Ran great until I stopped for ice cream

[Old Henry]

Originally Posted by 1938FordPickup

Any of the lead additives a good idea?

I add CD2 lead substitute just in case it is needed. I think it is but some others don't think so. Not made new any more but still a lot available on ebay here: http://www.ebay.com/itm/CD-2-Lead-Su...99101c&vxp=mtr At the price he's selling it at it comes out to 8 cents per gallon of gas. I figure it's worth it if it will save me a valve job. It's the cheapest lead additive there is. I've stockpiled a bunch for when it really does become unavailable.

The index on the side of the distributor is in the middle and the vacuum brake is adjusted till pinging occurs. Question, screwing the vacuum brake adjuster in or out does what to change the advance curve?

Twisting the vacuum brake adjustment screw in reduces the advance curve and retards the advance timing to eliminate ping. Keep twisting it in a turn or two at a time until the ping is gone when accelerating or climbing a hill.

On my distributor it is right on 4 BTDC when the mark is in the middle on the side of the carburetor but that isn't the best initial timing for my engine at 4,800 feet. I have to push the timing screw all the way down (maximum advance) to maximize my vacuum and power at my altitude.

[41ford1]

The vacuum brake adjustment only changes the engine load point where advance is limited to prevent ping. Screwing the adjuster in provides more braking at a lower engine load or less throttle input = higher manifold vacuum. You want to adjust the brake to only eliminate ping under normal driving conditions. The vacuum brake should have nothing to do with your problem.
You have either a primary circuit issue or a secondary circuit short brought on by heat. On the primary side the usual suspects are ignition switch, ballast resistor, coil, condenser and points. On the secondary side check coil, lead from coil to the distributor, the brush from the adaptor/coil to the rotor and the rotor. The original type rotors have been known to arc to the distributor shaft.

[Old Henry]

From the service manual:



So, vacuum brake adjustment test must be "under load." But, like 41ford1 said, there is no adjustment of the vacuum brake that would cause nor fix your problem. He listed well the ignition components to check, and, as I have said before, isolate and test each one individually before replacing any of them.

[BUBBAS IGNITION]

My vote would be the condensor is going bad when hot , i would wire me up a spare condensor (any will do for this test) and when the truck acts up replace the condensor to check.
If the truck runs good cold it isnt the points or dwell as that dont change when hot.

Cold be a coil breaking down , however a lot of coils are replaced because of a condensor >>>

[1938FordPickup]

The vacuum brake was more of a "What happens" thing, just so I know what not to touch or adjust. So, it seems that there is no initial setting on the vacuum brake. Just adjust till the pinging occurs.
I'm not much of a carb person but in reading some posts, there was a few people who mentioned boiling fuel in the fuel bowl of the carb. With the hot weather we have been having, could this be the issue? I know if I add a electric fuel pump to the fuel line, I can prevent vapor lock. But, if the carb's fuel bowl is that hot, the fuel pump wouldn't matter. Any negative reasons to use a phenolic spacer to cut down on the carb's temperature?

[Old Henry]

Sponsored Links (Register now to hide all advertisements)

Originally Posted by 1938FordPickup

The vacuum brake was more of a "What happens" thing, just so I know what not to touch or adjust. So, it seems that there is no initial setting on the vacuum brake. Just adjust till the pinging occurs.

Yes, but then adjust it the other way until the pinging does NOT occur. Then you have it right. The vacumm brake adjustment is to prevent pinging not to create it. Pinging is bad. It is premature detonation of the fuel in the piston exploding as the piston is still coming up. Don't want that.

Originally Posted by 1938FordPickup

I'm not much of a carb person but in reading some posts, there was a few people who mentioned boiling fuel in the fuel bowl of the carb. With the hot weather we have been having, could this be the issue? I know if I add a electric fuel pump to the fuel line, I can prevent vapor lock. But, if the carb's fuel bowl is that hot, the fuel pump wouldn't matter.

The fuel pump does solve the problem of gas boiling in the carburetor bowl. It fills the carburetor bowl with liquid gas to replace the vaporized gas just like in the mechanical pump.

[1938FordPickup]

Yes, yes, I would screw in the adjuster till pinging disappears. Another question, in what case would cause back-firing to occur? Speaking from a distributor adjustment only. I had the engine back-fire once or twice when stumbling or bogging.

