In tank electric fuel pumps?? - Page 5

partsman · 10-27-2009, 07:38 PM

Okay, here is an update for you.

He brought schematics and all checked out, but he noticed the feed came and went and noticed sometimes he heard a buzzer and sometimes he didn't.
So by now he had checked the relay and fed power to the pump and I know he had a test light and a fused jumper and continuity tester and then he said "it all checked out, but what was I seeing when I turned the switch?"
And I said what I saw and what happened when I hit the switch, so while I turned the key on and off he was doing something under the hood and finally he watched my dash and noticed while I turned the key nothing lit up on the dash, so he said keep turning the key on and off and said when I see the symbols light up on the dash, turn the key all the way to start, well low and behold no lights, no start, saw the symbols and it started, first time everytime, so now he is going to get more schematics of ignition switch and stuff as he says as far as he is concerned it is related to the column say or at least it is not a problem with anything under the hood.
He wants me to price out a ignition switch just to see if I need one can I get it, and he is coming back tomorrow to look inside the drivers area.
So it turned out interesting, I have been out and played and sure enough no start unless I see the dash lite up.

crabtruck · 10-28-2009, 12:00 AM

1996 GMC K250 4X4 219.000Km/137.000M 7.4/454 engine with auto trans.
(just refreshing my memory)

Wow, that's kind of a large detail to skip: Dash dies same time as truck.
Probably are looking for a new key,
good news is you don't have to drop tank to do it.

Let's hope your man's diagrams for that are better than what I have seen
for at least 96-99. Every one of those has errors on switch wiring.

Specifically for the wires you need in this case.

Should be a fairly quick fix, let us know.

chadwickthomas · 10-28-2009, 01:03 AM

If you run the test that crab truck explained in his forum you should hear your pump run for 2 seconds then quit.IF your truck runs for a second and dies your trouble could be that your ecm is not getting a cam sensor signal in the distributor to keep it running after the two second period.Also your oil pressure switch is also tied to the fuel pump circuit and will kill the fuel to the injectors if it is faulty.another item is if you have theft lock on your system and it is energized by your vin code instead of a programmable code into your radio the ecm will not give the fuel pump relay a ground signal until the theftlock problem is corrected and the theftlock light is out,and no you cannot just remove the fuse for that type of system, it has to be in and functioning.If you cannot get the light out you will have to relearn the system to the ecm. To do this hook a battery charger to your battery, turn the ignition switch to the on position and leave it like that for twenty minutes and the light should go out and engine should crank. These are your options to look at if your pump tests good and your not getting fuel through your injectors

partsman · 10-28-2009, 10:40 AM

This has been a quiting problem out of the blue after driving for a bit, but would restart after trying to crank a couple times, then it became no start at all after it quit the last time, so towed it home.
Now he pointed out that which I did not see, which is turn the key you here all sorts of things activating, but none of the symbols lit up on the dash, which I missed, I guess cause I was just trying to get going, and I had the daughter turning key while I was stuck in traffic, anyway, then he showed me keep turning key on/off and as soon as I see lights on dash to turn all the way to start and off she goes and she will sit there running it seems for ever.
But don't shut it off or you are there for a bit again.
The only anti theft is the radio itself, no other system on this 1996.

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10-27-2009, 07:38 PM	#41
partsman Senior Member Join Date: Jul 2008 Location: Poco BC Posts: 83	Okay, here is an update for you. He brought schematics and all checked out, but he noticed the feed came and went and noticed sometimes he heard a buzzer and sometimes he didn't. So by now he had checked the relay and fed power to the pump and I know he had a test light and a fused jumper and continuity tester and then he said "it all checked out, but what was I seeing when I turned the switch?" And I said what I saw and what happened when I hit the switch, so while I turned the key on and off he was doing something under the hood and finally he watched my dash and noticed while I turned the key nothing lit up on the dash, so he said keep turning the key on and off and said when I see the symbols light up on the dash, turn the key all the way to start, well low and behold no lights, no start, saw the symbols and it started, first time everytime, so now he is going to get more schematics of ignition switch and stuff as he says as far as he is concerned it is related to the column say or at least it is not a problem with anything under the hood. He wants me to price out a ignition switch just to see if I need one can I get it, and he is coming back tomorrow to look inside the drivers area. So it turned out interesting, I have been out and played and sure enough no start unless I see the dash lite up.

10-28-2009, 12:00 AM	#42
crabtruck Senior Member Join Date: Jul 2007 Location: on your 9 Posts: 3,366	1996 GMC K250 4X4 219.000Km/137.000M 7.4/454 engine with auto trans. (just refreshing my memory) Wow, that's kind of a large detail to skip: Dash dies same time as truck. Probably are looking for a new key, good news is you don't have to drop tank to do it. Let's hope your man's diagrams for that are better than what I have seen for at least 96-99. Every one of those has errors on switch wiring. Specifically for the wires you need in this case. Should be a fairly quick fix, let us know.

10-28-2009, 01:03 AM	#43
chadwickthomas Junior Member Join Date: Oct 2009 Posts: 11	If you run the test that crab truck explained in his forum you should hear your pump run for 2 seconds then quit.IF your truck runs for a second and dies your trouble could be that your ecm is not getting a cam sensor signal in the distributor to keep it running after the two second period.Also your oil pressure switch is also tied to the fuel pump circuit and will kill the fuel to the injectors if it is faulty.another item is if you have theft lock on your system and it is energized by your vin code instead of a programmable code into your radio the ecm will not give the fuel pump relay a ground signal until the theftlock problem is corrected and the theftlock light is out,and no you cannot just remove the fuse for that type of system, it has to be in and functioning.If you cannot get the light out you will have to relearn the system to the ecm. To do this hook a battery charger to your battery, turn the ignition switch to the on position and leave it like that for twenty minutes and the light should go out and engine should crank. These are your options to look at if your pump tests good and your not getting fuel through your injectors

10-28-2009, 10:40 AM	#44
partsman Senior Member Join Date: Jul 2008 Location: Poco BC Posts: 83	This has been a quiting problem out of the blue after driving for a bit, but would restart after trying to crank a couple times, then it became no start at all after it quit the last time, so towed it home. Now he pointed out that which I did not see, which is turn the key you here all sorts of things activating, but none of the symbols lit up on the dash, which I missed, I guess cause I was just trying to get going, and I had the daughter turning key while I was stuck in traffic, anyway, then he showed me keep turning key on/off and as soon as I see lights on dash to turn all the way to start and off she goes and she will sit there running it seems for ever. But don't shut it off or you are there for a bit again. The only anti theft is the radio itself, no other system on this 1996.