FUEL SELECTOR SWITCH-caution

M

michael bozardt

New member
Jan 3, 2007
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My fuel gauge failed. First the main tank part and later the reserve tank part. I managed by stopping every 125 miles for fuel. For over a year, I
could not find the problem. Dropped the tanks, installed new sending units, no change.
For. no apparent reason, I decided to change the fuel selector valve. I had already changed all the fuel filters and fuel pump to no advantage. I
bought the part locally and installed it near where the original fuel selector valve is, removing the original part. When I finally managed to get the
engine running, I noticed the fuel gauges were working. Since someone had stolen my fuel while it was in storage( only 4-5 drops remained of 20
gallons), I added 15-17 gallons of fresh fuel from different containers. The gauges were reading almost half full?????? Surprise, surprise, the fuel
selector valve must have conked out (before the fuel was stolen, I might add). So, if you have a problem with your fuel gauge, this is one more thing
to check, maybe before you pull the tanks, which is not a fun job.
 
Where is this fuel selector switch that you replaced located?

Sent from my iPhone

>
> My fuel gauge failed. First the main tank part and later the reserve tank part. I managed by stopping every 125 miles for fuel. For over a year, I
> could not find the problem. Dropped the tanks, installed new sending units, no change.
> For. no apparent reason, I decided to change the fuel selector valve. I had already changed all the fuel filters and fuel pump to no advantage. I
> bought the part locally and installed it near where the original fuel selector valve is, removing the original part. When I finally managed to get the
> engine running, I noticed the fuel gauges were working. Since someone had stolen my fuel while it was in storage( only 4-5 drops remained of 20
> gallons), I added 15-17 gallons of fresh fuel from different containers. The gauges were reading almost half full?????? Surprise, surprise, the fuel
> selector valve must have conked out (before the fuel was stolen, I might add). So, if you have a problem with your fuel gauge, this is one more thing
> to check, maybe before you pull the tanks, which is not a fun job.
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
Mike,
From my reading of Michael's post, he replaced the fuel selector valve, not the switch as mentioned in the posting title.

Michael, in the OEM configuration, the fuel selector valve has nothing to do with the gauges. However from my recollection, there is a connector back
by the tanks which carry both the fuel gauges and the fuel selector valve wiring through it. It could be that this connector is/was oxidized causing
the fuel gauge issues. When you installed the new fuel selector valve, you may have disturbed this connector cause the contacts to move against each
other removing some oxide and restoring connection.

To troubleshoot, use the chassis wiring diagram for your year of manufacturs. The gauges will read Full if the gauge circuit is Open and Empty if it
is at or near ground. If reading Full, simply ground each gauge wire and the gauge should go to Empty. Trace through to find where your open
connection is. If the gauge always reads Empty, then you have a short to ground. Open the connectors at the Fuel selector switch, then at the rear
connector to isolate where the ground fault is.

Of course you could have an open or shorted tank sensor but at least you know that was the issue before buying and installing a new sensor. Also
remember it would be unusual for both sensors to fail in the same condition at the same time.

The switch and the gauge are common to both tanks, so if both tanks are reading the same condition, I would start with testing the switch (most likely
to fail) then test the gauge right at the back of the gauge.

If you don't troubleshoot right down to the exact problem, then whatever caused the issue in the first place is very likely to re-occur. I hate it
when something starts working before I trace to the exact cause.

On the other hand, if the fuel selector valve is not OEM, then the gauge sensor may indeed run though the valve. I have one of these selector valves
with 6 wires, however I did not wire the gauges through the valve, I just left that OEM.

Just my farmboy mechanic way of looking at it with no formal edgeyoucation in mikanics or enjunearing

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
Hubler 1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
MIchael,

I'm trying to figure out HOW your fuel was stolen. Did they remove the
drain plugs? If so, have you made sure they're properly replaced and
tightened? Did they disconnect a fuel line(s) to drain it? Again, have
you correctly re-connected them?

OR, did they siphon it out? If so, I want to meet them; they're some kind
of magicians, IMHO!

Ken H.

> My fuel gauge failed. First the main tank part and later the reserve tank
> part. I managed by stopping every 125 miles for fuel. For over a year, I
> could not find the problem. Dropped the tanks, installed new sending
> units, no change.
> For. no apparent reason, I decided to change the fuel selector valve. I
> had already changed all the fuel filters and fuel pump to no advantage. I
> bought the part locally and installed it near where the original fuel
> selector valve is, removing the original part. When I finally managed to
> get the
> engine running, I noticed the fuel gauges were working. Since someone had
> stolen my fuel while it was in storage( only 4-5 drops remained of 20
> gallons), I added 15-17 gallons of fresh fuel from different containers.
> The gauges were reading almost half full?????? Surprise, surprise, the fuel
> selector valve must have conked out (before the fuel was stolen, I might
> add). So, if you have a problem with your fuel gauge, this is one more thing
> to check, maybe before you pull the tanks, which is not a fun job.
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
> MIchael,
>
> I'm trying to figure out HOW your fuel was stolen. Did they remove the
> drain plugs? If so, have you made sure they're properly replaced and
> tightened? Did they disconnect a fuel line(s) to drain it? Again, have
> you correctly re-connected them?
>
> OR, did they siphon it out? If so, I want to meet them; they're some kind
> of magicians, IMHO!
>
> Ken H.

Ken,

Maybe we Don't want to meet him.....

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Still Loving OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
Location: Driver's side in the frame rail about18-24 inches in front of the first rear wheel

O-----------OO
| is about the location|
 
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