Left tank "WT?!"s - The 1947 - Present Chevrolet & GMC Truck Message Board Network

magnethead · 08-09-2006, 02:21 PM

Got some What The .....?!'s for my left tank.

We just dropped the tank to replace both lines to it. Well now, fuel flow is random at best and the fuel needle is all but horizontal to the full side. Now when we dropped it, there was something bouncing around in it or otherwise making noise (it was flat empty), sounded like maybe a rock, but i'm assuming it's the sending unit float. Well put it back in, put 19.2 gallons in the tank, and I have the mentioned problems.

I'm completely baffled on the gauge, I already double checked that it's connected and that it's not shorting to ground. I followed it (the blue wire) all the way from the connector to the firewall.

On the fuel flow, While checking the sending unit wire, I noticed a kink in the supply hose from it being a little too long. Is it safe to just back off on the bracket and move the extra length to the crossmember so that it isn't kinked?

Also, when filling it (keep in mind the tank was flat empty for about 2 months) I noticed a puddle of gas under the tank. It appears to be the vent line for the filler neck..it's cracked all to heck. Only thing is, I thought it's for venting vapors, and the actual gas doesn't flow through it. The filler neck hose itself appears in good shape, it was the drier of the two.

**Captkaos** · 08-09-2006, 06:24 PM

Quick thought on the guage, is the ground wire going to the frame still connected to the sending unit.

boxrodz · 08-09-2006, 07:54 PM

If your fuel gauge is registering at the 3 o'clock position when ignition power is switched on, then you have a bad (read: open) connection between the gauge 'sensor' terminal and the sending unit. It could be the wiring, but it's probably the sending unit since you mentioned that it was amiss when you dropped the tank. If you can gain access to the sending unit, you should be able to use VOM (meter) to determine whether it is functioning correctly or not. To do this, move the sending unit lever up and down while observing the ohms reading. You should observe a resistance range between 0 and 90 ohms. But, like Captkaos said, double check your connections.

magnethead · 08-09-2006, 08:59 PM

that makes sense...But when we dropped it there weren't any grounds that I remmeber..where does it attach on the SU?

magnethead · 08-10-2006, 06:20 PM

bump

I dont remember any ground bolts or wires when we dropped the tank. It worked before we dropped it.

boxrodz · 08-13-2006, 08:22 PM

Quote:

Originally Posted by magnethead

that makes sense...But when we dropped it there weren't any grounds that I remmeber..where does it attach on the SU?

I haven't been under the truck in a while, so I'm not certain where the ground is located. But, you should have two wires coming from the sending unit. One (Blue, Purple, or Light Green (?)) goes to frame ground. And, the other (Pink/White or Pink/Black(?)) is the sensor wire feeding the connector which then goes to the dash fuel gauge.

magnethead · 08-13-2006, 10:17 PM

Quote:

Originally Posted by boxrodz

I haven't been under the truck in a while, so I'm not certain where the ground is located. But, you should have two wires coming from the sending unit. One (Blue, Purple, or Light Green (?)) goes to frame ground. And, the other (Pink/White or Pink/Black(?)) is the sensor wire feeding the connector which then goes to the dash fuel gauge.

Only one there is a 22 gauge blue wire that goes from the tank to the firewall

There wasn't anything that went from SU to frame...

magnethead · 08-13-2006, 10:25 PM

these are the only pics that I have showing the tank and it's mounting area..

boxrodz · 08-13-2006, 11:04 PM

I noticed you didn't mentioned that when you dropped the tank, you loosened the sending unit ground from the frame. If that's the case, maybe you accidently pulled out the ground wire when you dropped the tank. Unless the configuration on your truck is different, the sending unit ground wire passes thru the frame rail and is grounded on the inside of the frame rail about an inch forward of the rear cab support bracket. If the sending unit is not grounded, the fuel meter would behave as you noticed (in the 3 o'clock position).

**Captkaos** · 08-15-2006, 12:09 AM

Quote:

Originally Posted by magnethead

bump

I dont remember any ground bolts or wires when we dropped the tank. It worked before we dropped it.

The wire that it STRETCHED out in this pic is the ground wire for the sending unit. Without it, the gauge won't work.

All my pics are here:
http://67-72chevytrucks.com/vboard/s...d.php?t=181888

magnethead · 08-15-2006, 07:55 AM

hmmm....ok. Do any tank support bolts hold the wire or is it a seperate bolt?

**Captkaos** · 08-15-2006, 08:33 AM

It is a seperate bolt and it typically goes to the top of the framerail

boxrodz · 08-15-2006, 02:51 PM

Chris -
The ground wire on the 83 is bolted to the inside of the frame rail with a 'large' tapered bolt near the rear cab support bracket. The wire passes through a ~1" hole in the frame rail lined with a rubber grommet.

I wonder if the configuration is slightly different for different years and models of the 73-87 trucks, especially for a dually.?

