I could use some help with fuel pump issue

Discussion in 'Engine Performance + Maintenance' started by BulldogSS, Jun 28, 2020.

Car Parts
  1. Schurkey

    Schurkey I'm Awesome

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    Excellent plan.
     
  2. BulldogSS

    BulldogSS Newbie

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    So I had a chance today to check voltage at the pump connector right at the filler neck. I solid 12.5 key on engine off. I went ahead and cleaned up the ground while I was there. So it looks like the pump is receiving proper voltage and has a good ground. Fuel pressure reading is a solid 10psi during prime at idle and while giving throttle up to 3000-3500 rpms. The regulator diaphragm is new and not showing any signs of leaking. Injector spray pattern is looking like a nice cone pattern, I shot the timing light at it when I made sure timing was at 0. So for the time being I’m going to try and find a scanner and get o2 readings. If o2 reading are with in spec great, if it’s showing lean I’m wondering if the fpr spring could possibly be weak from being 26yrs old and having 220,000 miles. The tbi rebuild kit I used did NOT include a new spring. What numbers should I be looking for on the o2 readings? Also if I can’t track down a scanner I’ve read that I can use a volt meter to get o2 readings, is that an option? I’ve got access to multiple obd2 scanners just haven’t found one for the truck.
     
  3. Busted Knuckle

    Busted Knuckle OBS Enthusiast

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    Prior to 1996, the fuel pump can't deliver enough at wide open throttle to feed the 454's. '94 and '95 454s use a 30psi spring and different injectors, vs all the earlier 454 and 350s. You will NOT over-supply the fuel with a '96 pump, it just bypasses. My top end has a noticeable pull improvement just from the pump. The pump swap does NOT change the fuel pressure. That is set by the spring inside the TBI unit. 5.7L might not gain any power, but for no add'l cost you guarantee you've got enough fuel pressure.

    3-wire O2 is only different by having a heater. In a 454 the heater is a joke and they are fine with 1-wire.
     
  4. BulldogSS

    BulldogSS Newbie

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    Yes that confirms other info I’ve read. If it turns out that I need a new fuel pump I’ll def get one for a 96 and up. For the time being I’ve got basically a stock 350. Once I’m able to get a reading from the o2 sensor I can determine what further action is needed. If it turns out that I need more fuel I’m going to try and adjust pressure at the regulator. If the pump won’t support that pressure increase then it get replaced.
     
  5. BulldogSS

    BulldogSS Newbie

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    Bustedknuckle did you replace only the pump or the whole assembly? If it turns out I need a pump I’d rather swap the entire thing simply because the wires inside the tank would be new as well.
     
  6. Busted Knuckle

    Busted Knuckle OBS Enthusiast

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    For the amount or work, replace the whole assy. Delphi DELPHI HP10003
     
  7. Busted Knuckle

    Busted Knuckle OBS Enthusiast

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    You shouldn't need more fuel without mods that affect the volumetric efficiency, such has a camshaft. The system as designed runs fine. You have to tune it with ALL sensors being replaced, ALL ignition (including distributor if over 150K miles) and fuel pump/filter working as designed. O2, I've used bosch. These are almost generic. ACDelco is probably under $15. (ALL includes the oil pressure sender and temp sensors. Critical are MAP and coolant at the front of the intake manifold, not the head, and KNOCK.)
     
  8. 98 Nitro

    98 Nitro I'm Awesome

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    The only mods I did to my 94 was Magnaflow exhaust and the power charger aka salad bowl, both helped performance. If you need a new fuel pump and plan on increased performance I would just go with the 94/95 454 TBI pump.
     
  9. Schurkey

    Schurkey I'm Awesome

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    When working properly, the O2 voltage is going to vary rapidly between about one volt and 0.2 volts. A voltmeter will not register fast enough to keep up.

    The other thing you need to verify is the O2 cross-counts--the speed at which it switches from "rich" to "lean". Old sensors get "lazy", the cross-count figure goes to single digits when it could be well into double-digits--20, or more, let's say.

    You need a real scan tool.
     
  10. BulldogSS

    BulldogSS Newbie

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    gotcha
     

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