Fuel line Pressure Test, How much PSI?

[theway]

I’m using a bike pump to pressure test my fuel lines on a Yanmar 3gm30.
I was wondering how much pressure to use.

Thanks.

[Compass790]

Originally Posted by theway

I’m using a bike pump to pressure test my fuel lines on a Yanmar 3gm30.
I was wondering how much pressure to use.

Thanks.

This is a guess but I think the lift pump pressure is around 3-5psi so if you did 15psi test pressure you would have a large margin of safety.
FWIW I use fuel line for my oil lines to a remote filter & it easily handles 40psi.


EDIT : After seeing Gord mays post I must stress I'm only talking about the fuel lines, NOT the fuel tank. Wouldn't try blowing any tanks up to 15psi.

[GordMay]

I'm NOT disagreeing with Compass, but ccording to a VERY OLD version of ABYC H-33:
After installation, the fuel system of every boat shall be pressure checked to at least 3 psi or at 1 1/2 times the maximum hydrostatic head to which it may be subjected in service, whichever is greater. The fuel system shall evidence no leakage under such testing, checked at a minimum of 5 minutes after application of the test pressure, for systems of 50 or less gallons capacity, with one additional minute for each increment of 10 gallons, or fraction thereof, from 50 to 500 gal-lons. On tanks over 500 gallons test for 50 minutes plus 1/2 minute for each increment of 10 gallons over 500 gallons. A leak detection method other than the pressure drop method must be used at every joint except at the deck fill and exterior vent fittings.

[Compass790]

Originally Posted by GordMay

I'm NOT disagreeing with Compass, but ccording to a VERY OLD version of ABYC H-33:
After installation, the fuel system of every boat shall be pressure checked to at least 3 psi or at 1 1/2 times the maximum hydrostatic head to which it may be subjected in service, whichever is greater. The fuel system shall evidence no leakage under such testing, checked at a minimum of 5 minutes after application of the test pressure, for systems of 50 or less gallons capacity, with one additional minute for each increment of 10 gallons, or fraction thereof, from 50 to 500 gal-lons. On tanks over 500 gallons test for 50 minutes plus 1/2 minute for each increment of 10 gallons over 500 gallons. A leak detection method other than the pressure drop method must be used at every joint except at the deck fill and exterior vent fittings.

I'm glad you spoke up as I was only talking about the fuel lines not the tank. Never would I try to blow a tank up to 15psi using air, could be very dangerous. It did not occur to me he could be pressurising the tank,
Thanks for posting quickly.

[theway]

Wow, that seems low, but if that enough for testing.
I did my test from the fuel line coming out of the tank, and through the 2 primary Racor filters. After the filters I close the valve so my primer bulb doesn’t explode, which I almost did once.

I was told it should be done the other way (from engine back) but the filters have preventative measures for back flow (little round/ball rubber stoppers).

Anyway, I had a very strange air leak, would kill the engine between 1hr and 2hrs. So I pump to 50psi and saws leak at the bottom of one of the bowls. I tightened that a bit and then waited. I added a little more pressure and blew out the O ring between the bowl and the filter! So, after I cleaned up the diesel mess, I replaced the O ring and upon further examination realized the prior ring wasn’t sitting right. I check the other filter and same thing. It just seemed like too much gap between the filter and the bowl. Too much of the ring was visible. So I pulled it off too and replaced both red rings with the black ones. The fit seemed better but not really sure why. After that I put some pressure on, close to 50psi and everything stayed put. Then ran the engine for 3hrs with no problems.

I guess I didn’t need so much pressure, but it definitely helped me solve the problem… at least for now.

[GordMay]

It's always nice to read a followup - especially a success story.

[Jack C]

Originally Posted by theway

I’m using a bike pump to pressure test my fuel lines on a Yanmar 3gm30.
I was wondering how much pressure to use.

Thanks.

I use suction not pressure to test fuel lines, valves, filters etc. when assembling my filtering and polishing system. The suction is applied from the low pressure pump to the valve at the tank. Before fuel is in the system I apply suction using my mouth and seal the pipe with my tongue. Any leak is noticed quickly by my tongue being released from the pipe. No problems with non return valves.

I don't advise this method if the components have experienced fuel. It does have the advantage or disadvantage of moving any dirt out of the system and into your mouth or lungs.

Air molecules are much smaller than fuel molecules, so pressurizing a fuel system with air if there is already fuel in the system may not show leaks that are small.

(This is a tongue in cheek, I mean in pipe response which has worked well for me)

[Compass790]

Originally Posted by Jack C

I use suction not pressure to test fuel lines, valves, filters etc. when assembling my filtering and polishing system. The suction is applied from the low pressure pump to the valve at the tank. Before fuel is in the system I apply suction using my mouth and seal the pipe with my tongue. Any leak is noticed quickly by my tongue being released from the pipe. No problems with non return valves.

I don't advise this method if the components have experienced fuel. It does have the advantage or disadvantage of moving any dirt out of the system and into your mouth or lungs.

Air molecules are much smaller than fuel molecules, so pressurizing a fuel system with air if there is already fuel in the system may not show leaks that are small.

(This is a tongue in cheek, I mean in pipe response which has worked well for me)

I like the theory. Do you know what vacuum you can pull sucking on the fuel hose? just out of curiosity, if you have a vacuum gauge fitted that is.
Dont imagine it's as much as a lift pump feeling how hard they suck on my finger.

I'm one of those mad bstds who would try it on used lines.

[Jack C]

Originally Posted by Compass790

I like the theory. Do you know what vacuum you can pull sucking on the fuel hose? just out of curiosity, if you have a vacuum gauge fitted that is.
Dont imagine it's as much as a lift pump feeling how hard they suck on my finger.

I'm one of those mad bstds who would try it on used lines.

I do have a vacuum gauge. See pic of polishing system. I checked (before installation that I can pull 15mm Hg easily with my mouth. I just checked vacuum with the electric lift pump. Same as what I have on my Universal Diesel 5444. With the inlet closed the pump gets to 11mm Hg. Of course an engine mounted lift pump may be different. I'll check my Perkins 4236 lift pump when I change the on engine filter.

Attached are before and after Pics showing the pump and the 13 or so valves and about 30 connections.

[Compass790]

Originally Posted by Jack C

I do have a vacuum gauge. See pic of polishing system. I checked (before installation that I can pull 15mm Hg easily with my mouth. I just checked vacuum with the electric lift pump. Same as what I have on my Universal Diesel 5444. With the inlet closed the pump gets to 11mm Hg. Of course an engine mounted lift pump may be different. I'll check my Perkins 4236 lift pump when I change the on engine filter.

Attached are before and after Pics showing the pump and the 13 or so valves and about 30 connections.

Thanks a lot for reporting back. Thats interesting, I know I'm gunna try the suck test sometime now that it's stuck in my brain altho it may not stay there. Hopefully I wont have to now I've renewed all the fuel lines.
Dont think an engine mounted pump will be much different.

I dont worry about polishing as i use a filter funnel & diesel here is ok & wont be going to coconut tree islands in our boat.