California Emissions Junk

[4D55 Performance]

I think I have all the answers you're looking for. You state your truck has a non-wastegated turbo which would make it an '83 model year. All '83 model year trucks were non-EGR vehicles. It may say it is California emissions but in '83 that just meant the timing was adjusted to reduce emissions. Some of the later model years like the 84-85 were outfitted with California emissions that included an EGR. The EGR recycled the hot exhaust back into the intake which kills MPG. If you are experiencing poor MPG I would guess that you need to have your turbo, fuel pump and injectors rebuilt. After rebuilding these 3 components you should expect to see 30-35MPG.

[CRIChouse]

I think I have all the answers you're looking for. You state your truck has a non-wastegated turbo which would make it an '83 model year. All '83 model year trucks were non-EGR vehicles. It may say it is California emissions but in '83 that just meant the timing was adjusted to reduce emissions. Some of the later model years like the 84-85 were outfitted with California emissions that included an EGR. The EGR recycled the hot exhaust back into the intake which kills MPG. If you are experiencing poor MPG I would guess that you need to have your turbo, fuel pump and injectors rebuilt. After rebuilding these 3 components you should expect to see 30-35MPG.

Aha, I was hoping you'd chime in. Yes, it's an '83.

So you're saying that there's no extra device, only that the static timing is retarded (in other words, a simple timing advance would put it at Federal spec)? This is my first diesel, so any extra gadgets on the injection pump would go unnoticed by me (unlike EGR).

I'm seeing 24; it doesn't seem to matter whether that's highway driving or mixed (mostly country backroads here, not much stop-n-go). That's pretty much exactly what the EPA says I should be getting.

Could you share what you did to your injection pump to see 32/44mpg? I'm new to diesels but generally competent with machinery; is rebuilding and customizing a pump a reasonable DIY task?