The Stovebolt Site Forums The Shop Area Engine Shop Engine cutting out

I raised this issue once before, but I did not have any history and little info. I am going to try again. The engine starts with little trouble. I can take short trips and never experience any problems. It is when I take longer trips the issue pops up.

Issue: I will be driving along at speed (45-55 MPH) and suddenly the engine will start sputtering as if starved for gas. Yesterday when this happened I was about 15 miles into my 30-mile drive. Because of my speed as the engine dies it will keep cutting out and restarting because it is kick starting. As this is happening the truck is bucking significantly and slowing down as it dies and restarts. Once I get pulled over to the side of the road, if I do nothing but wait a few minutes it will start right up but if I try to go down the road it won't make it 100 yards without cutting out again.

I am running a fairly new Carter M2090 mechanical fuel pump that puts out a max 5 PSI. Unrelated to this issue I have an inline electric fuel pump that puts out 5-8 PSI. I added this fuel pump to help prime the system for when the truck has sat a while. I typically run with the electric fuel pump turned off.

Something I discovered. At first, I thought the mechanical fuel pump was failing so as a desperate measure to allow myself to get home I tried turning on the electric pump and the truck took off and ran fine, Problem solved, bad fuel pump, so I thought. I then discovered on short trips the truck ran fine without the electric pump. I also discovered if the truck started cutting out while driving, if I flipped on the electric pump within 5-10 seconds the engine smoothed out and down the road I went. I have not solved the problem but for now this appears to be a work around.

After having the scenario happen maybe 10 times, on the 11th event the electric fuel pump did not solve the problem and I was force to the side of the road again. I got under the hood and looked around for any leaks or anything that stood out. I tapped the carburetor a few times and the truck started right up and gave me no more trouble on that trip.

My carburetor was rebuilt less than 200 miles ago. Fuel is one of the see through and looks clean.

the first thought I had, this might be a crazy thought, was the float was sticking and the added pressure from the electric pump forced the float loose? I thought possibly the one time turning on the electric pump that is did not solve the problem the float was just "too stuck" and the couple taps freed it up again????

I am grasping at straws.

Hi Dave,
What type of carburetor? With the Carter YF I have had a few float issues, but they don't mimic what you described. What happens with mine is that if the fuel dries out in the float bowl (allowing the float to drop to the lowest point) the 3 piece spring-loaded needle valve will stick and then when I start the engine (I use a 3~3.5 psi electric pump for everything) it will flood.

I was about to suggest doing some ignition troubleshooting. But then I re-read your post and the result you got from tapping on the needle/seat doesn’t align well ignition stuff.

Nevertheless, doing a quick spark check during your next breakdown would be quick and easy to do.

I think that’s where I’d start. Reproduce the symptom and try to narrow it to spark or fuel (fuel being more likely).

To verify that your bowl has gone empty for one reason or another. Look down the throat soon after it shuts down. Goose the throttle by hand and see if you can see the squirt from the accelerator pump. No squirt is pretty easy to intepret. Getting a squirt doesn’t necessarily rule out carb/fueling issues, but gives you a good data point to decide on next steps. If I DID get a squirt, my next test would be holding WOT and cranking to see if that clears a potential flood.

It would appear from your pics that we are dealing with a Rochester B. Is that the case? Just throwing out an idea. It’s pretty hard to get the RIGHT kit for a B since the tags are most often long gone. Could be a case of mismatched needle/seat stuff. That’s a spitball at best.

Make sure the gas cap is vented. Drive it with the cap loose & see if that makes a difference. Check the sock on the bottom of the fuel pickup tube in the tank if it has one. Look over the fuel lines from the tank to the carb for any filters that may have been installed. See if they are clogged up.
You didn't say what year truck it is & what model carb.
Jon G it sounds like your float drop is not adjusted correctly.

George

Tapping on the side of the carb might or might not have been related to the engine starting back up. I think to know if it is related, I need at least one more example of that solving the problem. The entire fuel system is new from a new gas tank, fuel lines, fuel pump, fuel filter and rebuilt carburetor. I will check the bowl as suggested to see if any fuel squirts. I will also try a spark test, but I should also point out all new wires, points, plugs, coil, cap and condenser.

The fuel pressure at the carb should be 2-4psi. I would test the fuel pressure and the fuel output volume at the carb to rule out (or in) the fuel pump. I'd replace the electric helper pump with one of appropriate pressure.

What kind of condenser? Is it a Jon G special?

Sadly, “new” is not the same thing as “good” in today’s world.

