Potential Vapor Lock?

[woodie49]

I was working on the car yesterday (a really hot day here) and it idled in the garage for quite some time. It seems to be running fairly cool.

After maybe 15 minutes of essentially idling, it died. The temp gauge was just about 190, and from testing the radiatior water temp the gauge is maybe a tad higher than actual temp.

I cranked it for 5 or 10 seconds with no luck. I then poured some gas down the carb and it fired up, but even with throttle, it would not stay running, just made big sucking noises as it died. I repeated the process and it started again, but with the same result. Really acted like it was running out of gas.

I just finished replacing the radiator and detailing the engine compartment. As part of that project, I did the following:

Removed and replaced both intake and exhaust manifolds

Installed a heat riser (old manifold didn't have one). I installed this outside the car, so the spring is definately at just less than one full turn.

Installed a new fuel pump (This I had bought maybe a year ago, the old one was probably good, but leaked a bit)

Re-routed the fuel line (around pump to the outside, then up between the fuel pump heat sheild and the lower water hose tube)

Replaced points, rotor, condenser, cap

Set timing with timing light to TDC.

Car has never had a problem dying before. But there are a lot of variables in terms of changes made.

A few observations that might help in determining the cause:

The first thing I thought was vapor lock because it acted fuel starved. The fuel line all the way from the pump to the carb was not at all hot to the touch and is not particularly close to the manifold. (BTW this came from NAPA and is actually brake line, I think, but same size as the old line)

The carb base was surprisingly cool to the touch (on my other flatty, it gets quite hot)

The glass bowl on the fuel pump was completely full of gas.

There was not a tremendous amount of heat coming off the engine, in fact, the engine bay is pretty comfortable to work around.

I did notice that when I poured in fuel, it immediately vaporized as I got a lot of vapor back out of the carb. I was holding the linkage open while pouring the gas in, so it was going through the carb to the manifold.

Also noted that the heat riser was still in the same position as when cool. It moves freely and does properly snap forward when I acclerate.

Is the heat riser supposed to move forward on its own as the engine heats up? If so and this isn't happening, leaving the valve directing hot air to the intake manifold, can this get hot enough to essentially cause vapor lock?

Obviously, I can be looking at completely the wrong issue. But the fact that I could fire the car up a couple times after pouring gas down the carb leads me to beleive the problem is fuel delivery.

I ran out of time so I couldn't do anything in the way of tests, but I will need to try to duplicate the issue this weekend. I took a couple pictures of the fuel line routing but can't make my camera cooperate on the download at the moment.

[BobT-47P15]

Woodie........here's what sounds like a totally dumb question, and may

prove to be one...........is your fuel pump hooked up correctly regarding

which way the gas goes thru?

My son-in-law put on a different fuel pump, hooked it up, and the car

wouldn't stay running after a point. Would start with pouring in some

gas.

He got to studying on the issue, and determined he had the inlet and

outlet hoses reversed. Apparently the pump in question had no

indicators of flow direction. He now has another pump that

says inlet or some such on it. May not be your problem, but just

tossing this out as a possibility.

[desoto1939]

I think you have a gas starvation issue.

What car or truck are you working on?

I woudl assume that you are using an AC fuel pump model 588 with a glass bowel. If you are using this model then when looking at the unit the right side hole in the input and the hole to the keft is the output to the carb.

Please be very careful wen pouring gas downthe car. If you get too much you risk a backfire situation and can cause some damage with a backfire and blowout the muffler and other things.

You might have a fuel line blockage. Blow some compressed air back from the fuel pump back into the tank. Have someone listen at the filler hole to hear airbubbles. The tank could be clogged at the bottom of the tank.

Wass the car running fine prior to making the changes? Brake line and fuel line can be used this is not a factor.

Hook up the fuel pump and do not hook up to the carb. Have a can at the end of the line have someone crank the car and see if fuel is coming up the line. Thsi willthen tell you that the carb is getting fuel to that point.

Rich Hartung

[woodie49]

Woodie........here's what sounds like a totally dumb question, and may

prove to be one...........is your fuel pump hooked up correctly regarding

which way the gas goes thru?

My son-in-law put on a different fuel pump, hooked it up, and the car

wouldn't stay running after a point. Would start with pouring in some

gas.

He got to studying on the issue, and determined he had the inlet and

outlet hoses reversed. Apparently the pump in question had no

indicators of flow direction. He now has another pump that

says inlet or some such on it. May not be your problem, but just

tossing this out as a possibility.

