|09-25-2019 10:29 PM|
You dont want to use your vent line because fuel can pool in a area of hose on top of tank blocking the vent which will cause filling problems or if stored could cake and block that line.
Tank, filter, pump, filter, regulatior, then back to the tank. System works. You can use your old tanks feed line as the return line. You just need to pull the sock off. Just try to point the return away from the feed so you do not aerate the fuel.
|09-25-2019 06:57 PM|
One thing I considered doing, since I'm near the tank anyway is to install a tee coming off the discharge of the pump and run a 1/4" line to the vent on the filler neck. That way some fuel is constantly be recirculated in the system even if it's not from the engine compartment. The downside is I'm going to loose a bit of fuel pressure but this pump is supposed to be rated for twice the HP my engine is making.
I don't think this Carboyle pump I plan on installing has any internal bypass mechanism inside it like the Holley pumps.
I have actually had better luck dead heading electric pumps than using a recirculating line.
Years ago I had a Fiat 124 Spider (still own one today) that came with electronic fuel injection. The system was botched so I had these dual Weber IDFs I wanted to try out.
I replaced the fuel injected pump with one of those Facet cube pumps. I thought it would be a good idea to use the fuel return line since there was already one on the car.
Every now and then the car would just act like it was running out of fuel and stall. If I let it sit for about 30 seconds, it would run fine.
I installed a pressure regulator before the carburetors set at 3 PSI and blocked off the return line going back to the pump. After that I never had any problems.
I'm wondering if more fuel was being diverted back to the tank than to the carburetors?
|09-25-2019 04:03 PM|
Bogie I might be misunderstanding what your saying and please forgive me if I do as I am not an expert as I don't have the years of experience like you and others as I am only 43 years old and have not come on to my own in doing things for myself until around 2009 as everything before that time I had no clue about hardly anything except changing fluids and checking levels and that is about it. I did not even know hardly anything about adjusting and tuning carbs let alone anything fuel system related. Its only in the last year that I have been reading on things and from others on here and also doing my first hookup of a return line.
I run my main line to the mechanical pump then run it out to my holley fuel pressure regulator which has the built in return line which is 5/16 and run it all the way back to my tank on the return port on my fuel sending unit. I have never had any more fuel related problems since doing this with my mechanical pump and I keep excellent pressure at all times and I also no longer have any fuel boiling issues like I did before when it was setup as a dead head system with the electric fuel pump. And I also don't mean anything negative towards you so if it sounds like I do I don't as sometimes I am not good with words and mean no harm or disrespect in anyway shape or form.
The electric fuel pump went out before I could even hook up my return line and got the regulator that has the return feature. Maybe its not the traditional way of hooking up one but its working for me and I would not know a different way of hooking up so please forgive me and I have seen a diagram before of a different way but my fuel is no longer getting overly hot like it did before since I have the return setup like it currently is.
Sorry for my lack of knowledge but I am wanting to learn of other ways but I have not seen them posted or I might have missed that and might have lost or forgot to write this information down to add to my other notes that I write off of these forums that may be helpful for future issues. I no longer use an electric fuel pump and only use a mechanical pump since my electric one went out and I had enough of it.
|09-25-2019 11:43 AM|
Eric, you're into the classic situation I harp on to which it seems no one pays attention too. Including the OP!
The self regulation Holley pump and other makers of these type pumps use an internal bypass.
With internal bypass there is no way for the bypassed fuel to cool. No length of line and certainly no ideal situation of retuning to the tank.
The fuel goes through the pumping element, gains pressure and of course heat. The amount not needed by the engine is bypassed within the pump to be delivered back at the intake side where it goes into the pumping element to be pressurized and heated again.
For some portion of the pumped fuel this process loop just keeps repeating. Obviously the less fuel the engine is consuming as at idle through cruise the greater is the amount of fuel that is making this bypass loop inside the pump. Which of course is heating all the delivered output whether that is the fraction that gets to the carburetor or has been bypassed.
1. A pump with a control module that reads pressure and either modulates pump speed through voltage reduction which results heating the pump motor or uses Rocket Science, Pulse Width Modulation to rapidly cycle the motor through off and on cycles of varying length to maintain the desired pressure without frying the motor's windings.
