Fuel Line / Pump / Filter Query

jpjeep26uk

jpjeep26uk

Causing havoc across Britain with my Wrangler!
Supporting Member
Joined
Nov 12, 2022
Messages
369
Location
UK
Hi all, A query to anyone with a retro fitted carb on a 2.5l 4 cyl. I know there are lots of posts on this and references to vapour lock but I thought I'd put some pics up to see if there is anything I can do to improve my filter, fuel line, pump, pressure valve set up??

Same issue as reported by plenty other folks really: drives fine for 30 miles at 60mph etc. But as soon as we hit traffic or slow down to a stop or crawl, the Jeep barely holds its revs and seems to want to stall, almost like it's running out of fuel (full tank so it's not a lack of fuel)

So here is my physical layout.
  1. Electric Fuel Pump/ Filter in tank has been removed.
  2. Fuel Filter (one year old) is the large canister type bolted to the rear D/S frame per original spec.
  3. Electric Fuel Pump is bolted to the D/S frame almost directly under the carb housing.
  4. Fuel line goes straight uphill from there to a Fuel Pressure regulator set at 3.5 psi.
  5. Then fuel line goes from there on a short curve into the Carb intake. It's wrapped in heat reflecting material.
Is there anything I can do to place things in a better way or reduce heat build up leading to possible vapour lock?
It seems to me there is a convoluted fuel line set up out of the tank and to the filter with a few ups and downs around the shocks and frame then down to the filter when a shorter more straight forward connection could be a better move? Is this advisable?
Should I move the filter closer to the pump?
Should I fit another filter in after the pump before the FPR or just before the carb?
Can I use one of those small see-through orange and plastic filters that let me see if it's getting dirty?
Any help would be really appreciated. Thanks all.
BTW, on the old Air Filter Housing box there was a pipe connected to the bottom of the box which led to a hole at the bottom of the engine block that apparently directed warming air from the block to the air filter to help with cold starts. The air box has long gone due to the carb conversion but the hole remains open on the engine block - should this hole be blocked off or a pipe fitted to it to divert the hot air coming out? I wonder if this is heating up the fuel lines or the pump, as it's right in the same area where the set-up below is........

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Hi Chief! It does not appear to be hooked up/ working anymore no. No sign of a return back to the tank. Just the fuel line in.
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Copy...I'm wondering if that could be the source of your problem. Did you plug that hose, or has it been that way for a while?
 
Chief Hof said:
Copy...I'm wondering if that could be the source of your problem. Did you plug that hose, or has it been that way for a while?
Click to expand...

I think it was plugged as a part of the Nov '24 EFI delete and Carb fitment. I'll check my photo collection to see if it was like that before Nov '24. Is that the fuel return pipe in normal situation?? Any idea what that red tube is above the filter?
 
Copy...not sure about the red tube...looks like a brake line with chafe wrap or insulation sheathing, have you tried tracing that line to its terminus on both ends?
 
Hopefully this makes sense.
Looks like someone hooked up my fuel lines in reverse.
The line with the in-line filter has been blocked off under the cab juat as it heads up to the engine bay.
The fuel appears to be coming from the return line and has no filter at all, just goes from tank to pump and into the carb.
There is no real return line, just one way.
There is no pump in the tank as this was turned off and a small electric one with a regulator was installed just below the carb.
Questions for you gurus!
1. Is there a way to tell the difference between the return line and fuel line at the tank so I can follow the lines to see if I'm dead right?
2. Is there any harm in swapping the lines over so the line with the filter is providing the fuel?
3, I bought a filter with the extra return outlet to replace the in-line one, so do I hook up the 'original' return line to the return outlet and she should run.
4. Could it be that the tank pump is still in place, and that's why someone used the return line as the new supply line as the tank pump won't allow fuel through without being turned on and the return line will?
5. Can I drop the tank, whip out the pump and reinsert only the line securely so it's free flowing to the filter and on to the new pump upstream and into the carb?

Any help would be greatly appreciated!
Thanks!
 
Normally it would have a fuel feed line to the carb, the return line and a vent line (red one Id bet) that goes to the charcoal canister. Where you have your filter is pretty much where the one on my 91 was. But not knowing its past history whats the inside of the tank like? rusty, crusty, filter impeded already?
I used to use those glass see thru filters or the semi see thru plastic ones so you could see the junk inside it. I think there is also a sock filter or other type screen on the original fuel pump so that may be partially plugged. Yeah, dropping the tank is probably a good idea to discovery and to set up your lines with 100% clarity on what's what. Just for chits and giggles next time its starts to peter out pop off the gas cap and listen for a hiss like the tank isnt vented and starving it for fuel.
 
Let me add this. From what I read its hard or not possible to draw fuel thru a dead OEM in tank fuel pump. Contradicts your ability to even drive the jeep, but who knows. maybe somebody has a stocker laying around they can experiment on.
 
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