After some of the dumd mistakes I have made, I don't think there is any question dumb enough not to ask.

In this case I am good, the "in" points front and hooks to a small rubber hose coming from the tank and the "out" points back so you wrap the carb feed line around. Pump if for the right car and certainly appeared to be identicle.

Thanks

[woodie49]

I think you have a gas starvation issue.

What car or truck are you working on?

I woudl assume that you are using an AC fuel pump model 588 with a glass bowel. If you are using this model then when looking at the unit the right side hole in the input and the hole to the keft is the output to the carb.

Please be very careful wen pouring gas downthe car. If you get too much you risk a backfire situation and can cause some damage with a backfire and blowout the muffler and other things.

You might have a fuel line blockage. Blow some compressed air back from the fuel pump back into the tank. Have someone listen at the filler hole to hear airbubbles. The tank could be clogged at the bottom of the tank.

Wass the car running fine prior to making the changes? Brake line and fuel line can be used this is not a factor.

Hook up the fuel pump and do not hook up to the carb. Have a can at the end of the line have someone crank the car and see if fuel is coming up the line. Thsi willthen tell you that the carb is getting fuel to that point.

Rich Hartung

Rick,

Yes, the car ran fine prior to all the changes. I frequently drove it through a canyon road to the beach and back. And sometimes drove it for several hours without stop, trying to work up to feeling good enough for a longer run. I doubt there is an issue like a clogged gas line as it was fine before and I was careful pulling the old pump and replacing.

If I can duplicate it this weekend, one of the first things I will do is pull the carb line and pump it into a bottle to see that I have decent fuel pressure and flow.

I know it sounds dumb (I am getting used to it) but I am kind of focused on the heat riser and wondering if it is not operating properly. There was no plate in my old one, just a shaft that would occasionally move out a bit and cause a loud exhaust leak. Now I do have the plate, but to me it seems like it continually directs hot exhaust up to the intake manifold. This happened while my car stood idle in the garage, so I was not constantly accelerating, causing the flap to open. But, once it heats up sufficiently, shouldn't the weight cause it to open anyway? Am I barking up the wrong tree?

[Plymouthy Adams]

if you can grab the counterwieght and trun the heat riser valve..you are ahead of the game..now if working proper..the exhaust pressure even when cold will be enough to rotate to valve on acceleration of the engine..if you see it rotating on acceleration when cold and ultimately fully rotated in that same direction when hot..you good to go..

[desoto1939]

Do you have an inline gas filter on the car that might not be visable. Is there a filter near the gas tank that could be clogged. This is just a thought.

Check your fuel lines. There was post last week inwhich a person had a similar issue and he founf that the gas line had been pinched and this was causing the car to starve for gas. Did you jack up the car on the driver side and happen to hit the fule line and pinch or crimp the line by accident.

Check the lines this might be your issue.

rich Hartung

[woodie49]

These are some good suggestions. I will inspect the line tonight - I definately used a jack and jack stands while working.

The Riser does rotate on acceleration, but does not seem to rotate under its own power even when hot. It sounds like that should be the case when fully hot?

I do have an inline gas filter right infront of the carb. It is about a year old. I do have a spare that I carry in the car, I'll change it out as part of this.

[greg g]

rotate the riser clockwise and clamp it or wire it in that position. Do you have a fuel pump heat shield in place??? Did you ascertain if there was any gas in the float bowl after the engine stalled, was the coil hot to the touch?

You need to determine the reason why the engine shut off, was it lack of fuel or lack of spark? Wothout dertermining the reason the fix will remain elusive.

[Niel Hoback]

Is there gas in the tank?

[woodie49]

My plan is to try to duplicate the stall this weekend. Once that happens, I will pull the line off the carb and crank the motor to see if I have gas pumping up. When this happened, line and pump were cool to the touch. Plenty of gas in the pump bowl, but the pump is new, so maybe it has a problem. I think I'll know this weekend as long as i can git it to happen again.

Defiantely have gas in the tank. And started up this morning, but I had to crank it a bit.

Going to check the line tonight.

[DutchEdwin]

Woody,

We are at the same point of this problem.

The heatriser, mine is operating very smoothly when I rotate it. Also, when I drove the car the heatriser is in hot position also at idle, so blocking the passage to the intake. I do not know how fast it happens when only idling.

