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Thread: Frame mount fuel pump

  1. #16
    Fuel Injected! dktool's Avatar
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    Thanks all for the good info.
    I have had in-tank pumps fail on various vehicles without warning and no rhyme or reason as to vehicle mileage.
    Izusu Rodeo @100k
    Jeep Cherokee @150
    Ford f250 v10 at less than 60k
    Dean

  2. #17
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    Quote Originally Posted by dktool View Post
    Thanks all for the good info.
    I have had in-tank pumps fail on various vehicles without warning and no rhyme or reason as to vehicle mileage.
    Izusu Rodeo @100k
    Jeep Cherokee @150
    Ford f250 v10 at less than 60k
    I have had 1 in-tank pump failure in 20 years and even it was only a weak pump. It had the old GM square 4-pin connector bulkhead plug and the connection was failing. Both of my Infiniti's that made it over 300K miles were on the factory pumps. My 07 G35 Sedan and my 2011 M56S. Recently had the pump changed in my 2011 Pathfinder with a replacement OE unit because the tank had to come out anyway from heavy fuel contamination. Made it about 2 miles after I filled the tank before the engine stalled. My 1997 Express was the one that burned up the bulkhead connector. I put a Delphi pump in it with the updated 4 flat bulkhead connector and a Racetronix Hotwire. I have run that van almost exclusively on E85 for the past 12 years and it is still feeding a 500 hp 383 on E85. The Delphi pump in the 1983 G20 I put in it back in 2005 is still running as well, feeding a cammed 8100.

  3. #18
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    I forgot to mention above. The past 20 years or so, the OE Nissan/Infiniti and many Toyota pumps are often Delphi. I have seen plenty of examples of Delphi pumps still going strong at 350K miles. The stock 80s and 90s GM pumps were garbage and I replace them with Delphi equivalents. The biggest issue with GM fuel pump reliability is the factory wiring is woefully imadequate. Lower voltage means it spins more slowly draws more amperage and it runs hotter. I use an external relay, a fused 10 awg wire off the alternator output stud and a 10awg ground wire to upgrade the pump harness on everything 80s and 90s GM now. The 1987 G20 I just built was updated in that regard as well and has a Delphi Vortec pump on a TBI sending unit. At hot idle, the pump gets 13.0V with the battery getting 13.3V.

  4. #19
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    The biggest issue with GM fuel pump reliability is the factory wiring is woefully imadequate.
    I have seen wiring issues on vehicles made after 2000. After 2000 GM began reducing wire diameter which caused all sorts of headaches. The fuel pump relay terminals in the Express cutaway chassis vehicles were getting so hot they would melt the fuse box. GM sold you a new fuse box that was the same design. Their tech support line reported the fuel pumps used less than 10 amps but the numbers told a different story. Not only was 10 amps too low for the required pressure, but we'd been measuring the new vans which were consistently showing 13-15 amps on a circuit with a 15a fuse. We ended up bypassing the OE fuse box to install an external relay and inline fuse to increase reliability. I guess this was the trade we got after GM improved pump reliability with their "fuel bucket" and jet pump design. There are definitely less failures in vehicles with this pump design.

    In regards to vehicles made before 2000, I would strongly disagree that wiring is a problem. I have changed many GM pumps in my years as a pro mechanic but have seen few wiring or connector issues. The carbon pads on the armature wear out and the pump is no longer able to operate. Typical failure is for the vehicle to drive to a location then fail to restart when its time to leave. One useful trick is to get a rubber mallet (this is the only thing that works ime) and hammer the bottom of the tank while power is applied to the fuel pump circuit. The vibration seems to be enough to get the pump to start turning. This can allow the vehicle to be driven to the shop.

    I have seen plenty of examples of Delphi pumps still going strong at 350K miles.
    I have not had to replace many fuel pumps in my personal vehicles. I always try to keep a decent amount of fuel in the tank because GM used to say lack of fuel or fuel starvation would lead to early pump failure. I believe their training was correct as we could often correlate our fleet vehicles' pump survival rate with how low the fuel level was allowed to go by looking at fill-up data. Drivers that typically purchased 25+ gallons of fuel each time were more likely to experience early pump failure vs drivers who topped off the tank with 10-15 gallons. I believe the "jet pump" design resolves fuel sloshing issues which may help today's pumps last longer.

