fuel pressure

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  #1  
Old 07-20-06, 05:51 PM
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Angry fuel pressure

Hi I have a 1995 GMC jimmy 4.3 W engine. Wont Start. Fuel pressure is 60lb with key on but drops to 54 when cranking,hit it with a shot of carb cleaner and it starts and runs fine at all speeds How can I tell if its the fuel pump (changed 6 months ago)or fuel regulator or something else?
Thanks
 
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  #2  
Old 07-20-06, 06:56 PM
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Your fuel pressure is fine according to the figures from GMC. What is your pressure once the vehicle starts? Also, hook up a noid light to one of the injectors and see if you are getting an injector pulse while cranking...



Originally Posted by Digger140
Hi I have a 1995 GMC jimmy 4.3 W engine. Wont Start. Fuel pressure is 60lb with key on but drops to 54 when cranking,hit it with a shot of carb cleaner and it starts and runs fine at all speeds How can I tell if its the fuel pump (changed 6 months ago)or fuel regulator or something else?
Thanks
 
  #3  
Old 07-20-06, 08:41 PM
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The fuel pressure running is 50lbs i have the 4.3 with the cpi (spider injector) under the plenom where do i check with the noid light? Also with key on the pressure is 60 dropsto 40 within a minute is that normal?
thanks Herbie
 
  #4  
Old 07-21-06, 02:52 AM
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it takes 55 psi to start the engine anything less can cause a no start condition on the cpi injection system and it should hold pressure alot longer than a couple of minutes seeing how it isnt flooded from a regulator or an injector leak would suspect that the fuel pump is bad you can pinch off the return line to see if pressure increases probably have to do it near the tank as that may be the only location of a rubber portion of the return line.
 
  #5  
Old 07-21-06, 04:08 AM
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I know exactly what your problem is...the spider itself. It's notorious for leaking. I bet you have an inch of standing fuel on top of your intake manifold. Remove the upper plenum and take a look at it. When replacing the spider...replace the WHOLE unit and all injectors at the same time. It's was some braniac's idea to make that thing of plastic. It sits right there in all that heat and vibration and ends up cracking/leaking. Last time I did one of those jobs I think I paid around $250-$300 for that assembly.
 
  #6  
Old 07-21-06, 05:05 AM
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dont think that his injector is leaking suspect the pump is bad if it was leaking he wouldnt need carb cleaner to start it and it would probably run very bad as it would be flooding the engine.
there is only 3 things that can cause the pressure to drop when you shut off the key after a few minutes, injector assembly leaking, fuel lines going to the injector wich is also under the intake plenum leaking, or a bad fuel pump,
 
  #7  
Old 07-21-06, 06:17 PM
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Smile fuel pressure

Hi guys I opened the relief on the fuel guage and cycled with key on. only got about a shot glass of fuel. I changed the pump. starts fine now. Thanks for all the help.

I Dont no why a $ 85.00 napa pump would only last 6 Months.
 
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