A new DMV registration sticker showed up in the mail recently, which reminded me that it was probably time for a quick update on what it’s been like owning and driving my 40-year-old Chevy Squarebody C10.
For the record, I’ve had the truck for a little over two years now, and in that time I’ve put about 3,700 miles on it.
Solving an Intermittent L98 Tuned Port Injection Problem
The biggest issue I had been chasing was an intermittent engine shutdown at idle. Every now and then, the L98 Tuned Port Injection (TPI) engine would simply shut itself off for no apparent reason. It never happened consistently, which made troubleshooting especially frustrating.
The L98 fuel system is fairly straightforward. Fuel is delivered from the BOSCH external electric fuel pump to the factory fuel pressure regulator and then on to the injectors. Any unused fuel is routed back to the tank through the return line.
What puzzled me was that my cousin Jim had installed a second, external fuel pressure regulator on the return line after the fuel rail. I could only assume he had encountered a problem with the factory regulator and installed the external regulator as a workaround. Getting to the factory regulator isn’t exactly a quick job since it’s located beneath the upper intake manifold, meaning the entire intake has to be removed to access it.
Fuel pressure regulator top center below the distributor
I talked to my buddy Michael about the setup, and after discussing how everything was plumbed, we came to the conclusion that the extra fuel pressure regulator wasn’t serving any useful purpose.
The extra regulator plumbed on the return line
So I ordered a new ACDelco fuel pressure regulator and tore everything apart. Once I removed the original regulator, the problem became obvious. The diaphragm had developed a small perforation. Needless to say, that’s not going to help maintain consistent fuel pressure and hence the shutoffs. I installed the new regulator, put everything back together, and fired it up.
The engine now idles perfectly, and the random shutdowns have completely disappeared. It runs much smoother under WOT and does not hesitate like it used to.
That was a huge relief. An engine that unexpectedly stalls while you’re sitting in traffic or preparing to pull into an intersection isn’t just annoying—it’s a genuine safety concern.
Ice-Cold Air Conditioning Again!
The next project was getting the air conditioning working properly.
When Jim performed the L98 swap years ago, he also converted the truck’s original R-12 air conditioning system to R-134a. That included replacing both the condenser and the A/C compressor, making the system compatible with the newer refrigerant. The conversion itself was done correctly; it simply needed a little refrigerant.
My friend Brian helped me add some R-134a from a cylinder we found in Jim’s workshop, and the results were impressive. The air conditioning is now blowing ice-cold air again!
That makes the truck much more enjoyable to drive during those hot South Carolina summer days. There’s only one downside: the MPG has taken a hit. Oh well. I guess you have to give something up for the comfort of a cool cab!
A Future Upgrade: SPAL Curved-Blade Fans
Another improvement that was still on my to-do list involved the cooling fans.
The truck currently uses a pair of straight-blade SPAL electric fans mounted to an aluminum shroud. While cleaning out Jim’s shop, I discovered two brand-new SPAL curved-blade fans that were the exact same size.
The curved-blade design is more efficient, moving more air while also being quieter than the straight-blade fans. I thought I had found a pretty easy upgrade.
I proceeded to remove the radiator shroud and immediately discovered something else that needed attention: several large dirt dauber nests wedged between the A/C condenser and the radiator.
Fortunately, the nests themselves were easy to remove. The residue they left behind between the fins of the condenser and radiator was another story. The solution was an old toothbrush and patience.
Once I had most of the mud and dirt removed, I applied a foaming cleaner to both the condenser and radiator to get rid of the remaining debris, bugs, dust, and general crud that had accumulated over the years. I highly recommend this stuff. It’s inexpensive and did a great job of cleaning up both components – thanks Brian for suggesting this.
That’s when I discovered a problem with my fan upgrade: The two new curved-blade SPAL fans weren’t actually a matched pair. One was a pusher fan and the other was a puller. That’s not going to work.
There was another issue. Because the new fans have larger motors, their current draw is considerably higher than that of the straight-blade fans Jim originally installed. The last thing I want to do is overload the electrical system, burn up a relay, or—worst case—create an electrical fire.
After thinking it through, I decided the best solution was to simply leave the existing straight-blade fans in place. They have been working fine, and there’s no reason to fix something that isn’t broken.
The curved-blade fans are now for sale on eBay. Sometimes an upgrade doesn’t quite work out as planned!
Rearview Mirror
Another little problem popped up with the rearview mirror.
Windshields from the vintage of my C10 had not only the built-in antenna but also a glued-on mounting shoe for the rearview mirror. As expected, after all these years, the shoe decided it had enough and parted ways with the windshield.
I found the rearview mirror lying on the floor of the truck.
Fortunately, this was an easy fix with one of those rearview mirror adhesive kits. The trick is to clean both the windshield and the mounting shoe extremely well before applying the adhesive.
In Summary
So far, so good.
I’m happy to say the truck is running about as well as can be expected for a 40-year-old Squarebody. It’s far from perfect, but for the way I use it, it’s perfect.
And honestly, that’s what I like about this truck. It doesn’t have to be perfect. It’s an old C10 with a modernized drivetrain, a few quirks, and plenty of character. I can drive it, enjoy it, and fix things as they come along.
There are still several things I’d like to address:
- The horn doesn’t work. I need to do some research on this one. It could be a bad relay, a blown fuse, or something else entirely. I’ll have to dig into it.
- The fuel pump is noisy. When Jim did the TPI conversion, he used something we were familiar with at the time—a Bosch fuel pump similar to what we used in the XJ6s. We were doing LT1 conversions in Jaguars back then, and the Bosch pump worked well for those applications. The downside is that it’s noisy. I’ve done some research and discovered that the 1987 C10s came with Throttle Body Injection (TBI), and the fuel tanks in those trucks were designed to accommodate an in-tank fuel pump. The problem is that I’d have to replace the fuel tank to make the conversion. I’m not sure I want to go to that much trouble right now. After all, the current setup has been running just fine for a lot of years.
- The upholstery is tired. The bench seat is showing its age. Jim installed one of those aftermarket blanket-style seat covers, and it’s okay, although it’s become pretty dusty over the years. At some point, it would be nice to have the original bench seat properly reupholstered.
For now, though, I’m happy.
The truck starts, runs, stops, has ice-cold A/C, and is a lot of fun to drive. What more could I ask from a 40-year-old Chevy Squarebody?