  5. #20
    Fuel Injected! dktool's Avatar
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    I have tried the rubber mallet re-start on every failure I had, only the Isuzu Rodeo responded to it.
    Dean

  6. #21
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    Quote Originally Posted by 1project2many View Post
    I have seen wiring issues on vehicles made after 2000. After 2000 GM began reducing wire diameter which caused all sorts of headaches. The fuel pump relay terminals in the Express cutaway chassis vehicles were getting so hot they would melt the fuse box. GM sold you a new fuse box that was the same design. Their tech support line reported the fuel pumps used less than 10 amps but the numbers told a different story. Not only was 10 amps too low for the required pressure, but we'd been measuring the new vans which were consistently showing 13-15 amps on a circuit with a 15a fuse. We ended up bypassing the OE fuse box to install an external relay and inline fuse to increase reliability. I guess this was the trade we got after GM improved pump reliability with their "fuel bucket" and jet pump design. There are definitely less failures in vehicles with this pump design.

    In regards to vehicles made before 2000, I would strongly disagree that wiring is a problem. I have changed many GM pumps in my years as a pro mechanic but have seen few wiring or connector issues. The carbon pads on the armature wear out and the pump is no longer able to operate. Typical failure is for the vehicle to drive to a location then fail to restart when its time to leave. One useful trick is to get a rubber mallet (this is the only thing that works ime) and hammer the bottom of the tank while power is applied to the fuel pump circuit. The vibration seems to be enough to get the pump to start turning. This can allow the vehicle to be driven to the shop.

    I have not had to replace many fuel pumps in my personal vehicles. I always try to keep a decent amount of fuel in the tank because GM used to say lack of fuel or fuel starvation would lead to early pump failure. I believe their training was correct as we could often correlate our fleet vehicles' pump survival rate with how low the fuel level was allowed to go by looking at fill-up data. Drivers that typically purchased 25+ gallons of fuel each time were more likely to experience early pump failure vs drivers who topped off the tank with 10-15 gallons. I believe the "jet pump" design resolves fuel sloshing issues which may help today's pumps last longer.
    I guess we will have to agree to disagree on the pump wiring. My 87 G20 had too much voltage drop through the wiring after swapping to a real EFI pump and port fuel injection pressures. The OE wiring was like 16 awg and combined with the OE wiring that fed the fuse panel through an inadequate junction block off the starter it was only seeing 10-10.5V at the pump. I rewired everything under the hood of that van. It has a large 4 post junction block with 5/16" studs now. 6 awg battery and alternator charge wiring through 10 awg fuse links. I upgraded the ground strap off the block to the floor above the transmission with a huge AC Delco ground strap and the battery cables to 2awg. Converted to a 24R top post battery as well. Also add a 2awg ground wire to the factory body ground on the core support. I put an AD244 145 alternator on the Vortec accessory setup as well. No more voltage issues in that van. The stock alternator had the external sense wire and was having to charge at nearly 16V to keep the battery at 13.2V. The AD-244 now charges 13.6 at the post and the system runs 13.3V, that is at hot idle with all the lights on, the a/c blasting and the condenser pusher fan in operation.

    My 97 van burned up the fuel pump connector and the relay terminals in the fuse box over the years. My 99 Tahoe also burned up the same square connection the van did. The replacement pumps do have the updated connector and matching pigtail though. T
    Last edited by Fast355; 1 Week Ago at 11:17 PM.

  7. #22
    Fuel Injected! dktool's Avatar
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    I am now playing with an inline pump, got a lot of it sorted out now but have a quick question that hopefully you guys can answer.

    I have the 7060 pcm, what is the function of the D7 input labeled fuel pump circuit.
    Is it just a checking input to confirm the fuel pump is receiving power and does not affect other program functions ?
    Attached Images Attached Images
    Dean

  8. #23
    Fuel Injected! dktool's Avatar
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    .20240715_132704.jpg
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    Dean

  9. #24
    Fuel Injected! dktool's Avatar
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    Also, my oil pressure switch is the type shown in the second full page picture, 3 wires.
    The manual shows the 2 wire type for my P30, which is wrong.
    GM factory manual !
    Dean

  10. #25
    Super Moderator dave w's Avatar
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    Perhaps these schematics will help.

    The schematics for the oil pressure switch has 3 wires, one of which is going to the Instrument Panel (IP).

    The Oil Press Switch is wired in Parallel to the Fuel Pump Relay.

    D7 is "TELLING" the computer the fuel pump is "ON".

    A1 is "TELLING" the Fuel Pump Relay to "Turn On".



    1993 Chevy Truck K 2500 Truck 4WD V8-454 7.4L_01.jpg

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    1993 Chevy Truck K 2500 Truck 4WD V8-454 7.4L_04.jpg

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  11. #26
    Fuel Injected! dktool's Avatar
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    Correct to your comments, I'm just trying to confirm that during my drive test with the inline pump there won't be any drivability issues with the ecm not seeing a voltage input on that line.

    I will be disabling the intank pump by unplugging the oil pressure switch and also the relay and powering the inline pump from the house battery for the test.

    I understand my oil pressure gauge will be inop.
    Dean

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