Cure for a nagging problem
 

Maybe this will help someone else. I have had 2 problems with a stock 389 in a 1962 Bonneville for the 3 years that I have owned the car. When the engine is dead cold and hasn't been started in a while it loads up when first started. Also it is hard to start when hot. It cranks over fine but you have to crank it over and clean it out before it will fire. I removed the Edelbrock carb that was on it to cure linkage, fuel line, vacuum line and air cleaner fitment issues. I thought changing it back to an AFB might cure the drivability issues. NO. I made sure the float level was good and the choke vacuum pull off was OK. Later I took the AFB off my 1964 GP. Bonneville carb worked fine on the GP but Bonneville still had same problems. Over the winter I decided that I would try one of the TRI-Powers that I had on the Bonneville. No better. That's 3 4bbls and the 3-2's also another fuel pump with no change. I decided "what do I have to lose"? I ran a return line back to the gas tank. (It already had the correct sending unit). Then added a GF-98 fuel filter with the return fitting. The car has never ran so good. Idle in park went from 750 rpm to 1100! This cured my problem for $30-$40. Maybe it will also improve my gas mileage. Also maybe this will help someone else.
PS There is a guy on ebay with a close out on the GF-98 fuel filters for about $17

The typical effects of today’s gas and too hot of an intake manifold.
Today’s fuel boils off at 150 degrees.
Do you shut the motor off the carb(s) heat soak, the fuel not only expands and raises the fuel level but slowly floods out the carb.
And this is not to mention the fuel vapor side issue .

Your return line releaves the pressure of hot fuel expansion.

A return from where? The float bowl?

Fuel 10% alcohol..
Ruins old style rubber seals.
Look for gasket seal kit resistant ethanol.

Thanks for the feedback.Good information.
How does the gf-98 filter work ? Does it somehow manage to return just vapor or does it return fuel like a bypass fuel regulator?
Glenn

I honestly don't know. Maybe someone else will answer. It was used on the early-mid 1960's V8's with AC so i figured I would give it a shot. It worked so well maybe I'll do it on my 1964 GP.

The idea of running a return line back to tank works because the fuel is continually moving in the line and doesn't sit stationary long enough to boil into vapor. Chrysler, as well as AMC, and a few other manufacturers used the fuel filters with a metered return to tank to solve vapor lock problems back in the 60s. Placed as close as possible to the carb the return system keeps cooler fuel constantly circulating avoiding boiling.

Article about what companies make filters with return lines and why they work, along with part numbers and pictures.

https://esgcapitalinc.com/fuel-filter-with-return-line/

Mopar used a return on their carb fuel filters up until they dropped carbs in the late 1980's.

Both my 67 and 68 FBs had a return line from factory fuel pump.

Have 10n line from mallory pump outside tank to pressure regulator before carb with 8n line back into tank.
Everyone said im supid back then.
Can adjust pressure from 0 to who knows how high.
Keep it constant 6.5
Also supplies 150 to 300 shot n20 if need.

Return
 

I had the same (hot) re-start problem on my 69 427/435HP Corvette with the 3 Holleys.
After it had been shut off for 15-20 minutes, it would crank & crank until it cleared out all the fuel- and then fire right up with black smoke out the side pipes.
I just lived with it- it didn't bother me much, and I had way too much other stuff going on to worry about it.
Couple years ago I decided to see what was going on.

Figured out that the problem was the accelerator pump well was heat soaking on the middle carb from the close proximity to the manifold- and the increased fuel pressure from temperature was pushing fuel out the acc pump nozzle.
The float bowl would continuously refill the well- and keep doing this until the fuel pressure inside the carb float bowl was reduced sufficiently- emptying the float bowl and flooding the engine.
I fixed it with a custom heat shield under the accelerator pump- but relieving the pressure from the fuel pump to the carb by installing a return on the fuel filter to the tank is a great solution, as you found.
That guy blowing out those fuel filters on ebay for 61-67 Pontiacs is Max Performance (Chris Casperson).

I have the same setup on my 63 Tempest currently- installed as a temporary main fuel supply- with a radiator support mounted Fuel Cell and a Mallory 140 down low on the frame rail.

Originally built & designed as an auxiliary dedicated fuel supply supporting the NOS Fogger jetted for a 250HP shot- integrated into the cast iron '65 TriPower intake I ran on my blue '65 back in the early 2000 timeframe.

Nothing stupid at all about that RW. It's an ideal setup.

Thanks for the info Sirrotica.
The feedback in that link certainly backs up Goatracer1's findings. I'm definitely going give this setup a try when I put my 69 Firebird back on the street.

Seems like all the people in the link must of had the return line and proper sending unit already existing on their cars because the common comment
was how easy it was to implement.
I guess having the return and sending unit not in use must be pretty common.

Glenn

A phenolic spacer under the carb may also help.
You need to get the correct style for whatever carb you are running.

My car didn't have the return line just an aftermarket sending unit with a capped off return fitting. I bought a 25-foot roll of the copper-nickel tubing for the return line. It wasn't as hard to run the line as I thought it would be.

One observation of these posts- there are some references to pressure on the fuel in the float chamber. I've never seen a carb without a vent to atmosphere from the the float chamber.

I may be missing the point of having a return-to-tank line from between the pump and carb. It sounds to me like a crutch for a failing float system (or too high a pump pressure). ???

