Fuel Lines: 4.0 EFI in a CJ7

Jeffncs

Jeffncs

Well-Known Member
Joined
Apr 4, 2017
Location
Wake Forest
Good evening!

im currently researching the 4.0l EFI going into a CJ7. I have the engine, harness, sensors.... In my reading, I’m not sure what to do about the EFI fuel lines. I know this is a high pressure system and that I can’t reuse my old rubber fuel lines. However, I’m not finding clear answers on a few things. Can anyone help?

Questions...
Using my CJ7 gas tank, there’s a short metal tube (supply) with a standard slip fitting. Can I attach my EFI rated fuel line and EFI fitting onto that tube safely?

what diameter should I run for the supply? 5/16”?

what diameter should I use for the return? 5/16”?

can I safely run EFI rated rubber lines from the front to back? Or should I plumb stainless lines as much as I can? Or are the hardlines nice to have and not required? if the hose is protected?

If i install the hardliners, with the lines hold the pressure rated fuel or do I have to install a special fitting to avoid blowing fuel across my exhaust?

I’m on a budget, it safety is a priority....and will spend money in the right places.

Thanks!
 
Hardlines are superior for heat, pressure, flow, reliability, etc. It's nice to not have to worry about flexible lines having problems where you can't see them, like getting melted, cut/rubbed, etc.. With the proper flares/beads/whatever depending on your type of connection, you should never have to worry about pressure. EFI pressure is pretty low, relatively speaking. A hardline bead and a proper clamp is all you need to transition from flex to hardline. Constant tension, spring clamps, or bolt clamps will do fine; don't bother with worm drive clamps.

5/16 is plenty big for a 4.0L that wheezes out sub-200HP or whatever it is.
 
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Jeffncs said:
Using my CJ7 gas tank, there’s a short metal tube (supply) with a standard slip fitting. Can I attach my EFI rated fuel line and EFI fitting onto that tube safely?
Click to expand...

Exactly what I did when converting to TBI... FI rated hose out of stock (Commando) tank to filter/pump/hardline to the front (which transitions to OE Cheby SS supply). As @Fabrik8 says, use NO stoopid worm clamps...
Someone will say the TBI only requires 15#, which is correct, but the E2000 pump pushing it is capable of 90+#... which is what the supply see between the pump & fuel pressure regulator on the TB

I'd recommend 3/8" supply (overkill for both our applications, but read the reasoning behind it somewhere... friction loss?) and 5/16" return...
 
Caver Dave said:
I'd recommend 3/8" supply (overkill for both our applications, but read the reasoning behind it somewhere... friction loss?) and 5/16" return...
Click to expand...

Yeah, it doesn't hurt to use 3/8 at all, especially when running new lines. The friction loss with 5/16 may be an issue for low pressure carb'd applications, I could see that being the case maybe.
 
Thanks to all! I’ll plumb 3/8 supply and 5/16 return using hardline. I may even just buy 25’ 3/8 and run that both directions...see what makes financial sense.
 
When I swapped the 1.6 16v EFI motor into my Samurai, I bought 'EFI high pressure' rubber fuel hose from O'Rielly's along with some 'EFI hose clamps'. I doubled up the clamps at each joint just for safety, and reused the stock hard lines. I think I plumbed in a Mustang 5.0 fuel filter with some kind of external fuel pump that was popular 15+ years ago. Never had a problem over 10+ years of wheeling.

I will be installing a Motobilt fuel cell in the rear of my YJ, and I plan to do it a little better. I am going to try and use proper (AN?) fittings and such at all joints along with high quality hose.
 
drkelly said:
I am going to try and use proper (AN?) fittings and such at all joints along with high quality hose.
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Just a little tip, JIC fittings are less than half the price of AN fittings and work just as well. You dont get the bling racer look like you get with the anodized aluminum AN fittings, but they're considerably cheaper.

