The Craftmans Shop > PowerSports
Reducing Fuel Consumption of an 30 Year Old 8 Cylinder Pickup Truck
vtsteam:
I've recently resurrected my 1996 Chevy Silverado 4WD pickup truck. She had been sitting in a field for four years with multiple issues, including, the need for new ball joints, new front axle hubs, new 4WD actuator, new front disks and rotors, rebuilding of the frames under the pickup bed, new rear bumper, new rear cab mounts, new emergency brake cables, new steering box, new upper control arms, new battery, new fuel tank, and patching a number of rust holes by welding in patch panels. I did all of that last summer.
Why did I do all that? I don't know. I like the truck. I don't know why. It feels good to drive it again. It feels good not to have brought it to a wrecking yard. It actually looks solid now, and drives very nicely. It does hard work around here, hauls cords of wood, steel shapes, and sand for when I have to deal with 600 feet of driveway after an ice storm. The poor thing deserved a second chance.
I like that truck. Despite all the time and money I put into it, it's a tiny fraction of what a new 21st century annoying piece of digitized plasticized oversized hype in the form of a pickup truck would now cost me. The only thing I don't like about it is..... it's original, when acquired used, average fuel consumption of 15 miles per gallon.
Well, I'm going to do my best to change that. In fact, even with no changes, other than adding a bluetooth monitor to the truck's OBDII port that communicates with my cellphone, I am able to monitor fuel consumption on the fly, as well as about a hundred other engine parameters, and have changed my driving habits to the point where average fuel consumption is about 18 mpg presently.
But that's just a start. I have plans. :zap:
The first one is, ummm, reprogramming the truck's computer, or PCM as it is called. Well actually not that one. I'm thinking about trading its old PCM for a later one, because it is more programmable with open source and free software called UniversalPatcher, PCM Hammer, and TuneRPro.
To make the swap, I would have to re-pin new connectors onto the old wiring harness, and this isn't a trivial undertaking as the old and new connectors are different styles (and number -- 5 in the old and 2 in the new) and have a total of 128 pins, with no correspondence of positioning for the wires.
Rather than re-pin the connector -- which is not easily reversible if I don't like the swap, I've decided to try to make an adapter cable.
More later......
cwelkie:
Well done on resurrecting the "ole girl". There are still many years of service available yet. It's always nice to hear of someone else that is of the opinion that it's cheaper to maintain than replace a vehicle. Besides, it's got to the point where one can't operate any "dash board controls" with gloves on in a new vehicle!
Building an adapter cable is likely the best way to go. It reminds me of installing a Ford V8 into a Volvo 245 (wagon) many years ago. I left the Volvo engine bay cable in place and added the Mustang cable alongside and connected to two together at the appropriate places.
Good luck with your quest ...
Charlie
AdeV:
If you really want to avoid the electrodigicals... you'd be better off with a 1966 Silverado with a quadrabog carburettor....
Extra points if you can tell which YouTube channel I've been watching way too much of, perfect!
vtsteam:
Thanks kindly, Charlie! :beer: What I like about the old truck is that it is very easy to work on, and parts are super available. You could practically build a new '96 Silverado from available parts.
I do like the fact that it is heavily built, though that tends to mitigate against fuel economy. But it does mean that the frame has lasted in the Northeastern winters where salt on roads is heavy. Most vehicles here die, not from mechanical issues but rust. This truck was somehow preserved when I bought it years ago, and after the repairs I now undercoat it with a commercial oil compound each fall to keep it that way. I've also reduced driving it in winter.
The cross frames under the bed were rusted away at the ends, since they were thin hat-shaped sections spot welded to the bed floor -- almost designed to rust. Last summer I pulled the bed off, ground them off, and replaced with much heavier steel square tube. The bed itself was fine, since it had a bed liner and someone had smeared grease under it before installing.
Square tube for frames:
A fabricated X main frame cross member and spare tire winch from channel iron:
Fair warning, the adapter cable Idea is kinda iffy for a lot of reasons, including fit in the space available, signal noise, and just the sheer difficulty of the solder work needed for all these crossing lines. We'll see. It's a real madmodder project, and may even seem a waste of time to a few. Not for me. I like learning things along the way, even if it turns out that a project idea isn't workable.
BTW, the cable is not intended for regular use. It's just for experimenting while deciding if I want to commit to a re-pin and the newer PCM. I could end up staying with the old one, if I don't like the change
Most people contemplating a PCM swap like this one are after increased performance, and that has clearly been achieved by others -- generally in combination with other mechanical changes like headers, air induction, etc. But my goal is solely in increasing fuel economy in an otherwise stock vehicle, and that is a questionable hope for a PCM swap. We'll see. No one else has done it for this purpose that I'm aware of. so it's a crap shoot.
vtsteam:
--- Quote from: AdeV on January 22, 2025, 04:21:52 PM ---If you really want to avoid the electrodigicals... you'd be better off with a 1966 Silverado with a quadrabog carburettor....
Extra points if you can tell which YouTube channel I've been watching way too much of, perfect!
--- End quote ---
HaHa Ade, I know exactly who you mean! Well rust here means that '66 Chevy pickups must be distant memories, at least within several hundred miles, and if they do exist, people want crazy money for clapped out rustbuckets of that vintage locally. For some reason, you can still find early nineties Silverados for $4K to $5K and occasionally not in bad shape within the neighboring states.
I'm pretty comfortable with the PCM in my truck -- heh, '96 is the computer era, when you think about it, earlier even than Windows 98. it's DOS era. It's really interesting how sophisticated nevertheless these control computers were for their time.
Here's the kind in my truck, called a "BlackBox" PCM by Chevy enthusiasts. This one is a junkyard donor box, which I am robbing for the connectors:
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