What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Engine Primer Plumbing

WingsOnWheels

Well Known Member
This is a writeup of how I installed my primer plumbing, that does not mean it is the best (or even good) methond for the installation. Feel free to poke holes/ let me know what I can do better.

There were three major considerations for me when I was planning how to install the primer lines.

A) No copper from the engine to the firewall (your results may vary, but I just don't like that solution)
B) I don't like using flared fittings on line this small, it is just prone to cracking.
C) SS hard lines are a great option, but for cost reasons I will stick with the copper.

I decided to use a hose from the primer valve to the engine, but how to connect that hose to the copper lines? I thought through a number of possibilities, but didn't have an answer. At the same time I was looking for a local source for the copper tube, but hadn't found any yet.

So the other day I was walking around autozone and out of the corner of my eye I spotted a package of coiled copper tubing. On closer inspection it was 6' of 1/8" line and came with a few compression fittings to adapt to male and female NPT fittings. This turned out to be a hookup line for sunpro mechanical pressure gauges P/N CP7584 for $10.99. What really caught my eye were the compression fittings that came with the line. The fittings are the exact same type as the primer fittings on my previously-enjoyed engine. Now I know what type of fittings those primer fittings are...yay.

While I was at autozone I bought the line kit and also bought a couple compression union fitting (straight through with a compression fitting on each end). The compression fittings have 5/16-18 machine thread for the caps and come with the compression sleeve for 1/8" tube. These were $3 for two.

I went about making a distribution block that will connect a single incoming hose to three outgoing ports for the copper primer line. For the outgoing ports I tapped for 5/16-24 and the incomming port is 1/8 NPT. The distribution block mounts to one of the bolt holes for the oil pan.

I fabbed the distrubution block out of a solid piece of 6061-T6 that I happen to have around. I would liked to have made it from brass so I could just silver-solder the fittings in, but with the aluminum I just used pro-seal to seal the 5/16-18 machine threads. The 1/8 NPT fitting can just use the same sealant I am using for all the NPT fittings (Perfect Seal No. 4).

Here is the completed distribution block:
FP20012013A00016.jpg


I routed the copper lines. I used the self-fusing silicon wrap to protect the oil lines and some small tubing over the copper line to protect them. The zips ties here aren't my favorite thing, but I couldn't think of anything better. I added a line clamp. I would like to have another line clamp closer to the distrubution block, but there is much I can mount it to in that area.

FP20012013A0000X.jpg

FP20012013A0000W.jpg

FP20012013A00015.jpg


I played around with the fittings and the best routing worked out to be with the 45* at the primer distribution block and the 90* at the valve. I used cushion clamps to keep the hose away from the engine mount and the cabin heat ducting

FP20012013A00017.jpg


FP20012013A00018.jpg
 
Last edited:
Just a few comments:

Napa carries 1/8" compression to 1/8" NPT fittings (behind the counter). I have also found them at the local ACE hardware store.

You can search The forums for debate on steel vs aluminim AN fittings FWF.

The fittings traditionally used on copper primer connections are solder on AN800 fittings. http://www.aircraftspruce.com/catalog/hapages/primerfittings.php?clickkey=4735

I'm not sure if AN primer fittings are compatible with automotive compression fittings.

I do like that the distribution block concept eliminates some connections, and allows for a teflon flex line.

Paige
 
Paige,

Thanks for the info. I have been trying to decide if it would be worthwhile to solder on the AN-800-2 fittings to the ends of the copper tube. I'm not quite sure what the advantages may be, but it is easy enough to do. Using the primer fittings installed in my engine for comparison, the fitting is an exact match to the automotive compression fittings so they should be compatable. However, the hole in the auto compression fitting cap is smaller so it would likely have to be drilled out.

I don't think I have ever seen a NAPA store in our area. Autozone has the compression fittings also out on the sales floor. Either should work just fine.

As for the steel vs aluminum, there are a lot of threads on this topic. I think for the primer especially it would be a waste of money and added weight to use steel AN fittings. The hardline I have from the gascolator to the primer valve is stainless steel.

Thanks,

Colin

Just a few comments:

Napa carries 1/8" compression to 1/8" NPT fittings (behind the counter). I have also found them at the local ACE hardware store.

You can search The forums for debate on steel vs aluminim AN fittings FWF.

The fittings traditionally used on copper primer connections are solder on AN800 fittings. http://www.aircraftspruce.com/catalog/hapages/primerfittings.php?clickkey=4735

I'm not sure if AN primer fittings are compatible with automotive compression fittings.

I do like that the distribution block concept eliminates some connections, and allows for a teflon flex line.

Paige
 
Back
Top