I would have thought the gasoline would still vaporize or boil in a unpressurized area (fuel bowl) as soon as it pumped in or does the fuel bowl maintain pressurization? It seems a standard carb is regulated to just a few pounds from the fuel pump (2-3 PSI), so that would keep it boiling in the bowls?

[George/Maine]

In post #23 the points gap can change timing if to close.
In your post direction of timing dist.
Looking from front the rotor turns clock wise,
so turning it up clockwise would retard it.
Down would ADVANCE it.
Note the points should be checked and set if out of adjustment.
If it ran good last year My guess its your points,and change the condenser.

[Old Henry]

Originally Posted by 1938FordPickup

I would have thought the gasoline would still vaporize or boil in a unpressurized area (fuel bowl) as soon as it pumped in or does the fuel bowl maintain pressurization?

All I know is that when my engine vapor locks and I turn the electic pump on all is well and I carry on down the road. I don't think the vapor lock is in the carburetor, it's in the mechanical fuel pump that quits pumping and pumps again when primed by the electric pump.

[1938FordPickup]

George/Maine... I should re-visit the points and see what's going on with the gaps. Thanks for the timing question.

Old Henry... I'm thinking vapor lock could prevent the mechanical pump from pushed gasoline into the carb so the electrical fuel pump is fixing the issue.

And I should be courteous also, thanks everyone for all the responses so far.

[DICK SPADARO]

I have been following this thread for a while now to see what has happened, I dont think changing out the ignition system will cure the problem. Because the problem manifest itself after a time period of operation and you swapped out the coil, it more likely is a fuel issue.

I have had serious problems with fuel percolation not only in the carb but in the fuel lines running up and along the frame rail if they are in close proximity to an exhaust pipe or muffler. Now the fuel line on your PU should run up the driver side and be opposite the exhaust unless you have installed dual exhaust, if you have this would be a place to check. You should also check the carb float level, I have been setting mine slightly to the high side so the extra fuel will not evaporate as easily after a hot engine has been stopped and is ready to be restarted.

My suggestion to check out a fuel issue is to find out where you can purchase some small engine fuel, marine use gas or even racing gasoline for carburetor engines and fill your tank with about a 50/50 mix using pump gas. Nothing will be damaged but the better quality fuel will eliminate may of the heat problems associated with the new ethanol based fuels and this will help you determine if you have a fuel problem. If the hot start problem or lack of power is eliminated you know its the fuel.

[1938FordPickup]

Spadaro - your suggestion on other types of gasoline was part of the reason why I was running only premium fuel. Others seemed to think it's a waste and locating race fuel or marine fuel is difficult at best. I've added MMO and a lead additive to a full tank each time it's has been filled. Also, pulling out the choke causes the engine's stumbling or sputtering to get much worse. But with that said, could my issue be an over rich condition? Some posts have talked about the "Power valve", could something leaking in the carb only show up after the engine is completely hot? The fuel line is on the other side of the body from the exhaust tubing. I am still considering a electric fuel pump with a built-in regulator (set to 3 PSI ?).

My diagnostic procedures so far but issue continues:

I've looked at the voltage at the coil (4 Volts) with engine running, coil is not hot but VERY warm on the old and new coil (I did change ballast resistor as needed)
Swapped condenser but I can swap again.
I've swapped out the Ford coil for a adapter plate with external coil.
Switched ballast resistors.
New fuel filter (First thing I did) and used a borescopes on the tank (In case of large objects)
Inspected the push rod for the fuel pump and fuel pump (Some dirt but clean now)
Ran new electric wire (10 gauge) back to the cab to insure proper voltage to all circuits.
Using a screwdriver, tested each sparkplug wire by shorting to the block and all spark.
The non contact infrared shows similar temperture at each spark plug location on cylinder but one is a little hotter (220 vs 250) and Carb's tempertures were about 120.

Just remember, truck runs great when cold and warm but not hot. I could go to a guy around here, very good mechanic but not yet.

[DICK SPADARO]

The hint is that the truck runs well as long as the air temp is cool so that reverts to a fuel issue to me. Pulling out the choke only makes it worse because you are choking the engine air flow so its going to skip with a rich mixture. With Premium fuel all you did was get a better grade of gas, the label still has 10% ethanol in it. I tried the MMO trick and it didn't change the condition, the fuel still vaporized, race gas cured the problem and I rerouted the fuel line away from the exhaust. At $8.00 per gallon its not the cheapest way to trouble shoot but it was the easiest way to determine if it was a fuel problem.

