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Author Topic: no fuel tbi ::solved  (Read 30571 times)

Offline Irish_Alley

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no fuel tbi ::solved
« on: December 01, 2014, 01:26:51 pm »
91 v3500 350 TBI. Its been acting up lately now its not running. Problem is its not getting and fuel will start and run for a second on starting fluid. Used to take 5 or so seconds to start when cold. Think that was due to a bad fuel pump relay. Replaced it but it didn't fix. Now I find out I'm not getting and power to the fuel pump relay.

Another weird part is the fuel gauge isn't working right now it was right before it wouldn't start but right now no matter if the switch is connected or if its on left or right tank it won't move off 1/8 tank
« Last Edit: January 16, 2015, 06:08:10 pm by Irish_Alley »
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Offline bd

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Re: no fuel tbi
« Reply #1 on: December 01, 2014, 01:46:22 pm »
Check the 10-amp ECM B fuse.  Will it start and run if you feed 12 volts to the 3" red pigtail off the fuel pump relay?
« Last Edit: December 01, 2014, 01:53:13 pm by bd »
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Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Irish_Alley

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Re: no fuel tbi
« Reply #2 on: December 01, 2014, 01:56:36 pm »
Injectors are getting signal. Ecm a and b are good
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Offline bd

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Re: no fuel tbi
« Reply #3 on: December 01, 2014, 02:00:54 pm »
Quote from: bd on December 01, 2014, 01:46:22 pm
...Will it start and run if you feed 12 volts to the 3" red pigtail off the fuel pump relay?

Verify that 12 volts is arriving to the fuel pump relay on the orange wire.

Make sure you don't have a loose bulkhead connector.
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Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Irish_Alley

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Re: no fuel tbi
« Reply #4 on: December 01, 2014, 02:01:14 pm »
12 will start the pump and it will start but once you remove 12 v it will slowly die
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Offline Irish_Alley

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Re: no fuel tbi
« Reply #5 on: December 01, 2014, 02:25:17 pm »
Orange wire has 12
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Offline Irish_Alley

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Re: no fuel tbi
« Reply #6 on: December 01, 2014, 02:29:55 pm »
It used to ark when I put 12 v to the red jumper wire. Now I'm now getting anything and cant hear the pump start up and the engine won't start
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Offline bd

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Re: no fuel tbi
« Reply #7 on: December 01, 2014, 03:11:22 pm »
The truck may have more than one problem.  "Not running" and the inability to prime the pump is beginning to sound like an open fuel pump feed (Ckt 120) or a faulty fuel pump.  Confirm that you don't have a loose bulkhead connector or loose fuel tank sender connector.  Unplug the fuel pump relay and jump orange (Ckt 440 - ECM B) to gray (Ckt 120) then check for power on the gray wire entering the bulkhead connector and on the tan/wht wire exiting the bulkhead connector and running to the fuel pump - circuit 120 switches from gray to tan/wht through the bulkhead.  For reference study the 1991 Wiring Manual, page 91. 

If the ECM simply isn't energizing the relay, you might want to take a few minutes to verify the ECM connections, as well.
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Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Irish_Alley

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Re: no fuel tbi
« Reply #8 on: December 01, 2014, 06:58:59 pm »
idk its dark and raining out now. took my 04 impala to dover de its about a 20 minute drive but i got a laptop from bestbuy, but when i got there my key wouldnt come out of the ignition. its a known problem with the impalas and its a broken wire in the sifter.

 but the problem im getting with the truck is the fuel gauge doesnt move no matter what tank you select i know one has 3/4 tank. even with it unhooked it still should default to the left tank and its the 3/4 tank.
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Offline Captkaos

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Re: no fuel tbi
« Reply #9 on: December 01, 2014, 09:44:50 pm »
Mine never "defaults" to one side.  I have had it stuck in the middle and it was the switch.  I pulled it apart to fix it. (tech section)
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Offline Irish_Alley

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Re: no fuel tbi
« Reply #10 on: December 01, 2014, 10:40:34 pm »
when i first had this "as soon as it starts it stalls" problem today i switched tanks to see if it was the problem (from 3/4 full on the left side to 1/8 full on the right) it didnt fix it so i tried to switch back and the gauge would move. went to remove the switch and it came apart as soon as i removed the pigtail. so i pulled my buddys off his 90 r3500. still no difference. but its years since his was used and idk if its any good.
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Offline Captkaos

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Re: no fuel tbi
« Reply #11 on: December 01, 2014, 10:42:26 pm »
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Offline Irish_Alley

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Re: no fuel tbi
« Reply #12 on: December 01, 2014, 10:59:25 pm »
how did you fix it? did you just clean the contacts? if run two jumpers parallel top to bottom i can bypass the switch right?
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Offline Captkaos

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Re: no fuel tbi
« Reply #13 on: December 01, 2014, 11:47:15 pm »
yeah I cleaned the contacts.  It was doing what you are describing.  Yes you can bypass it.
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Offline Irish_Alley

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Re: no fuel tbi
« Reply #14 on: December 02, 2014, 12:36:37 am »
ok ill give that a try in the am. then ill have to figure out why my pumps aint priming.
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When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes
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