I mention the ignition stuff because it is fairly common to chase fuel issues to the ends of the earth and later figure out it was ignition. Yours truly is guilty of the same. Someone around here (Carl?) has a catch phrase that “it’s never the carb.” It’s truer than one might guess.

Given the symptoms you have described, I would still place my bets on fuel. Spark is just so easy to check that you might as well just do it. A crummy coil can operate fine and then act up once it gets warm.

Wrenchbender gave you some good ideas about tank venting and intermittent tank/sock plug-ups. Easy things to check off the list.

Have you blown back through the fuel line from the fuel pump to the tank? Sounds like there may be some trash restricting flow, then falls back out of the way when the engine stops. My similar problem ended up being the new sock on the end of the new sending unit on my 54 3100 collapsed and stopped the flow. Replaced with a stainless screen and all is well.

Or do without the sock altogether. With a new tank, I don't think there's a need for the sock. The sock is a filter and the purpose of a filter is to get clogged up.

My Mustang uses a straight tube with no sock. The earlier AD trucks just let the gas flow out the bottom via gravity. Same for my Cadillac.

Hi George,
No, the drop on my float is adjusted okay but thanks for the suggestion. Once it falls all the way down, it is easy for the pin, spring and needle to sort of cock sideways just enough to hang and then you need to tap as the bowl fills up to make sure everything is Jake again. I have the original Carter 3 piece needle, also...and the float. It was an NOS carburetor only needing new gaskets, new diaphragm and a check of things like air passages (for spiders, dust, etc). Guess I could fudge and raise the float drop but I figure there's a reason they wanted the measurement they wanted.

I've seen both Carter and Rochester floats hang up on the side of the carburetor body and act sort of like this, but I'm at this point assuming whoever rebuilt the carburetor checked that.

On the YF, the float pin must be installed with the little nubbin on the side facing outward (not facing inward toward the carburetor's throat. If they get installed backwards, they'll work their way out pretty quickly and this will free up one side of the float. This will allow the float to ride at an angle (where it will hit the side of the float bowl and it will make the needle/seat fail to work properly, too. Finally it will start flooding a lot and stop working altogether. If you look at the image below you can see the little bump on the rod and where it must be located to prevent it from moving inward.

How old is your ignition switch? I had a similar mystery issue still present after a carb rebuild and replacing ALL ignition components. All except the ignition switch, that is. This was 2015 and I finally realized the switch had never been changed since 1982 when I got the truck and probably not for many years before that.

Even though the fuel system is new, I'd still pull the sending unit and look for trash in the tank. It really sound like fuel starvation to me. All it costs is a little time to check it off the list.

How much gas is in the tank?

Mike B

That sounds exactly like the problem I had with my Beetle years ago. It was the filter in the tank. It was collapsing. I replaced it and it was all good again.

I am looking into the possibility of a Petronix conversion, but I have a hard time thinking this particular issue is electrical. The fact that 9 out of 10 times turning on the electric fuel pump smooths things out and I continue down the road with no issues points hard at a fuel issue. I have one of those cheap snake cameras from Harbour Freight. Once the fuel level is lower, I will inspect the inside of the gas tank.

I recently had a similar problem with the Cadillac. Random fuel starvation. Everybody screamed vapor lock but it was happening on cool days as well as hot summer.

They also told me to get an electric pump. After a couple trips on a flatbed wherein the car would immediately start after being dumped off, I started looking for problems in the fuel line and tank.

I used a plumbing snake camera like you describe and found nothing amiss in the tank. Air could be blown freely through the line from the fuel pump to the tank. I put aside the idea that the tank or line was the problem and a newly rebuilt, and properly tested, mechanical pump was installed.

The problem occurred again. No fuel was getting to the carb and none was visible in the filter after the pump. I unscrewed the tank drain plug and verified that the tank indeed had plenty of fuel. I disconnected the the fuel line at the fuel pump and installed a rubber hose which I placed in a 5 gallon gasoline can on the front floorboard.

The car started immediately and I drove 27 miles home. I replaced the tank and the entire fuel line and have had no other conk-outs since then.

My point is that if there is a problem inside the tank, you might not find it with a scope. Hopefully you find a smoking gun. First, I would install a rubber hose and a gas can to the mechanical pump and go for a drive. See what happens.

You may then be able to determine whether the problem lies upstream or downstream from the fuel pump. Perhaps a piece of solder or something is in there partially clogging the works.

Your over-pressurized electric pump may be able to overcome the blockage.

