The Stovebolt Site Forums The Shop Area Engine Shop Vapor Lock?? continued breakdowns᠁help!

Hello all, I am still having Issues with my 1945 Chevy pick up breaking down. The engine is all all stock, Rochester carb, mechanical fuel
pump, oil bath, still 6v. Over the last few months it has left me stranded many times. The symptoms are that I will be driving typically at a speed above 35 miles an hour when it starts to hesitate begins to stammer and then dies. Once pulled over, it will not start. After sitting awhile, it Will eventually start up again but most times when you start to takeoff and go the same thing will happen. To troubleshoot so far, My first check fuel flow to the carburetor when the fuel line is disconnected from the carburetor and I turn it over sitting in the Park position it will give a strong stream of fuel every couple seconds indicating what appears to be strong fuel flow. (at rest of course). I’ve not only disassembled the carburetor to clean it but I actually replace the carburetor with a new old stock one and then have even since rebuilt that one a second time to make sure things like the Excelerator pump and other issues were not the cause; The fuel pump has already been replaced in the last couple years with an aftermarket one. (mechanical of course). I also recently flushed out the tank which had been previously restored a few years back I put a new visible plastic fuel filter on the fuel line between the tank and the fuel pump. The fuel line from the pump to the carb is the original hard line That goes up the front of the motor and then over to the carb it has two or three Bends and curves, but it appears to be the stock “route”. Just to rule out any electrical problem, I have since replaced the points the cap rotor plugs plug wires and even the coil, re-timed the engine it will always start when parked and will I will just fine even after 5 to 10 minutes; it will still continue to idle without any issue the problem only happens when the truck is moving and typically in third or fourth gear at a speed of 30 mph or higher. I Recently considered the problem may been related to my aftermarket fuel cap being non-vented and maybe creating pressure in the tank or something? but I even attempted to drive the truck home the other day with the fuel cap entirely removed and half way home the same thing happened. A friend and mechanic, is now talking about vapor lock as a possibly. But if the Fuel system and the route of the fuel lines are the way they have always been from the factory, how could this be such an ongoing problem? it was also early in the morning around 64 degrees outside when it happened most recently. I am fairly certain it’s a fuel issue because once it breaks down I am able to restart the truck using starting fluid shot directly down the carburetor. Any help or thoughts would be greatly appreciated as I an at my wits end here. Thank you all!

I doubt you're having vapor lock problems. All I own and drive are antique vehicles and I have never had one suffer from vapor lock. I've had problems that I thought might be vapor lock but further investigation and testing proved otherwise.

New aftermarket fuel pumps are absolute junk straight out of the box, all made in China regardless of brand name. Send your original pump to Then & Now Automotive to have it rebuilt.

I had two new ones fail in quick succession as did another member of this forum.

Another common part with the same reputation is the condenser. All are junk, all are from China. One failed on me after less that 1500 miles. Go to the electrical section of this forum (pinned at the top) and read the article by Jon G who makes 200,000 hr condensers for our trucks. I put them in everything I own.

You first need to test the fuel pressure of your pump and test its output. When it dies, is fuel actually making it to the carburetor? Disconnect the line at the inlet and cranks the starter to find out.

When the truck dies, look down the throat of the carburetor and manually goose the throttle. You should see good solid squirts of fuel from the accelerator pump.

Also after the truck dies, test to see if you have spark at the distributor cable on the top of the dizzy. You may have a coil that's breaking down in the heat.

If you're sure its a fuel problem after testing everything, consider replacing the Rochester with a Carter.

What is the condition of the fuel tank and what are you using as a fuel filter?

Also, a weak spark might easily ignite ether but not gasoline. Don't rely on that to blame the problem on fuel.

If there is something floating around in the bottom of the tank and sometimes finds its way to partially block the pipe at the bottom of the tank, you will have symptoms like what you describe. The fact that it will eventually restart after a period of time could indicate that the blockage is not complete, allowing some fuel to make it from the tank to the carburetor bowl, allowing the engine to run for a while. I had this happen to me with an old tank.
I did what everyone above is recommending about testing for spark and for squirt of gas form goosing the throttle as soon as the engine dies.
These tests are much easier than trying to determine if you have an intermittent or partial blockage in the tank. Do the other tests to rule them out.

I had a similar issue with vapor lock. Non-ethanol gas cured it for me.

https://www.pure-gas.org/

I would advise against using starting fluid for testing, easy to cause damage.
Spray choke cleaner works great, used it many times to diagnose no starts.

How much ethanol in your fuel?

