namz7791 Posted August 6, 2004 Share Posted August 6, 2004 I finally got my new 3/8" fuel line ran from the rear of my 77 Z to the engine compartment and hooked up the new Holley red pump. I placed a 3/8" hose on the original fuel tank outlet went 6" to a filter and then to the red pump that is mounted where the stock Z pump was located with new 3/8" fuel line along the original route used for the Z line. When I hooked up the power to make sure the pump worked I get a very irregular flow, almost as if it is sucking air or something, is this normal on an electric pump or should the flow be a steady stream? It quickly fills up a 2 gallon gas can that I was using to catch the gas near the engine but it just wasn't very steady. The pump never missed a beat so I know it is not an electrical problem with the pump. I even tried blocking of the fuel line to see if it built up pressure it would help but it still did the "spurty flow". I also noticed that the plastic filter is almost full when I start the pump but goes almost empty when the pump is on and the fuel seems to get "foamy" in the filter. Holley did recommend that 2 filters in parallel be used between the pump and the tank, is this because there are no filters that can flow as fast as a pump can pump? Also, I cannot seem to locate a "Y" fitting for 3/8" hose to do this. Any suggestions would be greatly appreciated! Quote Link to comment Share on other sites More sharing options...
Pyro Posted August 6, 2004 Share Posted August 6, 2004 I should be a consistant flow. How much fuel is in your tank when you did the flow experiment? My tank has pick-up problems below 1/2 tank. I'm planning to pull my tank and weld in a 1/2 gallon sump below the tank. Quote Link to comment Share on other sites More sharing options...
namz7791 Posted August 6, 2004 Author Share Posted August 6, 2004 I have about 6 gallons in the tank right now, so it is common for the pumps to not do well without a sump of some kind? I did block my vent line and have the return line blocked as well and then pressurized the tank with my air compressor. This really didn't help. I did pressurize the tank before I hooked up the pump and had a nice steady siphon going thru the filter and all. Does anyone know if the return line inlet can be used as an additional suction point for the fuel pump to aid in the parallel filters that holley recommends? I don't know if it places fuel into the bottom of the tank or runs it up to the top and then in. The inlet is lower than the actual outlet on the tank unless I grabbed the wrong one. Thanks! Quote Link to comment Share on other sites More sharing options...
Tekira Posted August 14, 2004 Share Posted August 14, 2004 Geeze my fuel system does the same thing!!! And no the return line cannot be used to send fuel to the pump. It just ends at the top of the tank where it comes in. I had changed pumps because my other one had gone bad. And now i have pulled all my hair out trying to get a steady flow from the tank to my carbs. When i stab it it either drains the float bowls or falls flat on its face and it barley makes it up hills!!! I fed the lin into a gas can and the fuel seemed to pulseate out of the line not a steady stream. I have got it fixed as best as i can for right now, i have the fuel comming from the tank drain instead of the stock send line. So al least i can drive it to work now. I have done every thing i can think of even boiling and cleaning trhe tank out. I am fed up with this fuel system crap and i am very close to buying a D fuel cell some expensive high volume pump and all new fuel lines and pump wiring. Ive got about 2 hairs left. Its been awhile since youve posted so Have you fixed it Yet???? AHHHHHHH I HATE MY GAS TANK!!!! Better for target practice i say Quote Link to comment Share on other sites More sharing options...
Guest 2slo4u Posted August 14, 2004 Share Posted August 14, 2004 Just make sure there is some type of vent for the tank. If there is no way for air to come into the tank, the fuel will create a vacumm in the tank. The air will try to come in through the outlet of the pump and cause the "foam". Otherwise, if you have venting, I have no clue. Good luck. Let us know. 81zxturbo 95slobaru Quote Link to comment Share on other sites More sharing options...
Tekira Posted August 14, 2004 Share Posted August 14, 2004 Its a stock 260z tank so it has vents. I even left the gas cap off to see if that was the prob and it still did it. Iam going to see if i can do the dual pick up thing. One from stock location and one from the drain tap. I ll see what that does and post it! Stupid fuel system, Imean gas has to get from one side of the car to the other HOW HARD CAN THAT BE AHHH!! (Pulls one more hair out) Quote Link to comment Share on other sites More sharing options...
