02 silverado 4.8 fuel pump

My engine was hesitating and now won't start, no fuel pressure at test fitting, removed fuel pump and test on bench. In upright position it will not run but lay it on it's side and it will. Is this confirmation I need a new pump? Also I get no power at connector for pump in any of the 4 pins. The service manual says the pcm will de-energize the relay to fuel pump if crankshaft rotation is not detected but shouldn't there be power for a few seconds at the beginning? Thanks for any help.

Reply to
mark
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No.

Yes, there should be. Go to the relay and make sure there is power there too.

--scott

Reply to
Scott Dorsey

Could you elaborate, why would the pump act like this? Also I should have mentioned that for the last few months the pump has been making a louder noise than it used to.  

How do I check this, the relay has 4 pins, do I just check for power at these pins, how many should light up?

Thanks again

Reply to
mark

Could just be worn brushes.

What you have are 2 wires that power the pump, one power one ground. The other two go to the level sensor.Since you have the pump out you can easily look at it and discern which wires do what. Just follow them to the socket. The two that power the pump should have power for 2-3 seconds when you first turn on the key. If they don't then check the FP relay and fuse.

Reply to
Steve W.

I figured out how to check the relays as per the service manual and they are all good, it takes me about 5-6 seconds to jump out of the truck and test the connectors after I turn the key so maybe I am not fast enough, I will have to extend the wires so I can see the test light from the drivers seat. I took the actual pump out of the plastic module housing and it is not servicable the top and bottom of the metal pump body are crimped, there is no way to disassemble it. I found a new pump for 323 canadian (Napa wanted 790).

Reply to
mark

_______________________________________________________________________

mark wrote: (2002 Silverado 4.8 Fuel Pump) . . . . I found a new pump for 323 canadian (Napa wanted 790). _______________________________________________________________________

If you definitely must buy a fuel pump, look at the Rockauto.com website for Silverado fuel pumps at USD$149.70 to USD$300.79. One of these may match your unit's part number.

Good luck.

Rodan. ______________________________________________________________________

Reply to
Rodan

5-6 seconds is WAY too long. 2 seconds is what you have. What I use is a simple 12 volt buzzer. No need to look at all.
Reply to
Steve W.

Some of those things have tip-over switches that shut off the pump unless it's in the correct position. This is a safety feature so if you roll your car over, the gas shuts off.

You're going to need a wiring diagram. The relay has a winding.... there should be 12V across the winding when it's closed. It also has two contacts... one contact should have 12V on it, the other contact is connected to the pump and should have 12V on it when it's closed also.

The wiring diagram will tell you the pinout and where all the individual wires go.

--scott

Reply to
Scott Dorsey

snipped-for-privacy@panix.com (Scott Dorsey) wrote in news:gj31i7$hcc$ snipped-for-privacy@panix2.panix.com:

wire color = gray from relay to pump connector

Reply to
bill

Reply to
man of machines

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