The Stovebolt Site Forums The Shop Area Engine Shop Is the gas really the problem?

I got past this issue but still looking for what the real problem was....
My '49 1/2 ton had the original engine which I converted to 12 volt (starter and generator), eliminated the points (Pertonix), new fuel pump, carb, water pump, etc. In other words all the outer gear. It started right up and ran fine but after about 5 mins it would seem to run out of gas. I checked the obvious stuff, debris in the lines, filter but that all checked out. After lots of unsuccessful troubleshooting I got another new carb and later another new fuel pump but still same problem. I found an old timer, I'm 69 so if I call him an old timer, you get the picture. He "fixed" it by suggesting I put an electric fuel pump inline between the gas tank and the mechanical fuel pump, like a helper. His theory is that today's gas is "weaker" and at least partially vaporizes once the engine warms up so it starts demanding more fuel than the mechanical pump delivers. I'm not sold and couldn't find anything about that here on Stovebolt or anywhere so, if everyone is doing this or something else to address it then it's a very well kept secret.
I am now running a small block but still very much want to know.... Is the gas really the problem? and if not then what's wrong that an electric fuel pump fixes?
I'm sure it can happen and with my luck it would happen to me, but two new fuel pumps that were both working but possibly both weak with identical symptoms? That seems far fetched.
BTW.... Me and my truck want to thank everyone here for all the great info, and I never even once had to ask cause all the answers were already asked, answered and waiting.

I don't own any modern cars and I use ethanol laced fuel exclusively. None of them have ever had a problem related to ethanol. The diaphragm in my Cadillac stretched due to ethanol in 2007 when that junk was mandated in Atlanta. After rebuilding the pump with ethanol resistant parts, I have not had another problem.

It's true that ethanol is more volatile than the old "real" gas but I doubt the problem you're experiencing is related to that. I drive my truck on E10 87 in 90+ degree heat during Atlanta rush hour without any issues.

There is nothing far fetched about two fuel pumps not working. They are ABSOLUTE JUNK right out of the box.

I had a new one fail in under 300 miles. The replacement failed to pump one drop of gas as soon as it was installed. Many others on this forum have experienced the same issues.

None of my vehicles have electric helper pumps, either. A properly rebuilt , mechanical pump will do the job just fine.

You're barking up the wrong tree if you're focusing on ethanol

There are two kinds of Pertronix ignition systems- - - -the ones that have failed, and the ones that will do so soon. As long as you run that system, anything you do with the fuel is probably going to end up with less than predictable results. The offshore-made fuel pumps available these days, regardless of the name on the box or the seller, are a crapshoot- - - -more likely to fail or give less than optimum performance than functioning properly, but at least consider going to a reliable ignition system. I have wasted billions of electrons over the past 20-something years describing the right way to test a fuel pump, and I've been ignored at least 90% of the time. It's not worth my time and effort to attempt to educate people who want an "easy button" fix.
Jerry

Thanks guys! I am going to blame the fuel pump and finally let it go.

Jerry,
As for the pertronix system I replaced it along with the whole engine.... I wont bore you with the details but I loved the sound and feel of the original build. Problem was that it was too slow for all the highway driving I have to do so I very rarely drove it. So, I put in a new front suspension with power steering, a crate small block, TH350 auto and a 10 bolt posi unit and can now drive my truck a lot more for some of my regular 2 and 3 hour drives up north whenever the weather is nice.

Intermittent issues such as you describe are virtually always ignition related.

If it was "fuel related", and it ALWAYS seemed to "run out of gas" after about 5 minutes, after checking the fuel filter (you did), and the tank vent (don't know if you did), I would have checked the fuel pump (apparently you did not test, just replaced). And then I would have found the ignition issue.

I am totally with Jerry on the pertronix.

I won't attempt to convince you that points are much more reliable (they are!), just suggest that if you are in love with the electronic gizmo, carry a complete spare in the glove box (also carry a complete spare distributor set up with points and condenser, just is case the spare also fails!).

