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Paul Workman · 03-19-2012

Quick current draw check to verify normal pump operation:

1) Leave the ingnition switch in the OFF position and set the VOM to the 10A setting with the RED lead PULLED OUT of the VOM (protects the meter)

2) Connect the RED lead PROBE end to the POS terminal of the battery and connect the RED lead METER end to the "A" connection on the VOM

3) Connect the black lead of the meter to the RED pump TEST POINT near the diagnostic plug on the wire harness (near the ECM).

You should hear the pumps come on as soon as the connection is made to the pump TEST POINT (RED wire with the black connector - a yellow alligator clip connects the test point on the harness to the black lead of the VOM in the picture). Each pump draws between 4-5 amperes. In the photo we see both pumps are running as the current draw (both are Airtec pumps in this example) is well in excess of 8A; commiserate with current draw of two pumps.

However, if the current draw is ZERO, then neither pump is running - not your situation, but if the current is only 4-5A, then one of the pumps is not running. Logically, since it is the secondaries that are having the problem, then the secondary pump fuse (under the passenger hush pannel) is suspect and you'll need refer to the FSM to check it.

Once both pumps are running, fuel pressure should be about 52 psi, but verification is best done with the FP gauge taped to the windshield and checked over a few quick WOT pulls. This will verify the pumps are working under load, and the fuel filter (on the passenger side frame rail, roughly in line with the door hing line) is not impeding FP/flow.

Another thing to verify is are the secondary throttle plates actually opening on demand?

One thing at a time, I recon...

P.

03-19-2012	#7
Paul Workman Join Date: Nov 2007 Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri Posts: 6,466	Re: Major Engine Miss above 3K Quick current draw check to verify normal pump operation: 1) Leave the ingnition switch in the OFF position and set the VOM to the 10A setting with the RED lead PULLED OUT of the VOM (protects the meter) 2) Connect the RED lead PROBE end to the POS terminal of the battery and connect the RED lead METER end to the "A" connection on the VOM 3) Connect the black lead of the meter to the RED pump TEST POINT near the diagnostic plug on the wire harness (near the ECM). You should hear the pumps come on as soon as the connection is made to the pump TEST POINT (RED wire with the black connector - a yellow alligator clip connects the test point on the harness to the black lead of the VOM in the picture). Each pump draws between 4-5 amperes. In the photo we see both pumps are running as the current draw (both are Airtec pumps in this example) is well in excess of 8A; commiserate with current draw of two pumps. However, if the current draw is ZERO, then neither pump is running - not your situation, but if the current is only 4-5A, then one of the pumps is not running. Logically, since it is the secondaries that are having the problem, then the secondary pump fuse (under the passenger hush pannel) is suspect and you'll need refer to the FSM to check it. Once both pumps are running, fuel pressure should be about 52 psi, but verification is best done with the FP gauge taped to the windshield and checked over a few quick WOT pulls. This will verify the pumps are working under load, and the fuel filter (on the passenger side frame rail, roughly in line with the door hing line) is not impeding FP/flow. Another thing to verify is are the secondary throttle plates actually opening on demand? One thing at a time, I recon... P.