Fueling Around Update We responded to a letter in the November issue of SRM from Al Aamodt about a fuel delivery problem his '40 Chevy was having. After running for a sustained period, the car's fuel pressure gauge would drop from 6 or 7 lbs down around zero to 1, and the engine would understandably loose power, cough, and not want to run. The list of repairs Al had made was long and included:
Cooking and relining the gas tank·Installing a fuel pressure regulator and gauge·Installing a new electric fuel pump by the tank·Replacing all soft line·Replacing the intake and carb·Installing a vented fuel cap·Installing/replacing fuel filter between the tank and the pump·Replacing /installing the fuel filter before the regulator, which is mounted on the firewall (not near the exhaust)
With everything Al had done, we concluded that the coated tank was the root of the fuel system's evil. Our suspicion was that the coating was breaking loose and various bits of debris were being sucked up against the fuel pickup in the tank, choking off the flow. After the car sat for a while, the trash in the tank would settle to the bottom and the car would run normally for a while. Given the information, and everything Al had done, that was our best guess.
We don't always hear back from our readers to know if we've solved their problem, but Al sent us the following update. In addition, we've included a number of the many comments we've received from readers on the subject.
Thanks to everyone who took the time to write. And remember, if you've come up with a solution to a problem, there's a good possibility a fellow rodder could benefit from your experience, so keep those letters and e-mails coming.
Hi Ron, just thought I would update you on my project. I said the heck with it and replaced the tank altogether. Got a new one from Tanks, and it went in nicely, by the way. I also installed a new Carter external electric fuel pump (so the only thing I have not replaced is the hard line). Then I took the car to a good shop, where a local rodder/technician I know works. I also gave him a copy of my letter to you, and your response. He checked the fuel system out from top to bottom. He found my expensive fuel pressure gauge was faulty. He also found air ubbles getting into the fuel line; however, the fuel flow was good.
Where those bubbles are coming from, we just plain don't know. He checked everything but couldn't find the source. And they only showed up after the pump ran for a bit. So, I took the pressure regulator out, took the pressure gauge out, and drove it about 70 miles yesterday, in 80-degree heat. All was fine. We'll see how it does on a longer trip, but that's where we are.
Thanks for your help and thoughts,Al AamodtHorace, ND
Top ThisI thought your answer to Al Aamodt's letter was inspired and here's why.
A few years ago, my brother Dave and I were on the way to a rod run in my small-block Chevy-powered '35 Ford coupe. It was an extremely hot day and the engine had been detonating on hard pulls, so at one of our gas stops, I asked Dave to dump in a bottle of octane booster I usually carry for such situations while I went inside and prepaid for the gas.
After driving for about a half-hour, the coupe started to sputter, then it died completely and we coasted to the side of the road. Dave and I sat and stared at each other for a moment, and then I tried to start the engine. It fired right up and ran fine for about 30 minutes, and then it did it again. As the level in the gas tank dropped, it would stall more frequently, finally getting to the point where it would only run for five minutes at a time, then die. But, every time it would restart and run fine.
At the next gas stop, I told Dave I just couldn't figure out what was going on. Then, while I was digging out the box with the octane booster, I noticed there was an empty bottle and lid in the box, but the little foil seal the bottles have wasn't there. On a hunch, I asked my little brother what he had done with it, and he said he had torn it part way off and it should still be attached to the bottle. You can probably guess the rest. When we took the fuel tank out that night in the motel parking lot, out came the little foil seal. Evidently, it was getting sucked against the pickup and would starve the engine, and then as soon as the electric pump was shut off, the foil would float away from the pickup and the engine would run fine until the foil got sucked up again.
You're either really smart or you have a knucklehead for a brother too.Bill GardinerVia the Internet
Let's just say I've spent lots of time with Brian Brennan and leave it at that.
Still Fueling AroundConcerning the column, "Fueling Around," a friend had a similar problem, and after many near breakdowns, he contacted Edelbrock and they told him to get a spacer gizmo between the carb and the manifold that acted as a heat sink. The problem, as they described it, was that the float bowl was small and upon heating up, the fuel boiled out and the engine starved. My friend bought the spacer and it solved the problem-worth looking at.