Tekira Posted August 15, 2004 Share Posted August 15, 2004 Ok guys check this out. I have been reading the board for ideas on how to fix my prob and i read about some one clamping down the return line to get enough pressure to carbs. Well i did the double send line thing but not much of a difference well anyway i tried that clamp thing with a pair of vice grips and now the fuel STOPED foaming in the filter between the tank and the pump, BUT now it will suck the filter dry if i let it idle for a while or if i drive it hard(i get to the top of 2nd and then the car cuts out hard). And when i clamp the return line down my fuel pressure goes up to about 4psi. When i had the return line open i only got about 1.5psi and i have a NEW 5.5 to 9psi pump but i am only getting such a small ammount of psi at the carbs. I try to set up a chart of probs here! With Return line | Without retun line Foamy fuel filter | Steady fuel filter Car stalls out because | Car stalls out because pump is sucking air | pump drains fuel filter Pump is very loud | Pump Just hums quitley 1.5psi | 4psi Hope That helps you guy think! Its seems like when i run with the return line it pushes air into the tank causing th filter to Bubble or "foam". But when i eliminate the return line the Filter is steady and so is the fuel srteam but it doesn't push (or pull) enough fuel into the filter and for that matter runs dry when i give more than 25% throttle. Could this be my fuel pump? Would a high volume fuel pump fix this.. I mean it seems like the pump just cant suck enough gas. Is it the tank vents? Not enough air pressing on the fuel inside the tank. Geeze! Who knew solving probs with z cars could be so much like playing Clue! Quote Link to comment Share on other sites More sharing options...
2126 Posted August 19, 2004 Share Posted August 19, 2004 Old Z car gas tank blues.......a commonly played tune!!! Seriously, it sounds as though you may have a restiction problem in the tank and or prior to the filter. Regarding the tank....well these things are old and many people have found some sort of crud inside. Remember that the fuel pickup line has no screen and is only about 3/16" inside diameter. It doesn't take much to restrict or block off the fuel flow. It can be a bear, since doing a visual inspection with tank installed and full of fuel requires a flexible bore scope. Then you have to navigate it past the baffle before you encounter the pickup opening. Been there done that! You may consider draining the tank, via the drain plug in the bottom, then disconnect your hose from the pickup line and back flush the pickup line, leaving the drain plug out. You may get the little bastard (crud) to come out. As you may suspect, its not the most fun job to do. Quote Link to comment Share on other sites More sharing options...
dapiper Posted August 20, 2004 Share Posted August 20, 2004 When I had my DynoJet and was qualifying my fuel flow after inj upgrade, discovered aeration when tank below 5 gal static. Best to mount pump at tank; pump may have high NPSH reqmts (may not siphon well) Quote Link to comment Share on other sites More sharing options...
Guest 2slo4u Posted August 20, 2004 Share Posted August 20, 2004 What about: -connection between pump and tank not totally sealed, allowing air in? -fuel inlet tube cracked or leaking in tank, allowing air in? -level of fuel not high enough causing small vortex in fuel (kinda like a tornado) air being drawn in? Any luck so far? I hope you figure it out soon, I'm curious to see what's causing this. 81zxturbo 95slobaru Quote Link to comment Share on other sites More sharing options...
datsunlover Posted August 20, 2004 Share Posted August 20, 2004 I didnt have a problem to start with, but I cant leave well enought alone.. I was switching to carbs, and had MAJOR welding to do in the rear of the car, so I pulled the tank off. (not bat really.. about 20 mins of work) I then discovered some awefull crapola inside so I filed it with 4-5 gal of varsol, sloshed it around a bit, and left it over night (in my garage.. wow what a stink the next day!) sloshed it around some more the next day, drained it, and let it sit in the sun for a day (to let it all evaporate). Put it back in, instaled new low psi fuel pump, and havn't had a problem at all in 3000 miles. (yah, I drive this thing twice a week.. you'd think it'd be less than that in only 2 months! ) Mind you when I put in the pump, I used all new rubber lines, and only reused the stock (which had been replaced 2 years ago) metal fuel feed/return lines from pump to engine bay. I have noticed though, at under 1/8 of a tank it sucks and starves sometimes if I corner hard or go up steep hills.. Quote Link to comment Share on other sites More sharing options...
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