2. Or to use a remote bypass regulator mounted as close to the end user by it carburetor or fuel injection. This does several favorable things:
a. the pressure everywhere is the same as the regulated setting. This alone helps reduce heating the pumped fuel.
b. a return line that has feet of distance allows pump heated fuel some cooling so even if the fuel is looped back to the pump inlet it has some time and distance to bleed heat before reentering the pump.
c. the best return situation is back into the tank. This provides the time and distance advantages of part "b." plus the dilution into the remaining fuel to both allow cooling and any trapped vapors to bleed out into the tank to either condense to liquid or to vent off.
Part "2." in general and section "c." in particular is my favored go to system in this age of highly volitile fuel, it solves about 99 percent of these problems with fuel vaporizing inside the delivery system.
Since fuel loss from carburetors after shut down is also a problem I put this system on a manual "Prime" switch that allows the pump to be turned on before bringing the elctrical system up with the ignition key switch. This provides some time to fill the bowls before commencing the start sequence. Once commencing the start sequence on the key switch, I shut off the pump prime switch. I use a toggle with a safety cover, one whack and it's off.
No difficulty, pump the throttle a couple times, crank it over it fires like it's got injection. Pretty much fits my KISS principle of keeping it simple as possible, easily repairable, and dependable.
|09-25-2019 10:18 AM|
Good luck with your electric fuel pump and hope you can get it working well and not have any issues. I ran a mechanical fuel pump on my small block chevy for ten plus years with a dead head system and no issues ever with fuel boiling or vapor lock what so ever regardless of how hot it got outside and fuel pressure always was fine at 6 psi.
Last year I hooked up a holley electric pump and forget what color as they have a red and a blue but mine is the one that does not require a fuel regulator and maxes out at 6 psi so they say but I had it bolted on my frame as close to my tank as possible and it would suck a tiny bit through the line starting off then it went down to the fuel filter then to the pump and it would then gravity feed and then run all the way to my carb.
At first it was ok but as the summer heat got hotter I then started to loose fuel pressure. It would start off at 6 psi then after it would get so hot it would slowly drop to 2 to 3 psi at the most and even though it would still run ok for how I drive it still can't run in all conditions with that low of a fuel pressure and then for the first time ever in my life time after I shut my truck off I had fuel boiling in my fuel bowls.
I did not get vapor lock though but the fuel boiling became an issue as it sat when I was done driving for the day it would not boil enough to drip out of my boosters it would evaporate and my fuel bowls would almost be empty after sitting for three days. I then tried to install a phenolic one inch spacer and it still boiled fuel after running it and still loose fuel pressure and my underhood temperatures was pretty hot all the time I owned the truck since its pretty compact in there but all my fuel lines were away from my exhaust.
So earlier this year at the end of spring time in early May I started to have my fuel pump loose pressure as always but then it would start to get so bad that my pump would kit working and loose pressure all together and left my truck quitting on me and had to wait a while before I could start driving it again so it could get some fuel pressure back after it my hunderhood temperatures cooled down enough. I got home after a 5 mile drive through town and it died.
I was done with that and went back to my mechanical fuel pump and then I installed a holley billet fuel pressure regulator with a built in return line and it got rid of my loosing fuel pressure issue and I also have no longer shown issues of any fuel boiling after shutting it off even though its still pretty under my hood. I also installed a cowl hood so it could vent more heat out as well.
I live in Ohio and from 2017 on back I never had any issues with fuel boiling or anything close to it but since 2018 I have not changed anything before all these issues started and I think they have changed the fuel formula even more because of EPA stuff and the fuel boils even at lower temperatures now and don't work as good with carbureted vehicles like in the past since they have gone to fuel injection and now direct injection its getting harder and harder to keep the old school stuff going without having to do a lot of tricks and parts to keep them running with out issues.
My next step just to help is wrap some heat wrap around my fuel lines under my hood as best as I can and the return line is almost a necessity with today's fuels and how picky they are.
|09-24-2019 09:44 PM|
If you want electric pump and can not mount it below the tank a in tank pump is your best option. You may be able to find an entire TBI tank that fits your application.
These pumps last for years. I had one running over 20 years 300k still making good fuel pressure feeding a tbi unit.
You do need to drop your tank and install new straps. But as far as keeping the things cool they can run the fuel up to the regulatior and back all day long. They can do this while staying cooler and quieter then many inline pumps.
