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Fuel Pump Options

Discussion in 'The Injection Section' started by ccj8008, Apr 21, 2007.

  1. ccj8008

    ccj8008 1/2 ton status

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    I think my in-the-tank fuel pump is going out. I have an inline pressure gauge and it reads 5-6 psi. The truck acts like it is running out of gas. My question:
    What are my fuel pump options?
    It is an 88 TBI on a 454. Are there mechanical pumps now that bolt to the stock fuel pump outlet that work for FI? Thanks for the help.
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    You need an electric pump for EFI.

    Your options are replace the one in there now, or run an in-line. IMO it's worth it to stick with the in-tank setup.

    Unlikely a problem, but make sure your pump is getting 12V when it's supposed to as well.
     
  3. Thunder

    Thunder 3/4 ton status

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    When was the last time the fuel filter was changed? Might try that before replacing the pump.

    IMO the intank pump is the best.
    But if you go with a inline pump. It must be designed for TBI. Holley and Carter make inline pumps that will work.
     
  4. sled_dog

    sled_dog 1 ton status

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    X2, seen fuel filters cause a couple of fuel pressure issues, usually in upper RPM supply.

    Something like a Walboro 255 that has no problem pushing 60psi all day long would be a fine inline pump for a TBI setup.

    However, inline pumps don't like to suck, just blow, hehe. So running through the factory pump isn't a stellar idea. They like it much better when you have a fuel cell with a drop sump feeding them.
     
  5. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Considering the fact that TBI is low pressure (9-13 psi) i don't think it would be adviseable to install a pump with such high pressure as it will certainly overcome the pressure regulator and give all kinds of trouble.
     
  6. bowtiepower00

    bowtiepower00 1/2 ton status

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    The Walbro is the way to go. They are available in 190 LPH and 255 LPH. The factory fuel system can handle the extra pressure and flow. Lots of F-body guys using them on HiPo TBI builds. They are available from Auto Performance Engineering (online, or 866 383 5786) for about a hundred bucks.

    The factory GM pumps go out frequently. I just did one today, as a matter of fact.
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    Frequently? 20 year old parts? :)
     
  8. camok5

    camok5 1/2 ton status Premium Member

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    This is a little off topic but has anybody cut a hole in the bed of their blazer to access the in tank pump. I bought a walbro pump to replace my factory one and was thinking of doing this instead of having to drop the tank. I would want to make a door for it so it wouldnt just be a hole and it would make changing them in the future a lot easier.
     
  9. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    If you search someone just did this within the last week.
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    Again, 20 year old part, cutting hole in good sheetmetal, work required to drop the tank once in 10-20 years, hmm.

    Dropping a tank is not hard, only people on the east coast and those that have it die when wheeling need a hatch. :)
     
  11. bowtiepower00

    bowtiepower00 1/2 ton status

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    I don't know anybody who has gotten 20 years out of a GM fuel pump. Less than 5 is more like it, especially on the higher pressure applications. I know of more than one person who has replaced pumps every couple of years, on vehicles serviced frequently and throughly.

    I think running with low fuel levels, which allows the pump to run uncovered and heat up, is a major contributer to early pump failure.

    If you don't mind the hole in the floor, cutting an access hole isn't a bad idea, particuarly on vehicles where removing the tank is a real PITA. If you do it right, install a hinge, and cover it with carpet who is going to know?
     
  12. ccj8008

    ccj8008 1/2 ton status

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    Good Points

    All good points, I appreciate the input. Looks like my pump has now given up altogether so I will be dropping the tank. This TBI is a retrofit from a 1990 V3500 into my 77 Blazer (454) as was done by the previous owner. What is odd is that the in-tank pump delivery line goes to the mechanical pump that is still on the engine. I am not sure why this wasn't bypassed but I plan on bypassing it now.

    I thought that I had seen in one of the four wheeler mags, new product section, a mechanical pump that could replace the in-tank electric pump. Even if this beast exists, it is my understanding that you cannot pull through the in-tank electric pump if the pump in not on, so... back to dropping the tank. I would still prefer a mechanical exterior pump if possible.

    Another note, How important is a VSS? The truck has always run well without one. I have swapped in an NP-241 with SYE and mechanical speedo. I do have another NP-241 with the VSS output. Is there any benefit to having the VSS input to the ECM?
     
