beebeecivic Posted October 11, 2009 Share Posted October 11, 2009 I have a 1978 280z California Model ; I just changed my FPR and my fuel psi is at 30. When i give it gas the PSI drops, I'm suspecting its either a weak fuel pump or a clogged catalytic converter. Can someone lead me the right direction. Also the intake pops (leaning out). Quote Link to comment Share on other sites More sharing options...
hoov100 Posted October 11, 2009 Share Posted October 11, 2009 I have a 1978 280z California Model ; I just changed my FPR and my fuel psi is at 30. When i give it gas the PSI drops, I'm suspecting its either a weak fuel pump or a clogged catalyic converter. Can someonelead me the right direction. Also the intake pops (leaning out). This needs to be under the trouble shooting forum. And if its popping most likely your AFM is going out. have you checked the basics, like cap, rotor, wires and plugs? how did you come across to the conclusion that it was down on power? Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted October 12, 2009 Administrators Share Posted October 12, 2009 I have a 1978 280z California Model ; I just changed my FPR and my fuel psi is at 30. When i give it gas the PSI drops, I'm suspecting its either a weak fuel pump or a clogged catalyic converter. Can someonelead me the right direction. Also the intake pops (leaning out). Your fuel pressure indications are key to your issue here. At WOT, fuel pressure should be a steady 36 PSI. If fuel pressure drops during WOT then you are not getting adequate fuel supply to the injectors, that will cause the popping out the intake, (lean misfires caused popping out of the intake, rich misfires cause popping out the exhaust). Typical causes for dropping fuel pressure, in order of priority to check; 1) Clogged fuel filter, (They're cheap enough, should be changed once a year any how). 2) Clogged inlet screen to the fuel pump. (Remove the large fuel hose, look inside the inlet of the pump, you will see and inverted cone type screen, which will get clogged up with rusty tank debris). 3) Fuel pump going out, (usually because of clogged inlet screen). 4) Crimped or restricted fuel supply hose/hard line, between the tank and injectors. Visually inspect all the fuel hoses and metal lines for kinks, crimps, dents, etc. Small dents in the lines usually aren’t an issue, it will take a noticeable pinch to cause this. 5) (This is a feeble stretch, but “could†happen I guess). Poor electrical connections to the fuel pump not allowing the pump to get full power. Hope this helps, keep us posted on your findings. Quote Link to comment Share on other sites More sharing options...
beebeecivic Posted October 12, 2009 Author Share Posted October 12, 2009 This needs to be under the trouble shooting forum. And if its popping most likely your AFM is going out. have you checked the basics, like cap, rotor, wires and plugs? how did you come across to the conclusion that it was down on power? Sorry about that (mod please move) Cap, Rotor, Wire, and Plugs are all brand new When I hold the acceleration , the RPM bounces up and down (like it starves then regains and starves again) And when I blip the gas , the rpm just drop. Quote Link to comment Share on other sites More sharing options...
beebeecivic Posted October 12, 2009 Author Share Posted October 12, 2009 1) Clogged fuel filter, (They're cheap enough, should be changed once a year any how). The filter is new 2) Clogged inlet screen to the fuel pump. (Remove the large fuel hose, look inside the inlet of the pump, you will see and inverted cone type screen, which will get clogged up with rusty tank debris). Its the hose from Tank to pump correct? 3) Fuel pump going out, (usually becauses of clogged inlet screen). I was thinking it was the fuel pump too but I am going to do more little test before I drop the ball on a new unit. 4) Crimped or restricted fuel supply hose/hard line, between the tank and injectors. Visually inspect all the fuel hoses and metal lines for kinks, crimps, dents, etc. Small dents in the lines usually aren’t an issue, it will take a noticeable pinch to cause this. I doubled checked for new crimped and kinked hose. I am planning on changing out the old Fuel line (from tank to pump) 5) (This is a feeble stretch, but “could” happen I guess). Poor electrical connections to the fuel pump not allowing the pump to get full power. This is one place I have not checked yet Also I have a G3 filter connected from the Tank to the Pump and it has nice clean gas. Thanks! Oh and I do have a Fuel PSI from my Fuel Filter to the Fuel Rail Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted October 12, 2009 Administrators Share Posted October 12, 2009 1) Clogged fuel filter, (They're cheap enough, should be changed once a year any how). The filter is new If the car sat for any period in its past, the tank could be rusty which will continue keep clogging the fuel filter. Clogging fuel filters show up as the description you described, drop in fuel pressure under load conditions, good pressure at idle and light cruise, depending on bad it is clogged at the time. If this drop in fuel pressure was present immediately after installing the new filter I'd be inclined to to think its not a clogging filter. 2) Clogged inlet screen to the fuel pump. (Remove the large fuel hose, look inside the inlet of the pump, you will see and inverted cone type screen, which will get clogged up with rusty tank debris). Its the hose from Tank to pump correct? Correct. Also I have a G3 filter connected from the Tank to the Pump and it has nice clean gas. That could be the issue. If that filter between the tank and pump presents enough of a restriction, even clean, (any filter will present some restriction depending on how fine it filters and its filter surface area), the fuel pump wont be able to draw adequately through it, causing the pump to cavitate and not "flow" adequate fuel under load. If it were me, I would remove the hose on the inlet of the pump and verify the pump inlet screen is clean, then remove that pre-filter G3 filter and drive the car again. Hope that helps, Paul Quote Link to comment Share on other sites More sharing options...
