Hot Gas Tank
 

I took my Camaro on a road trip yesterday that lasted for about two hours. It was the longest trip that I had taken it on. Most are half hour to an hour. When I got home after the two hour drive, I noticed a weird sound. It was a low hiss that I tracked down to the vented gas cap on my gas tank. I slowly removed the cap and it sounded as though the fuel in the tank started to boil. Needless to say, that scared me a little. I touched the bottom of the stainless tank and I couldn't hold my hand there for more than a couple of seconds. There isn't any source of heat close to the tank, my exhaust dumps in front of the rear axle and isn't closet to any fuel lines. The only thing that I can guess is that my fuel pump is circulating the fuel so much that the gas isn't cooling off in the tank like is should. I run a MangaFuel ProStar EFI 600 pump that is rated at 850GPH. I bought this pump so that when I do twin turbos in the car I wouldn't have to buy a new pump. Am I thinking right that the fuel isn't allowed to cool off properly and also that the vented cap and the vent in the top of the tank aren't big enough to relieve the pressure, which is higher because the tank is so hot? It's definitely only going to be short trips until I can figure out what is going on.

I guess if I put cooling fins on the gas tank I'd have a second radiator.:lol:

Sounds like vapor lock... anyone else?

What brand is it?

-Paul

Hey Mike, where's your return plumbed?

Wow, sounds spooky.

Fuel pump generated heat sounds like a likely scenario but I can't say with any certainty.
What is your fuel line routing like?
I sure wouldn't drive the thing till you sort it out.

The guy that I bought it off of said it was a Rock Valley, but when I called them about tank straps they didn't think it was one of theirs. So, I'm not sure who made it. I don't think that the tank is causing the problem though.

Hey Matt, Haven't talked to you in a while. How's it going? The return is plumbed back in to the top front of the tank. It's the line that goes in above the fuel filter in this picture:
http://www.camaroheaven.org/images/a...rebuild623.jpg

That's exactly how I feel!

I have the pump mounted between the rear axle and the tank and it's connected to the tank with -10 braided with a filter in between. A short piece of -10 braded connects to 5/8" stainless that runs up to the front. Then braided to another fuel filter to hardline that goes to the fuel rails then back to the tank using -8 braided and 1/2" stainless. The return line follows the feed line back to the tank and dumps in to the tank through a fitting in the top-front of the tank. I have more pictures of my fuel system on my site.
Pictures of the back of the system are on this page
http://www.camaroheaven.org/modules....id=2&start=616
and for the front are on this page
http://www.camaroheaven.org/modules....id=2&start=560

Thanks for the help guys.

You've got a big pump which bypasses a lot of fuel. Compound that with the fuel running through the heated fuel rails before being bypassed to the tank. There are a couple things that would help a lot.


#1 Get the regulator bypassing before the fuel rails. That way the engine doesn't get to heat all the fuel.

#2 You may need to install a pump controller on that pump to lower the voltage during cruise/idling conditions. This creates a lot less heat in the pump and heats the fuel less.

#3 Install one of these nifty cool cans on the return line to the tank to cool the fuel!

http://www.yenko.net/photos/data/548...r_2005_055.jpg



Jody

Thanks Jody. The oversized fuel system is all because of the turbo headers I bought off of you:D .

I might try the regulator before the fuel rails. I set the system up accourding to the MagnaFlow (now MagnaFuel) diagrams and they put the pressure control unit after it flowed through the fuel rails.

MagnaFuel says on their website not to use a voltage step-down device and now looking at the page that is on (http://www.magnafuel.com/support/index.htm) they say that the tank vent needs to be at least a -8 which it isn't close to. I will try that first to at least get it up to their specifications.

If I can't figure it out, I'll definately be mounting a big fuel cooler box in the trunk. I think that instead of ice, I'll have my A/C system dedicated to cooling it off. :lol:

Regulation prior to the fuel rails is a good idea. Send only the fuel you need to the engine compartment.

Another thing to look at is the number and type of fittings you have in the entire circuit. The more fittings (especially if they are 90deg) and the more tubing bends you have the greater the restriction. This may be contributing as well.

My question about the routing was aimed at the lines and their proximity to your engine/trans and exhaust.

Thanks True.

