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Fuel pumps go bad. At 100,00 miles get ready. Can do your self if you drop tank. Make sure all connections are good. Just turn key to on, you will hear pump. Might take 2 people. Make sure you are in place near pump to hear.
 

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2002 chevy trailblazer_lt
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Discussion Starter #22
Thanks Chris.
TEST NEW PUMP: With the tank removed and out of the way, can the new pump be plugged in, the ignition turned On (no crank) and hear the elusive hum to confirm 1) new pump good and 2) wiring good?
 

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Had to retrieve my floor jack from a forgetful friend... Got the rear end up on jack stands and cider blocks under tires. Relay working. Jumped relay plugs (lower right to upper left); no hum, no start when cranked. Can't get a meter on the plug at the relay without dropping tank, so...
The good news is the vehicle is at 307K, so got mu' monies worth. Bad news is good options run about 300+ scoots.
Any advice?
Thanks Chris.
TEST NEW PUMP: With the tank removed and out of the way, can the new pump be plugged in, the ignition turned On (no crank) and hear the elusive hum to confirm 1) new pump good and 2) wiring good?
Yes, you can. Doesn't last long, but you will hear something. Stay close to tank. Be careful. The noise means things are pressurized
 

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Discussion Starter #24
Yes, you can. Doesn't last long, but you will hear something. Stay close to tank. Be careful. The noise means things are pressurized
I meant with the tank away from the vehicle. New pump plugged in by itself under the vehicle (supported, or course) just to confirm before installation and tank re-mount.
 

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Discussion Starter #26
Good point. Maybe I could just put a meter on the plug and check that there is a power reading for that 1-2 sec pre-start interval. That'd be a little piece of mind before reassembly.
 

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New battery about a month ago. Started on first try, like usual. Now, when ignition is turned on there is no 2-3 sec hum or buzz. I assume that's the fuel pump not priming.
We definitely need more information.
Like How long was the old battery un-connected before connecting the new battery?
Was the Old battery completely Dead for awhile before unconnecting it?

If the vehicle had low power, or no power for 30+ minutes, you could assume, that the vehicle had reset- and is re-training / re-learning itself.
You probably have a clogged air filter, and dirty mass air flow sensor/tube, and greasy/sticky throttle body Coin Flipper thingy.
If you haven't replaced your fuel filter in the last 7 years, I would install a new one of those also, there very easy to replace, takes 5 minutes tops.


Also I had a 2005 Trailblazer with the 4.2, I couldn't hear the fuel pump kicking in, while I was inside the vehicle.
Could only hear it, when i put my head near rear tire.

If your talking about the Humming Noise under the hood when you turn your key, thats something else.
I forget what it was, but it wasn't fuel related. Could be washer fluid pump starting up, otherwise Starter as well.
 

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I corrected my initial response concerning the initial KOEO 2 second prime in my response right before your post. Mitchel On Demand actually doesn't clarify initial KOEO priming. If you want to sling a little mud my way for a little misinformation fine but when I visit these DIY forums they are chalk full of mis-information & mis-guided diagnostics.
Mitchel On Demand is not chalk (sic) full of bad info, but most sites would have a cadre of either retired professionals versed by the moderators or currently working in-the-field techs who make corrections of bad advice.

There are a few actual techs who jump in here once in a while (I've met a couple myself, in a Corvid-way).... their days are full of correcting customer's pretzel logic .... all the way to full on voodoo exorcisms.... but letting a wrong statement stand for a day does not appear to be much of an immediate retraction.... not to me anyway.

I don't need to take any lip from someone who justifies falsehoods with their own un-timeliness and then blames it on a lackadaisical site

I'm outta here.... you guys can have all the fun you want, BS'ing each other into oblivion.... I've got better things to do than roll around in the mud with ignorance that defends itself by character assasination when it gets caught.
 

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Discussion Starter #32
Wish I was helpful. Good luck.
Got a Delphi fuel pump installed. Doesn't make an audible whining sound when ignition is ON (no crank), but I hear a click after 1-2 sec. Perhaps the new pump doesn't whine. With ignition off I disconnected the fuel filter OUT line and got a small spray and 2-4 oz of fuel from line. I'll get a loaner pressure tester from AZ, but the line/filter was full of fuel under enough pressure to spray when disconnected. Fully charged batt cranks engine fine, but no ignition.
 

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Discussion Starter #35
No fuel pressure at test port on fuel filter. Relay ports checkout per video above ie batt power, ECM power, ground and no pump activation when jumped. So it seems that wiring or (new OEM) pump issue.
Any known issues or suggestions on course of action?
I would figure dropping tank midway down to unplug the pump harness and test for power. Four pin plug, I believe.
After that I would need to bench test the new pump; not sure of best practice to bench.
 

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Listen for the electric fuel pump in the fuel tank to make a buzzing noise when the ignition is turned on (you may have to open the gas cap to hear it). You won't hear anything if the pump has died.
 

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Discussion Starter #37
New pump. Plugged it in and it turned on (very quiet) while I held it. It whirled to prime but won't start. Is 2 gallons of fuel enough after I cleaned and dried tank? Turned key On for 5+ seconds 10 or so times to prime empty line. Ideas?
 

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It really takes about 5 gallons to prime correctly., since there needs to be enough fuel to actually fill the small reservoir inside the pump cartridge itself.

The click after a couple of seconds is the Time-Out Safety Disconnect Relay, dropping OUT. It would have to have been ON for it to click OUT at time-out.
This is a safety device for a rollover accident or if you leave the key ON and the engine's not running.​

You may not hear the pump but you can certainly test the B+ going to it at the relay under the hood. Brand names up- or down- quality would make little difference in pump noise.

For testing purposes, you can swap relay #41 with relay #58. Actually ... any of the mini relays are interchangeable... but obey their orientation and 5th pin configuration!

So-oźo ... if you have a good relay (Relay #41) ... and B+ at both ends of the fuse that serves the Relay and(pin 30 to 87, which is N/O unless pins 85 to 86 are activated with 12VDC and a GROUND) circuit at the relay, there might be a problem under the vehicle where the wires break out from the floor to the Weatherhead connector with both the ECS, the Pump B+, the fuel level sending unit.
FYI Pin 87a is N/C whereas #87 is N/O. Make a note of that,, TV​


Did you get the new electrical connex with the new pump? This is a critical part to install in replacing the pump.... because many times the previous pump pulled too much amperage, and the small pins burned up.
 

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Turned key On for 5+ seconds 10 or so times to prime empty line. Ideas?
I would start over and do the normal crank-no-start procedures. Spray some starting fluid in the air filter box then try to start the vehicle. If it starts then dies you have a fuel delivery issue. Get a pressure tester and test the fuel pump pressure.

If the starter flhid sprayed in the air filter box doesn't change anything and there is still no attempted start from the engine then your issue is likely a no spark issue.
 

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I agree with TJ here.... try the ether... but use it sparingly.... better still, use a carb cleaner since it is designed to burn decently under combustion pressure. Ether is for diesels... and they too can be damaged by overzealous use.

The idea of priming the fuel system by repeatedly turning the key on for a few seconds is a false flag.

All the priming this system needs is accomplished in one cycle.
 
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