For my case, my engine starts to stall after 20 minutes of idling.

Also after driving and I shut it down I cannot start it after it sits about 2 minutes. After 15 to 30 minutes it starts up after a few cranks.

diagnose:

-) In my case the fuel in the carb is still there.

-) The glasbowl is still full but that doesn't matter. The bowl is a filter that reduces the flow rate of the fuel by creating a big volume thus letting the particles in the fuel sink to the bottom of the bowl. If there is no fuel getting to the bowl, it still looks full because the inlet and outlet are above the bowl glass.

-) fuel line between pump (mechanical type) and carb. I did disconnect the fuel line at the bowl (mine is just before the carb). There was no fuel coming when cranking. When cold to fuel immediately.

-) inline fuel filter. I have a transparent plastic one just before the fuel pump. I can see there is fuel in this filter and also see the fuel moving when I crank the engine (the filter is placed horizontal). The fuel line and filter are very far away from the engine to prevent heating up.

My guess what's wrong:

The fuel pump is attached to the engine. The big hollow arm that goes to the engine is really hot (too hot to touch). I think there is a vapour lock created in the fuel pump. I have no heat shield to protect the pump. If someone can post a picture I would appreciate it.

Possibilities:

In my case it can be the pump is bad. I have one coming from rockauto at the moment.

If the vapour lock is a heat problem to the pump, a shield could help.

If that is not enough, an extra inline electric fuel pump could do the trick.

I saw that Roberts has an 6V electric pump for $65. Can anyone explain how to put an electric pump in with still the mechanical pump in place without causing a problem (we do not have a return fuel line to the tank like modern cars have)? And do I need the pump from Roberts or are there other posibilities?

[Frank Elder]

Both you guys should go simple......buy a brand new small plastic gas can, run it to your current fuel pump, fill it with fresh gas and run your cars. If the problem persists you know it is not a blocked line or contaminated fuel from your gas tank....then you can clean your sediment bowl or change your in line filter and try again.

If it runs fine after the second test, you need to clean your gas tank and hardlines to get rid of any blockage/contamination, don't blow the ferrule out off the line into the tank if you can help it.

Then replace your soft lines' the one with fittings under the fuel pump tends to softer wth age and pinch shut, restricting fuel flow.

Good luck.

[woodie49]

Woody,

We are at the same point of this problem.

The heatriser, mine is operating very smoothly when I rotate it. Also, when I drove the car the heatriser is in hot position also at idle, so blocking the passage to the intake. I do not know how fast it happens when only idling.

For my case, my engine starts to stall after 20 minutes of idling.

Also after driving and I shut it down I cannot start it after it sits about 2 minutes. After 15 to 30 minutes it starts up after a few cranks.

diagnose:

-) In my case the fuel in the carb is still there.

-) The glasbowl is still full but that doesn't matter. The bowl is a filter that reduces the flow rate of the fuel by creating a big volume thus letting the particles in the fuel sink to the bottom of the bowl. If there is no fuel getting to the bowl, it still looks full because the inlet and outlet are above the bowl glass.

-) fuel line between pump (mechanical type) and carb. I did disconnect the fuel line at the bowl (mine is just before the carb). There was no fuel coming when cranking. When cold to fuel immediately.

-) inline fuel filter. I have a transparent plastic one just before the fuel pump. I can see there is fuel in this filter and also see the fuel moving when I crank the engine (the filter is placed horizontal). The fuel line and filter are very far away from the engine to prevent heating up.

My guess what's wrong:

The fuel pump is attached to the engine. The big hollow arm that goes to the engine is really hot (too hot to touch). I think there is a vapour lock created in the fuel pump. I have no heat shield to protect the pump. If someone can post a picture I would appreciate it.

Possibilities:

In my case it can be the pump is bad. I have one coming from rockauto at the moment.

If the vapour lock is a heat problem to the pump, a shield could help.

If that is not enough, an extra inline electric fuel pump could do the trick.

I saw that Roberts has an 6V electric pump for $65. Can anyone explain how to put an electric pump in with still the mechanical pump in place without causing a problem (we do not have a return fuel line to the tank like modern cars have)? And do I need the pump from Roberts or are there other posibilities?

Hi Dutch,

Isn't this fun? I have a heat shield. i will check the temp of the arm on the pump as part of what I look at tomorrow.

If it is a picture of the heat shield you are looking for, maybe these help.

