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2000 Astro Van, no fuel pump power. I've checked both 20a

Sent to Chevy Experts August 20 2008 at 9:10 AM
   

2000 Astro Van, no fuel pump power. I've checked both 20a fuses for ECM-1 and ECM-B, both are good. In the unlikely event that I have a bad relay, I've swapped the Fuel pump relay with the identical A/C relay. I've pulled the connector from the top of the sender assembly and sorted the sender wires from the pump wires. I have no power at gray wire (either B or C on that connector). I know this is the wire that must have power, I just can't figure out why it does not.

 

Optional Information:
2000 Chevrolet Astro 4.3

Already Tried:
Checked ECM 1 and ECM B fuses, both good.

Swapped relays with A/C enable relay, no change.

I've pulled the connector from the top of the sender assembly and sorted the sender wires from the pump wires. I have no power at gray wire (either B or C).

Customer (name blocked for privacy)
Status:  Closed   Value: $15
Answer
August 20 2008 at 9:24 AM (13 minutes and 34 seconds later)
         
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Super Mechanic -- Master technician -- 99% Positive Feedback on 584 Chevy Accepts
29 yrs. exp., ASE master, cert. in G.M. electrical, a/c, susspension, brakes, electronic steering
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August 20 2008 at 9:36 AM (12 minutes and 18 seconds later)
         

OK... this will be helpful and confirms what I knew. I have unplugged 310 and have no power to the gray wire there. I tracked the loom containing the gray wire (as shown in the diagram) back up over the transmission but from there it goes to NeverLand.

 

Your diagrams confirm that there is no other connector somewhere that I'm missing, and that the power does NOT pass through the interior fuse block (as I feared it might)

 

I am begining to think that the relay is not getting any signal from the BCM to run. I'll work from that angle and come back once I prove or disprove.

 

One quick follow up. You say: "Remember, there will only be power at the fuel pump for 2 seconds when the key is first turned on." True, IF the vehicle builds rail pressure. If the pump isn't running and not building any fuel pressure, it would STILL only have power for 2 seconds? I would think that if it isn'm making pressure that the pump would continue to run... thus the wire would stay energized. Just trying to confirm my thinking is inaccurate...

Customer (name blocked for privacy)
Answer
August 20 2008 at 9:44 AM (8 minutes and 22 seconds later)
         
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Super Mechanic -- Master technician -- 99% Positive Feedback on 584 Chevy Accepts
29 yrs. exp., ASE master, cert. in G.M. electrical, a/c, susspension, brakes, electronic steering
Reply
August 20 2008 at 9:46 AM (1 minute and 52 seconds later)
         
Thanks, I was just looking at the schematic sorting out which terminals to test/jump. You've saved me that trouble! I'll report back in a bit.
Customer (name blocked for privacy)
Reply
August 20 2008 at 11:49 AM (2 hours and 2 minutes and 56 seconds later)
         

OK... Now I'm really confused.

 

87 is + always, as expected. From there it is all downhill.

 

86, yes 86 (not 85) is + for 2 seconds after turning ON the key, and for 2 seconds when you turn OFF the key.

 

30 - This is the ONLY place I have ground.

 

Jumping + (either from 87 or from the battery post) to 30 would just make sparks fly.

 

85 is not grounded.

 

From this it seems to me that either we have a short on the gray (120) wire, or that the diagram may be from the wrong model year (highly unlikely, though if 85 is NOT ground, then...)

 

On the upside, after taking out the relays and testing, then putting the relay back, I tried again, and NOW I have power at the connector (310) for 2 seconds after turning on or off the key. Even better I have power all the way to the connector on the pump/sender head... I don't know what is different NOW, but there IS power where before there was not.... The brand new pump still won't run, so I guess it's off to get a different one...

 

Customer (name blocked for privacy)
Info Request
August 20 2008 at 2:50 PM (3 hours and 1 minute and 14 seconds later)
         

It does sound like the new pump may be shorted out, however you will want to make sure that there is a good ground at the balck wire in the back that goes to the fuel pump.

 

You might also try jumping the relay with the fuel pump unplugged to see if it still sparks

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Super Mechanic -- Master technician -- 99% Positive Feedback on 584 Chevy Accepts
29 yrs. exp., ASE master, cert. in G.M. electrical, a/c, susspension, brakes, electronic steering
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