I started using parker push-loc stuff for fuel, power steering return and transmission. Great stuff that's easier to install and MUCH cheaper. Plus you don't end up bleeding all over the place like I always do when dealing with braided stainless lines. I also use -3 for all that stuff then you only have to carry one piece of spare line to work with the trans, power steering return or fuel.
 
Actually... I cheated out a bit. I bought 25’ of SS 1/4” line for the supply and return lines, a flaring tool and a crimping tool with locking clamps.

I ain’t gonna have none of that fancy anodized stuff going on under the hood of my old Jeep! I’m simple (and cheap)... OK that’s a lie. I spend way too much on this darn Jeep!!!
 
I ran -6AN steel braided line for supply and return on my 4.0 and at the end of the day what’s it matter. I considered running a hardline like stock, but since I was trying to be a cool kid I just closed my eyes and swiped the card for everything. As long as everything is fuel rated and fittings are installed correctly, you can’t really go wrong with a 4.0 tractor motor.

x2 on JIC vs AN. Same stuff really. I started to find that all out after the fact.
x2 keeping it all the same, so its a “one size fits all” approach.
 
I used a 3/8 aluminum tubing for my supply/return on my LS swap. It's held that magic 58 psi (or whatever it is) like a boss for the last 4,5 years. I'm digging through the archive depths here, but these were as easy as it gets. And IIRC, these were self flaring.
IMG_20160630_190524153.jpg

I'm sure, there's better options available now.
 
Self flaring/swagelok is the way to go. You can’t really mess that up. Flaring tools (especially cheap-o’s) can make it a pain in the ass.
 
Going on memory here but I did a 4.0 swap into a CJ for a buddy back around early 2000's. I spliced into the original 5/16" steel line a fuel filter and inline pump using fuel injection rubber hose just above the fuel tank. In the engine bay I used the same rubber hose to connect the steel line where it ends to the injection system. The return back to the tank stayed original, I just connected to it.
 
NCJeeplover said:
Just a little tip, JIC fittings are less than half the price of AN fittings and work just as well. You dont get the bling racer look like you get with the anodized aluminum AN fittings, but they're considerably cheaper.

I started using parker push-loc stuff for fuel, power steering return and transmission. Great stuff that's easier to install and MUCH cheaper. Plus you don't end up bleeding all over the place like I always do when dealing with braided stainless lines. I also use -3 for all that stuff then you only have to carry one piece of spare line to work with the trans, power steering return or fuel.
Click to expand...

So you used AN-3 lines for trans cooler lines, PS return and fuel lines ?

JIC and AN fittings are compatible but hardly the same thing. At our level it doesn't matter to mix and match but the tolerances during fabrication and the materials are different.
 
Bebop said:
So you used AN-3 lines for trans cooler lines, PS return and fuel lines ?
Click to expand...

I use -3 for fuel feed and return plus trans lines. I use -6 for power steering return. That was my bad. I actually don't carry spare power steering return line. I need to look into that.

Bebop said:
JIC and AN fittings are compatible but hardly the same thing. At our level it doesn't matter to mix and match but the tolerances during fabrication and the materials are different.
Click to expand...

I know AN is built to a much higher standard, but I have yet to find the need for that in what I do. Regular old JIC has worked fine for me for years. I'm not a racer or rock bouncer, just a simple guy with trail rigs.
 
NCJeeplover said:
I use -3 for fuel feed and return plus trans lines. I use -6 for power steering return. That was my bad. I actually don't carry spare power steering return line. I need to look into that.
Click to expand...

AN3 is brake line sizing. (3/16 ID). Way too small for any kind of V8 (I know we're talking about a 4.0 here, but I figured it would be nice for people to know).
AN6 (3/8 ID) is ok for trans cooling. I still have pressure spikes on mine with some AN6.
AN8 (1/2 ID) is minimum recommended for PS return on a full hydro set up (the bigger the ID, the less backpressure your fluid has to fight).

Basically, I'm glad this works for you, but the line sizes you're sharing are grossly undersized.
 
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