912 starting issue?

[phintz]

Hello, I've had such good luck lately finishing my series 6, I have one last obstacle to overcome! I'm hoping the huge amount of knowledge here will help solve the problem!

I moved the kitfox to the airport today and planned on starting it again and triple check everything before Wed. when my FAA inspector was to arrive ( may need to postpone).

This would have been the second time I actually started the plane! When I purchased the Kit it had a plastic battery box and a battery that was not filled with acid yet. This battery would not fit all the way down into the battery box(bad mold). I decided to buy a battery that would fit instead of retro fitting the box. On first start up day the battery would not crank the engine enough to start it. It would only move the blades 3 or 4 positions then start to chatter. So I took a full size car battery with 800 CCA and made some leads and had the intial engine start that way, thinking the battery was not adequate. Next I purchased a Odessey PC 680 which many 912 owners have, thinking this will solve the problem. Today I tried with the new battery, I tested it and it read 13.98 volts. It started off ok but then slowed to a crawl then the chattering again. So, I visited with another pilot this afternoon and he mentioned putting a volt meter on the battery while turning over the engine. I did and while cranking It dropping to 10.54v. I then took the battery out and took it to my local napa store and they load tested it at the name plate rating of 170 CCA. the machine said the battery is good. So I am stumped at what is causing this????? Is the engine so tight that the compressions are high and needs yet another bigger battery, could it be the starter ( I have the light duty, black starter), could it be the starter solenoid?. My battery is on the back side of the firewall. The leads are as short as I'm gonna get them and I used #6 awg stranded copper that came with the kit. All ends are crimped and tight. Last thought, what about the diode that is attached from the starter solenoid to ground? Heck my trouble shooting skills are fried!!! All thoughts are appreciated

Patrick
series 6 (still building)

[kauaicuda]

Try using a jumper cable from the battery negative to engine ground for a quick and easy check for ground problems.

[Dave S]

Patrick,

You did well in diagnosing this problem by first determining if the battery is OK....the numbers you observed indicates it is good.

Diagnosing this stuff is a stepwise procedure ruling out one thing at a time.

The fact that the solenoid went to chattering, while the battery is good and the starter is not drawing too much power to drop the voltage, indicates a good next point to consider is the solenoid primary and the solenoid actuating circuit. Almost sounds like a potential (certainly not for sure, but a potential) that there could be a high resistance point in the actuating circuit somewhere that drops or limits the voltage the solenoid primary is getting.

Sincerely,

Dave S.

KF7 Trigear
912ULS Warp Drive
St PAul, MN

[phintz]

I'm Wondering if I could take a ohm meter and check the readings, if I found a extremely high reading. Maybe that is my problem. Could my wire size be too small? The # 6 came with the kit. When I put the crimps on I didn't put any anti corrosion inhibitor on since it was copper, I know on Aluminum you should.

[DanB]

Just an outside thought...Did you purge the oil system by the book?

[tommg13780]

Another thought, depending on the type/configuration of your starter solenoid it may require a case ground. If it needs a case ground and doesn't have one it probably wouldn't crank at all.

[phintz]

Just an outside thought...Did you purge the oil system by the book?

Yes! I purged the engine as the manual said, I started the motor 3 weeks ago with the large car battery and pressure came right up.

tonight when I get home I'm gonna swap batteries from a KF 3 and see once just to verify the battery is good for my own satisfaction, next I'm goning to bypass the starter solenoid.

What I can't seem to understand, is why would it start with a large battery vs. my new pc 680. 12 volts is 12 volts , must have something to do with the amount of amperage.

[Dave S]

Patrick,


There is some addittional historic information on the list...try this link; or do a search on "starter solenoid" - might help some figuring out the problem

http://www.teamkitfox.com/Forums/sho...arter+solenoid

A person should confirm the circuit from the battery through the switch is good in the start position of the switch too. Not saying that is the culprit - but maybe something to check

Sincererly,

Daev S

[PapuaPilot]

I think someone mentioned checking the grounding. To do this you can check the voltage between battery negative and airframe ground while cranking the engine. If you have a good ground there should be very little or no voltage indicated on the meter. You can use this same procedure across the starter solenoid.

If cables are sized right you should not have more than a one volt drop between the opposite ends of wiring in any system. This is true for both the power and ground wires.

[phintz]

tonight after a full mothers day meal from the inlaws, I swapped batteries with a KF 3 , to much surprise same thing. It didn't want to turn over hardly at all. I then disconnected the battery and bypassed the starting solenoid by bolting the two leads together. I reattached the battery leads and flipped on the master swich and man alive did it turn over!!!! Faster than it did with the big car battery. SO I'm pretty sure its the starter solenoid. I'll post again after a short trip to NAPA tomorrow.

I also weighed it today.

copilot/right side 335 lbs
pilot /left side 310 lbs
nose 115


total weight 760lbs

With 4 gal of fuel.