454 94' 454 stall while driving and knock sound under the cab

[Tom_1991]

Model= 1994 Chevy Suburban K2500 Silverado

Engine= 454 TBI

Transmission= AT

Fault down des. :

    Location= Albany, Berkeley, Calif., I80E;

    Trans. pos.= D (O/D Off);

    Transfer case pos.=2H

    Last operation= OD  --> D, fully release throttle pedal;

    Speed= around 40 mph;

    Coolant temp.= around 210(heated up), normal operation temp., enough;

    Engine Oil= normal pressure, enough, just changed (incl. filter);

    Trans. oil= enough, just changed(incl. filter);

    Fuel= enough, #87 from Chevron or Shell, I only fuel my vehicles in these 2 brand, I've burnout old fuel, now is new fuel in tank;

    Symptom= engine stall, hear knock sound from under the cab.

        Attempt 1: shift to N then crank, crank no start, pull over, shift to P.

        Attempt 2: crank, start, shift to D(O/D Off), accelerate, around 40mph, stall and knock sound again, pull over, shift to P.

        Attempt 3: crank, start, shift to OD, accelerate with little throttle, around 40mph, stall with knock sound again, pull over, shift to P.

        Inspection at break down site: crank, start, noticed check engine light is on, press throttle pedal to 2000 then 3000 rpm, no knock sound, inspected engine driving belt area, belt and all pulleys are okay. 

        Inspection at home (Towed): OBD scanner get DTC 54. Inspected drive shaft for both front axle and rear axle, no loss.

    Repair attempt=

        Change: fuel pump relay (as DTC 54), spark plugs, ignition wires, ignition coil (noticed serous oxidation on the terminal to distributor), all from AC Delco, OE or above product line, purchased via O'reilly or Autozone store.

        Clean: distributor, all terminals (outer for ignition wires and inner for roter), rotor.

Current status=normal.

Other info. maybe useful=I found a maintenance label on wind screen, its next maintenance supposed to be on 05/22/2014 at mileage 153,000. But now is early 2020, 151,000, so most time it was just sit there.

Question=

    Is this only the fuel pump relay?

    What is the knock sound?

    Is there any thing I should inspect or replace a new one?

Edited February 24, 2020 by Tom_1991

[riverbanks]

Fuel pressure check,pump working very hard, about to fail

[Tom_1991]

11 hours ago, riverbanks said:

Fuel pressure check,pump working very hard, about to fail

Yes, I am suspecting this.

I have read this section in the shop manual, seems like it need an adapter to insect before and after the fuel filter, and if change fuel pump, gonna need much job because this need to take the fuel tank.

Maybe I can change fuel filter first? Though I think faulty fuel filter can cause power reduce but can't cause stall. My Ford F-250 used to have fuel filter problem when I got it.

Edited February 24, 2020 by Tom_1991

[riverbanks]

Filter, always a good idea, peace of mind, anyway,and how did relay connections look,any discoloration?

[Tom_1991]

10 hours ago, riverbanks said:

Filter, always a good idea, peace of mind, anyway,and how did relay connections look,any discoloration?

About the fuel pump relay, the original one looks okay, the socket and the feet of relay are okay, no sign of problem, and I tried to give 12V to coil, it acts normally, and the circuit on and off are also act normally.

 

Just have the filter changed.

For fuel pressure, I don't have the tool to measure the fuel pressure, so I tried another way.

Loose the nut for the fuel injector's input pipe, use jump wire on fuel pump relay socket to manually activate fuel pump, I can see fuel come out.

According my shop manual, the 454 engine should have 26-32psi, that's about a car's tire pressure, but I see the fuel come out very soft, not like 26-32psi.

So looks like I need to change fuel pump?

I gonna visit local junk yard this weekend to have some practice for take out tank and pump.