Figured I would share this in hopes to save someone the headache.

We recently had an intermittent fluctuation in a fuel flow indication. This C185 has a CGR-30P and -30C. The flow indication was stable at some points, then would rise and fall seemingly without reason about 1 GPH both sides. The engine was not actually getting this flow, as there was no surging or indication on any other engine gauge that would support an uneven fuel flow of that level.

The E.I. trouble shooting was done, new wiring was installed, the transducer was relocated to the "optimum" position. The problem showed no change. The throttle and mixture linkage was rebuilt/replaced to remove all slack/movement. Problem persisted. The aircraft was flown and all electrical loads were shed, we systematically turned things on and off, trying to find the culprit if caused by some stray EMI. When we came to killing the alternator via the field switch, the indication smoothed out.

After a short troubleshooting session with the charging system, an intermittent open was located in the field wire. This break was causing the alternator output to rapidly start and stop...fast enough that the drop in voltage was not indicated by the CGR's voltmeter. However the build and collapse of the magnetic field around the alternator output was inducing a voltage in the fuel flow wiring, causing extra pulses which the CGR interpreted as FF. Apparently the FF samples/displays at a faster rate than the voltmeter. The voltmeter and ammeter never fluctuated a bit.

According to SavvyAviation, they have never seen this cause of a wild FF indication. Electronics International tech support also said "well thats a new one". Hope this may help someone out there save a few of the hairs on their head.

I’ve had a carb’d version EI cube fail before. Have a friend on his second one too (in a cub). I did the troubleshooting and ended up replacing it. No issues with new one. Been couple years now on new one. The original one died an insidious death somewhat similar to what you describe.

Glad you sorted yours out.

Haven’t had any issues with my injected version EI cube.

I like the EI stuff and have had good experiences with them on the phone.

My EI fuel flow transducer is back at EI for repair right now. Just quit working and after all of the checks I sent it back. Waiting for results.

Jim