Texas is a strange place for a classic car aficionado. Growing up in Detroit, I was always well-acquainted with the biannual rituals practiced by my father and most other gearheads: warm up the hot rod in the springtime, then put it away for the winter. Down here, it’s more like a quarterly ritual: we still drive in the springtime and put away in the fall, but there’s another whole pseudo-hibernation event that takes places during the summer months, when it’s too hot to even contemplate exposing your precious wheels to the scorching Texas sun. This year was no different for me and my 1979 Trans Am Special Edition. But unlike previous years, this time the usual November reawakening didn’t go as planned.
Since February of 2017 when my dad’s classic Trans Am made its way into my possession here in the Lone Star State, my son Connor and I have happily partaken of the spring/autumn driving season with it. A couple of weeks ago, when the 90-degree temperatures finally dissipated for good and the weather was ideal for a cruise sans T-tops, I disconnected the battery tender, jumped behind the wheel of the old black ‘bird and eagerly turned the key.
Unfortunately, all I got was cranking…and more cranking…and more cranking. Old cars with carburetors instead of fuel injection are often finicky like this — after all, today the only reason we need “warm up” a modern car is for the benefit of the passenger on a cold winter morning — but the Trans Am wasn’t starting for love or money on this fateful morning. It was cranking just fine, and I knew it had plenty of power thanks to the battery tender which had kept it on “hot standby” during those equally heat-soaked summer months. But it wasn’t catching. At all.
The old adage about internal combustion engines is that they need basically three things to run: air, fuel, and spark. While this is true of even modern cars, a 40-year-old muscle car is perhaps one of the crudest implementations of that truth, making troubleshooting a fairly by-the-numbers affair. With that in mind, and with Connor anxiously watching for any signs of progress, I started poking around under the hood.
The first thing I found notable about the state of the car was that, despite ten minutes of on-and-off cranking, I couldn’t smell one whiff of fuel. Normally our Trans Am wears the odor of gasoline like it’s a Victoria’s Secret body spray, thanks in large part to a detached hose that’s meant to carry emissions from its carburetor bowl vent to a vapor-soaking charcoal canister. But there was nothing. I’d been afraid of flooding the carb from all the cranking and accelerator pumping, but it didn’t smell like there was even a drop of fuel in there.
Back in high school, my friends always tried to goad me into taking the shaker off the car and running the carb wide open to the elements, having heard the story of how loud the motor was in this configuration. I never caved to their wishes, but was reminded of those many occasions with a wry smile as I finally detached the shaker scoop from the air cleaner dish — and the air cleaner itself, too — until I could stare down the throat of the Rochester QuadraJet M4MC. Peering into the choke valve and secondary bores revealed no sign of any fuel whatsoever. Actuating the throttle linkage by hand, there wasn’t even a spray of fuel from the jets. Wherever all that fuel I’d just cranked from the tank had gone, it sure hadn’t ended up in the carburetor.
Rochester QuadraJet M4MC Parts Diagram
The carburetor was professionally rebuilt in 2017 and less than 200 miles had probably been put on it since then, so I wasn’t apt to believe we had a stuck float or other internal failure (though of course anything was possible). All the other parts of the fuel system were fairly new as well, except for the fuel pump, which was still 1979 factory original. I started to wonder if the pump had finally given up the ghost. This almost put me off the idea of even checking for air or spark abnormalities; almost certainly we had a fuel delivery issue here. However, I decided to perform a test to make sure.
After consulting on the phone with my dad to confirm my next course of action, I fetched a gallon of 93 octane from the local gas station and poured a small amount of it into the carb through the choke valve. Turning the key in the ignition, I watched the T/A start right up and idle happily for about two seconds before consuming all of the fuel in the carb. I repeated the process and got the same results. Okay, so provided enough fuel, it runs without issue. That was enough to confirm a fuel delivery problem in my mind.
At this point I had started catastrophizing in earnest, as is usual for me. If it was the fuel pump — and by now I was well on my way to convincing myself — how was I going to replace it? Where even was the damn thing? Fortunately, on the old Pontiac W72 and most engines of its vintage, the fuel pump is a mechanical device mounted to the front of the engine block, requiring nothing so complex as putting the car on a lift and dropping the fuel tank like many modern cars would require. Even so, this was pretty far outside my mechanical comfort zone. If the car’s got a problem that involves electronics or wires, I’m pretty confident that I can do something about it — or at least learn my way through it. When the wrenches come out, I start to expect things to go south in a hurry.
There was still one more possibility. Between the fuel line and the carburetor is a small 2″ paper fuel filter, a common source of clogs and fuel system failures. But that filter was replaced when the carb was rebuilt and had just as few miles on it. My thinking was that it couldn’t have gone bad already, but it was an extremely cheap part and easy to replace, so best to check it out. While I had the fuel line disconnected, I could test the fuel pump by turning the engine over a couple of times and seeing if any gasoline spewed out of the line. If so, it would mean the pump was still working.
However, my efforts to remove and examine the Trans Am’s fuel filter were stymied by the fact that I couldn’t loosen the fitting on the main fuel inlet line. (What did I say about what happens when the wrenches come out?) It’s not like I had a lack of tools on hand — there must be close to 500 mechanic’s wrenches in my tool chest — but that sucker was seized on there like glue. My dad grimly recounted having a similar issue with the fuel line fitting way back in the day, to the point where he ended up having to cut the fuel line and unscrew the carb’s fuel filter nut instead, reconnecting the clipped line with a cobbled-together rubber collar and aircraft clamps. I hoped that I wasn’t doomed to the same fate!
