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What should I read for volts at fuel pump? (fixed)

shady

shady

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I'm tyring to diagnose my 88 burb with 350 tbi. I have narrowed it down to no fuel, then to pump not running. But my chilton and haynes manuals suck and wont tell you chit about injection:angry1: I did a search on here and found a lot of stuff to check but figured I'd run one past you guys.

At the pump plug by the tank I have no volts to the frame ground from either wire and 8 volts between the wires:dunno: I thought I read some where in one of the searched threads that I should have 12v to both of them wires (may have meant between them but thats not how it was written) Help please:confused:
 
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I'm really not quite sure what your saying, but you shouldn't have voltage at the grd..

i'm guessing what you mean by between is using those 2 connections for your meter.. you have to use a "known good" to verify and break things down.... grd to a known good grd, should have 12 on the pos feed...

known good hot, check the grd side of the plug... which is where you'll more than likely find the issue, the grd side of the circuit...

jumper wires are your friend....
 
when I put one meter lead to the good clean bolt on the frame (The one that the tank ground goes to) and the other meter lead to either one of the 2 wires in the plug coming from the front of the truck I get nothing. If I take both leads of my meter and stick one in each hole of the plug from the front I get 8v:dunno:
 
Well, for the pump to run, you have to have full battery voltage. But, depending on your setup, the pump may not be turned on.
Let me check my schematics. One wire may be ground and the other hot, or one might be the gauge wire, not sure.
Someone here will know.

But, either way, you will not get power until the fuel pump relay pulls in, and that is controlled by the computer I think.

Little fuzzy right now.
 
you've got one power feed coming back, the other is the sender wire.. so your second test is totally invalid...

got jumper cables? hook to your battery, lay the other end towasrds the back the truck for known good pos and grd...

from your first test, it sounds like a power feed issue... you should have seen 12v at the power wire with the known good grd at the bolt.. iirc, ones pink and ones tan? been awhile, I do have the factory diagram around here somewhere if need be.....

the most common prob is a failure in the grd to tank somewhere, dirty connection, etc..
 
After further investigation (and making the GF help) I found that it has to be turning over to get the 12v at the plug. and the pump is running. it ran for a while after she let of the key and sounded like it was pressurizing the line then cut off. with the drivers side fuel line Off entirely at the tbi I get no gas though:doah: I hope a filter fixes it but the threads I read on here last night ended up being the rubber line in the tank being bad (I've seen it before too). I wouldnt think it would pressure up the line if that was the case but:dunno:

I wasnt even thinking about the sender either:doah: so yeah that was a stupid test:rolleyes:
 
Yep, it only runs for a few seconds if the engine is not running. If you are not getting fuel out with it running, then its the filter, pump, or no gas in the tank.........
 
shady said:
After further investigation (and making the GF help) I found that it has to be turning over to get the 12v at the plug. and the pump is running. it ran for a while after she let of the key and sounded like it was pressurizing the line then cut off. with the drivers side fuel line Off entirely at the tbi I get no gas though:doah: I hope a filter fixes it but the threads I read on here last night ended up being the rubber line in the tank being bad (I've seen it before too). I wouldnt think it would pressure up the line if that was the case but:dunno:

I wasnt even thinking about the sender either:doah: so yeah that was a stupid test:rolleyes:
Click to expand...

It should do the same thing when you put the key in and turn it on. The pump should run a couple of seconds before you turn the key to start.
 
Changed the filter with no luck. Looks like I'm dropping the tank. Probly 10 gallons left in there. hope it aint too bad. gonna spray it all with PB blaster tonight and my dads coming into town tomorrow to help me pull it apart. We'll only have a 6 hour window to get it out fixed and back together before I have to go to work:rolleyes: I hope it goes well

Thanks for the help
 
looks like I may have to pull the bumper to drop the skid plate to GET to the tank. Thats gonna be fun. youd think they coulda put the bolts in from the bottom.
 
Before dropping the tank -- Get a chunk of wire and hook it up to the power wire for the fuel pump (grey, IIRC) and run it up to the battery. You should hear the pump start running. Crack the driver's side supply line at the back of the throttle body and see if fuel comes gushing out or not.

If you've got noise but no fuel, then either the pump is plugged up (done this before, twice!), the hose between the pump and sending unit has burst (happened once to me) or there is a blockage in the line between the pump and the injector pod (never happened to me).

If you've got fuel flowing up to the injector pod, then make sure that your injectors are being pulsed. Hook up a noid light (or a 168 marker light) to the injector wiring and make sure it flashes. If it doesn't, check for 12V ignition on one side of the plug. If it has 12V, but still isn't flashing, check your ignition module. If your ignition module is good, replace the ECM (extremely rare and almost unheard of failure...). If your injectors are being pulsed and you've got fuel, then check the filter screens on the injectors for blockages or replace your injectors if they are siezed.

I wouldn't drop the fuel tank until you are 100% sure that it is a failed fuel pump. That's a ton of work, esspecially on a burban.
 
I'm sure, I had the line off of the tbi completely and I can feel/hear the pump running back at the tank. Not even a dribble out of the line. I'm guessing its the rubber line burst in the tank. seen it on my dads and 2 buddies trucks. i bought a new pump anyway, and it comes with the rubber line.
 
Could be either a plugged inlet or prehaps the hose in the tank popped right off. When they rupture, there is still some fluid that goes through the hose into the fuel line... Either way, sucks you gotta drop the tank!
 
(Copied from my burnt burb build thread)

"Found it, The rubber line in the tank was completely broke. pump was facing 2" to the side of the pipe its supposed to hook to. I'm way glad it did it in the driveway:waytogo: Whole job took 3 hours from start to test drive."

I got lots of great info from this site and troubleshooting to finish went smooth, Thanks to all who helped and had the problems before so I could search your threads:rolleyes: :bow::bow:
 
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