I tried to use only a couple of 90* fittings to try and cut down on restriction but there are quite a few bends in the system because of the way I followed the frame. I think that the lines are far enough away from the exhaust. They run on the inside of the frame just up to the subframe connectors and then they run outside all the way to the front. The closest that they might get to the exhaust is by the front of the header. This is the best picture that I could find.

http://www.camaroheaven.org/images/a...rebuild653.jpg

It's hard to tell how close it is. I'll measure it tomorrow and let you know.

Interesting...
 

I've had a similar experience with our '62 Galaxie, but not so the tank was too hot to touch.

You may also want to plumb in a fuel cooler... Flex-A-Lite has one that looks like a steering cooler, Barry Grant has a heat sink type... it's a tubular piece of extruded aluminum about 10 inches long with fins on it and AN fittings on both sides. Of course, the scrapyards are full of ideas... a power steering cooler from a Ford cop car with the correct fittings on it would work well, too.

I'm concerned about the fuel tank vent. I've got the stock vent in our 62 ragtop, and the airflow around the car always keeps a healthy supply of gasoline vapors flowing up the back and into the cabin when the top is down... which is just about always. Any suggestions on alternative venting?

- Kevin Oeste

I measured the distance that the fuel line is from the front of the header and it is about 1.75" from it. How close is too close? I am going to try and build a metal shield to block the heat from the lines to try and keep as much heat out as possible.

Bingo, i'd bet that is your problem right there. Stainless line and pumping that much fuel will heat things up pretty quickly. As well the fuel in the tank very well could have been on the verge of boiling, depending on the grade etc. gasoline can have a boiling point in the 120F range.

I would keep the fuel line as far away from a huge heat source as possible. Think about it this way, with the engine running at 2500+rpm for an hour straight, would you want to hold your hand 2" from the header tubes?


I'm curious why they advised against using a voltage regulator. From my experience they work very well and reduce load on the pump as well as electrical system. Dial-a-flow is good stuff.

Thanks ProStreet R/T. Here's what they have on there website about voltage step-down devices.

I had the same problem. I went through 3 Aeromotive pumps before adding a controller and making my vent 1/2". Very expensive lesson!!!

I think you mean 850 lb. per hour of fuel is what the fuel pump pushes. If you figure it up you will see how long it takes to recycle the whole tank to the engine and back. That will make it easier to understand the problem.

The pump pushes enough to support around 1000 hp. at WOT. You are pushing that much fuel at idle and while cruising and you engine needs 1/2 of that at WOT. That is your problem main problem along with the fuel line being too close to tthe header. You can insulate the line to help or move it.

The pump issue is going to need some work/money. If you have a pump that moves allot less fuel put it on until you get the turbos on. I assume your engine makes no more than 400fwhp now at WOT, so any oem external pump for an injected V8 car will work. I am sure there are many 4 or 6 cyl. also that will work.

Most aftermarket pumps are not continious duty pumps made for the street. They are made to run for short time frames on race cars. They build up heat in the fuel and make the pump cavitate which leads to more heat and vapor lock and/or a pump failure when used in a street car. The pump usually will let you know by getting louder and louder before quiting.

If you are going to drive your high hp turbo/blower/nitrous car on the street for any distance then look for a pump that can use a controller. I prefer to use oem stuff because it will last. Bosch makes some good pumps (I use two on my car with a controller) that are quite. I use an aeromotive controller. Weldon makes a controller but their fuel pumps are very loud.

The aeromotive controller is a pwm controller, as I understand it, the pump gets the full voltage, only it gets turned on and off so the motor does not run as fast.

i two have been fighting the same problem after going to fuel injection i get to a half tank and the pump caviitates and the car quits running i added a aeromotive controller this weekend but the msd went bad so did not get to try it. the controller steps down the voltage to the pump.

A PWM controller is OK, a voltage step down box is a no-no.

Simply lowering the voltage makes the pump very "lazy" and at very low voltage it can stall.

A fuel cooler, as was stated, would be a very good investment in addition to the controller. Put it in the return line.

Thanks. I'm going to put a heat shield on the lines by the front of the engine and see about adding a bigger vent in the tank. I'll then check in to getting a controller and fuel cooler as the funds allow. I guess I can use the time to install the mini-tubs in the back since I won't be driving it until I get it fixed...

