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  #1  
Old 11-19-2007, 07:13 PM
 
Join Date: Aug 2007
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Posts: 20
BradZ01 is an unknown quantity at this point
Default How can I tell if fuel pump is OK?

Hey guys....I need some help if possible. I have been working on some continuing problems for awhile now. I have fixed and replaced alot of parts, but still having problems. I was wondering if my fuel pump or sending unit was bad, but I dont know how to tell. Basically, the engine just wont start. It cranks and cranks, and every now and then after repeated trys, it will spit and sputter a little. Maybe my repeated key turning is putting just enough gas into it to make it sputter, but not enough to make it run. When I turn the key, I can hear the fuel pump run, which I assume means it is pressurizing the system, but when I do what I call the finger test ( aka pushing in the pin in the middle of the schrader valve), I only get one very small spray of gasoline onto my finger. After this quick spray----thats it....no more pressure. Oh, and I am leaving the key turned ON while doing this. Shouldnt it have constant pressure with the key on?

What I have replaced so far is........

FPR, then actually got the entire Spider unit
Plugs
Cap and Rotor
Plug wires
Nut kit
cleaned the EGR
had the ignition module tested.......it is good
Removed cat converter
Fuel filter

All of my issues started after I had a new gastank installed.Ran bad and figured out my FPR was bad. Replaced it and all seemed fine until FPR popped out of place(head broke offmounting screw) and it flooded the engine with gas. I have had it running a couple times since then, and replaced all of those things. Now I cant even get it to start. Is it possible that a fuel pump that is dying out could overpressurize the system, thus contributing to the head breaking off that screw and popping out the FPR like it did?? Maybe not?? I dont know....any ideas?? How can I teat the Fuel pump and sending unit, or is this not likly my problem.. I am stumped and with Xmas coming up, I cant afford to take it to the dealer and get taken to the cleaners with shop rates what they are nowadays.........Please help.. Thanks in advance for any tips.

Brad
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  #2  
Old 11-20-2007, 12:03 AM
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Default RE: How can I tell if fuel pump is OK?

You're "finger test" only shows that you will get fuel from the pump to the fuel rail.
When you turn on the key the fuel pump relay powers up the fuel pump for 3 seconds, then the power to the pump is delivered by the oil pressure switch. If there's no oil pressure ( engine not running) then the power to the pump is cut.
Put away the finger and install a fuel pressure tester. You should get 55-60psi when the pump pressurizes, then the pressure should hold (due to an in-pump check valve)
You need at least 55psi to start the engine.
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  #3  
Old 11-20-2007, 06:48 PM
 
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Default RE: How can I tell if fuel pump is OK?

OK, Thanks for the tip. That helps. I need to find somebody with a tester I guess. Autozone wanted 41.99 for one. I heard Harbor Freight has cheap ones for less than $10.
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  #4  
Old 12-03-2007, 09:39 PM
 
Join Date: Dec 2007
Posts: 2
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Default RE: How can I tell if fuel pump is OK?

i need a diagram for the fuel pump and the fuel pressure regulator. only getting up to 40-43 psi.need to know why or where the leak is coming from? help me!
  #5  
Old 12-05-2007, 08:36 PM
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Default RE: How can I tell if fuel pump is OK?

Typically the fuel pressure tells you if the pump is bad. 40psi would be too low for anything other then a TBI engine. Which only needs 12-15psi.

Autozone has a rent a tool program. Tell them you want to rent it, you give them a cash deposit to cover the cost of the tool if you were buying it, when finished you return it for refund. If you keep it, you already bought it. Pretty good deal.
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  #6  
Old 12-05-2007, 10:13 PM
 
Join Date: Oct 2007
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docta J is an unknown quantity at this point
Default RE: How can I tell if fuel pump is OK?

my fuel pump doesnt pump period. one day i went to start the car and no pump noise. someone told me it was the pump itself, but i think otherwise. so far, i have replaced the entire sending unit along with the pump. i hooked the pump to a battery, so i know that works. the purple wire off the car to the sending unitis hot when i turn the key. i think im getting a bad ground, but i tried re-rigging all the ground wires and the fuel pump is still silent. someone told me that i need a full 12 volts to the sending unit or it wont work. tomorrow im going to see if its getting enough voltage. other than that, someone please help me!!! there's snow on the ground and i dont have a car right now!!!

thank you

p.s. sorry for hijackingthis forum for my problems
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Old 12-05-2007, 10:13 PM
 
 
 
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20, 2006, 43, 94, blazer, diagram, dying, fuel, giving, problems, psi, pump, s10, schrader, sputtering, trailblazer, valve


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