Well, Im in California, so our fuel is junk. But this has been a California truck his whole life, previous owner had it 50 years and drove it often, no issues. The problems just started to rise about two months ago…

What Otto said about fuel pumps!
You said you replaced the fuel pump ( mechanical).
They have been a crap shoot as far as being reliable for years now.
I know you said you checked to see if it was pumping fuel, take it to the next level and see exactly what psi it is pumping at? And if it's consistent.
Todd

There's not much point in even mentioning the right way to test a fuel pump, since nobody is willing to do it. Good luck!
Jerry

I developed the same kind of trouble with my 55.1 p/u when I was stationed at Tinker, OK in late 80s. Drive about 10 miles, would sputter, backfire and die. Sit on roadside about 30 minutes and could start it up, 5-10 miles, same thing. After 2 or 3 times of going thru this crap (was actually going leave it on roadside) remembered that I had the same trouble with an old AF '62 trashnational semi I used to drive to Gila Bend, AZ back in the later 70s. Replaced the metal fuel line with a rubber one on my p/u and never had vapor lock again. Not saying that's what is wrong with yours but if it is.......

S2

I appreciate all the input. I am very skeptical That it is vapor lock because the fuel line and the route the fuel line takes in proximity to the engine and everything is stock which has been the same for the last 60 years and this problem only started recently I have also had this problem in the morning what it is low 60° so it’s not even very hot out. I decided that although the fuel pump (which is an aftermarket one), seems to be delivering a strong stream of fuel while parked; (I can disconnect the fuel line from the carburetor put it into a clear water bottle and I can turn the engine over and it will squirt a very strong stream of fuel every couple of seconds);
I decided that MAYBE There’s just some issue of it delivering fuel at a higher rpm so I decided to purchase another fuel pump and put that on this morning. I’m trying to source and original fuel pump and then have it rebuilt but that’s not something I can do on short order as I have been looking around. So I got one from Napa auto parts which looks much better than the piece of junk that’s on the engine now in my opinion. However, Upon completion of installing the new pump I was not able to get the truck started at all when I went to check the fuel pressure I’m getting zero fuel to the carburetor from the pump. (FYI it WILL start with a little choke cleaner or gas down the carb.) it seems like the cam lobe is not actuating the lever enough to really pump it if I take the pump that I just recently removed from the engine and compare it to the one that I just bought today, it seems that the other one starts pumping fuel with very little movement on the arm whereas the one that I just bought this morning doesn’t even start to actuate until you have moved the lever probably a quarter inch at least or more. So after investigating the movement of the lobe, using a simple rod with various marking, inserted in the opening of the engine block, i turn the fan by hand, watching the movements of the rod as it rides on the lobe. I can see the minimum and maximum that the lobe is moving, and of course how far it is even pushing the fuel pump arm. I do NOT thing it is even actuating the arm on the new pump at all.
So…… back to square one. Could it be that the lobe is worn and even on the previous pump, not delivering enough fuel at higher speeds? Will seem to be good at low speed but not high?? (I have thought about just installing a 6 foot electric fuel pump to bypass to ensure consistent and solid fuel delivery.
Thoughts anyone???

Harvey,

I too thought I had a wiped cam lobe.

The first pump quit after 300 miles, the second one wouldn't pump straight from the box. Just like yours, the second one "looked" like a good quality unit. That's the one in the photo with the silver top. The gold top one is the 300 miler with the pump arm that was riveted together improperly by the slave laborers.

Take a look at my cam lobe with the varnish and shiny streak and then look at the arm of the pump that worked for a short time. The shiny part of the cam is where the thin part of the pump arm rode. The rest of it is varnished up because the arm made no contact there.

The pump arm only made contact on 1/16" of an inch on the cam instead of the full width of the arm. They are absolute Chinese garbage from the get go and will not work and cannot be made to work.

The pump arms are too short or the throw is incorrect or something but trust me, your cam is not worn out.

The original pump was rebuilt and I've put over 4000 miles on it in the last year.

Thanks for the pics. Yes, the one I just bought looks identical to one you tried, the one with the silver top. It’s like you have depress the arm almost an inch before it does anything! I guess I will attempt to source an original one and either it or of I can find one already gone through. I called the “filling station” parts place as someone suggested,
but he said they are out of stock on OG pumps and not sure when they will have more. They do have the rebuild kit though. Ill try ebay maybe, or post on here if someone has one for sale.
So, what do you think the odds are that this is the issue the whole time? do you think it is possible that the pump I had before (which would work most of the time at low speed), but then what caused the symptoms that I’m having once I get up to a certain speed???