How much is a new Aeromotive controller ? I have a used one off the Mule I'll sell you for whatever is fair. Less than new. I switched over to two Bosch pumps.

IMO the bosch pumps are the way to go. Quite and oem stuff that is made to run for long periods. I also went to two of them and used the aeromotive controller for them.

The cool can might help, but is just something else you have to package and plumb inside the trunk.

I think I gave 150.00 for my Aeromotive controller used.

Does anyone know for sure if it is a PWM device? I tried looking on their website, but there are no technical specs other than the install document. They do say that it "automatically steps voltage down", but I don't know how to interpret that.

I just spent an hour talking with Bret at Aeromotive about my fuel system and we discussed your problem.

The main issue is that you are moving way too much fuel in a circle since you pump is so big for your current need.

You could go to a smaller pump or Add a voltage controler to the pump you have.

You could also add a cooler with a fan (permacool?) to the return line back by the tank. This would cool the returned fuel quite a bit.

Having the regulator after the fuel rail (I was told) is the best setup with the "horseshoe" method (before the rail) being second. Returning back by the tank is the worst of the three.

I suggest you call up thier tech line, nice guys with lots of info.

I'm all for any return other than after the rails; grab ahold of the fuel rails after the engine is completely up to temp and been driven for a while. The gas is in there much longer than if the exhaust pipe gets close at a small point in the line. Neither are good however, but I think insulating the fuel line near the exhaust will definitely help, but if you're going through the rails to bypass you still may have issues.

By the way, many of the new oem cars are regulated in the tank (Vettes, GTO's, etc.) or do not have a bypass from the fuel rails back to the tank (Lightning, etc.). I ran a couple cars regulated back by the tank and they worked flawlessly.

Jody

I may be mistaken, but I believe the vette LS7 fuel system is set up just as you describe. Regulated at the tank, or somewhere way back aft, with no return from the engine compartment.

The Aeromotive Controller - looks like it varies voltage to the pump.

http://www.aeromotiveinc.com/pdetail.php?prod=31

The reason is that you get the most consitant fuel rail pressure (at the injectors) by having the reg after the fuel rail. This also eliminates cavitation and other problems.

Also, having the reg after the rail means the fuel flows through the rails at a pretty quick pace is not sitting there when the car is running.

The Aeromotive fuel guy says OEM companies regulate at the tank only to meet emissions standards an evap not necessarily because it's the best way. Also, what works for a 400hp engine may not work as good for a 600hp engine.

I think he could go a long way to fixing his prob by running the return line through a cooler (heat sink) and/or going to a smaller pump (or pump controler)

This is just from my discussions with Aeromotive :shrug:

It is, in fact 4th gen fbodies return INSIDE the tank. Just cause the OEMs do something a certain way does not make it the best way. They have to confirm to a whole set of regs we don't.

Also, the only constant flow of fuel is before your regulator. After the reg it fluctuates a bit based on need. When the return and reg is way back by the tank the regulated fuel has to flow quite a ways to the engine. This leaves room for changes in the pressure and such. This is why in a factory deal there's a supplemental "regulator" up in the fuel rail.

Anyways, it sounded more intelligent when Bret explained it to me.. lol

Nah, that makes perfect sense and in fact with that sort of OE setup your fuel may actually pick up more heat sitting in the rail waiting to be deployed to an injector than it would if it were being circulated. Of course, it wouldn't be going back to the tank either.

Looks like both have their +'s and -'s.

I agree on most of that, but I still won't run the regulator on the back side of the rails, if it bypasses fuel to the tank. I made well over 800 rwhp with the regulator at the tank, worked great, no pressure issues at all. The closer to the injectors the better probably, but doesn't mean the rear ones don't work fine.

The Vettes have been regulating back there for several years. My GTO was the same and the fuel pressure cannot be more steady.

I also agree with you, the cooler is a good idea along with a pump controller if available, or better yet OEM pumps.

Jody

Also, do not forget that many late model OEM apps use a PWM controller to drive the fuel pump only as fast as required to relieve stress and wear on the pump; they spin the pump just fast enough to deliver the correct volume and pressure at the injectors for a given load criteria. Some even control the fuel pressure via pump speed.

OEM apps with deadhead setups also tend to use pulsation dampers up near the injectors to even out the pressure given the uneven on-off-on fuel delivery of the injectors which is more pronounced in a deadhead setup.

