THUNDERZ Posted April 22, 2004 Share Posted April 22, 2004 OK this started out with hot wires to the pump, this problem was cured with larger wire. Now...The fuel pressure continues dropping to 0 after it drives for 2 minutes. At this point I can see into the glass fuel filter and it look like someone pouring a glass of ginger ale ( lots of bubbles). OK. This is after I relocated the pick up line hose to a fitting that I made to go into the drain plug hole in the bottom of the tank. I did this because I suspected that there may be a "sock" on the end of the original pick up tube that may be clogged. So...I am still experiencing a problem that I cannot define exactly. Any ideas will help. Oh yeah ...this car is a 74 260 with a Holley blue pump to a built L28 with tripple Dellortos(40mm)and I am running a return line. I also have a gate valve in line after the carbs to create pressure at the carbs. Other wise it runs at 0 through straight 5/16 line. Quote Link to comment Share on other sites More sharing options...
Tim240z Posted April 22, 2004 Share Posted April 22, 2004 Either the pump is going out, or some crud is blocking the tank outlet. Quote Link to comment Share on other sites More sharing options...
z-ya Posted April 22, 2004 Share Posted April 22, 2004 Do 260Zs have tank drain plugs? If they do, drain the tank, and see what kind of junk comes out. You can use the drain hole as a fuel pump pickup. I used mine like that until I had a mini sump welded in. Pete Quote Link to comment Share on other sites More sharing options...
dmyntti Posted April 22, 2004 Share Posted April 22, 2004 You might have a hole or a leak in the line between the tank and the pump. This will cause the pump to pull in some air through the hole. I found this on two old Oldsmobiles. The fuel line was routed in such a way that it rubbed agaunst the floor board and wore a hole in the top of the line. It acted very similiar to what you are describing. Quote Link to comment Share on other sites More sharing options...
THUNDERZ Posted April 22, 2004 Author Share Posted April 22, 2004 You might have a hole or a leak in the line between the tank and the pump. This will cause the pump to pull in some air through the hole. I found this on two old Oldsmobiles. The fuel line was routed in such a way that it rubbed agaunst the floor board and wore a hole in the top of the line. It acted very similiar to what you are describing. Don, I am thinking something similar. I have drained the tank 3 times, The pump is brand new...has ran for about 20min.I am going to try pulling from the original pick up and the drain plug fitting...see what happens. Oh! I wanted to ask about the third line. I think it went to the charcoal canister to the expansion tank or to the top of the gas tank. Does that need to be uncapped or doesnt it matter? Quote Link to comment Share on other sites More sharing options...
Tim240z Posted April 22, 2004 Share Posted April 22, 2004 Hmmmm....that make me think....is your tank properly vented. pumping fuel out could be causing a vacuum and not allowing the fuel to flow to the pump. Try taking off your filler cap and see if it works better.....it's a place to start... Tim Quote Link to comment Share on other sites More sharing options...
THUNDERZ Posted April 22, 2004 Author Share Posted April 22, 2004 Good idea Tim...I will try it. I just installed a different filter at the rear and for some reason it maintained a 3psi level at idle in the garage wth the gate valve wide open! I love adding in little things to the soup that make no sense. Oh... now get this...I do the ceremonial test drive and it drops off the scale as soon as I give it gas(as usual) . Then I hit the brakes kind of hard in frustration and the gauge shot up! I gave it gas and it zeroed ...hit the brakes and it shot up! What the heck does that say??? Quote Link to comment Share on other sites More sharing options...
Tim240z Posted April 22, 2004 Share Posted April 22, 2004 How full is your tank? Sounds like fuel is rushing away from the pick up on accelleration and recovering the pick up on braking.... Fill the tank up and try again... Quote Link to comment Share on other sites More sharing options...
dmyntti Posted April 22, 2004 Share Posted April 22, 2004 This gae valve idea concerns me. You should be running a regulator to control fuel pressure. With a gate valve your pressure will be totally dependent on the flow from the pump and the amount of fuel going in the carbs. Your pressure will be all over the place if I understand what you are using the gate valve for. Quote Link to comment Share on other sites More sharing options...
THUNDERZ Posted April 22, 2004 Author Share Posted April 22, 2004 How full is your tank? Sounds like fuel is rushing away from the pick up on accelleration and recovering the pick up on braking.... Fill the tank up and try again... Tim...I filled it up with gas I had in the garage to a little over 1/4 tank...I wasnt paying attention. That made a difference. It couldnt have been the problem all along because I have had the same amount of gas in it when it acted up before. Somewhere along the line it seems like something worked. I am not going to get my hopes up yet but I went for like a 7 minute drive and watched the gauge maintain 3-4 psi. I guess it would behave different now running a high volume pump and return line than it would act with a reg pump and dead head set up...I mean on a low tank, because it is constantly sucking up gas compared to intermitantly moving it with a dead head set up. It would be more sensitive on a low tank with the gas sloshing about. Quote Link to comment Share on other sites More sharing options...
THUNDERZ Posted April 22, 2004 Author Share Posted April 22, 2004 This gae valve idea concerns me. You should be running a regulator to control fuel pressure. With a gate valve your pressure will be totally dependent on the flow from the pump and the amount of fuel going in the carbs. Your pressure will be all over the place if I understand what you are using the gate valve for. I agree with you . Initially I had no pressure running it wide open to the return line. Thats why I put a valve in...so I could back it up and increase pressure. Now that I installed a different fuel filter in the back I somehow have 3-4 psi with the valve wide open. Now that I have pressure to work with I will put in a regulator. Quote Link to comment Share on other sites More sharing options...
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