...but I'm unsure about how to proceed. I got my other problems solved on my '98 Jimmy (HVAC, lock cylinder unlocking) so I've been driving it regularly since Saturday. This morning I noticed a new problem: when I accelerated from a light I left a large cloud of smoke behind me. It looked like the usual post-Seafoam cloud only less opaque. I couldn't tell exactly what color the cloud was; it wasn't white and steamy like boiled coolant. At the time I thought it might have been oil.

I got it home and ran it out in front of the shop. It idled without any noticeable problems but when I hit the throttle hard it spit a bunch of black junk out of the tailpipe. That made me think it was excess gas, not oil. I checked the fuel pressure and it pumped right up to 60psi. After twenty minutes it was down to 40psi. If this were my '94 Blazer or '93 Sonoma with the original Vortec I would know exactly what to do: pull the manifold tuning valve, check for washdown, and replace the spider injectors. I don't exactly know how to check the newer (96+) intakes. I looked at the sticky for the 96+ Vortecs but I couldn't figure out how to check whether the problem was with the fuel pressure regulator or with the injectors themselves as I think they're separate on the newer trucks.

All guidance is greatly appreciated!

 

https://blazerforum.com/forum/tech-articles-diy-29/96-fuel-system-diagnosis-23038/
That should help.

 

I've read through that and I think I know what to do next: check the fuel pressure and leakdown at the fuel filter connection. When I went to the hardware store this morning to get adapters to attach my fuel pressure gauge to the fuel line they couldn't find any pipe fittings to fit. I tried AutoZone and they didn't have anything. I went to NAPA and they told me that the inlet nut on the fuel line is metric—16 x 1.5—and that no regular pipe fittings would work. Is there something I'm missing? Are these parts just not available in Pierce County? Is there some way to test the fuel pressure regulator without first isolating the fuel pump check valve as a possibility? Given that the cloud of smoke appeared under acceleration after idling it really makes me suspect the fuel pressure regulator malfunctioning and letting too much fuel in under those conditions.

 

You can look down the throttle body towards the passenger side. If it looks really clean or shows signs of washing then its leaking and I imagine your fuel economy has been bad aswell.

 

I've only run two tanks of fuel through it in the past six weeks I've owned it. I'm guessing the fuel mileage is bad but since I haven't put it into service yet as a daily driver I don't have actual data.

I tried more this afternoon to find the proper fittings and gave up on that and instead decided to pull the upper plenum and inspect. I found the left side around the #3 and #5 injectors was washed down which suggests a leak either in the fuel pressure regulator or one of the injector nozzle hoses.

It was too late to get into Dr. Injector in Tacoma before closing time to have the injectors tested so I just decided to bite the bullet and replace the injectors. They were the original injectors from 1998. At worst I would be upgrading to the modern MFI system.

It runs much better now and has no more clouds of blue smoke. Maybe tomorrow as a treat I'll replace the rear wiper switch that keeps falling out of the dash.