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-   -   Vapor lock thoughts- fuel return line flow rate? (https://www.jeepforum.com/forum/f19/vapor-lock-thoughts-fuel-return-line-flow-rate-4432057/)

Beninct 05-04-2021 08:07 PM

Vapor lock thoughts- fuel return line flow rate?
 
So my CJ7 is giving me trouble for obvious reasons (fuel return not connected, no carb spacer, rubber fuel lines on top of engine etc.) all of which I can fix relatively easily.

Wondering if anyone has ever run their 258 with the mechanical fuel pump and observed the flow from the return nipple on the top of the outlet side of the fuel filter? Curious on flow rates- I am assuming its next to nothing until higher rpm but thatís just a guess? Anyone?

Beninct 05-06-2021 05:06 AM

Anyone?

I realize this is an odd question.

Canít be much though because mine is currently running without it (filter with single inlet/outlet). My suspicion is that there is no actual flow rather its just vapor when the engine is hot more like a pressure relief. Have the right filter coming and will set it up with the return to see if I can reduce my vapor lock.

V8GCZJ 05-08-2021 09:10 AM

Are you sure it's vapor lock? If it is it will only happen after the engine/fuel gets hot enough to boil. You can also install one of the clear fuel filters in line and see it. What temp is the engine at when at operating temp? Also i had a mechanical pump brake a loop in the spring so it wasn't pumping the correct amount. May want to do a pressure test.

Beninct 05-09-2021 09:45 AM

Piped the fuel filter outlet right to the fuel return and vapor lock issue is 100% gone. No charcoal canister on my rig.

Also since have rerouted fuel lines and coolant lines to keep them apart.

Beninct 05-09-2021 11:52 AM

Quote:

Originally Posted by V8GCZJ (Post 41266671)
Are you sure it's vapor lock? If it is it will only happen after the engine/fuel gets hot enough to boil. You can also install one of the clear fuel filters in line and see it. What temp is the engine at when at operating temp? Also i had a mechanical pump brake a loop in the spring so it wasn't pumping the correct amount. May want to do a pressure test.

I think it was. I replaced the fuel pump and the new unit was bad and fully broke after an hour of use. New (2nd new) pump works fine and I did add a clear filter so i can see the fuel running through it nicely. This jeep is new to me and I am trouble shooting most of its systems. So far I have done thermostat, battery/cables, starter, alt, motor mounts to move engine forward about 1Ē (old ones were that bad- had to use come a long to pull it forward).

Fuel lines are original steel under the body but under the hood all rubber fuel line and they were zip tied tight to the heater hoses so combine that with a bad pump and no where for the vapor to go it was great on its first cold start then after getting up to temp it would not start after being shut off for maybe 10 mins. Routed fuel lines elsewhere and actually put a piece of 1/2 hose over the rubber fuel line where it gets near heater hoses plus adding the factory filter back and piping that to the return did it.


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