1990 GMC K1500 No Uphill Power Part 2

[ChevyTech]

The son of a friend on mine had two fuel pumps fail under warranty from the local auto parts store and asked me what is going on. I convinced him to cut the fuel pump open instead of turning it in for warranty. We then compared the impeller from the auto parts store pump to an impeller from the original factory pump. The factory pump impeller had about twice as many veins (fingers). It took no more talking to convince him to go buy a quality pump. They owned the truck several more years and never replaced the pump again.

The fuel pressure on TBI trucks should not fluctuate.

My guess is the new regulator spring brought the pressure up a bit, but the problem was a weak pump. Most springs being sold do not match the stock spring and will raise the pressure a few pounds. If you replace the pump with a quality pump you may find you need to change the fuel regulator spring back to a stock one, if it is a spring designed to raise the pressure a little over spec.

Fix the fuel pressure, and the code 43 could go away, if it is caused by a little pining from a lean mixture, from low pressure.