The factory air conditioning equipped cars had the vapor return line. Along with that a smaller water pump pulley to speed up the pump for better cooling.

Both helped prevent vapor lock, so the engineers saw the need to prevent vapor lock and made changes which cost money. Money wasn’t spent unless there was a valid need to do so.

Now with today’s fuels whether your car is air conditioned or not there’s a need for the vapor return line more than ever.

Hi Jack,
You are absolutely correct. Thanks for pointing that out.
There is and should be no pressure in the float bowl- it is vented to atmosphere.
My response was poorly worded. Sorry about that.
The accelerator pump obviously requires a one way check valve- refilling from the float bowl- which in my case was the cause of the float bowl emptying- through the accelerator pump discharge nozzle.
The Shield I installed reflected the source of that thermal and its effect on the constraints of the accelerator pump volume.

The bowl vent on later engines (and possibly early ones) was vented inside the closed air filter. Fumes or condensed fumes are cranked into engine when started.

Years ago I figured out a way to find out if the suction side of the fuel system was drawing in air while running. You just put your fingers over the bowl vents on the carb while the car is idling, and it would immediately flood the carb. This doesn't pinpoint where the problem is, but it is a quick tool to find out if all the connections should be scrutinized for suction leakage. I sometimes used this to trouble shoot a fuel starvation problem.

I've found over the years if there is no air intrusion the car will continue to run the same as if the bowl vents were uncovered. It worked well over the years for me.

:2cents:

1. Wix and Purolator are both owned by the same parent company--Mann + Hummel. Best guess is that the Wix and Purolator filters are identical...buy whichever is less expensive.

2. MOST GM cars with "vapor return" have the vapor outlet on the engine-driven fuel pump. Connects to the same sort of plumbing as these filters would connect to, only the location is different. Specifically, the filter--placed between pump and carb--would vent vapor AFTER the outlet check valve(s) in the fuel pump, while a vapor-return nipple on the pump vents vapor after the inlet check valve(s) but before the outlet check valve(s). I have no idea how the before/after check valve issue affects operation except that you can expect all fuel between the fuel filter vapor-vent, and the needle/seat area of the carb(s) to vanish down the vapor-return plumbing when the vehicle sits awhile--and it's going to take some cranking to push the fuel back up to fill that plumbing again. OTOH, venting vapor directly from the engine-driven fuel pump will make the pump more efficient.

3. I am VERY hesitant to put HOSE on the pressure side of a fuel pump. Installing these filters between pump and carb means you've got sections of hose on the inlet, and the two outlets of the filter. There are plenty of OEM applications that do this...but you'd better be inspecting that hose on a regular and frequent basis.

The return limes usually have orifices in them to only meter vapor at a high rate, and fluids at a much reduced rate. The return lines usually are plumbed above the siphon point of the carb, and the tank so that they don't empty the lines upon shut down.

The Kawasaki engine on my Ariens mower is plumbed like this and one time it came detached from the clip that held it elevated, the gas flooded the carb until I realized the hose was no longer at a raised position. as soon as I clipped it back the flooding ceased.

I have seen some bypass filters on certain applications that were hard line plumbed between the carb and pump, but that is the exception, most are neoprene hose. To be fair when this type system was implemented in the 60s there was no ethanol added fuels to accelerate the deterioration of gas lines. The gas line material was also of better grade that it is today.

Chrysler was the most outspoken when ethanol blended fuels were mandated in the 70s that the OEM materials they used in manufacture were breaking down prematurely when exposed to the ethanol blended fuels. They argued that they weren't going to warranty the problems associated with ethanol fuel deterioration because their systems were designed for pure gasoline.

Hi Bob, did you ever check the fuel pressure before- and then after you made the swap to the new filter/return?

I went to a Holley Blue pump at my tank many many years ago for this reason. Refills the carb when Key on so there no more 3 min of cranking to get fuel up. LOL
Right now I am also incorporating a Oil Press Sw and a push button. So, havent run her in a few days, I know carb will be empty, I can push the button for 5 sec or so. You can hear the pump note change when bowl is full. Then start as per normal. But if I just came out of a store, Just start her, Fuel pump will automatically start when oil press switch closes. AND, if engine stalls, or an accident, oil press drops, switch opens and fuel pump shuts off for safety.

Sorry never did a before and after comparison.

Fuel pressure is/was clearly the root of the problem.
If you swapped carbs, then whole intakes (to TriPower carbs)- and still had the same exact issue- that's telling you something.
The return you installed is now bleeding off just enough fuel pressure through that orifice to make things happy.
Should have checked the fuel pressure first, before going through all that work you did.
At that point, you might have said "Wow- 9psi- must be time for a new Fuel Pump!".
What is interesting to me though- is that 61-67 Pontiacs actually used that Filter with the return in production.

Something I ran into decades ago when Pontiac was having all the nylon timing gear failures. I had a customer car that a timing gear replaced, someone didn't get the eccentric installed properly making the fuel pump stroke much longer than it would normally be, raising the fuel pressure too high because of the increased stroke.

Replacing the eccentric to it's original position cured the problem, just something I ran into many years ago that can cause too much fuel pressure with a stock style pump. Might be worth checking if your fuel pressure is exceeding the capacity of the needle and seat.