I've got a 460 in my motorhome and its vapor locking on me. I've rerouted my gas line but every now and then it still vapor locks. Any suggestions would be helpful and thanks.

 

Are you sure it's vapor-lock? How did you re-route your gas lines? are they near ANY heat source? (mufflers down the line, exhaust mans, etc?) post back.

J/.c

1965 Ford Galaxie 500 (okay, so not quite a truck)
460/C6 transplant @ 389hp/491 lb.ft.
14.29@103.8, 13-14 mpg heheheheheh

 

Where's the gas tank? If the tanks way back and you're only using a mechanical pump then I'd add an electric pump near the tank.

Bob
'66 7 Litre, top loader, 3.25 Traction-lock, Sidewinder Intake, SCJ Exhaust
'88 F150 LWB 4x2, XLT Lariat, 302, 5 speed, 3.08
'99 Ranger, 4x2, 3.0, 5 speed, 3.73 posi

 

I rerouted the gas line where it comes out of the fuel pump out and away from the motor. I tried to stay in front so the fan could help cool the line and at the last few inches it comes down and in the carb. The rest of the fuel line going back to the tank looks ok. I checked into an electric fuel pump at car qwest. They had one for 80 bucks which I don't mind spending but the pressure on the punp was 4.5 to 5.7 psi. I thought mechanical pumps were around 4 to 6 psi so what would I gain useing a electric pump. They also had ones that would go higher but he said I risk the chance of flooding the carb. He said those are for fuel injected engines. A friend I work with use to work for Herbert motors and when jeeps came in for vapor locking he would put on electric fuel pumps. He said some times it would work and other times it would'nt. I was told by someone else to take off my clutch fan and go with a straight fan and insulate my gas line. I'm open to suggestions.

 

If the gas rank is very far from the engine an electric pump would help. Pumps are not very good at pulling gas from the tank; they are much better at pushing it. You could check the pressure and volume of gas delivered to see if your current pumps is up to specs.

JC WHitney has several in the $40.00 range and I have used the fixed pressure Walbo pump with good success in the past.

Bob
'66 7 Litre, top loader, 3.25 Traction-lock, Sidewinder Intake, SCJ Exhaust
'88 F150 LWB 4x2, XLT Lariat, 302, 5 speed, 3.08
'99 Ranger, 4x2, 3.0, 5 speed, 3.73 posi

 

I agree. If your tank is rear-mounted, an electric may well help a lot.
As stated, pumps do not pull very well.. all the pressure is built up on the output side, and if you have a long ways from your tank to your pump, it's going to be harder to suck the gas up to the pump..
JCW DOES sell a selection, ranging from around 40$ and up..

J/.c

1965 Ford Galaxie 500 (okay, so not quite a truck)
460/C6 transplant @ 389hp/491 lb.ft.
14.29@103.8, 13-14 mpg heheheheheh

 

 

I have the same problem. If I drive on a hot or semi hot day, the motor will sputter and will not idle and then backfires. I am suprised that a modern engine with a pressured fuel system will do this but it seems like vapor lock is the culprit. My motorhome is a 95 coachmen with a ford 460. anyone got an ideas on how to solve this problem.

 

I think you should get readey to change the pump. This is a clasical descripton of a failing in tank pump. This is probley one of the most commen problems with Fords. You can do a serch on hear and on some of the RV forums.
http://www.rv.net/forum/
I would switch to a good electric pump and a regulator before the carb.
Good luck
Bill

 

Carb systems use what is called a hot fuel return system. A line with a fixed orifice (0.040 is common) pass fuel continuously back to the tank from a fitting near the carb. This keeps the fuel in the line cooler and also passes bubbles of vapor back to the tank.

A fuel injected engine will not vapor lock because the fuel pressure regulator always bypasses some fuel back to the tank while maintaining pressure.

 

NAPA has a 4-6 lb pump for around 32.00.My 79 L-800 with a 429 won't run without it,after it warms up.I also wrapped the fuel line from the mech. pump to the carb with aluminum foam type tape.You might also consider increasing the airflow in the engine compartment,as high underhood temps is usually the culprit.

 

Couple of things, first, I don't think you have an issue with vapor lock, as that's pretty much been a non-issue since the mid '70's.

Secondly, mechanicxal pump are designed to suck fuel, so no reason to upgrade to an electric pump, you gain nothing unless your current pump is failing.

It was mentioned above, and it's true, FI engine CANNOT vapor lock by design, just cannot happen.

All my jabbering aside, it's possible that you could change the FP and fix the problem, but most likely you would not be fixing vapor lock, but fixing a failing pump....assuming it cures the issue.

 

Actually the vaporlock issue stayed with us until the carb was phased out.

Pumps do not really "suck", atmospheric pressure above the fuel in the tank pushes fuel into a void caused by mechanical action. If air can enter the lines on the inlet side of the pump it will enter the line rather than that heavy sluggish fuel. If the tank vents do not operate properly the pressure above the fuel in the tank will be reduced as fuel is used reducing the pressure on the fuel that is pushing it into the pump.

An external electric pump can be used to replace most in tank pumps.

A pressure gage can be T'd off the fuel line to check for failing pumps or inadequate fuel delivery. A compound gage like the following can be used to test fuel system pressure and also used for engine diagnosis.

 

In reality, when the mechanical fuel pumps were being phased out, is when vapor lock went away, I should have said mid 80's, not 70's...my mistake.

Thing is, a mechanical pump drwas fuel under a vacuum, you can say it;s shift/change in atmospheric pressure, but it';s still a vacuum

As we know, and liquid under a vacuum has a reduced boiling point, combine a reduced boiling point with a hot day or fuel line routed near exhaust without a heat sheild, and fuel would boil and separate in the lines.

In tank pumps and external electric pumps to some extent, eliminate this, since fuel is pushed and under pressure...even without a return line to keep the fuel cool, the fuels boiling point is rasied while under pressure.

That's why I mentioned before rerouting the fuel line after the pump near the engine would most likely not help, since vapor lock would occur before the fuel got to the pump

 

Here's my experience ...

1984 F250HD as in the signature.

I had major vapor lock problems until I insulated the fuel line from below the engine to the "Hot Fuel Option" splitter valve and again to the carb. Now I have minor vapor lock problems.

The "Hot Fuel Option" was put on later carb'd 460's and consists of an electric pump in each tank and a valve to send excess fuel that the carb didn't need back to the tank, thereby keeping cool(er) fuel in the lines and hence, theoretically, avoiding vapor lock.

There was a follow up Ford recall that involved installing a "snap on" insulation material over the fuel lines ... even on the HFO engines. I got my insulation kit from a Ford mechanic that had leftovers in his toolbox.

Clyde builds up so much heat from the radiator, engine, exhaust, etc., that I have had the fuel literally boiling in the front tank. I'm talking a full rolling boil here! I now make a point of draining the front tank first so I don't have to use it after it gets a chance to heat up on the road.

We were doing July trips in triple digit temperatures but changed our vacation scheduled because of this HEAT problem. Our last trip, ~2000+ miles in 70-80* late May temps still left me vapor locked after a half hour "nap stop" in Sioux City, IA and I had to bleed the fuel line at the carb to get us going again.

My advice .... heavily insulate the fuel lines (and tanks) when ever and where ever possible. Even with this recall kit insulation already on the truck I'm going to try to add more. I'm looking at stuff to insulate the tank, which runs parallel to the exhaust on the other side of the driveshaft, just to lower the tank temperature. Even considering wrapping the exhaust system to cut down on underbody temperatures.

A working 460 generates a lot of heat. We can only hope to deal with it.