Always read your stuff, it's good.ChuckVia the Internet
Got my SR today and read the "Fueling Around" thing. For what it's worth, I reached a different conclusion. He has a filter between the coated tank and the fuel pump; when the pressure drops, the fuel pump gets loud. He's replaced the pump five times, so I think it's the fuel pump. He doesn't say so, but my guess is that things get better for a while with a new pump. If not, why would he replace it five times and everything else only once? Why do I think I'm so smart? I don't, but the exact same thing happened to me! Well, maybe only three pumps. With help from my local speed shop, I now run a fuel pump designed to work with both alcohol and gasoline, which is pretty much what we have these days
Let me pass along a related item. I spent some time working on a carburetion problem and eventually called Jere Job. All new needles and seats come with a rubber-like tip on the needle that is supposed to be a big improvement over the old solid style. But guess what? One of them softened up and stuck in the seat. My one-weekend problem took one minute to fix. What to do? My two 97s now have stainless needles I had saved from old carburetors
I've talked to Sacramento Vintage Ford and an expert on the new 97s, and they both assured me that the problem has been solved with a new compound. But what about all those new old stock kits that are out there? Are they problems waiting to happen?Russ YoungVia the Internet
About the letter from Al Aamodt, his symptoms reminded me of a Rambler we bought new around 1970. Turned out the gas cap was supposed to be vented but was not, causing negative pressure in the fuel tank. This resulted in poor running, and sometimes even complete stalling of the engine. Maybe Al should check the cap.Jerry UsreyAnother longtime subscriber
I read the "Shop Manual" in the November 2006 STREET RODDER and had some input on the subject of the fuel problem that reader Al Aamodt is having. The symptoms do sound like he is starving the fuel pump, either the mentioned possibility of something moving around in the tank that blocks the intake or even the soft line to the pump collapsing. A couple of other things also need to be considered:
1. Where is the pump mounted? The letter says "near the tank," but an electric pump is a "pusher" and needs to be mounted low, either at or below the bottom of the tank. If it is mounted high, it will eventually stop sucking fuel from the tank. That can happen in a few minutes or hours of running. Both my father-in-law and one of my co-workers had problems with this situation. The co-worker had the unfortunate experience of driving roughly 1,000 miles in 50- to 100-mile increments. He was traveling cross-country in the middle of nowhere after the car was "fixed," and the car would stall and not start until the fuel pump had cooled off for an hour or so. This was because a mechanic replaced his mechanical fuel pump with an electrical pump when the mechanical pump for his unusual engine wasn't readily available. The mechanic mounted the pump too high and it would stop sucking fuel when it heated up.
2. What gauge of wires was used to wire the pump? If the wire is too small, it will heat up as the pump runs. The resistance of the wire increases as the wire heats up. Eventually the resistance of the wire becomes so high that the amount of power supplied to the pump is not enough to keep it running and the pump will start to run slow or not at all. This can be checked by measuring the voltage at the pump after running the engine until it starts to hesitate. The voltage should not be much lower than the battery voltage. Something is not right in the wiring if it is more than about a volt below the battery voltage. Some would say it should be within 1/2-volt or less. The wires could be too small or the switch could be too small (amperage rating).
A quick and dirty check of the wiring is to run the car until the pump stops. Turn off the power and touch the pump, the wire connectors, the switch, and the wire itself to see if it is warm or hot. If any of these are warm, it is a problem that needs to be corrected. Be careful because they could be HOT, so don't burn yourself. The pump may be warm but should not be hot. Remember that the higher gauge number on the wire indicates a smaller wire, so a lower gauge needs to be used to replace the wires if this is a problem. Charts do exist that tell what gauge of wire to use for a certain amperage. The pumps should note the amperage. Running too large of a wire is not a problem, so if in doubt, use a larger wire.
Based on the information provided, it really sounds like something blocking the intake or the pump being mounted too high. Both cases will starve the pump and make it noisy.
An irregular reader who really likes your magazine,Paul SyndergaardVia the Internet