[DutchEdwin]

Hi woody,

I'm enjoying this for 10 years now, going from 1 problem to the next ten.

But step by step getting closer to the solution.

Thanks for the pics of the heat shield, but I think I do not need one because my fuel pump is at the front of the engine, unlike yours, that is under the exhaust. But my pump is still hot at the base. Theoratically it can cause a vapour lock inside the pump. I'm thinking of putting in a plastic shim of 1/4 inch or so to insulate between the pump base and the chain cover where the pump is bolted on, like you can do with the carb or shield it from the heat coming from the radiator cooling.

As an extra insurance I'm going to install a small fan at the pump temporary to cool it when I stop the car, to reduce or eliminate the possible vapour lock until I solved it. It will also indicate if I'm on the right track.

Franky, thanks for the comment, but I had the tanks cleaned out and blew the line with 8 bar (116 psi). The flex line is new.

Also I did the gas can trick with the same result.

Ps, woody, I'm not trying to hijack your tread, but contribute to share the knowledge.

[woodie49]

Dutch,

After I posted the pix I looked up your profile and realized you aren't running an L-head. Heat shield may not help you, but i am wondering if a 1/4 shim won't affect the performance of the pump my moving the arm away from the cam lobe a little. You have probably thopught through this.

Don't worry about highjacking the thread. The more ideas and comments the better. It is still really on point.

[DutchEdwin]

I thought of that point. What I do is measure the wear point on the area where the arm touches the cam. Then estimate how much I can move it forward with only reducing the stroke just a very little bit.

I hope I get some time to do it this weekend.

Further, as you probably have read in the other post about vapor lock, not starting engine after you turn off the ignition, it could be solved by cooling the fuel pump. Gives me the idea we are thinking in the right direction, either keep the pump cool or put an extra electric fuel pump in line to break the vapor lock.

[suntennis]

My guess is that you are getting vapor lock because of the new fuel line from fuel pump to carb. The only way you could prove or disprove this would be to make up a rubber flex line without the filter, but long enough go to the side of the engine instead of to the front of the engine. Then of course you would have to prime the carb again. Recently, I installed an electric fuel pump on my 52 car to aid in starting. I only use it prior to start to fill the carb with gas. Starting is easy now plus there is help if a vapor lock happens. The original pump is still in the system and everything works great.

[MiltYergens]

I just red this... it may be of help when interpolated into Flathead cars

the theory... change to flexible rubber lines

so you're no longer boiling fuel in that metal line when you shut off the engine.

Fuel Line Mod Improves Starting & Driveability

http://www.slantsix.org/forum/viewtopic.php?t=15778

[woodie49]

To follow up on this thread, I worked on this more this weekend. Nice and hot here, so no trouble heating everything (including me) to a boiling point.

First, I was able to duplicate the condition noted earlier after about 20 minutes of idling.

At that point:

1. tried to restart with no luck, AND noted that it was very hard to turn the engine over - sounded like a timing issue to me (and I did dial in the timing to TDC AFTER the initial issue).

2. I pulled the coil wire; gas line at the carb and pumped about 6 ounces of gas into a bottle on about 12 turns. So, that seemed to be fine.

3. I re-installed the original pump to carb line (pre-detailing) which routs differently. Still would not fire.

4. Poured some gas down the carb. Much harder to start than before (due to T/O) but did attempt to start breifly and then starved quickly. It backfired once through the carb when it died.

It was hot, I was hot, so we walked to breakfast. A couple hours later, everything was cooled down enough to start again.

I then turned the heat-riser (which had stayed in the cold position earlier) fully clock-wise and weighted it with a magnate. Put back the pump to carb line and let it idle. After about a half hour, it was still idling, but did not sound really responsive when I would gun it. It would restart, but not really easily when I would shut it off. I drove the car around the block and it ran really poorly. Seemed somewhat louder thru the exhaust than normal and low power.

When I first experienced this issue, the car otherwise sounded fine, revved well, etc. Started up quickly even when hot (until it locked). When I tested the timing (with a strobe), I think it was almost 10 degrees retarded (I think it was retarded, if you think of our indicator being at about 1:00, the timing mark was above the indicator tword twelve o'clock).

I did:

1. Hooked up my vacuum gauge, which was in the low end of the normal range, needle steady.

2. Pulled the carb and adjusted the float, which was somewhat low.

3. I re-timed to about 6 degress ATDC (closer to the twelve o'clock position), this also brought the vacuum gauge to the middle of the normal range.