Maybe some model specific forum somewhere knows of a Tbi tank that will swap in with minimum modifications.
|09-24-2019 05:45 PM|
|55 Tony||Good luck with that. Get it done in a couple days and you will still have some hot days to test it.|
|09-24-2019 05:21 PM|
I hate to beat this subject like a dead horse and all....
After thinking this thing through, looks like I'm going to just mount this electric fuel pump I got on my 68 Fairlane, insulate the supply line in the engine compartment and see what happens. If I still have issues, I will tee off at the carburetor run a fuel return line back to the tank.
Once last question. Any chance this vapor locking issue is happening in the line before it even get's to the mechanical fuel pump and not after it as I visualized?
The fuel line runs on the bottom of the car instead of inside the cabin (like some other of my cars) protected from the elements. My car is also lowered about 4". So I got this 10 to 15 foot exposed fuel line sitting 6" off the hot asphalt which is probably well over 130 degrees on a 90 degree day. So if the fuel is vaporizing in the line before it even get's to the mechanical pump, could that be what's happening? Also considering the length of the line. That's allot more fuel to get hot while idling and allot more work the mechanical pump has to do.
From what I've read a mechanical fuel pump basically just creates a negative pressure on the fuel line. They don't actually "pump". This acts like a straw to draw the fuel out of the tank. So if fuel is boiling or turning to vapor in this section of line, it could be even pushing fuel backwards into the tank causing an even bigger void in the system. Kind of like trying to suck the last bit of soda out of the bottom of a drink cup filled with ice. Is that a good analogy?
So by pushing "cooler" fuel from the tank using an electric pump, should force or compress any vapor that may build up. That's the theory. Unless of course the pressure in the line exceeds the pump pressure.
I'm starting to wonder if the fuel line almost touching the timing chain cover was what was causing my problems all along but I like the idea of being able to pump fuel after the car sits for awhile without having to crank and crank. So I'll see what happens.
So after racking my brain on where to mount this electric fuel pump, I watched this video and BINGO!
Skip to 1:58 on this Youtube video. He's installing EFI on a Chevelle but the under the rear end of the car looks just like my Fairlane. He makes a bracket, bolts it to the underside of the trunk and mounts it parallel with the bottom of the tank. Sweet!
The pump I bought is made by Carboyle. But they don't even have a corporate website! It looks like a rebranded version of the Mr. Gasket 12S that sells for twice as much and other pumps on Ebay. It has the same specs as the Mr. Gasket 12S pump. Just another example of rebranding. It's probably made by a company in China and 10 different companies just put their name on it.
I downloaded the instructions from Mr. Gasket's website because this pump came with no instructions. I know how to wire up a fuel pump, I just wanted to know if it said anything about where and how to mount it.
It's not very forgiving! The pump has to be mounted 12" from the fuel tank supply and it has to be clocked at a 45 degree angle with the outlet pointed upwards. It doesn't say anything about mounting it vertically. Any idea why mounting it at a 45 degrees angle is required?
I hear complaints about electric fuel pumps failing. I wonder if it's because people ignore where to mount them. You can pick an ideal place to mount a fuel pump on any car but that doesn't mean it's going to work.
A friend once mounted one of those Facet cube pumps in the engine compartment at the top of the firewall on a Fiat 124 Spider! I looked at it and thought, how in the world is that thing possibly pumping any fuel.
|09-21-2019 11:37 AM|
Good point on the copper tubing. Years ago when I built my first turbo system I had used copper tubing for the oil supply line and it cracked at the fitting going into the turbo. I forgot about that.
I picked up that "special" AMC/JEEP fuel filter with the 5/16" ports and the 1/4" "vapor" port with the small orifice yesterday from O'Relieys. It's the store brand version so I got it for $5.99. The WIX filter was $20.
I capped off the outlet port with my finger and blew through the inlet and heard air coming out the 1/4" port so doesn't look like I could just run a line coming off of it to the ground. So as Tony says, It would most likely puke gasoline as the engine is running.
Since everybody (on Youtube anyway) seems to have their own version of how to cure this vapor locking issue on their old cars, I've been thinking of ideas since I can't be working on my car.
If running an electric pump and a return line is the only option, I'll do it but I thought of another idea requiring less plumbing that might allow me to keep my mechanical pump.