[George/Maine]

For the back yard mechanic.
Ign Timeing having no fixture.

[G.M.]

If it is a fuel boiling problem you have a laser pointed thermometer and can see where the problem is. A fuel pressure gauge mounted in the line between the pump and carb would also show if high fuel temperature is causeing the problem. When every thing is cool the fuel should be over 2-1/2 lbs. Close to 4 lbs would be better with the new fuel. The fuel pump will raise in temperature as the intake manifold, the back of the exhaust manifold and heat off the heads heat the pump. This gas starts to boil in the 125 degree range. By watching the heat gun you can see the pump temperature rise and as the pump gets hotter the fuel pressure drops. If your pump starts out at 2 lbs or less cold and the pump gets over 125 the fuel pressure can drop below 3/4 lb. When this happens the pressure will start jumping up and down. This is the fuel vapor that causes the problem. This hot fuel pumped into the carb along with the base of the carb being heated by by the 200 degree intake manifold boils the fuel in the carb bowl. Check the temperature of the carb bowl and at 125 it is a problem. The fuel line from where it is clamped to the firewall is also heated from from the rear engine heat. With the fuel line insulated this heat will also heat the brass fittings on the flex hose these look like heat magnets. Your 38 pick up has a lot more air flow in the rear of the engine than a 39 deluxe from the generator mounted fan and the side panels of the hood. If these temperatures and fuel pressures indicate the problem is 125 + degree fuel and low fuel pressure the following changes will correct the problem.

Increase the fuel pressure to close to 3 3/4lbs cold.
Install Gadgiteers 1/2" ventlated insulated spacer below the carb.
Reduce the heat riser holes from .625 to .325 Thin shims with .325 holes.

This should cure the problem in most cases. If not there are a few other things that can be done. Get to this point first. There is no pressure in the carb bowl. G.M.

[Old Henry]

I agree with Dick that it's a fuel issue. I didn't see in your list of tests any test of the fuel pump. Might test that but even my mechanical pump that works great can't pump vaporized gas. These last few days when it's been over 95 every day I've had to constantly turn my electric pump on to prime the mechanical one when the fuel vaporizes and that now happens when driving fast, driving slow, or stopped at a traffic light. Gotta be the new gas cause I never had this much trouble before. I would have been dead in the middle of the road so many times without the electric backup pump. That may be what yours in going to take.

My one reservation about a diagnosis of vapor lock is that your engine doesn't actually die like mine does every time it vapor locks - just like it ran out of gas which is what it does when all of the gas is gone from the carb bowel. It doesn't spit or sputter much before it just dies.

[41ford1]

"Also, pulling out the choke causes the engine's stumbling or sputtering to get much worse."
That statement indicates a rich fuel condition. Pull the carb top and reset the float 1/16" TO an 1/8" lower. A lot of the sheets that come with the kit give a 1 1/4" dimension to set the float. Go for a float setting of 1 5/16 to 1 3/8". Your problem may go away. Also check the PV gasket. With a warm engine any fuel leak there will be a problem.

[George/Maine]

Swapped condenser but I can swap again.
I've swapped out the Ford coil for a adapter plate with external coil.
Switched ballast resistors.

First off with adapter plate you need a 6 volt coil round type not a 12 volt one.
you want one for a 50 to54 chevy or 1950 to 1954 ford.
NO RESISTER full 6 volt to coil.
Now can you drive with out stopping in traffic,and what is tempature keep moving does it run ok.If you keep stopping for lights you are heating it up.
your raditor could need cleaning.

[Yeti]

I had the exact same problem, was pulling my hair out,

mine is a 21 studd with a pilot distributor, man I was ready to walk away and call the thing 3D art, checked the coil all seemd fine, new condecsor same issue, like you a 50min drive and she was sweet more than that and she ran like a busted bum

I shanged the coil and no change changed the leads and BAM hasnt missed a beat since yet if you ran a multi meter over them there was no problem, I even checked them hot and cold still no joy

I had nothing to point me to this only there really was nothing left to change, I hate doing diagnostics like that but some times its your only shot

[1938FordPickup]

G.M. / 41Ford1 Thanks, very good info and I'll get a fuel pressure gauge in place and check the carb float settings as soon as I'm back home from this business trip.

Yeti, question, didn't quite understand what you said, did you mean you changed the wiring to the coil?