Using a gas can and hose removes a lot of variables. Maybe your mechanical pump can't suck fuel through the electric one. Did you replace the filter on the electric pump?

Also, I would not put any faith in the "new" Carter fuel pump. They are all garbage. Unless you test the volume output as well as the pressure, you cannot assume that it is working properly. 5psi seems pretty high. My mechanical fuel pump operates at 2.5psi.

You're better off looking for an original pump and rebuilding it.

Check that your gas cap is okay if on a long trip it may not allow air in to allow the pump to pull the fuel .On the short trips it is okay as it may not build up enough pressure to hinder the pump.

Thanks Otto. I am aware of the fuel pump issues/quality. This is the second "New" Chinese fuel pump. Fortunately, the first had a 1-year warranty. the one on there now is the replacement. The first one gave me issues right off the bat. I thought the second one solved the problem because I went a while before the issue popped up again. If/when this one fails, I do plan on either a rebuild or 100% electric fuel pump. I will try the cap. Sometimes the simplest answers are the right one.

Dave,
Please think long and hard about a Pertronix conversion. You may not have any problem with your ignition system now, but that could change if you choose Pertronix. Sorry...I hate to seem arbitrarily negative but honestly it isn't arbitrary. The negativity has been caused by countless failures, past and present. If Pertronix was still selling their little modules for $29, I would say "fine, just buy 2 of them and keep one in the glove box for when failure strikes." Bottom line for me is any product that causes people to carry a points distributor under their seat is not an advancement.

That having been said, I continue to do and have done a decent bit of work on the imported HEI distributors, chronicling the steps necessary to convert those to the Stovebolt engines and I can tell you the one I'm using now will make a healthy spark across a .050" gap and it will light up a timing light nicely also. They aren't pretty but truth be told neither am I. Anyone curious about those, please contact me.

I like long-lived products and the fuel pump I've used since 1997 is the AutoBest number F4027.

https://www.amazon.com/Autobest-F4027-Externally-Universal-Electric/dp/B00496RE82

The psi output is 3 to 3.5 (checked on two different gauges). I replaced the old one I had purchased in 1997 simply because of the age and the fact Amazon had them for $30 each at that time. But they're still only $33, so my savings wasn't monumental. I ran my oil lines out the old pump spot and added a spin-on filter.

I like the gas cap theory because:

1) It’s plausible
2) It might be the easiest of all the suggestions to test and prove/disprove.

Can you confirm your gas cap is venting inbound to tank when needed? I did not see a response to this.

If it isn't venting you'll notice a suction when trying to remove it.

I do have a new gas cap, but I was having the same issue with the original gas cap. My new one is a Duralast Fuel Cap 6023. According to the description it is "Specifically designed pressure and vacuum relief valves to prevent evaporation of fuel. ". That said. it is an easy test. I will try loosening the cap.

That cap needs a 1/8" hole drilled in the plastic piece. The springs they use to save the planet do not allow air to move into the tank as the engine removes gas from it. This is a very common problem which is easy to fix.

IF you determine it is in fact the cap (don't drill it yet)
make a decision if you want to add a charcoal vent in the line so that you don't get the gas smell around the window and in the garage.

It will vent thru the cannister in that setup and the cap will need to be like it is not venting out or in. The suction back thru the cannister pulls the fumes and clears cannister as well.

if you going old school stock setup with all the smells that go with that because the is what you want. then drill or change caps or adjust springs however you desire.

My new cap ceased working and a vacuum was created in the tank. I took the valve out of cap.

I will be taking a long drive in a couple days. I hope to test the cap theory. Never heard of the charcoal vent. I will look into that also if nothing else so I can learn something new. It might be a good choice for me.

How would one install a charcoal vent system in 70 year old truck with the tank behind the seat? Will this charcoal vent system also be incorporated with the road draft tube and the open vents in the valve cover? There are likely much nastier fumes coming from those items than from a free-breathing gas cap.

Yes there is. I am sure. But it all depend on what he plans on doing in his overall build.
But I just spliced a T in the vent hose between filler neck and tank ran a loop inside the sheet metal so it’s above the filler neck and back down and under truck to a modern charcoal canister. But I am also not running a stock engine with all those other smell spots.

Someone recently told me that a return style fuel system can run without a true “vent.” Is that true?

That doesn’t seem right.