**Captkaos** · 08-15-2006, 04:58 PM

They must just put it where they can then.
All the ones I have ever pulled out had them behind the body mount on the top of the frame. This included my '73, the 75 I had, the 80 and my DD 87 model. Regardless of where you put it to ground, the gauge won't work without it.

magnethead · 08-15-2006, 07:28 PM

I'll look at it nextime I have time....

Here's a tidbit. I revved my engine to 4400 (spiked to 4200, held at 2600-3000 for 5 seconds, spiked to 4400) Showing off i guess you could say and the oil pan is still in 1 piece....

piecesparts · 08-17-2006, 04:27 PM

I would say that revving the engine is definitely a non-GOOD thing. Unless you have the motor loaded and the tranny is taking the torque that is being generated from the pistons to the crankshaft (ERGO--massive tire burnout). This type of evolution could find the weak spots in your lower end. Just free-wheeling the RPMs will give a lot of wear to the rod bearings.

As for the cyclic performance of the motor from that tank, did you check the filter sock on the tank's pickup line? There were problems with this sock getting to the point that it would suck up to the suction line opening and restrict flow of fuel to the fuel pump. Just a thought....

magnethead · 08-17-2006, 04:38 PM

we didnt remove the sending unit. we only changed fuel lines. We kept the tank itself together.

08-09-2006, 02:21 PM	#1
magnethead 7000 #'s of american IRON Join Date: Dec 2004 Location: north tx Posts: 883	Left tank "WT?!"s Got some What The .....?!'s for my left tank. We just dropped the tank to replace both lines to it. Well now, fuel flow is random at best and the fuel needle is all but horizontal to the full side. Now when we dropped it, there was something bouncing around in it or otherwise making noise (it was flat empty), sounded like maybe a rock, but i'm assuming it's the sending unit float. Well put it back in, put 19.2 gallons in the tank, and I have the mentioned problems. I'm completely baffled on the gauge, I already double checked that it's connected and that it's not shorting to ground. I followed it (the blue wire) all the way from the connector to the firewall. On the fuel flow, While checking the sending unit wire, I noticed a kink in the supply hose from it being a little too long. Is it safe to just back off on the bracket and move the extra length to the crossmember so that it isn't kinked? Also, when filling it (keep in mind the tank was flat empty for about 2 months) I noticed a puddle of gas under the tank. It appears to be the vent line for the filler neck..it's cracked all to heck. Only thing is, I thought it's for venting vapors, and the actual gas doesn't flow through it. The filler neck hose itself appears in good shape, it was the drier of the two. Last edited by magnethead; 08-09-2006 at 02:27 PM.

08-09-2006, 06:24 PM	#2
Captkaos www.73-87chevytrucks.com Join Date: Dec 1999 Location: Birmingham, AL Posts: 6,935	Re: Left tank "WT?!"s Quick thought on the guage, is the ground wire going to the frame still connected to the sending unit. __________________ Chris Lucas 1973 Chevy C-10 1978 GMC Jimmy (2WD) - SOLD 1987 R10 twin turbo LS 1991 R3500 SRW CrewCab 1985 K5 diesel swapped project 1989 K5 2WD conversion w/ Vette susp Project Captkaos Customs 73-87chevytrucks.com

08-09-2006, 07:54 PM	#3
boxrodz Until Seventy Times Seven Join Date: Feb 2005 Location: Rocky Mountain Front Range Posts: 1,301	Re: Left tank "WT?!"s If your fuel gauge is registering at the 3 o'clock position when ignition power is switched on, then you have a bad (read: open) connection between the gauge 'sensor' terminal and the sending unit. It could be the wiring, but it's probably the sending unit since you mentioned that it was amiss when you dropped the tank. If you can gain access to the sending unit, you should be able to use VOM (meter) to determine whether it is functioning correctly or not. To do this, move the sending unit lever up and down while observing the ohms reading. You should observe a resistance range between 0 and 90 ohms. But, like Captkaos said, double check your connections. __________________ boxRODz 1983 C10 SWB Fleetside When two halves is gone, there's nuthin left. Two nothings is nuthin. That's mathematics son. You can argue with me but you can't argue with figures. Two half nothings is a whole nuthin...

08-09-2006, 08:59 PM	#4
magnethead 7000 #'s of american IRON Join Date: Dec 2004 Location: north tx Posts: 883	Re: Left tank "WT?!"s that makes sense...But when we dropped it there weren't any grounds that I remmeber..where does it attach on the SU?

08-10-2006, 06:20 PM	#5
magnethead 7000 #'s of american IRON Join Date: Dec 2004 Location: north tx Posts: 883	Re: Left tank "WT?!"s bump I dont remember any ground bolts or wires when we dropped the tank. It worked before we dropped it.

