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Started Solenoid and Gascolator Location

PostPosted: Fri Sep 04, 2015 11:04 am
by jjacky
OK, I'm hesitant to ask this because it defies the design of every airplane and car I've ever seen....but!...Why locate the gascolator and starter solenoid on the engine side of the firewall? It seems to me if you located the solenoid in the cabin you 'd avoid having an always "hot" "welding cable" in the engine compartment. Also if you located the gascolator in the cabin you'd avoid having a cup of gas (Molotov cocktail) in the engine in the engine compartment as well.
Also is there a reason not to use a marine 250 amp battery switch rather than a master solenoid? The idea of that hot solenoid just sitting back there burning up my precious amps just does not sit well with me. Also they weigh about the same and some have a "key". Thanks in advance for your thoughts...bird

Re: Started Solenoid and Gascolator Location

PostPosted: Fri Sep 04, 2015 2:40 pm
by danerazz
Depending on your battery location, you certainly could use a switch instead of a contractor. The contractors are used to allow the shut off point to be as close as possible to the battery while not having to run a wire that is big enough to carry hundreds of amps to a large switch. If you mount the battery under the glare shield it should be acceptable. What you don't want is a large, long, un-protected wire running from your baggage compartment to the panel mounted switch with no way to turn it off if it chaffs through before the switch. The contractors are usually on the front of the firewall when the battery is there, otherwise no real reason they have to be mounted there.

As for the gas orator, you want it mounted at the fuel system low point. This is usually easy to achieve on the firewall. In level flight it will be most likely the lowest point, but on the ground in a tail dragged with a rear header tank it might not be. Also, the drains tend to drip, I would rather have that on the non-human occupied side of the firewall. Also, you have to be able to open them and clean them. If they are slapped on the firewall this makes it easy. If they are in the cabin you are likely to make a large gasoline mess. And lastly, I try to eliminate unnecessary fuel connections in the cabin. The firewall is there to keep the fire out of the livable space, so I want to give it the best chance I can.

Re: Started Solenoid and Gascolator Location

PostPosted: Fri Sep 04, 2015 8:19 pm
by R Rinker
Just a few thoughts..
The only time a solenoid would have really high amperage flowing through it is during the few seconds the starter is engaged, or if something shorted out. So 'any' wire could be looked at as a potential 'welding cable'. I agree it should be as close to the battery as practical.

Re: Started Solenoid and Gascolator Location

PostPosted: Sat Sep 05, 2015 9:43 pm
by User GDS
I use an Odyssey Battery, laying on its side, in a tray under the right seat. The solenoid is mounted on the battery tray.

For all the reasons Danerazz said, I put the gascolator on the engine side of the firewall. When the plane is on the ground, the bottom of the header tank is the lowest part of the system and acts like a sump. Undissolved water should be captured there. The pre-flight includes sampling fuel from the header tank sump and the gascolator. I don't use an in-line fuel filter.