96 Chevy Lumina - Fuel Pump or Pressure Regulator

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  #1  
Old 10-29-07, 09:59 AM
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96 Chevy Lumina - Fuel Pump or Pressure Regulator

I have a 1996 Chevy Lumina Sedan with a 3.1 engine. Over the last couple of weeks I started having problems cranking the car when cold. I changed the fuel filter guessing that maybe flow was restricted, but it did not seem to help. Finally last week I was driving at highway speed and the check engine light came on and I felt a loss in power. When I came to a stop I noticed a very rough idle and some clicking noise for a little bit which sounded like an injector. The clicking subsided, but the rough idle continued. I pulled off the road and used my scan tool to check the engine codes. A 301 code was read which my tool reports is a misfire on #1. I had the car towed home as I was not sure if I could damage my engine driving it that way.

Anyhow I ran some fuel pressure tests over the weekend and found these results.

Static Fuel pressure when turing on the key before cranking is low varies between 20-25psi. According to my Hanes manual it should be around 47. I think this explains my hard starting.

After several tries I can still get the engine to start and running fuel pressure is around 43psi.

What is the most likely cause of a failure like this? I'm guessing one of the following. Weak pump, Bad fuel pressure regulator, Leaky fuel injector?

Thanks,
Ryan
 
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  #2  
Old 10-31-07, 02:07 PM
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Try cycling your key for three or four times while you watch the pressure. If you can get it up to 43 by doing that, turn the key off and see if the pressure drops significantly.

If it does the lean would be toward the regulator, but all things you've mentioned are possibilities.

Hope this helps,

Bob
 
  #3  
Old 10-31-07, 03:42 PM
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I was re-reading your post and saw you had a 301 code. I can't say a general fault like regulator = low rail pressure would bring on that code. I believe the leaky injector = low pressure could though.
 
  #4  
Old 10-31-07, 04:05 PM
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Injector check

Its easy to check the injector and clean it at the same time. Pop the injector out, use solvent (carb cleaner), and a 9 volt batt to confirm the injector is working properly. Fuel pumps work or not as a rule. Ceck the injector(s) first. Regulator going bad should be "noisy".
 
  #5  
Old 11-09-07, 05:53 AM
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Problem Found

Thanks for the replies everyone! I was pretty off on this one. Although my static fuel pressure is low it does build a little when cycling on and off the ignition.

It turns out the one of my Valve rocker arms on #1 was loose and caused the push rod to detach! Luckily no damage to the rod was done as far as I could tell. I've fixed the issue and reassembled the engine and everything is well now.
 
  #6  
Old 11-13-07, 08:48 PM
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Problem Back!

It is always extra fun when you really have two issues instead of just one! My fuel pressure problem is back, but I no longer get the misfire since I fixed the loose valve rocker arm. Here is the deal.

I replaced the FPR when I did the rocker arm since I suspected a fuel pressure issue and had most of the engine already apart. I have to assume that my pump must be failing.

This evening I connected my fuel pressure gauge to the test port and first ran a static test. First time I turned the key pressure went to about 20 psi, should be in the 40's. So I turned the key off and then back on. Pressure increased to 30psi. I tried it again and it would not go higher than 30psi. I attempted to start the engine and it started! Pressure stabilized around 40psi. I removed the vac hose from the FPR and pressure increased about 7 psi. Then I turned off the engine. Depressurized the fuel system and attempted to start the car on one turn of the key. It would not start and fuel pressure refused to rise after multiple key cycles.

Could this be a failing pump? I don't think it could be a bad electrical connection, because if I get the car to start it normally runs fine, although pressure is still lower then my manual says it should be.

I'm planning to replace the fuel pump next.

Thanks
 
  #7  
Old 11-19-07, 10:56 AM
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Fuel Pump was dying and fuel vapor lines deteriorating

It turned out to be the fuel pump! I swapped it out the other day and my static pressure will now rise above 45psi when I turn the key on! Starts great now.

I did notice that my fuel vapor lines by the tank were starting to deteriorate. When I twisted them a bit to take them off some rubber flaked off the outside. The inside seemed fine still. Should these lines be replaced and how dangerous would it be if one was leaking? Since they are fuel vapor lines I do not know if I could detect a leak.

Thanks
 
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