure sender provided by GRT with the EIS package is located about 1" from the right magneto harness and about 3" from the automotive-style distributor. Suspicion is that arcing between the rotor and distributor cap is impressing emf pulses on the sender somehow. Removing the 2 wires to the sender result in zero spikes on the EGT/CHT traces and any other phantom alarms. Hmmm... Victim identified? Fuel hoses to sender are lengthened and an extension for the electrical connections is fabricated from 22AWG wire using faston connectors- this "pigtail" is about 12" in length with the wires tightly twisted. Idea is to experiment with sender location by manually moving it around in the engine compartment with engine running and review effects on EGT trace spikes.
On initial engine start, trace spikes are completely gone, regardless of sender positioning or orientation between the engine and firewall. Locating sender in close proximity to either distributor or magneto results in clean spike-free EGT traces. Sender is re-mounted to engine mount about 2" farther away from previous location to magneto harness with pigtail still installed. EIS is fat, dumb & happy with no phantom alarms, no spikes present on EGT or CHT traces.
Ya think I'd be shickled titless by this, but I can't explain WHY, dammit...
Measured resistance using a Fluke multimeter indicates .2 ohms on each lead of extension. Here's the question: Is it the additional resistance in the connections to the sender (length of extension), or the fact that they are tightly twisted (about 10 turns per inch) that resolved (band-aided?) this issue?
"Problem" "appears" to be solved, but without knowing why. Serendipity? I don't buy it. Awaiting knowledgeable insights or explanations...
A big THANKS! for all of those who have chimed in with their thoughts and suggestions...
Mark
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