Tapping into fuel line behind lift pump?

[Angelo]

I need to connect a 12v diesel inside of my ambulance build which is a 1996 K3500 with the 6.5. It runs on 12v and diesel fuel and has it's own fuel pump, and will only consume 0.1-0.35 liters/hour according to spec although I haven't tested that. The heater comes with a separate tank that I can use but I'd rather tap into the vehicle's fuel supply if it's feasible. I don't want to drop the fuel tank and mess with that but let me know if that's the better route to go. If there's an auxillary tap that may work too. I have 2 tanks and do not know the condition of the secondary tank yet.
So what I was thinking about doing is this instead - why not put a T in the line behind the lift pump? . I would think the lift pump will still be able to push enough to run without issue. Does that sound right?

 

[Supercharged111]

Sounds legit to me, let us know how it goes. Those are o ring fittings behind the lift pump. Same as what goes into a gasser fuel filter.

 

[thinger2]

I would install a good quality shutoff valve on the line going to the heater That way, if it starts sucking air on the heater side, you can shut it off and still bleed the air out of the main and get ot to start.
I would also make sure it has its own filter setup
It used to be really common on commercial boats to have a diesal stove and heater.
Usually they are setup to run off of a "day tank" as is the main.
The only time a tapped common fuel line caused us any problems was due to a cracked flare on the stove line that sucked air into the pressure timing system on a Cummins JN130M and caused it to surge all over the place.
No main and no heat for two days.
The stove line was sucking air into the day tank and foaming the fuel on its way to the injector pump.
At least with a split system, you have a chance of having the engine run with no heat, or having heat while you fix the engine.
The 6.5 works a lot differently than the old Cummins PTS but it is something to consider.
Curious as hell to see what you come up with
Good Luck and for sure let us know

 

[thinger2]

Just got off the phone with a old freind who is an actual marine engineer and he said you might want to take a look at a "Y" valve system.
I forgot to mention this, my "bilge rat " days were long ago.
Basically, your fuel line feeds into a Y valve that has two filters and an air bleed on it. If one filter clogs, you flip the valve, give it a burp and away you go.
Then you prime the replacement filter while its running and you are ready incase it happens again.
In the boat world, if you are in rough seas, all the crud in the fuel tank gets stirred up and plugs the filters.
I can also see that happening in the offroad ambulance world.
The systems we used way back in the last century were made by Raycor and they were da bomb
No plastic.

 

[Angelo]

Just got off the phone with a old freind who is an actual marine engineer and he said you might want to take a look at a "Y" valve system.
I forgot to mention this, my "bilge rat " days were long ago.
Basically, your fuel line feeds into a Y valve that has two filters and an air bleed on it. If one filter clogs, you flip the valve, give it a burp and away you go.
Then you prime the replacement filter while its running and you are ready incase it happens again.
.

The heater has arrived, so time to begin the addition. Thanks for the tips on this. Especially around the necessary shutoff valve. Using a Y would make installation with fuel in the truck's tank way less messy since it has the 2 valves on it!
This electronic controlled heater has a priming function, where it will purge the system of air, and the 6.5 has the bleeder on the fuel filter so I guess I should be good as far as air goes. Gotta keep an eye on the filters I will update here

 

[Angelo]

This is the plan:

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[Angelo]

Those are o ring fittings behind the lift pump. Same as what goes into a gasser fuel filter.

I'm unable to find a male M16 x 1.5 with o ring to go into LP. This adapter would need to have some kind of way to go to 3/8 fuel line, ideally just a 3/8 barb. Do you know if the LP has an o ring inside? I opened a thread asking about using teflon tape for this application.

 

[Angelo]

Y valve behind LP. It's very tight, had to loop the 3/8 around back to the LP with no space to push LP further forward. Bleed/prime the auxilliary and LP fuel lines to get rid of air in lines. Seems to be working

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