4. Adjusted the idle withthe vacuum gauge.

The engine sounded pretty good at that point, so (with my cell phone in hand, just incase), I took her for about a 1/2 hour spin.

It ran as good as it ever has, with good power all the way thru the curve, and more bottom end than I am used to. Pulled back into the garage and shut it off and started it right back up with half throttle as it should. I repeated this after about 15 minutes.

So, for now, everything seems OK. But with this kind of issue, I don't really know that I have found the source yet, so time till tell.

I am bothered at the need to run the timing off TDC. Last time I timed it was probably a year and a half ago, with a dampener that was very hard to read, but I really beleive that before I has it at TDC. It is now idleing a little lower RMP, but I don't think that should make much difference.

Not sure the effect of retarding the timing?? But it sure seems to be running nice!

[desoto1939]

On my 39 Desoto my timing mark is 2 degrees before TDC. ANd when looking at the front of the car the timing mark roates clockwise so the timing mark is always coming in the direction to the driver side of the car.

You have noted that you are several degress ATDC. I would check your car specs to see what the proper timing mark should be for this car. Can you tell us what year your car is. I can look in my motors manaul and tell you what the proper timing mark should.

My might have jumped the timing chain and timing mark onthe car. The dampened if i remember should have a key to keep it in place if i remember correctly. Check to see if there is a key missing onthe timing dampener maybe the dampener has shifted and now you are off the mark. This is just my two cents of data since I can not look at the car.

Any thoughts from some of the more experienced members of the forum that have rebuilt their engines.

Rich Hartung

Desoto1939@aol.com

[woodie49]

On my 39 Desoto my timing mark is 2 degrees before TDC. ANd when looking at the front of the car the timing mark roates clockwise so the timing mark is always coming in the direction to the driver side of the car.

You have noted that you are several degress ATDC. I would check your car specs to see what the proper timing mark should be for this car. Can you tell us what year your car is. I can look in my motors manaul and tell you what the proper timing mark should.

My might have jumped the timing chain and timing mark onthe car. The dampened if i remember should have a key to keep it in place if i remember correctly. Check to see if there is a key missing onthe timing dampener maybe the dampener has shifted and now you are off the mark. This is just my two cents of data since I can not look at the car.

Any thoughts from some of the more experienced members of the forum that have rebuilt their engines.

Rich Hartung

Desoto1939@aol.com

Hi Rick,

I am running an L-head 6. The specs are for the timing to be right at TDC.

[desoto1939]

Woodie,

I did verify in my motors book that the timing mark is TDC or at the 0 zero mark on the crankshaft pully from 39-53.

If you are 6-12 degrees after this then something seems wrong to me.

Rich Hartung

[woodie49]

Woodie,

I did verify in my motors book that the timing mark is TDC or at the 0 zero mark on the crankshaft pully from 39-53.

If you are 6-12 degrees after this then something seems wrong to me.

Rich Hartung

Yes, I agree. Something seems strange. But it certainly ran poorly at TDC. I am not sure what would cause this. I assume the cam is stock, but I didn't install it. The engine has been rebuilt (I don't know when), it is .040 over (bore), and the crank is ground to .020 (rods) and .010 (mains), according to the Monkey wards tag on the black. I don't know if this should require a difference in timing? I am fairly certain it has also been rebuilt since the install of the Wards rebuilt, from pulling the pan, flushing the block, etc. so I don't know if the overbore, etc. are still accurate.

I don't have a 6V dwell meter, but I gapped the points with the dist out of the car, so it can't be too far off.

I am quite sure the balancer has not moved, spun, etc., and I did not pull it as part of the detailing. That is not to say that the scale can't be off, but that seems unlikely, and I did use it to adjust the valves.

I am running at about 6 degrees ATDC, but I actually think i was at about 12 degress ATDC just after the detailing and it ran very well (at idle in my garage, no under load) and ran pretty cool as well.

I am more concerned with the potential consequence of running with the spark retarded. Maybe some of the more experienced guys can advise: is it likely to cause serious damage?

[DutchEdwin]

Woody, Are you sure you are at ATDC and not at BTDC? At modern fuel your car will probably run best about 4 deg earlier than on old fuel from 1950 as it burns more slowly. Greg G has written a few posts in this issue. When I did my timing I came to the same conclusion reading the vacuum meter.