First I'd install a 3/8" check valve in the hose between the pickup tube on the sending unit and tubing going to the pump. I've got one coming. That way no fuel get's pushed backwards into the tank.
Place a TEE (or this three port filter) before the carburetor and run the smaller line into another TEE before the mechanical fuel pump. This would create a closed loop fuel system. I might have to plumb in a regulator before the carburetor just in case (couldn't hurt anyway). I don't know if feeding pressurized fuel before the pump would multiply the fuel pressure. The reason I wonder is I've heard of people running fuel pumps in series on turbocharged engines to boost fuel pressure.
I've also heard of people tapping into the weep hole on mechanical pumps to increase fuel pressure under boost applications. I believe Paxton used this method back in the early 70s on their centrifugal blower systems.
Getting rid of the heat: Running a closed loop system wouldn't do anything as far as reducing the heat from the fuel. Since heat is the main cause of this. It may make it worse, so that is a concern. But would help equalize the pressure and reduce any voids in the fuel lines.
From what I've read, the mechanical fuel pump is a heat source itself since it's mounted to the engine block. But if this is where vapor locking is starting at then an electric pump upstream maybe the only way around it.
Before sending the fuel coming off the tee back to the pump, I've got this small transmission fluid cooler I could mount in front of the radiator so the fuel could be cooled before returning it before the pump. That maybe required after all. I'm trying to visualize what's going to happen. I was going to use clear poly tubing as fuel line while testing so I can see what's going inside the fuel lines.
I realize this sounds like a Rube Goldberg contraption and all.
One sure way to test this is to zip tie the fuel line going to the carburetor to the upper radiator hose and let the engine idle. That would maximize heat transfer. If it passes that test, then it should work.
I've actually got all of this stuff already so it's not like I'm going to have to spend allot of money on brass fittings and parts.
Something else that comes to mind. When the fuel in the line starts to boil and expand after I shut the engine off, I'm wondering if fuel is being pushed past the float valve. And that's what causes fuel to leak all over the carburetor during a heat soak. That's why I wonder if installing a regulator might be of some benefit in that regards.
I'm still convinced this issue has more to do with the 10% butane content in gasoline than the ethanol!
Adding the check valve at the tank might be of some benefit anyway. Because on both incidents when the car stalled on me, I pulled the 3/8" hose off going to the fuel pump, there was no fuel in this hose. Just a few dribbles. I would have expected some fuel to pour out. I kind of wondered if there was some void in the line going to the pump. Maybe the exhaust or hot asphalt was actually heating the fuel in the line before it even got to the fuel pump. On some of my other cars, the fuel line runs inside the cabin to protect it from the elements. Ford chose to mount the tubing on the frame rail and inside the front wheel well on this car!
My boss told me his parent's were driving through the Arizona desert in their 2005 Toyota Previa minivan and the engine just quit. They had it towed to the dealership. The dealership said that the asphalt on the interstate that day was so hot, it actually caused the fuel in the lines to get hot and boil. This is on a modern fuel injected vehicle!
Apparently they have seen this before. They just let the car cool down for about 12 hours, the van started up and they said, "you are good to go!". That was their fix.
So apparently this problem doesn't happen to old carbureted cars but modern fuel injected cars as well.
|09-21-2019 07:29 AM|
I'd order some Ni Copp line, 25' rolls are pretty cheap now on Amazon. Also go as large as your fuel line coming in.
Oh, and no guarantee's. Like I think I mentioned on mine it fixed the problem 95%. Only when going WOT with a 454 from nearly a stop, at about 70mph it would still sometimes "run out of gas". The electric fuel pump fixed that. I even had a 1/8" insulating spacer on my mechanical fuel pump.
|09-20-2019 03:47 PM|
I am using copper for my vent lines mainly because they are highly visable. Worst case it cracks and vents to the atmosphere till i notice it.
But I would never use it for a direct fuel line.
Use rubber line. In most cases fuel injection line is only 1 to 2 dollars more a foot and better built.
Brake line will work well for straight stretches using rubber for bends. Double flare the ends and double clamp for years of trouble free issues.
|09-20-2019 12:42 PM|
There are two places I could dump the fuel. One is a drain plug in the corner of the tank. Maybe not the best place.
