this fuel line cant be right
tracing my fuel line from where it leaves the frame under the firewall, it transitions to hose from the metal, goes to the fuel pump by draping over the drivers side motor mount then dangles in a loop under the engine at about the level of the front diff up to the pump, with no clamp on the pump/hose attatchment. the hose must have been cut because in the midpoint of the loop it has 2 clamps around a metal insert and the second part of hose, the part then continuing to the pump is a weaker gauge hose
1. this cant be right, it looks like a disaster, should i just replace this hose all the way to the pump, and if so does it need to be a special hose
2would no clamp on the infeed at the pump suck air and cause the suspected pump probs i am having?
3where do i secure this hose so it wont catch on anything i drive over but not be close to the engine(how close can it be?)
4as always thanks, derm
ahh, the dreaded fuel line
first- exactly what pump problems do you suspect?
as to the line proper, ( and I dont keep OEM routings to memory) where you mount it isnt as importand as HOW you mount it
chances are, the line from engine to tank is ok but i always replace them when doing a fuel system
there are plenty of lines out there ( SS is pretty much the std)
just remember this about pumps and flow ( this comes from designing heavy pump systems and the laws of physics dont change)
*around EVERY bend is line resistance, pressure drop, flow drop- keep them to the absolute minimum and as gentle an angle as possible
*route the trunk line along the frame( use 1 or 2 hole straps)
* I STRONGLY recommend oversizing the trunk line( reason being- the FIRST restriction in any pump system should be the pump- this eliminates cavitation and fluid hammer
* from frame to engine- since there is movement here- there MUST be a flex joint ( for movement and vibration)- most people use fuel line and clamps( which works very well)- I prefer SS vibration lines( available from most industrial supplys)
* there is much debate on fluid thermodynamics as applied to heating a fluid in a closed system- in the case of a vehicle- a few inches is adequate distance and there are SS lines with heat fins on them( use a stiff arm to keep distance at a constant)
what you want to avoid is heating the fuel in the line( you can get vapor lock, or reverse pressure due to fluid expansion)
hope that helps you out a bit
joe MSME, PE.
here is my thinking, it started ok a few days ago, but idled poorly, now there is no fuel at the carb(there is fuel in the tank)
the filter is new, i will disconnect the line at the filter, put the hose into a jar or something and turn it over to see if i have anything coming out, the pump is old on the jeep and probably needs replaced, but the line from pump to filter is frozen hard to the pump so if i replace the pump it gets a new metal line bent and fitted as well(cheap but work i have little time for), if there is decent gas coming out of the line(what amount do i expect/rate?)
then i will rebuild the carb(i ordered a kit from tellico), i hope to not have to trace all the way to the tank due to funds, but the tank needs replaced someday soon. can you think of anything basic i am missing with this? thanks derm
OK, Im gonna give you some advice here on how to approach this
1) you say you dont have fuel to the carb?
>>but idled poorly, now there is no fuel at the carb(there is fuel in the tank)
chances are- the fuel pump is at the point of failure- get ready to replace it
2)but the line from pump to filter is frozen hard to the pump so if i replace the pump it gets a new metal line bent and fitted as well(cheap but work i have little time for
>>> prepare for this contingency- but if you have a buddy and good wrenches- you probably wont need to replace the fuel line
3)>>>> if there is decent gas coming out of the line(what amount do i expect/rate?)