Harvey, If your fuel pump was a piece of junk, there's no telling what it might do. The one I had that worked for 300 miles eventually started "acting up" where I thought vapor lock might be the problem. The engine started running rough, conking out, etc. when hot.

It was only after the second pump didn't work at all that I realized that either the cam was bad or the pumps were bad.

I tested the "original" pump, which was actually an Airtex re-man from 30 years or so ago that I was able to get the pump arm to pump fuel when I moved it manually. It was removed a couple years prior after the vehicle sat for a long time without being started. Ethanol had gummed it up pretty badly but even in poor condition it was better than the new ones.

You are now the 3rd person on this forum with an identical fuel pump story - 2 new pumps failed and cam lobe was suspected.

I think once you get the fuel pump problem sorted out, you'll be able to quickly determine whether there are other fuel problems or not. I'm betting not unless you have a dodgy carburetor.

It is immensely frustrating that new parts can't even be relied upon to work when brand new. It's hit or miss with just about everything these days. I've opted to rebuild old parts from now on rather than buy new parts. Even if I buy a new part just to get back on the road, I save the originals for future rebuilding.

My pump was rebuilt by Then & Now Automotive. Maybe they'll have good cores. Keep looking on ebay. They seem to come up for sale pretty often.

See if you can find the correct AC part number for the pump. There are a bunch for sale for other makes of vehicles which might be identical to the Chevrolet pump.

I've probably got half a dozen or more "rebuildable" OEM fuel pumps stashed away, the kind that are assembled with screws, not crimped together. Has anyone thought about fabricating an adapter to run a more easily accessible and possibly more reliable mechanical pump on a stovebolt engine- - - -like maybe one for a small block V8? I think I'll add that project to the "one of these days" list. I'm already accumulating the raw materials and tooling to convert a stovebolt engine to run big block Chevy V8 main bearings.
Jerry

Another thought I had was asking Then & Now if they can rebuild one of the brand new pumps to work properly. I suspect an old pump arm would be needed but who knows?

I will mention this only because it happed to me. 235 would start, run, halfway down the street it would conk out. Would not start. Let it sit a few minutes, start and would drive a short while and then it would act up all over again. I did it all. Rebuilt fuel pump, checked the output pressure. Checked the arm, cam lobe. Changed the condenser. Wrapped the fuel lines in tin foil, Changed the filters, rebuilt the carbs, blew air in the lines to clear them. Nothing.

It took me a year or better to finally find the culprit. The fuel tank pick up. Lacquer had built up at the intake pipe. The intake pipe was covered with a filter sock. There was enough fuel passing the buildup on the intake pipe to get the motor started and it would run on the volume in the lines but after a few minutes, the volume passing could not keep up with the use and the motor would stutter, stumble and shut off. After a few units, enough fuel wold trickle into the lines to get the motor started and then it would start all over again.

So maybe one thing to look at, as awful as it sounds, pull the pick up and make sure there is nothing restricting the flow to the pump.

It wouldn't be terribly difficult to build a spacer block with a built-in pushrod running in a brass bushing to contact the cam lobe, and shape it to allow a small block V8 fuel pump to be bolted to the outboard end of the adapter. It might be that the aftermarket V8 pumps aren't any better that the stovebolt stuff, but they're probably less expensive, and available at the local FLAPS without making a special order!
Jerry

I’m with drag6 and 52 Carl, my ‘49 216 had exact same symptoms soon after I brought it home. After trying everything you did, discovered a dead spider, and a tiny leaf hanging around the pipe at the bottom of the tank. Car would idle all day but couldn’t get a mile without shutting down, would restart after a bit but rinse and repeat. Cleaned the tank and that problem went away. I removed the sending unit which gave a clear view of the bottom of the tank – didn’t think a small partial blockage would impact that much but it did.

Thanks guys, these are all interesting things to check. I Flush the gas tank pretty well when it was still in the truck but I will remove the sending unit and take a peek in there at some of the things that were mentioned! First though, I did receive the original style fuel pump that I purchased today and I noticed some interesting observations between it and the Napa Carter brand aftermarket one that I just tried to install. When seen side by side the angle of the arm that actuator pump is much different from one to the other. On the Carter, I measure the angle and it is about 30° and you have to actuator arm about a half an inch before it actually starts pumping; On the OG style pump, The arm measured at about 45° and still has a slight bit of play in it but begins to starts to pump ALREADY at about the same position that the other one before you factor in the play. So in summary, The original style pump will clearly perform a better function and a full range of actuation on the arm compared to the aftermarket one…..

Your gas tank feeds by gravity from a hole in the bottom so the sending unit is for the gas gauge only - no sock to clog. The drain hole could certainly have rust in it, though.