I just can?t do it captain, I need more power

[N941WR]

Originally Posted by emsvitil

Measure voltage at P-mag lead and see how low.

Then as a test, wire up separate battery just for the P-mags and see what happens.

The voltage won't drop as much with just the P-mag load.

If you wire a separate battery to just the P-mag, be careful you aren't back feeding the rest of the electrical system. That's why, in the sample I linked to above, the switch isolates the P-mag from the electrical system.

However, you could run the test, knowing it won't start and/or put the test wires on the other P-mag to see what happens.

[N208ET]

Originally Posted by Mike S

Rather than a lithium based battery, you need to go straight to the dilithium crystal.

Make it so...

Best idea I?ve heard yet!

The starter solenoid was the first thing I tried replacing, cause I figured it?s only $20. No effect. I had a bad ground experience on the Sky-Tec a long time ago, I doubt that?s the problem but it?s worth a try.

I thought about doing the 9 volt battery trick just to see if that could get me started in a pinch, which I?m sure it would. But that seems like a band-aid over a bigger problem that would still be unfixed.

If I leave the sump heater plugged in, she?ll spin much easier and as a result doesn?t pull the voltage down as much, she fires right up. My battery is on the firewall, so it isn?t far away from the starter to begin with.

[highflight42x]

With regard to "barely swing enough to start": I was having groaningly slow starts that kept getting worse with time. New battery seemed to solve it but then it was back. Old alternator? Weak starter? At a remote airfield getting fuel an hour till dark - prop *barely* turned over to start. That did it -

Turned out I was getting 0.7volt drop across the master solenoid, and 0.3volt drop across the starter solenoid. 30 year old solenoids (yes I know, duh). A full volt loss! That's why a new battery seemed to solve it. I spent some cash to get the best solenoids around: Lamar P52-0034-1 master and X61-0030 starter.

Engine starts like a whirling dervish now. I'm looking fwd to opening up those old relays to see just how messed up they actually were

cheers,

- Steven
(1300 RV3 hours - another one yesterday!)

[9GT]

I am curious what type/size of wire used for you battery/solenoid/starter/ground. If it isn't mil-spec there could be some internal corrosion going on causing high resistance. Check all the terminals for signs of corrosion and loose terminals. I know some people use welding cable instead of the mil-spec tin plated copper. Is it a minimum AWG 2 gauge?

[Carl Froehlich]

Originally Posted by 9GT

I am curious what type/size of wire used for you battery/solenoid/starter/ground. If it isn't mil-spec there could be some internal corrosion going on causing high resistance. Check all the terminals for signs of corrosion and loose terminals. I know some people use welding cable instead of the mil-spec tin plated copper. Is it a minimum AWG 2 gauge?

Are you sure about this? I far prefer welding cable offer mil-spec as it is much less susceptible to fatigue failure and doing my own ?torch test? find quality welding cable insulation to be more robust than mil-spec. I have never seen ?internal corrosion? - and considering welding cable spends decades in the sun and weather on the back of welder?s trucks I suspect internal corrosion is not an issue.

Carl

[N208ET]

Wire looks to be in great shape. The plane sat for 3 years between engine overhauls, so the wiring and connections was the first thing I checked, next was replacing the starter and master solenoids, then replaced the battery with another PC 680 thinking the old battery sitting for 3 years was probably toast. No effect. Then I got the B&C starter. Now she?ll spin plenty fast but the voltage is dropping enough that the PMags don?t have enough umph to spark with the starter pulling that much current.

If a new battery doesn?t do it, I?m pulling everything out and installing a Coffman Starter!

[Raymo]

I don't know that an EarthX battery will solve your problem but my -7A spins at least 3 times faster vs the PC680 it replaced. If you go this route, don't be surprised when your alternator maxes out (amps) for a little after enabling the alt field. Those batteries dump power like mad and take it back in as quickly as possible. Hot starts are also much improved.

[mike newall]

Originally Posted by Mike S

Rather than a lithium based battery, you need to go straight to the dilithium crystal.

Make it so...

You took the words out of my mouth.....

Live long and prosper

[9GT]

Originally Posted by Carl Froehlich

Are you sure about this? I far prefer welding cable offer mil-spec as it is much less susceptible to fatigue failure and doing my own ?torch test? find quality welding cable insulation to be more robust than mil-spec. I have never seen ?internal corrosion? - and considering welding cable spends decades in the sun and weather on the back of welder?s trucks I suspect internal corrosion is not an issue.

Carl

I have never done a torch test on the welding cable vs Mil-spec. I did use welding cable in the Cozy MKIV and it has so far held up very well going on 12 years now. No problems with corrosion on it and we did solder the ring terminals in solid. I bought a 500' roll of surplus mil-spec wire when I was building the RV-10. It was severally corroded from one end to the other. I kept cutting it at 10' intervals hoping to find the end of the corrosion but ended up tossing the whole roll. The corrosion was easily identifiable as a whiteish gray colored powder in the strands. Just making suggestions as there is obvious high resistance somewhere and the obvious seems to have been addressed.

[olyolson]

Randy,

Have you checked out the Skytec high torque NL starter? If not I would bet that is the solution to your problem. I bought an RV-4 many years ago (now have an -8) and always had trouble starting just like you described. It had an Aerobatic AEIO-360 and a big fat aerobatic prop.

I tried all the electrical issues you talked about and had no luck until I put in a Skytec 149NL high torque starter. Problem solved for the most part. Sometimes on a hot start if I didn’t get it just right and had to make a couple tries then the battery would start struggling. Enter: the EarthX battery, engine never turned so fast and never, ever had a starting issue again.

Neither option is cheap but this ain’t a cheap hobby anyway. I would try the NL starter first if it fits in your cowl. If that solves your issue, good to go. If not then consider the EarthX battery- tiny package but those batteries are monster starters