fuel pump wont suck

car develped a problem as fuel will not suck up from the pump once car fires on primer bottle. car fired normally a week ago on jack stands but was running a little rough left it for a couple days and now the only way it will stay running is holding primer bottle at butterflies. checked all fitting to insure they are tight no change so i had a older smaller pump put that on and same thing. so i am sucking air somewhere any body have tricks to make it easier to pin point also can it be on the motor side from the barrel valve between the distribution block.i will take apart and put new orings where they are used

 

I know it will sound silly but make sure there is enough fuel in the tank, been there, done that

 

fuel tank is 3/4 full i inserted a hex key to observe that the fuel drive was indeed turning and it is.

 

Pump is worn -how high is the pump from the fuel-take line off the bottom of the pump a look fuel should be right at the fitting if lower pump don't like to draw air hard on pump do you ever lube your pump?

 

Are you priming it long enough? When it sits the lines drain back and it can take awhile for it all to pickup. Here locally a guy bought a monster truck with a blown BBC in it. Got a phone call that something was wrong, they couldn’t keep it running. Crawled up in the body gave her a dose of methanol and keep feedin her till she idle’d back down. Ran fine. Once that thing would light off they would jet from out under the body. Suppose it’s pretty scary if you’ve never done it before.

To answer your question, if you legitly have a leak and all your connections look good and isn’t leaking you may have a cracked fitting somewhere. One of your return fittings, return hose, pump adapter or something of that nature.

 

on both pumps it does the same i get it to fire and twice i let a large 1 litre bottle that was full empty while i bottle fed the motor for 25 seconds and fuel pump would not suck . i also took the line from barrel valve and filled it with from the top with methanol to try and aid it and that did not help both fuel pumps had there own inlet fitting and shut off i have double checked barrel valve leakdown and fuel poppets and they are fine i unhooked all fuel lines for pump sizer and hi speed removed fitting for adapter for fuel pressure and capped fuel line for the port fittings as they are not required till 35 psi. i think i am going to try using a an line pressure cap and force compresssed air into systen and use soapy water solution like they use on large trucks to find air leaks as all connections have been removed and appear fine

 

yes we took all pieces off fuel system to insure working and not plugged with something. basic we removed entire fuel system took apart pices such as the pump and replaced them

 

Stupid question, did you somehow get the pump rotation mixed up? Switch from belt driven to cam driven? Put the fittings in the pump backwards?

 

Blockage in the fuel pickup?

 

as we put fuel pump back together we checked to insure correct positioning for cam driven . we have fuel in the line to the bottom inlet at fuel pump . we drained fuel tank and put a new batch of fuel in and we also picked front end of car up to insure fuel line inlet was below fuel tank level . fuel tank has an 6 line for vent, also tried leaving fuel cap of tank

 

with line off from pump to bv put this line to a container that you can screw the inlet line onto a fitting - to avoid any danger. fire engine on the bottle, this should check pump is actually pumping fuel.

you could even take pump off engine and perform this test with a drill onto pump hex.

it only takes the drive hex engagement out a little to not operate the pump properly

after this and the above sounds like a worn pump. im pretty sure from reading replies we have all at some stage had some form of issue here.

 

I’m betting that the pump is backwards. If you pull it off and spin it with a drill it will tell you whether or not it’s pumping or not very quickly.

 

So you've tried 2 different pumps with the same results so chances of 2 bad pumps are pretty high, what kind of line from tank to pump and any filters between tank and pump?
Also, like someone else suggested, check the fuel shut-off, take line off of the fuel shut-off at the outlet and blow air back into the pump while working the shut-off.

 

every line and piece have been removed and checked for correct operation. no filter in system as it was removed to insure it was not a issue both pumps had different fuel shut offs and the are opening correctly. also if i am not mistaken on operation of these pumps they need the suction from the motor running to get fuel thru the fuel pump hence the need for bottle priming. as years ago i had a bad loop line that prevented it from priming and wound not start. both pumps where always used for cam shaft mount the second pump i tried was one that worked good when we took it off and we lubed it up but was to small of a pump to use for increased motor and blower overdrive so it was put in the parts bin. we did verify correct location of gear for cam pump operation of fuel pumps. the fuel tank is new it has a 8 an breather line and a 12 an fuel line with a 6 an return all fitting where checked to insure they where not blocked. i also left the fuel cap off once to insure tank was vented

 

Have you reversed the pump front cover? We had an Enderle pump flowed, and the flow bench ran in the opposite direction. When we got it back, no fuel to the injectors. Took the cap off the fuel tank, and noticed air was being pumped into the tank. Replaced the pump front cover, and problem gone.

 

i hooked up a air pressure to all lines found no issues anywhere when using dish soap and water solution. so i removed all the lines from the inlet line and up thru the pump took everything apart and put all new orings in every fitting that required it and basically insured all fitting where tight and in there proper postion took fuel pump apart cleaned it and greased it up on the shaft and gears and also re oringed lines past the barrel valve and insured those lines where tight , she is now able to fire up and run on it s own. just need to install better starter as motor is not quite spinning quick enough for the msd magneto to fire without a lot of cranking it worked not bad with the mallory magneto but does not like the new msd mag 20

 

Starting on gas?

 

yes