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Fuel Pressure Problems

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27K views 7 replies 4 participants last post by  Barfurd  
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#1 ·
I have a 2005 Colorado with 105,000 miles on it, I've been noticing some start-up problems and now know its the fuel pressure. I bought a test kit and it read that my fuel pressure was only at 15 psi and the truck had only been sitting for about 10 hours. I turned the key to the on position to let the pump run for those few seconds that it does and the gauge shot up to 55 psi. But it immediately started dropping after the the pump stopped. It decreased pretty rapidly; about 5 psi every minute or so. What needs to replaced? I've already replaced the fuel filter, and fuel pressure regulator. Could the pressure be leaking from anywhere else? Personally I think its the check valve part of the fuel pump. Does the fuel pump need to be replaced. Any advice, help, and/or suggestions would be greatly appreciated.
 
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#2 ·
Is it possible to check injectors? Does it seem to run smooth when it runs, not as if it were rich? An injector stuck open will contribute to rapid pressure loss when not energized. But it would be dumping fuel in when you are running causing it to run rough.

That's the only suggestion I have if you have already done the regulator. I am not familiar with the pump or any recirc system our truck have.
 
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#3 ·
You have the classic symptom of a leaking check valve in the fuel pump. It won't hurt anything with the engine running except make it a little harder to start. The hard staring is due to the delay while the pump brings the system back up to operating pressure again. The pump only runs for 3 to 5 seconds when you turn the key on. It is shut off if the engine is not running after that 3 to 5 seconds. If the vehicle does not start, turn off the key and wait for 5 to 10 seconds and try again. This will give you another fuel pump cycle and should give you enough pressure to start.

I have a Blazer here with a bad check valve. When it does not start, I do the above and it always immediately starts on the second try. I should replace the pump but I'm too lazy to do so.

So I'm guessing you have a bad check valve in the fuel pump.
 
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#4 ·
Second on the check valve (very common) and highly doubt the injectors are leaking down. It is good that your pump is still producing 55 PSI on the fly. If the pressure was lower I would definitely suggest you replace the pump. But seeing as you are only losing 5 PSI/min, I'm not sure I would just replace the expensive pump yet.

Would replacing it fix your problem, yes.. can you get a little more out of that pump, yes.. will it need replacement eventually, yes..
 
E
#7 ·
From experience, I highly recommend a OEM Delco pump. I have replaced more warranty Airtex and knock-off pumps than I can even remember. The extra $200 or so pump hurts, but so does being stranded, paying a tow bill, and doing the job twice.

As far as a DIY tutorial, I'm sure some youtube or google searches will turn something up. I have not seen one yet. I do know a lot of people just remove the bed on Chevy trucks (6 or 8 bolts, a ground or two, and a tail light connector typically) to get at it from the top.

I'm sure someone will chime in with more help.
 
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