fuel delivery issue

Posted By: BTTG

fuel delivery issue - 08/07/14 02:15 AM

69 440

Twice in the past 2 weeks i've been having a fuel delivery issue. My usual starting routine is to use a syringe to put 2 ounces of gas in the fuel bowl via the external bowl vent (Carter AVS) and put 1/2 an ounce down the primaries and then turn over. it lights instantly. first time it ran about 10 seconds and stalled and would not restart. pull the accelerator linkage back and it was dry. so i refilled the bowl and it lit and ran for a few seconds... no pump shot afterwards. assumed it was the fuel pump. next day I tapped carb body with hammer and disconnected fuel fitting at carb and turned it over... it pumped gas. so i reconnected put a bit of gas in the bowl and it started and ran till i powerd down 10 minutes later... fast forward to today same thing it started and ran for about 10 seconds. after stall no pump shot and bowl was dry. pulled line at carb and turned over. it didn't pump. then i pulled the fuel line feed at the fuel pump and put my mityvac on it. easily pulled gas from tank. so i reconnected the line and went back to end of line at carb and turned it over again. this time it pumped gas. so I primed the bowl and it started and ran fine.

I'm guessing my fuel pump is fine, but what could cause this? first time it happened car was cold and hadn't run in weeks. second time i had run it for about 20 minutes several hours prior and it was fine.

scared to take it out of the garage at this point before resolving this issue.

Thanks for any help.

Posted By: Cab_Burge

Re: fuel delivery issue - 08/07/14 02:58 AM

Check the little brass check needle under the accelerator squirters to see if it is sticking closed after sitting.

I would pull the carb. off and remove the two screws that hold the nozzles in place and turn the carb. over, if it will fall out without tapping on the carb. your good, if not it is sticking shut

Let us know what you find out.

Posted By: RapidRobert

Re: fuel delivery issue - 08/07/14 05:29 AM

The symptoms are pointing in too many directions. The heat/E10 could be evaping the fuel out of the bowl. I'd fill the bowl/pump several shots & see if it will stay runnning. if it does then a thick base gasket may help & it may just have to be tolerated if it sits for that long (heat riser not shut closed I'm assuming). If it dont stay running I would plumb a can of gas to the pump inlet which would eliminate the rear hard line/2 short neoprene hoses/tank/sock. All that is left is the pump/pushrod (it should be ~3.250" iirc)

Posted By: BTTG

Re: fuel delivery issue - 08/07/14 01:30 PM

Thanks for the response.

If this was stuck closed that wouldn't explain why the carb is dry (bowl is empty) when it stalls would it? After it stalls if I pull the linkage back there is no pump shot, but if i fill the bowl with a syringe and then pull the linkage it does give a shot... I'll be happy to try as you said just wanted to clarify the need to do so first.

Thanks

Posted By: BTTG

Re: fuel delivery issue - 08/07/14 01:40 PM

Not sure if it helps or not, but when this happened last and i pulled the main fuel line at the inlet of the fuel pump it was dry... gas did not flow out. when i hooked the mityvac up to the end i easily got a strong flow of gas in short order (about 3-5 s of pumping)... could this be an issue of air entering the main line somewhere and it correcting itself when I crack the fuel lines at the carb or fuel pump?

my main fuel line is 3/8 inch and i am runnning a 1/4 return line and factory type fuel seperator

thanks

Posted By: RapidRobert

Re: fuel delivery issue - 08/07/14 03:07 PM

Quote:

After it stalls if I pull the linkage back there is no pump shot, but if i fill the bowl with a syringe and then pull the linkage it does give a shot.

If it runs OK after you prime it then that points to an evap issue but 2 weeks (or less) doesn't seem like a long time but I cant say for sure on that. It's hot here but I dont run E10 as luckily we still have a choice here. You might see if the AP squirts good shots right when you shut it down then next time you come out see if it still squirts good before you even turn the key. If it is full when you shut it down then not full when you come back days later that would isolate it to an evap issue without you having to do any other testing procedures. Holler how it turns out

Posted By: BTTG

Re: fuel delivery issue - 08/07/14 03:33 PM

Hi Robert,
Thanks for the reply. I get what you are saying. If I leave the car sitting for over a week I do not get a pump shot if i just walk up to it and pull the linkege back. This means that the gas has left the bowl via some mechanisms (evaporation, porosity of carb body, etc.). But in this case I am saying that after manually filling the bowl with enough gas for it to run for 15 seconds (about 2 ounces or so)... It then has stalled twice on me and failed to restart. At that time (literally seconds after it stalled after running for a number of seconds)it had no pump shot AFTER. To me this means it stalled cause the bowl volume wasn't replenished and it went dry. This is not an evaporation issue as only seconds have gone by... so it needs to be something else that is fixed by opening up of the fuel lines (which I have done in both case diagnosing) or truly is random and has just fixed itself. for me it has got to be something else that can be identified and fixed. I am just not knowledgable enough to know what it could be... from my knowledge fuel pumps work or they don't. the fact that one time after a stall I got flow at the carb inlet and 1 time did not while cranking is puzzling. When i did get flow it actually was the next day as i had walked away thinking it was the fuel pump and didn't wan to diagnose at that time. When I did not get flow at the carb inlet opening the fuel line at the pump inlet and pulling gas with my vacuum pump seemed to fix it????

Posted By: RapidRobert

Re: fuel delivery issue - 08/07/14 03:45 PM

Quote:

If I leave the car sitting for over a week I do not get a pump shot if i just walk up to it and pull the linkege back. This means that the gas has left the bowl via some mechanisms (evaporation, porosity of carb body, etc.). But in this case I am saying that after manually filling the bowl with enough gas for it to run for 15 seconds (about 2 ounces or so)... It then has stalled twice on me and failed to restart. At that time (literally seconds after it stalled after running for a number of seconds)it had no pump shot AFTER. To me this means it stalled cause the bowl volume wasn't replenished and it went dry. This is not an evaporation issue as only seconds have gone by

Ok so there is 2 things going on if I am reading it right: (1) the evap issue and (2) You prime it to take care of the evap issue & after running for some seconds it should be full & it ain't. On #(2) I would plumb a can of gas to the pump inlet to either pin it to the pump inlet rearward or to the pump/pushrod & I'm leaning toward the pump/pushrod

Posted By: 383man

Re: fuel delivery issue - 08/07/14 07:16 PM

If you have any rubber fuel line between the fuel pump and the tank check it real close for any cracks where the pump could pull in air when trying to pull fuel from the tank. I have seen it before as once you get the fuel to the pump it works for a bit but because of cracks in the suction side it bleeds off the fuel in the suction side and wont start again later. You most likely pulled much more vacum with the mighty vac pump the the fuel pump makes so that may be why it worked like that. But I would check the suction lines for small crack. Not big enough to cause a fuel leak problem but enough to pull in air on the suction side. Course an electric fuel pump back by the tank is a good idea. Ron

Posted By: BTTG

Re: fuel delivery issue - 08/08/14 01:38 PM

Hi Ron,
Thanks for the helpful reply. I'll look into this and report back.

Thanks