soga280z Posted September 4, 2010 Share Posted September 4, 2010 Hi all - 1978 280z has me stumped. During the troubleshooting I discovered extremely low fuel pressure. I changed the fuel pump (MSD 2225) and the pressure regulator. No help and the fuel pressure remains irradic. Is there any way the tank is creating a vacuum and not allowing fule to flow smoothly to the pump? I have blown air thru all the lines and they seem to be clear so I cant figure exactly what can be creating the vacuum. Has anyone seen this issue before? I have replaced all 6 leaky injectors, the fuel cap, tank has been removed and cleaned and sealed as well. Is this is a restoration for my son and we just cant seem to get past this fuel pressure issue. Any and all help will be greatly appreciated. PS I have a FSM but havent seen anything that addresses this issue. Keith Quote Link to comment Share on other sites More sharing options...
Challenger Posted September 4, 2010 Share Posted September 4, 2010 Is there a way to check the fuel dampener? Have you tried starting the car without the gas cap? Quote Link to comment Share on other sites More sharing options...
19762802+2 Posted September 4, 2010 Share Posted September 4, 2010 Also are you sure you have lines in the correct spot on the fuel tank? also did you replace the lines on the Evaporator tank, and if you did, did you put them in the correct spots? Quote Link to comment Share on other sites More sharing options...
NewZed Posted September 4, 2010 Share Posted September 4, 2010 (edited) I just fixed some bad FPR and pressure measuring issues on my essentially stock 1976. What do you mean by erratic fuel pressure? Erratic while driving, or while testing the pump and FPR? And what was the initial extremely low pressure that you measured? Numbers help. I now have 25 psi at idle with the vacuum line connected to the FPR and engine running, and 36 psi (the factory test value) with just the fuel pump running (engine off), and the engine runs great. Your 78 has essentially the same engine as my 76. Edited September 4, 2010 by NewZed Quote Link to comment Share on other sites More sharing options...
soga280z Posted September 6, 2010 Author Share Posted September 6, 2010 hey guys, I've got this fuel issue narrowed down to a problem in the tank. If I bypass the tank and let the car run by siphening fuel from a container the car runs perfect. The minute the tank is used the car will run until the vacuum in the tank builds enough to stop the flow of fuel and even this new MSD fuel pump can not pull fuel. The return line is not blocked and the large hose on top of the tank is completely clear. The only slight resistance I can feel is in the smaller tube on top of the tank. I should note that I have used "redline" tank sealer recetly but used it exactly as the instructions said. Is there anyone that has seen inside a tank and is there something that I could have inedvertantly blocked? the plan tomorrow is to use muriatic acid to remove all of the redline possible. Just curious if anyone has had this same kind of result while using a tank sealer. Thanks everyone for all your help! I really appreciate it. Quote Link to comment Share on other sites More sharing options...
19762802+2 Posted September 6, 2010 Share Posted September 6, 2010 hey guys, I've got this fuel issue narrowed down to a problem in the tank. If I bypass the tank and let the car run by siphening fuel from a container the car runs perfect. The minute the tank is used the car will run until the vacuum in the tank builds enough to stop the flow of fuel and even this new MSD fuel pump can not pull fuel. The return line is not blocked and the large hose on top of the tank is completely clear. The only slight resistance I can feel is in the smaller tube on top of the tank. I should note that I have used "redline" tank sealer recetly but used it exactly as the instructions said. Is there anyone that has seen inside a tank and is there something that I could have inedvertantly blocked? the plan tomorrow is to use muriatic acid to remove all of the redline possible. Just curious if anyone has had this same kind of result while using a tank sealer. Thanks everyone for all your help! I really appreciate it. Before you start cleaning out the redline tank sealer first make sure you have your fuel line from the pump on the correct barb and that you have the fuel return on the correct barb, If they are already correct try sticking a long strong wire like a oil dipstick type of thing through the fuel lines on the tank before you wash everything out. If there is too much coating you may just be able to clear out the lines with the wire. Quote Link to comment Share on other sites More sharing options...
soga280z Posted September 6, 2010 Author Share Posted September 6, 2010 Before you start cleaning out the redline tank sealer first make sure you have your fuel line from the pump on the correct barb and that you have the fuel return on the correct barb, If they are already correct try sticking a long strong wire like a oil dipstick type of thing through the fuel lines on the tank before you wash everything out. If there is too much coating you may just be able to clear out the lines with the wire. ah good idea thanks. Quote Link to comment Share on other sites More sharing options...
soga280z Posted September 13, 2010 Author Share Posted September 13, 2010 hey guys, tonight after i put the tank back on after stripping the coating, it ran perfect and at idle it had 34 psi of fuel pressure. it had no hesitation when revving. thanks guys for all of your help Quote Link to comment Share on other sites More sharing options...
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