  13. bowtiepower00

    bowtiepower00 1/2 ton status

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    Theoretically, if you could provide the TBI with an adequate supply of fuel, then it shouldn't matter what type of pump you use. The problems are that:

    1) Most mechanical pumps do not provide enough pressure to feed EFI. TBI only requires 15+ PSI, depending on year and setup, but most mechanical pumps only provide 5-10 PSI.

    2) More importantly, most mechanical pumps provide fuel in a surging manner as they pump.

    That being said, there are Mechanical pumps that provide enough PSI. There is a new design (as well as some older ones) on the market that can provide 50+ PSI, but I'm not sure about the surging issue. I would like to experiment with said pump and a good regulator on a TBI system to see if it can provide adequate and steady flow. Ideally, I would like to install a mechanically fed TBI system on my 80, along with a large cap HEI, so that I can bolt my Q-jet back on if I'm in the sticks and have issues with my EFI. That and it would make conversion much easier if I didn't have to deal with any fuel system upgrades and or return lines.
     
  14. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    TBI requires a return line no matter what you do.
     
  15. Thunder

    Thunder 3/4 ton status

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    I have a 89 Blazer with the orginal FP. 18 years and counting. I am sure many on this board have had similar use out of their stock pumps. I trust my electric pump far more than a mechaical pump which are far, far mor prone to failure.
     
  16. dyeager535

    dyeager535 1 ton status Premium Member

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    I think cutting holes in the floorpan wouldn't be so much an issue if they failed every five years, it would already be done to every K5 out there. *I'd* consider it if my pumps only lasted five years.

    Every EFI GM car made from probably 1986-1993 used the exact same fuel pump setup, 13-45PSI, there is nothing inherently wrong with the idea. The only improvement I could possibly see is mounting it horizontally to get it to cool better even at low fuel levels. But then again, GM EFI tanks have sumps, and the return line dumps directly into them.
     
  17. ccj8008

    ccj8008 1/2 ton status

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    Chiltons

    Got the Chiltons manual. Surprising enough, for an 89 7.4l engine, the required fuel pressure is 5 p.s.i. In 1990, it jumps way up to 6.5-8 p.s.i.

    Learned some troubleshooting tips. Found that I wasn't getting my 3 second prime when I turned the key on. However, I could get the electric fuel pump to work when i ran a jumper wire direct to it from a 12V source. Checked the fuel pump relay and there was no voltage to it. Turns out, the previous owner had wired the ECM without a fuse and a power surge had taken out the ECM. I went ahead and verified the whole system wiring, cleaned it up and ordered a new hypertech chip while I was at it.

    I had been hesitant to dive into all this as it seemed like it would be complicated. Turns out that TBI systems are not so bad once you really take a look at them. I need to learn more but at least now I feel like I can at least troubleshoot if I need to.

    Thanks again for all the input.
     
  18. dyeager535

    dyeager535 1 ton status Premium Member

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    Send that hypertech chip back.

    Even if it was free you got robbed. As long as it's not opened you shouldn't have a problem returning it I'd hope.

    I'd really be surprised if Chiltons is right. I've never heard a TBI pump spec out at less than 13PSI. You have not had it running yet?

    There's a red wire hanging off the fuel pump relay, putting 12V to that forces the pump to run BTW, easier than trying to do it under the truck.

    I'm kinda curious about the ECM, did it have burned parts on the board or something? How did you know it was fried? No check engine light?
     
  19. ccj8008

    ccj8008 1/2 ton status

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    hypertech

    Yeah, I can still send the chip back. I found a short at the oil pressure sending unit that was screwing things up. There was no fuse to the ECM (that has been remedied).
    I am still wondering how critical a VSS signal is. I have another NP241 that has the VSS and I am checking with JB Conversions for compatability with their SYE kit. If there is no problem, I will swap this in. Should be good to go by this weekend. Thanks for the tip on the fuel relay.
     
  20. dyeager535

    dyeager535 1 ton status Premium Member

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    Is your wiring that messed up? The ECM wasn't on the ECM fuse? PO's, all I've got to say.

    VSS signal is critical. (even though it will run without it) Fair number of things the ECM cares how fast the vehicle is going.
     

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