Go4DaMo Posted March 20, 2014 Report Share Posted March 20, 2014 Would love input from my family on here. Briefing: Mom's 3.1, fuel pressure: 10-12 psi, manually...0 PSI turning key. No fuel seeping from regulator, replaced fuel filter, replaced pump. Realized triangular "bumper" between pump and pulse dampener was missing...disassembled. While sending unit is on my workbench, should I remove dampener, altogether? and if so, using rubber hose and worm clamp? Gonna start back at it at 8:15 AM. Thank you all very much for any input you have. Sincerely, Samuel Quote Link to comment Share on other sites More sharing options...
Imp558 Posted March 20, 2014 Report Share Posted March 20, 2014 Could it be insufficient power due to old and poorly engineered FP wiring like the rest of the Gen1 W's? Quote Link to comment Share on other sites More sharing options...
DefEddie Posted March 20, 2014 Report Share Posted March 20, 2014 Get rid of the pulse dampner and just use the hose,clamp it on good as well. They can leak but generally they will still charge the line and keep okay pressure till you rev,then the volume loss will drop pressure. After putting it back together if you still have an issue deadhead the pump with the gauge. Attach it to the fuel filter line and check pressure there,that will narrow an issue down to the pump/lines. If that is good,put it back on the rail and block the return line. If you have pressure drop it will be in an injector/rail or line between filter/rail. If you still find nothing hook the return back up and see if the regulator in jacked. Hopefully something there works for you. Quote Link to comment Share on other sites More sharing options...
Go4DaMo Posted March 20, 2014 Author Report Share Posted March 20, 2014 Really appreciate ya, DefEddie. I will move forward with this! Quote Link to comment Share on other sites More sharing options...
Schurkey Posted March 20, 2014 Report Share Posted March 20, 2014 (edited) Could it be insufficient power due to old and poorly engineered FP wiring like the rest of the Gen1 W's? You got that right! Both of my Luminas ('92 and '93) have excessive voltage drop at the pump for no other reason that the wires GM used are 16 gauge when industry standard for that amperage draw and length would suggest 12 gauge. I lose over a volt on the supply side, and another volt on the ground side. Alternator charges at 14-something volts, but the fuel pump gets less than 12 at best. Way less than that at startup. Electrical diagnosis of the fuel pump is made much easier with an amperage probe and an oscilloscope to go along with that voltmeter. You can then measure pump RPM and the current draw of each commutator bar in the motor. If one or more bars is significantly different from the rest...you know the electric motor of the pump is toast. Edited March 20, 2014 by Schurkey Quote Link to comment Share on other sites More sharing options...
Go4DaMo Posted March 21, 2014 Author Report Share Posted March 21, 2014 (edited) it's 16 gauge all the way from the engine compartment, right? I can't just put thicker wiring in the sending unit You got that right! Electrical diagnosis of the fuel pump is made much easier with an amperage probe and an oscilloscope to go along with that voltmeter. You can then measure pump RPM and the current draw of each commutator bar in the motor. If one or more bars is significantly different from the rest...you know the electric motor of the pump is toast. I'm unfamiliar with both of these, but they may have come with the fuel pressure gauge and multimeter I borrowed from AutoZone with a $160 deposit. Edited March 21, 2014 by Go4DaMo Quote Link to comment Share on other sites More sharing options...
Go4DaMo Posted March 21, 2014 Author Report Share Posted March 21, 2014 my replacement pump is not a turbo design (e.g. Bosch's pump). would removing the dampener still be ideal? thanks. Quote Link to comment Share on other sites More sharing options...
Schurkey Posted March 21, 2014 Report Share Posted March 21, 2014 (edited) it's 16 gauge all the way from the engine compartment, right? I can't just put thicker wiring in the sending unit Yes, the OEM wire is thin from front to back. Replacement wire harnesses for the sending unit are available for about $20. Longer harness is the new one, shorter is the original one. I got mine from NAPA, p/n 888536 This is what you're likely to find when you pop the fuel tank wiring harness wires out of the plastic connector bodies for inspection: (new versus old) I'm unfamiliar with both of these, but they may have come with the fuel pressure gauge and multimeter I borrowed from AutoZone with a $160 deposit. An oscilloscope and a current probe? Not likely. my replacement pump is not a turbo design (e.g. Bosch's pump). would removing the dampener still be ideal? thanks. I can't figure out why a person would remove the damper at all. Either it's working fine, and it goes right back in...or it leaks and it gets replaced. It's not like they're expensive. NAPA # 6751149 fits my '93 Lumina, and again it's under twenty bucks. Edited March 21, 2014 by Schurkey Quote Link to comment Share on other sites More sharing options...
Go4DaMo Posted March 21, 2014 Author Report Share Posted March 21, 2014 Thx for the pics! Turbo pumps don't require a pulse dampener, so cutting it out prevents it leaking and causing a problem later. I wanted the Bosch pump, but it was special order, so I bought a factory replacement off the shelf in a pinch. Quote Link to comment Share on other sites More sharing options...
Go4DaMo Posted March 24, 2014 Author Report Share Posted March 24, 2014 Wiring kit gave me a fuel gauge lead wire that didnt fit. That's the only one I reused. Car is back on the road. Thanks, again, for all of your input! Quote Link to comment Share on other sites More sharing options...
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