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sprinkles08, ASE Certified Technician
Category: Chevy
Satisfied Customers: 22653
Experience:  ASE Master and Advanced level certified. Factory trained with 15 years dealership experience
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Tidmore fuel pump, 1990 s10 2.5l the fuel pump is not coming

Customer Question

tidmore fuel pump
JA: Thanks. Can you give me any more details about your issue?
Customer: 1990 s10 2.5l the fuel pump is not coming on for the from or to run. I replaced the relay (4wire) fuel pump the icm and still nothing.
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Submitted: 1 year ago.
Category: Chevy
Expert:  sprinkles08 replied 1 year ago.

Hello and welcome to JustAnswer!

I'm assuming fuses have been checked.

The fuel pump may not be running due to a lack of power or ground or a failure of the pump itself. You may have a wiring problem or the powertrain control module may not be awake, or it may simply be a failed fuel pump.

Do you have spark?
Have you tested power and ground at the pump?

Customer: replied 1 year ago.
I have spark and 12 v at the relay. Their is no fuse on the fuel pump i changed fuse ecm b And nothing. I have 8.76 volts countious to the fuel pump connector. I took the fuel sending unit out and I have 8volts to the sending unit. Something is not letting the pump get the full 12 volts?
Expert:  sprinkles08 replied 1 year ago.

You may be looking at the sending unit circuit rather than pump control, there wouldn't be power on the pump control wire without cycling the key or when cranking.

Using an incandescent test light does it light when touching the terminal for the tan/white wire in the fuel pump connector while cranking the engine?

Customer: replied 1 year ago.
With a volt meter you turn the key off its 0.00 volts turn the key on its at 8.75 countious volts to that wire to the splitter block on the unit do we have a schematic for the sending unit?
Expert:  sprinkles08 replied 1 year ago.

What is the voltage at relay pin 87 when cranking?

What is battery voltage when cranking?

Customer: replied 1 year ago.
Which one is relay pin 87?
Expert:  sprinkles08 replied 1 year ago.

Relay terminals are labeled on the bottom of the relay.

Customer: replied 1 year ago.
Okay the voltage that is at that terminal is 11.34 while cranking.
Expert:  sprinkles08 replied 1 year ago.

If the voltage is 11.34v at the relay but 8.75v at the fuel pump then there is a wiring issue in between the pump and relay. The easiest thing to do would be to hardwire the circuit, soldering the connections and sealing them with heatshrink.

Customer: replied 1 year ago.
from the relay to the pump as a hardwire with a switch?
Expert:  sprinkles08 replied 1 year ago.

There wouldn't be a need to install a switch in the circuit, you'd want to run a new wire in place of the old one from the relay to the pump.

Customer: replied 1 year ago.
Okay I'll do that tomorrow and let you know.....would the oil pressure sensor cause this also?
Expert:  sprinkles08 replied 1 year ago.

The oil pressure sensor won't cause voltage drop between the relay and fuel pump.