Jon

carbking - I have an MSD setup running on 20 years now. It is triggered by..... wait for it......points. I disconnected the condenser and tucked the wire aside in the dist. and I carry a spare dist.-to-coil wire with my spares. I've never needed either. Occasionally I have to dress the points if the truck has been sitting in the wet for a while but that is all the attention I've paid to the ignition other than plugs and wires, etc. Now fuel pumps... don't get me started.

When it does stall get out & check to see if it has spark or is starved for gas. Pull the air cleaner & look down the throat of the carb. Pump the accel. & see if gas is sprayed into the carb throat. Remove the wire from the center of the coil & hold it close to metal on the engine. Have someone turn the engine with the starter with the key on. See if spark jumps from the wire to the engine. This will narrow it down to weather the problem is fuel or spark.
Newer vehicles have a filter bag on the end of the fuel pickup tube in the tank. They can cause a problem like this if it gets stopped up.
Yours probably has an outlet on the bottom of the tank & maybe a shut off valve. Sediment can collect in the fittings & cause fuel starvation.

George

Sorry, had to Edit. Failed to realize this motor is no longer being used and is a rhetorical question.

My guess it was gas cap not venting. You would run it without a gas cap for awhile to test. I never figured out if the old timers suggestion did anything.
I do not think it was the pertronix.

Where is the motor now?

SBC good choice.

bartamos.
Dude doesn't have that engine in his truck any longer. He's just curious about what happened in the past.

Wonder what was edited by Peg.

Whatever was edited did not change the value of this thread , because there wasn't much value in trying to diagnose a no longer existent engine.
It has been an exercise in futility similar to a tailless dog chasing a nonexistent tail IMHO.
The only real question posed by the OP was almost completely ignored.
"Is today's gas "weaker", therefore a good fuel pump can't pump enough of it to run the engine?" (Paraphrasing obviously.)

Fewer BTU/gallon (does that mean "weaker"?), but not that many fewer.

Gasoline has 117,600 BTU/gallon
Ethanol has 67,000 BTU/gallon

E10 by definition is 10 % ethanol, 90 % gasoline

Thus:

E10 BTU would be (.1) times 67000 plus (.9) times 117,600
E10 BTU = 6700 + 105840
E10 BTI = 112540

Difference 117600 - 112540 = 5060 BTU/gallon fewer
112540/117600 95.7 percent

So E10 is 4.3 percent "weaker" than gasoline.

E15 or E85 figures may be calculated in the same manner.

Jon

Glad you asked Bart. It's not really necessary to quote the person when your reply is next. At the least, just keeping the posters name is good enough. In this case "bart." It is a "virtual conversation" of sorts.

In some of these quote boxes, it does takes a lot of space. Some folks use quotes just to get the "meat" of the reply, and removing parts that don't mater (see my quote of Carl's below). THAT is a great way (best way) to do it. That works especially well if a reply is just for a portion of the post, especially when too many questions are posted at once. That happens some times in the Welcome Centre and it's best to responsd one question, or there abouts, at a time.

Also, on a PC that quote box is more manageable. Looking thru the screen on a cell, it's a LOT of space, plus you have to scroll since the box is wider than the screen. In the post referenced here, Carl had quoted your entire post, and it wasn't necessary. I was looking via my phone at night, so it was easy to see again how it was tedious to get to Carl's reply. Bart, was that the one that you had a long list of things to check?? I thought it was but I don't see that post now??? Your discussions the last day were here and in the turn signal one. Did you edit it all out then, Bart?
Looks like some "clean up in aisle three" for me. Something we have to do occasionally for folks seeing this discussion later down Search Road, so they don't get confused. Like digging thru a pile of instructions, looking for the right version.

Back to Carl and the OP ... I think Carl is on track with answering.
That's not always the case with some quotes and editing that some folks do.

I guess this is one to add to those in the IT Shortbus. ITMT, after last night's edit of Carl's post, I did make a note to self to let Carl know what I had been doing with some of his posts that had quotes ... but I hadn't got that Round Tuit yet.

The day's festivities continue.....