08-13-2006, 10:25 PM	#8
magnethead 7000 #'s of american IRON Join Date: Dec 2004 Location: north tx Posts: 883	Re: Left tank "WT?!"s these are the only pics that I have showing the tank and it's mounting area..

08-13-2006, 11:04 PM	#9
boxrodz Until Seventy Times Seven Join Date: Feb 2005 Location: Rocky Mountain Front Range Posts: 1,301	Re: Left tank "WT?!"s I noticed you didn't mentioned that when you dropped the tank, you loosened the sending unit ground from the frame. If that's the case, maybe you accidently pulled out the ground wire when you dropped the tank. Unless the configuration on your truck is different, the sending unit ground wire passes thru the frame rail and is grounded on the inside of the frame rail about an inch forward of the rear cab support bracket. If the sending unit is not grounded, the fuel meter would behave as you noticed (in the 3 o'clock position). Attached Images __________________ boxRODz 1983 C10 SWB Fleetside When two halves is gone, there's nuthin left. Two nothings is nuthin. That's mathematics son. You can argue with me but you can't argue with figures. Two half nothings is a whole nuthin... Last edited by boxrodz; 08-13-2006 at 11:13 PM.

08-15-2006, 07:55 AM	#11
magnethead 7000 #'s of american IRON Join Date: Dec 2004 Location: north tx Posts: 883	Re: Left tank "WT?!"s hmmm....ok. Do any tank support bolts hold the wire or is it a seperate bolt?

08-15-2006, 08:33 AM	#12
Captkaos www.73-87chevytrucks.com Join Date: Dec 1999 Location: Birmingham, AL Posts: 6,935	Re: Left tank "WT?!"s It is a seperate bolt and it typically goes to the top of the framerail __________________ Chris Lucas 1973 Chevy C-10 1978 GMC Jimmy (2WD) - SOLD 1987 R10 twin turbo LS 1991 R3500 SRW CrewCab 1985 K5 diesel swapped project 1989 K5 2WD conversion w/ Vette susp Project Captkaos Customs 73-87chevytrucks.com

08-15-2006, 02:51 PM	#13
boxrodz Until Seventy Times Seven Join Date: Feb 2005 Location: Rocky Mountain Front Range Posts: 1,301	Re: Left tank "WT?!"s Chris - The ground wire on the 83 is bolted to the inside of the frame rail with a 'large' tapered bolt near the rear cab support bracket. The wire passes through a ~1" hole in the frame rail lined with a rubber grommet. I wonder if the configuration is slightly different for different years and models of the 73-87 trucks, especially for a dually.? __________________ boxRODz 1983 C10 SWB Fleetside When two halves is gone, there's nuthin left. Two nothings is nuthin. That's mathematics son. You can argue with me but you can't argue with figures. Two half nothings is a whole nuthin...

08-15-2006, 04:58 PM	#14
Captkaos www.73-87chevytrucks.com Join Date: Dec 1999 Location: Birmingham, AL Posts: 6,935	Re: Left tank "WT?!"s They must just put it where they can then. All the ones I have ever pulled out had them behind the body mount on the top of the frame. This included my '73, the 75 I had, the 80 and my DD 87 model. Regardless of where you put it to ground, the gauge won't work without it. __________________ Chris Lucas 1973 Chevy C-10 1978 GMC Jimmy (2WD) - SOLD 1987 R10 twin turbo LS 1991 R3500 SRW CrewCab 1985 K5 diesel swapped project 1989 K5 2WD conversion w/ Vette susp Project Captkaos Customs 73-87chevytrucks.com

08-15-2006, 07:28 PM	#15
magnethead 7000 #'s of american IRON Join Date: Dec 2004 Location: north tx Posts: 883	Re: Left tank "WT?!"s I'll look at it nextime I have time.... Here's a tidbit. I revved my engine to 4400 (spiked to 4200, held at 2600-3000 for 5 seconds, spiked to 4400) Showing off i guess you could say and the oil pan is still in 1 piece....

08-17-2006, 04:27 PM	#16
piecesparts Parts and more parts Join Date: Nov 2003 Location: Lebo, Kansas (middle of nowhere Posts: 6,821	Re: Left tank "WT?!"s I would say that revving the engine is definitely a non-GOOD thing. Unless you have the motor loaded and the tranny is taking the torque that is being generated from the pistons to the crankshaft (ERGO--massive tire burnout). This type of evolution could find the weak spots in your lower end. Just free-wheeling the RPMs will give a lot of wear to the rod bearings. As for the cyclic performance of the motor from that tank, did you check the filter sock on the tank's pickup line? There were problems with this sock getting to the point that it would suck up to the suction line opening and restrict flow of fuel to the fuel pump. Just a thought....

08-17-2006, 04:38 PM	#17
magnethead 7000 #'s of american IRON Join Date: Dec 2004 Location: north tx Posts: 883	Re: Left tank "WT?!"s we didnt remove the sending unit. we only changed fuel lines. We kept the tank itself together.



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