beebeecivic Posted October 12, 2009 Author Share Posted October 12, 2009 If the car sat for any period in its past, the tank could be rusty which will continue keep clogging the fuel filter. Clogging fuel filters show up as the description you described, drop in fuel pressure under load conditions, good pressure at idle and light cruise, depending on bad it is clogged at the time. If this drop in fuel pressure was present immediately after installing the new filter I'd be inclined to to think its not a clogging filter. Correct. That could be the issue. If that filter between the tank and pump presents enough of a restriction, even clean, (any filter will present some restriction depending on how fine it filters and its filter surface area), the fuel pump wont be able to draw adequately through it, causing the pump to cavitate and not "flow" adequate fuel under load. If it were me, I would remove the hose on the inlet of the pump and verify the pump inlet screen is clean, then remove that pre-filter G3 filter and drive the car again. Hope that helps, Paul Hey braap, Thanks for the reply. I am going to try your suggested methods this week and report back to you. Thanks again -bee Quote Link to comment Share on other sites More sharing options...
beebeecivic Posted October 15, 2009 Author Share Posted October 15, 2009 Hey braap so I Changed out the Hose from Tank to Pump and also removed the Fram Filter, I also checked the sock filter in the pump and it was clean. What should I do next? thanks! Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted October 16, 2009 Administrators Share Posted October 16, 2009 Problem still exists I take it? Fuel pressure is dropping on a fuel pressure gauge under WOT conditions? If so, then it sounds like the pump. Quote Link to comment Share on other sites More sharing options...
beebeecivic Posted October 16, 2009 Author Share Posted October 16, 2009 Problem still exists I take it? Fuel pressure is dropping on a fuel pressure gauge under WOT conditions? If so, then it sounds like the pump. Crud! Thats the last thing I want to change Well good news, I changed the vac hoses from manifold to FPR and a hose from manifold to Emissions Components. It made a major diffrence, the PSI now goes up during acceleration rather then drop! So im happy about that.. but PSI still low. I am going to save up! I might get the walbro 255 ? Or something.. hahah Thanks again Braap! Quote Link to comment Share on other sites More sharing options...
beebeecivic Posted December 23, 2009 Author Share Posted December 23, 2009 Hey Braap, so I finished installing my walbro 255 gsl 392. The pump gets a constant 14.4v and runs flawlessly. I even blew out the hard lines and also checked the fuel filter (it was clean). I am seriosuly out of ideas of what can cause me to have such low psi. Please chime in! Quote Link to comment Share on other sites More sharing options...
datsun723 Posted December 23, 2009 Share Posted December 23, 2009 Could it be the injectors themselves? I know getting a flush makes a world of difference. Quote Link to comment Share on other sites More sharing options...
beebeecivic Posted December 23, 2009 Author Share Posted December 23, 2009 Could it be the injectors themselves? I know getting a flush makes a world of difference. hey sir. But the psi measured is before the injectors. I have the psi measure from filter to rails. Quote Link to comment Share on other sites More sharing options...
beebeecivic Posted August 11, 2010 Author Share Posted August 11, 2010 (edited) Problem has finally been resloved! the Injectors were stuck / clogged! now motor revs freely! Edited August 11, 2010 by beebeecivic Quote Link to comment Share on other sites More sharing options...
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