Technical > Spud Miller's Cave
fuel tank to fuel pump elevation
noslin:
im wondering if we are having fuel draw issues on our rig. yesterday on the stand it started no problem three times. we filled it to the top in the tank and proceeded to start three times using most of the 5 gallons in the tank without issue. at the track we started it on the stands no problem and im pretty sure i filled it up to say 1/2" of full. made a test pass and it started no problems in the staging lanes like it should.
we went up for the second pass and it just would not prime/start. i dont know how full the tank was, im guessing within an 1" of full. the pump was just rebuilt by Enderle, its an 1100. it has six startups on it. the second you take the fuel bottle away it dies. the last time trying to start he just squeezed the bottle to keep running and it should of primed but it didnt. so we are wondering if there is a problem with height of tank and pump elevation.
all feds have the tanks way up front. I just put solid 1.25 alum tubing straight from tank to the pump thinking the braided i had on there was sucking air. we just stuck on the new pump inlet fitting on it, new o-ring etc and made sure it was seated correctly.
its just frustrating to us seeing how it ran fine one time and then next time its a little bitch and wont run. its a simple system but we are wondering if the fuel level and pump elevation might be part of the problem. what perplexes me is how can you start it three times without refilling the tank and it starts perfect each time with varied fuel levels and then when its time to go play it decides not to. he was pouring the fuel in to keep running and long enough to prime and second he pulled the fuel away it dies so we know the pump isnt priming as the feed line up to the BV is dry. I checked the pump drive shaft and its just fine.
Lets talk about fuel level and pump elevation. sitting on the ground the tank is 11" to the top. so full would be about 10.5". the bottom of the pump inlet fitting is 10", the barb is 1", the bottom of the pump is 13.5", the center of the pump is about 14.5 (guess).
Do we need to make a taller tank?
my buddy was doing some research and he noticed a lot of the older feds the motors sat lower in the frame (guessing) so the tanks were tall enough to prime etc no issue. whats the history on evolution to the new modern chassis design to the older ones if there is one? I know each chassis is custom fabricated and no industry standard. is there a target crank shaft height guys shoot for or does that matter.
Thank you
Dean
Rat:
I hope someone has a solution as we are having the same issues. We have discussed but not yet tried these idea's - a check valve, primer pump and raising the tank. Look forward to hearing the feedback.
Curly1:
The pump can draw fuel up some but you do want to make it easy as possible. I think it is always difficult to make a MFI system start nice and clean on alcohol. They are touchy, too much alcohol it floods and does not want to start. Same if there is not enough fuel. Mechanical injection dumps a lot of Fuel at low RPM because it does not have pump shot. And alcohol is harder to start in colder weather. Mine runs better when motor is hot but is harder to start. So you are trying to get the right fuel mixture to get it started and run.
hemidakota:
Dean take the outlet line to barrel valve off at fuel shut off and crank engine to see if pump is working. Have seen a couple good pumps just stop working. Easy check before any changes.
noslin:
--- Quote from: Curly1 on July 22, 2019, 10:59:10 AM ---The pump can draw fuel up some but you do want to make it easy as possible. I think it is always difficult to make a MFI system start nice and clean on alcohol. They are touchy, too much alcohol it floods and does not want to start. Same if there is not enough fuel. Mechanical injection dumps a lot of Fuel at low RPM because it does not have pump shot. And alcohol is harder to start in colder weather. Mine runs better when motor is hot but is harder to start. So you are trying to get the right fuel mixture to get it started and run.
--- End quote ---
where learning that too. was using gas, then went to meth and a mixture of gas/meth, now back to gas.
--- Quote from: hemidakota on July 22, 2019, 12:09:37 PM ---Dean take the outlet line to barrel valve off at fuel shut off and crank engine to see if pump is working. Have seen a couple good pumps just stop working. Easy check before any changes.
--- End quote ---
weve ran the pump couple times with just a drill and tried that. it actually pumped fuel. this pump is basically brand new. enderle just rebuilt it and put new cover plate on it. just counted and we have one pass and seven starts on it. the drive is ok too.
we will get the fed out of trailer and get solid numbers on elevations. i think the differential is about an 1".
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