I know of no engineering specs here- but the universal std. is about 5-7 psi- do NOT trust a "calibrated eyeball"- get a pressure gauge and check it
summary- there is a 99.9% probability that your steel lines are fine and do not need replacement( even when contaminated- its due to something else and cleaning them will restore them)
as to the potential "air sucking" of the rubber to metal fit- in the "perfect world' scenario- rest assurred there is some- but we are in the nano liters here and insignificant- good rule of thumb- if its NOT leaking- its probably OK
what you DO need to look for- when you replace the pump- check the pump arm for polishing and wear- I have found many times-the pump lobe can wear and cause a pump to loose effeciency( even tho the pump is good)
my suggestion is to try this- get rid of the mechanical pump completely and use an electrical pump( this eliminates the worn lobe problem and ensures constant pumping regardless of RPM)[ cut a plate and make a gasket to cover the hole]
THEN- make a glass bowl "receiver" tank directly before the carb( in industry- a receiver system is how we remove pulses and flow issues on compressed air and powered fluids for usage)
lastly, put an additional fuel filter between the tank and pump if you feel contamination is present- do NOT forget water contamination
see, the "sudden" onset is what concerns me here- FEW parts just "fail"- most degrade over time
also- you may want to pull the top of the carb and inspect the bowl also- make sure it isnt full of water and other stuff
let me know what you find
joe MSME, PE.
thanks for your time, i replaced the fuel pump last night, will start and run with starter fluid a few secs but then nothing, i will try to check flow output when my neighbor gets home later to help me, if the flow stops at the carb i will rebuild it, if not i will keep looking. i am going to check the metal insert in the fuel hose loop to see if it is an inline filter and will replace if needed, if still no fuel i will trace back for any other filters. the sending unit ground will then need checked as well as me cleaning the other grounds off the battery and if all that fails i will email you back, that work load will take me three weeks at the one hour per week i get to work on the beast, wish me luck, derm
ahh- the "troubleshooting" mode
if there is NOT fuel at the carb......
first- on certain pumps( especially when all fuel has drained back to the tank) it may take that starting fluid AND some gas in a funnel to keep the engine running a minute or so to prime it( IMPORTANT SAFETY NOTE- do NOT attempt to run with starting fluid- it can EXPLODE and is basically a solvent and can wash upper cylinder lubrication off and cause engine damage)
next- look for kinked/crimped lines restricting flow
look for collapsed fuel lines( many times they separate at the support and look "fine" from the outside but are shut off on the inside)- is you get a "soft" squeeze- replace the line
next check the pump and make sure it is cycling( i have seen 2 cars in my auto career that had damaged lobes and wouldnt actuate the pump)
a way to check for blockage is to use compressed air and blow from the pump entrance pipe to the tank ( listen for gurgling) ( another IMPORTANT SAFETY NOTE)- this will atomize gas and create a potentially explosive environment and ALSO[ remove the gas cap] this procedure CAN pressurize the tank and create IMMEDIATE blow back in your face the minute you stop the air)
so have PPE( personal protective equipment) an extinguisher,another person for a safety and a rag or other diffusing device prepared if you attempt this
final thought here- I assume you have made certain preliminaries and the ignition is firing etc
joe MSME, PE
i just replaced some gnarly cracked and soft hose from the metal line to the pump, and will be trying a new pump hopefully this afternoon. i tried blowing air into the tank and i heard the gurgling/bubbling noises in the tank, those safety precautions sound interesting-perhaps i will integrate them next time. if the attempt still fails i will put the input hose to the pump in a can of gas to try to start it and if that fails i will start posting about options to the factory fuel pump setup. thanks for your time, today is last day of vacation, probably wont get this resolved for a couple of weekends, i will let you know, derm
with a new input hose(to a new pump) stuck in can of gas i got the engine to fire up after 3 blasts of starter, it then proceeded to run poorly and suck one and one quarter gallons of gas down in about 4 minutes.
i will do a rebuild on the carb, replace the lines to the tank(and the tank someday), and check for vacuum leaks. everything is disconnected but the pcv's, and choke vacuum. some of the tubes are wide open, does anything have to be hooked up(no e testing in columbus) or can i just plug all the rest, does anyone know what the tube is (whitish yellow) top of the carb forward of the air cleaner mount pointing towards the valve cover(258/carter/78cj5), it is wide open and needs plugged or dealt with in some manner, thanks everyone, derm
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