Determined not to chop up the fuel line and deal with the ramifications of such an act, I spent the next week performing near-nightly soakings of the fuel line fittings with PB Blaster. This stuff is supposed to help penetrate and loosen seized threads and such like. You’re supposed to tap on the fitting with a screwdriver to create vibrations that will help loosen the parts, then let it marinate for a while. I didn’t have time to do any serious wrenching during the work week, so I settled for a period of prolonged soaking instead.
The next weekend it was time to see if all that PB Blaster had done its job. I found a 5/8″ line wrench that perfectly fit the fuel fitting. I then fished out a 1″ wrench that was the right size for the carb’s fuel filter nut. Because the fitting is screwed into the nut, which itself is screwed into the carb, I needed to hold the nut in place with the 1″ wrench while trying to unscrew the fitting, otherwise I could twist the fuel line if both started to come off at once. Finally, after a massive amount of levering force and some not-very-nice words, the fitting finally came loose.
The first thing I tried was the fuel pump test. Here, I got some more good news: the fuel pump was fine, at least according to the larger-than-expected splash of gas that ended up mostly in the baggie I had wrapped around the fuel line when I turned the key in the ignition. Okay, so that’s one repair I don’t have to do, and another indication that the fuel filter may be at fault.
I pulled the fuel filter out and looked at it. What can I say? It was a fuel filter, and it didn’t look that dirty to me, but then again it was also the first in-service fuel filter I’ve ever laid eyes on. At the inlet end was a check valve that’s intended to prevent fuel from backflowing out of the carb and into the fuel pump. My dad mentioned that I should be able to fairly easily blow air through the filter from this end, but I was unable to do so. Eventually I fetched a screwdriver and tested the check valve, and not only did it require a fair bit of force to break loose the first time, it also felt stiffer than I expected. Maybe this was really the problem after all. Well, even if it wasn’t, I’d only have to pay about $5 to find out.
I headed to NAPA auto parts and picked up a NAPA Gold 3052 fuel filter with integrated check valve (manufactured by Wix). The guys at the store weren’t sure what the hell I was talking about when I asked for a fuel filter like this, showing me a deck of slides and continually asking “Is this it? Is this it?” until I eventually just pulled up the part number on their website and had them fetch it. Of course I had to perform the air test on the new filter right away, and it was incredibly easy to blow air through its check valve. I started to — dare I say it — become hopeful that the replacement fuel filter was going to work. “I’m 100% sure it’ll work,” Connor said, after which I had to knock on several wooden surfaces and bless six different deities to undo the jinxing that phrase had undoubtedly cast upon our efforts.
Finally, this weekend, the moment of truth arrived. I cleaned and lubricated the threads of the filter nut and fuel line fitting, inserted the new fuel filter, and screwed everything back together, taking care not to cross-thread anything. My next step was to turn the engine over two or three times, then open the carb choke plate and watch for jets of fuel being sprayed into the carb while I actuated the throttle by hand. This time I saw and heard the spurts of gasoline as I worked the throttle. Yes! This was gonna work!
Climbing back behind the wheel, I turned the key and the engine sprang to life instantly (having already been primed by my throttle test a moment earlier). And thus ended my first successful diagnosis-and-repair procedure on the old Trans Am. Boy, what smiles Connor and I had on our faces at that moment!
We spent the rest of this weekend tooling around in the Firebird. Even my wife joined in; we took the car out for dinner on Saturday night, after which we made our way home after sunset (it had been a long time since the T/A did any night driving, but all the lights were working as intended). “This car can handle more than I thought,” my wife remarked as we growled our way back home. “I was thinking it was only reliable enough to drive around the neighborhood.” I wouldn’t take it on any road trips, but I’m sure the T/A is up for more than a community parade!
It’s supposed to be freezing cold (literally) this week, but I’m hoping that there’s still enough good fall weather left in the year for us to enjoy the Trans Am several more times before it’s time for the winter hiatus. Connor and I have made a tradition out of taking her out on Thanksgiving while the turkey’s cooking, and if the weather cooperates, it looks like we’ll be able to do it again this year — thanks to my successfully solving the mystery of the disappearing fuel supply (with special thanks to my dad for his advice and pertinent lore).
Postscript, November 18, 2019:
Well, it looks like our problems with the Trans Am are not quite over, as I erroneously believed. This weekend the car once again wouldn’t start, although with slightly different symptoms this time. Checking the engine oil, I found it significantly diluted with gasoline, which means it’s very likely the fuel pump was the source of our problem after all. When these old mechanical fuel pumps fail, it’s usually because a rubber diaphragm inside ruptures due to age, resulting in fuel being drawn into the crankcase as we are now witnessing.
I’ve got a new pump on the way and a neighbor who’s familiar with these engines who’s willing to help me change it out, after which fresh oil will obviously be required as well. With any luck I’ll be able to get this done over the weekend so that our Thanksgiving cruise can go on uninterrupted. Stay tuned for the after-action report on that job…