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Dan, Technician
Category: Chevy
Satisfied Customers: 24582
Experience:  Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database
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I have a customer with a 1998 tahoe 5.7. And it is having a

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I have a customer with a 1998 tahoe 5.7. And it is having a fuel delivery issue. It will run fine for a bit then it will start to bog down and not accelerate seems to backfire if you really give it throttle, just like the fuel pump is bad. I scanned for codes and no codes. I put a pressure gauge on it and the pressures are within spec, until it acts up. Once it acts up the pressure drops to about 52 psi and stays there, no matter how much throttle you give it. Here's the weird thing, It will act up a couple times, then it will drive fine for a bit, then it will act up again, and so on and so forth. I'm wondering if we have a pressure regulator issue, and not a fuel pump issue, I know these vortec's are very touchy when it comes to their fuel pressure, I'm wondering if there is a suitable way to isolate the regulator, therefore letting me do the proper diag whether its the pump, or the regulator, Personally, I'm leaning towards the pump, but I'd like to be 100% sure.
Any information would be appreciated

Hello, my name is ***** ***** I'm here to help get your problem solved.

Have you monitored pressure when it runs good and compared to when it bogs?

Customer: replied 28 days ago.
when its running good, the pressure is about 55-58, and when you throttle it, it goes up to 60+

Thanks for info, this most likely means fuel pump is problem as pressure regulator wouldn't be intermittent. Since problem is intermittent it would be hard to test to be 100% sure but I'd feel safe replacing the pump. I'd go ahead and replace the filter first then if problem still exists replace the pump. To know for sure you could check pressure at filter during problem, if good at filter but low under hood this would mean regulator. If low at filter this would mean the pump is problem. But I'm assuming it runs better when cold so pressure might test out fine by the time you were able to test at filter which is why I'd just replace the pump. Let me know if you have more questions, thanks.

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