Fuel Pump Voltage Problem

[John Dozer]

Our fuel pump seems to be losing voltage while running. We seem to be losing pressure and power while the engine is running. The fuel pump is strong enough to run the vehicle, but we seem to be losing juice, while it is running. Why is the fuel pump losing power with the engine running? Would a new relay possibly fix the problem or could it be a ground issue that might be the problem? Tomorrow I'm going to try and run a lead wire to check the voltage to the pump with engine running in drive position. To see if there is a drop in voltage that causing the pump not too reach its full potential.

Question: What is the voltage for the OEM fuel pump supposed to be at the pump?

Here are the specs on the aftermaket fuel pump we are using:

Brand Summit Racing
Manufacturer's Part Number SUM-G3138
Part Type Fuel Pumps, Electric External
Product Line Summit Racing® High-Flow Electric Fuel Pumps
Summit Racing Part Number SUM-G3138

Free Flow Rate 43 gph
Maximum Pressure (psi) 85 psi
Inlet Size 5/16 in.
Inlet Quantity One
Inlet Attachment Nipple
Outlet Size 5/16 in.
Outlet Quantity One
Outlet Attachment Male threads
Quantity Sold individually.
Notes Fuel pump overall length is 7.250 and diameter is 1.812.



Multi-port EFI systems need a stable fuel supply at any rpm, and Summit® high-pressure, high-flow electric fuel pumps supply it. They feature a free-flow rate of 43 gph at up to 85 psi. Summit® high-flow pumps also have 5/16 in. inlet and outlets, brass stud terminals for secure connections, and two included cushioned clamps for inline mounting. They're ideal as stand-alone pumps for multi-port EFI systems on engines making up to 500 hp, or as boosters for nitrous applications. Mounting bolts are included

 

[MrShorty]

Question: What is the voltage for the OEM fuel pump supposed to be at the pump?

It should be steady at battery/alternator voltage (12-14 V).

When I've tested while driving, I've preferred to initially test at the inertia switch (to the right of the tranny hump by the passenger's feet). Just easier to get to than the tank connector.