A setup with the regulator at the tank and "deadheaded" rails can be prone to vapor locking after you shut the engine off. When you shut off the engine and the fuel flow stops the fuel in the rails can boil off from heatsoak creating a hard start condition. Simply cycling the fuel pump won't fix this since there isn't a constant flow of fuel through the rails back to the tank as in a system plumbed with the regulator after the rails which will have fresh fuel go through the rails and displace the vapor. Granted, if the regulator is working properly it will hold the fuel pressure in the rails after engine shut off which is to prevent vapor locking. Once that pressure subsides then vapor lock can be a problem. Most OEM manuals I've seen specify that pressure at the rails be maintained for a minimum of 20 minutes after engine/fuel pump shut off to combat vapor locking from heat soak.

Even putting the regulator back at the tank will still heat the fuel, although not as much as running it through the hot engine compartment and rails first and then sending it back to the tank. Regardless of where you put the regulator by pumping the fuel you are adding heat to it. As long as the fuel can shed its heat through the tank to ambient air faster than you can put the heat in everything's OK; once you start putting more heat into the fuel faster than you can dissipate it you are on your way to overheating the fuel and creating a vapor lock condition which can not only strand you on the side of the road but can lead to fuel pump cavitation and damage.

Yep.. the OEM setup used the pulse dampner in the OEM fuel rail. When you switch to and aftermarket fuel log system you loose this item.

Good post, sounded very much like what Aeromotive told me today.

Steve
 

Do you have Bret's number at aeromotive?

Just call and hit the number (#2 i thing) for tech assist.. if you get someone else just ask for him.. Bret Clow

Tell him that jabbering guy from PHR sent ya.. He had lots of good info.

Thanks guys. I'm looking at a cooler of some sort to put in-line and possibly swapping to a smaller pump. In looking through Summit's online catalog, I have only found one that says it's for gasoline. It's a dual circuit unit ( http://store.summitracing.com/partde...5&autoview=sku ). I guess I could just tie one circuit to the other and get all six passes to cool the fuel. What would keep one that is made for a transmission or oil cooler from being used for gasoline instead? I would think that as long as it sealed it would be ok, but not sure if there is another reason for not having it listed on the Application list.


I think that it's possible to add a PWM output on the MegaSquirt controller that I am using. I'll see if I can figure out what I need to do to use it to slow a pump down, whether it is the one that I have or a smaller one that I replace it with.

I will save you the time calling Aeromotive. I spent hours talking to them two years ago.

1) Put the pump as close to the tank as possible.
2) Put the pump level with the bottom of the tank so gravity will feed it.
3) Use -12 feed line to fuel rail and make sure the filter is the -12 opening and not the -10
4) Use as big as you can for the return
5) Use a controller for the pump/pumps.
6) Insulate lines from heat.
7) Use a sump in the tank.
8) Return line needs to spray fuel into the top of the tank not into the gas. let it hit the side of the tank and run into the fuel so air will cool it.
9) Run as big a vent as possible.

IMO.....Most aftermarket pumps are not made for continious duty use on the street without a controller. Every drop of gas in your tank goes to the engine bay about every 12 minutes. That is where the heat comes from unless you have cavitation from some other reason. The pump will get loud from cavitation, fuel pressure will vary and the pump will eventually shut off and you will be standed until it cools or you put fresh gas is to cool it.

Most coolers can be used for gas.. here's a new one from Barry Grant that I'm looking at. Plumb it into your return line.

http://www.barrygrant.com/news/artic...oduct_005.aspx

The other one I'm looking at is this small fanned unit from B&M.

http://www.bmracing.com/index.php?id...bcat=28&pid=75

I would make sure it will withstand 50-60 psi. When you go into boost your fuel pressure goes up above 45psi.

I really don't think you will need a cooler with a controller. I have no problem with my car now.

2 bosch pumps
1 Aeromotive controller
-12 line to the fuel "Y" at the engine.
-8 return

FYI, the cooler should be installed on the *return* line and won't see more than a few PSI of pressure, whatever the backpressure is from the cooler back to the tank.

Thanks Steve. I like the idea of the fan on it to help push air over the cooler.

Thanks Turbo Duece. Are the Bosch pumps in tank units or do they make external ones also?

Good to know. I'll keep it in mind. Thanks.