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p7100 12v Fuel system upgrade


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After reading the fuel system threads that Cowboy and Dauntless89 (thank you both for the info) have posted over on cummins forum I decided to do some work to my fuel system since I have been having some issues with fuel supply since going to bigger injectors.

 

What I did was run new 1/2" supply line from the fuel tank all the way up to the injection pump.

At the tank I have a G&R diesel sump with integrated return (return unused atm) with a 1/2" NPT to 8jic push lock onto the fuel line.

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From the tank it goes straight to the lift pump where I have a 1/2" NPT 90° with another 1/2" NPT to 8jic push lock onto the fuel line on the fuel inlet, and on the fuel outlet I have a m14 to 8jic 90° push lock.

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Then it goes up to the filter housing which I changed out from the 97 style canister filter housing to the earlier spin on filter housing. I drilled and tapped the ports on the top of the filter housing out to 3/8" NPT and drilled the center of the filter thread adapter out to 3/8" as well. (didn't get pictures of that though) On the filter housing I have a 3/8" NPT to 8jic in each port and have tight 90° 8jic to 1/2" push lock with 1/8" NPT ports tapped in them. On the clean side of the filter I have my fuel pressure guage sender in the 1/8" port and on the "dirty" side of the filter I have a 1/8" NPT to 4jic onto a 4jic 1/4" push lock that goes to the injector return line where I cut the steal line and used a 3/16" compression fitting going into a 1/4" hose barb. then to the filter housing.

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At the injection pump I put a m14 to 8jic adapter with a 8jic to 1/2" push lock into the hose from the filter housing.

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Besides the fuel line upgrades I also upgraded the spring in my stock lift pump to a 973-1 comp cams valve spring. Here it is side by side with the old stock spring. (this is the original lift pump the truck has had on since the factory 18 years ago)

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After these upgrades with NO other changes I my fuel pressure at idle went from ranging in the 5-20psi range to holding steady at 25-27. and at 3000 RPM (no load) it holds 45-50psi  under WOT conditions I have yet to see it drop any lower than 37psi.

I can definitely tell that I was starving for fuel before the upgrades, I have better response, better spool up, less smoke, and more power (according to the butt dyno) than before.

I had planned on doing some things to the return system as well but after seeing the results I got from these upgrades I feel for my current setup I don't have to worry about my return system for now.

All the hose and steel fittings came from Vulcan performance, the black fittings came with the fuel sump, and the brass is from the local hardware store.

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  • 2 months later...

Very Cool!  Glad to hear you about your results.

You don't appear to be running any sort of snubbed for your pressure gauge, and you're not having any pulsation issues?    

With the 90* going into the Injector pump, I had mine like that for a while, then found that it was rubbing against the throttle linkage, so I replaced it with a 45*.  Just something to check.

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No snubber at the moment on the fuel pressure sender, I was using a banjo bolt with a snubber built in on the old filter housing, I was meaning to move the fuel pressure sender and add a snubber but I totally forgot about it, but I'm not having any pulsation issues with it either surprisingly.

I'll have to take a look at the 90 going into the injection pump but I haven't had any noticeable issue with it rubbing the throttle linkage.

 

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