The other place is the vent line coming off the filler neck. This car did not come with a charcoal canister from the factory so I don't know why they didn't just use a vented gas cap.
Then just tee off just before the carburetor.
After all is said and done, will this return line allow me to keep my mechanical fuel pump? Or would I still need to use this 4 to 7 PSI electric pump? It's supposed to move 35 GPH.
Not to get off the main subject....
I maybe repeating myself but I've got an MGB that has an electric fuel pump that makes a mere 1-2 PSI and has a Weber conversion. It has no return line.
After I got the car running, I connected a pressure guage to see what kind of dead head pressure this pump was producing and if I needed a regulator because Weber's do not like more than 3 PSI. The guage barely registered. Yet the car has never starved for fuel. Of course it's only around 80 BHP.
I have never experienced vapor lock or hard starting after a hot soak on that car. Despite the fact that the intake and exhaust are on the same side of the engine, the fuel line is about one foot from the exhaust header.
Look at the fuel filter mounted on the firewall to the right of the black heater box and follow the hose going up to the Y fitting on the carburetor.
The only thing I can think of as to why this car does not suffer from vapor locking is the fuel hose is just not getting that particularly hot.
I've got several old cars (too many actually) and this one is not that particularly hard to start after a heat soak and I am somewhat baffled as to why.
I do run 93 E10 in it. On 87, the engine tended to "run-on" after I shut the engine off. On 93 is does not. But someone had the idle speed bumped up to 1000 rpms so that may have been why. I've since turned the idle speed down. Static timing is spot on.
Some goober had removed the thermostat so it's probably been running cold and may have developed carbon buildup.
I put a new thermostat in it and it has never overheated on me.
|09-20-2019 07:34 AM|
Yes it does sound that way, big time.
Yes to Butane, finally someone else knows it's not the ethanol.
Insulation won't help since the fuel gets the hottest in the pump mounted to the engine, insulation would just hold the heat in.
Just bite the bullet and run a return line. Anything else is just wasting your time. To tap into the tank, remove the fill tube and add a bung to attach to the return. No need to tap into the tank itself.
|09-20-2019 07:25 AM|
This may sound like a Rube Goldberg contraption but I have one of those small transmission coolers I could mount in front of the radiator, so the mechanical fan could pull air through it. I could feed the vapor line into this cooler then return it before the pump.
One concern is if the return line goes empty, could it suck in air?
I could just use a 5/16" tee before the original filter that screws into the carburetor, feed the hose through this transmission cooler then back in before the fuel pump.
Another concern. If the pump produces around 6 PSI and I'm sending fuel back before this pump, will this multiply the fuel pressure?
I ordered a 3/8" check valve I plan on installing between the sending unit pickup tube and supply tubing at the tank just in case I decide to experiment. That way no fuel get's pushed backwards.
It's a shame we have to find ways to modify our old cars to get around this new modern fuel with such a lower boiling point than leaded gasoline. People think ethanol is the problem but I think it's more the butane they put in fuel. Gasoline is made up of about 10 different chemicals.
Below is just one gasoline MSDS. I'm sure the the recipe changes from company to company, season to season and state to state.
Ethanol tends to boil around 173F. Butane will boil as low as 30F! Some gasoline contains Isobutane which boils off at 10F! I think that's in California.
Who knows, maybe just insulating the fuel line coming off the fuel pump would be good enough.
|09-20-2019 06:13 AM|
Nope, I look a little rough but not that rough. I have a short non narrated video on there somewhere that shows me using a plastic filter to see the vapor, then me putting a garden hose on the fuel pump to cool it down. I think in that video I actually have the bypass filter up very close to the carb, and added the plastic just for a "site glass". If you do do it, put the bypass as close to the carb as possible.
I don't think a tee and a loop would give you a fair idea if it would work unless the hose ran for quite a while in cool air and gave the vapor a chance to cool and return to liquid again. Otherwise you will be pumping vapor into the fuel pump.
I skipped through most of the video but caught enough to see that he also says the vapor starts in the fuel pump. So pumping vapor to where the vapor starts... Oh, I didn't know they made one without an orifice, you will certainly need an orifice or your fuel pressure may go down so low that it will have new problems.
|This thread has more than 15 replies. Click here to review the whole thread.|