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Fuel problems

Tiny
MILLERBREWS
  • MEMBER
  • 1999 OLDSMOBILE BRAVADA
  • 130,000 MILES
I am having a fuel issue and my truck will usually not start. I have replaced the fuel pump thinking that was the issue but it wasnt. So now I have a new fuel pump and if I hook it up directly it will run fine if hooked to connector on vehicle when I turn key I hear nothing with little to no fuel pressure at all. I have checked the fuse and relay and took of ground under battery sanded and reconnected. Also has new spider injectors that I just replaced. Gas gauge reads empty now but has about 10 gallons in so maybe them wires are backwards but dont think thats an issue I did get it started once and was able to drive it but after shutoff wouldnt restart. I am lost please help
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Monday, March 7th, 2011 AT 3:59 PM

20 Replies

Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Did you check voltage and ground at fuel pump connector for pump motor. Engine cranking, gray wire is voltage, black c-terminal is ground. If no voltage we'll have to check circuits at fuel pump relay. Any electrical part, if there is a problem with wiring circuit, replacing the part won't fix it.
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Monday, March 7th, 2011 AT 4:23 PM
Tiny
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I didnt check that no. How can I do that with my meter I just have your basic meter nothing special what settings should I use
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Monday, March 7th, 2011 AT 5:01 PM
Tiny
JDL
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Is it a digital multimeter? Take pump connector loose, place meter leads between gray and c-terminal black wire, engine cranking, what is the voltage reading? You will need a helper to crank it. Usually you can get at the fuel pump connector, at the gas tank.
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Monday, March 7th, 2011 AT 5:39 PM
Tiny
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Ok so I have checked for voltage at pump connector and I have no voltage
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Tuesday, March 8th, 2011 AT 2:24 PM
Tiny
JDL
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Also, use chassis ground, metal part of vehicle, to check voltage on the gray. Just to make sure there is no problem with ground wire.

If no voltage, we'll have to check relay circuits. Engine cranking, do you have spark at the plugs?
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Tuesday, March 8th, 2011 AT 3:13 PM
Tiny
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Yes enginge cranks and sparks fine
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Tuesday, March 8th, 2011 AT 3:24 PM
Tiny
JDL
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Check the ecm B fuse, use a voltage tester on the fuse circuit. Below is diagram for fuel pump relay.
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Tuesday, March 8th, 2011 AT 4:10 PM
Tiny
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Ok so it read 5 volts but then I tried starting and fired right up but I heard no pump turn on when I turned key but I did hear it run when I turned key off
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Tuesday, March 8th, 2011 AT 4:45 PM
Tiny
JDL
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What read 5 volts? That ecm B fuse should show close battery voltage. Will it start and run or not?
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Tuesday, March 8th, 2011 AT 4:49 PM
Tiny
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Ok maybe I read that wrong it tested the fuse with a meter and it read 5 volts did I check wrong thing? Yes it was running but sometimes it will start and other times it wont. I just had it on and off 5 times most I had since this problem started
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Tuesday, March 8th, 2011 AT 4:59 PM
Tiny
JDL
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Double-check your meter. Digital multimeter setting on 20 volts. With everything off, check voltage across battery posts. A fully charged battery should show around 12.6 volts, generic spec.
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Tuesday, March 8th, 2011 AT 5:12 PM
Tiny
JDL
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Intermittent issues can be very frustrating, you have to test when the problem is ongoing.
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Tuesday, March 8th, 2011 AT 5:14 PM
Tiny
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Yes I have 12.7 across battery
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Tuesday, March 8th, 2011 AT 5:26 PM
Tiny
JDL
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It should be close to same at fuse. Is it? Using the meter, sometimes you have to scratch a little with the probes to get good contact.
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Tuesday, March 8th, 2011 AT 5:38 PM
Tiny
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Best reading I can get from that 15 fuse is a 3.8 maybe this is not normal or my problem but again at the moment it is starting fine
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Tuesday, March 8th, 2011 AT 6:12 PM
Tiny
JDL
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Are you sure your on the right fuse? Underhood fuse block, 20 amp fuse. Diagram below.
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Tuesday, March 8th, 2011 AT 6:42 PM
Tiny
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Ok sorry was checking ecmi but now I got the right one not running I got 0 when motor is running I have 41?
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Tuesday, March 8th, 2011 AT 6:55 PM
Tiny
JDL
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Are you using chassis ground/metal part for meter ground? One of those fuse legs should be hot all the time. Are you saying 41 volts, that isn't right.
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Tuesday, March 8th, 2011 AT 7:12 PM
Tiny
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No I wasnt so recheck I have 12.85 and vehicle is starting fine at the moment and I can hear pump prime and run after I turn off
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Tuesday, March 8th, 2011 AT 7:43 PM
Tiny
JDL
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As long as it is doing fine, we probably aren't going to find anything. I don't think the pump should run after you turn the key off? My hearing is no good, I couldn't hear the pump anyway, I have to use a fuel pressure gage.
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Tuesday, March 8th, 2011 AT 7:58 PM

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