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Tim Basham
Tim Basham, ASE Certified Master Technician
Category: Chevy
Satisfied Customers: 743
Experience:  30 years multi line tech ASE cert master tech ASE engine machinist, 9 years GM dealer exp.
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Fuel system diagram

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93 Chevy Astro Van CE fuel pump will not start/engage. Already replaced fuel pump relay, fuse is fine. How would I know if fuel pump has failed? What other electrical items with relation to the fuel system should I be looking/testing for?

You need to check fuel pressure to verify if system is building enough pressure. Remember the fuel pump only runs momentarily to charge the system then comes back on once engine starts. Below see test procedure.

Also check all connection at pump and pass through on sending unit for any signs of heat build up.

Customer: replied 11 years ago.
Reply to Tim Basham's Post: Tim there are 3 wires that run back to the fuel pump should there be any kind of voltage present with the ignition switch on? The van will not turn on to be able to run through the check list you sent. I beleive it might be electrical or worst fuel pump failure. There is 12 volts present all the time at the fuel pump relay but when I switch the ignition on no other legs energize (new relay just installed). I am at a loss and a little frustrated :(. Where would the fuel pressure regulator be located at? I am new at this so please bare with me.

The 3 wires to your sending unit purple is fuel level signal to cluster,gray power to fuel pump, black/white ground. Below is the basic circuit for the fuel pump relay. the Ecm controls the relay and the ecm b fuse supplies voltage to relay. Find the fuel pump test lead and apply battery voltage to it and see if the pump runs.

As far as regulator do you have a tbi system or cpi system if your not sure then get me the 8th digit of vin it will either be a w (cpi) or z (tbi)

Customer: replied 11 years ago.
Reply to Tim Basham's Post: Sorry Tim it's a TBI. Is the fuel pump test lead a grey wire with a connector black connector on the end taped up on the the connector going into the fuel pump relay? Tim I just cut into the harness leading to the fuel pump I applied 12 volts (grey wire) there and nothing, fuel pump did not engage. Was I correct in doing so? Did the ignition need to be in the on position while applying the 12 volts?
if you applied 12 volts to the gray wire where it goes back to the fuel tank and pump didn't run then you have either a bad pump or a wiring problem between there and the pump. Fuel pump failures are fairly common along with problems with the harness connections at fuel tank and sending unit pass through. Inspect all connections for signs of heat build up or corrosion. As for the pressure regulator it is on top of the throttle body. I bolts onto it. It sounds like you will need to inspect the wiring harness and then mst likely drop the tank and pull the tank unit.
Customer: replied 11 years ago.
Reply to Tim Basham's Post: Tim after considerable trouble and limited space I have dropped the tank and pulled the fuel pump. Tested the fuel pump it runs smooth. Will test section by section of the wiring going to the pump to for any possible problems. After the fuel pump relay, is it a straight shot to the pump or is there anything in between?

Voltage goes from the relay to a splice that connects wires from the fuel pump, ecm, oil pressure switch. I have seen alot of problems where the wires go through the sending unit inspect it closely for and darking as signs of heat build up.

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