No still needs a vent. When that fuel heats up going around that engine it still heats up. and you need the expansion in the tank as well as leaving it out ins the sun all day.
When you fill it up you put in cold gas from the tank underground. and it you don't drive it far and park it. its going to expand as it heats up.

and when you use fuel it has to be replaced by air so it has to vent in as well even on a return style system. This may be the issue this thread is working on.

^^^^

That’s what I thought. Was confused by what I heard.

Still having this issue. I took a long trip today. About 30 miles in it cut out again. I have ruled out the gas cap. New information. This time when I pulled over I removed the air filter and was checking to see if any fuel sprayed in the carb when I pump the accelerator and it did not. I then saw my in line fuel filter bowl, about 10 inches in front to the carburetor, was empty. One of those clear in line filters. I went into the cab, flipped the electric fuel pump back on and watch the bowl fill up with gas. I had it running while driving and flipped it off when I pulled over. I got back in the truck and it fired right up. I probably got another 20-30 miles and it happened again. This time I just push in the clutch, coasted on down the road and gave the electric fuel pump time to fill the bowl again. About 20-30 seconds. I popped the clutch, the truck fired up and away I went. My next step is to look inside the tank for any debris or sediment as someone suggested before. Does this new information showing I am no doubt being starved for fuel narrow this down any more. I am at a loss. New fuel tank. New fuel lines, and there are no other fuel filters.

Where does the electric fuel pump pull fuel from? is it in series with the mechanical pump?

I'm certain you already know this, but mechanical and electric pumps are different. Mechanical pumps are designed to suck gas to the engine and can be mounted right up front. Electric pumps are designed (all of them) to push fuel and therefore work best when they're as close to the gas tank as possible. Please tell us where your electric pump is...or please answer this: is your electric pump for some reason between the mechanical pump and the carburetor?

I ran into a similar issue quite a few years ago now. Same thing, drive for a bit, motor would shut off, cold weather, hot weather. I did the whole thing, tune up, rebuilt the carb, blew air through the lines, fuel filters.
installed a Carter 4070 and that did the trick, for a while any way. Then the problem was back, but worse in some ways. I would drive halfway down the street and it would shut off. I pulled the tank, pulled the pick up and lo and behold, there was the problem. When I removed the sock from the pickup, the very end of the pick up tube had accumulated some lacquered up fuel that had over time hardened little by little reducing the id of the tube. The electric pump over came this issue, for a while anyway, by pressure and volume.

So when the tube became really really narrow, the motor would start on the fuel that had been in the line. It would run until the line was empty (because the electric pump was no longer receiving fuel to pump forward) so the motor would shut off.

Then it would sit, fuel would trickle back into the lines over the 15 -20 minutes I let it sit, and of course it would then start right up baffling me as to the problem.

So you might pull the pick up, make sure all the lines are clear, the pick up is clear and unobstructed. Also, and just a matter of personal opinion, I think those glass fuel filters are a fire waiting to happen and you might consider replacing it with a non-glass, non-plastic filter.

.

First, the electric pump is about 12 inches from the gas tank.it is in the same line as the mechanical pump. I had installed it for completely different reason. It was just supposed to be used to prime the line when the truck sat for a long time. If it wasn't for having it, I would have been stranded more than once.The description for the electric pump stated in could be used by itself and it could be turned off and it allows gas to pass through. I will pull the pickup and check it but it is a new tank and lines and has never sat for any length of time that would allow gas to go bad. At this point I don't know how it could be anything but the pickup.

I recently had the same/similar problem with my '56 Cadillac. All the stuff you mentioned didn't solve the conk-outs. Replacing the gas tank and fuel line fixed it right up. Something was stuck in the pickup tube or the line that would allow enough fuel to pass through but would eventually starve the engine and the engine would die.

A 2 inch long Tennessee grasshopper is exactly the right size to plug up the fuel tank pickup tube on a 47 Mercury convertible, the first car I ever bought, in 1962. The car would run almost exactly a mile before the fuel in the carburetor float bowl and the fuel line ran out. Wait 30 minutes, and the engine would restart and run another mile. Two fuel pumps, an inline fuel filter, and a carburetor got changed before I found the real problem!
Jerry

Update on the engine cutting out. I had a gas leak from my tank. It only happened when I filled up past a certain point. I dropped the tank to inspect and discovered it was not a new tank like I thought. Just fresh spray paint. It was rusting and the seam and the rust was spreading the seam causing the leak. What I also discovered was it appeared to be the original sending unit in the tank. It had a cork float that had started to deteriorate and I am assuming releasing pieces of cort into the fuel. Fingers crossed, once I install the new tank and sending unit my problem will be solved.