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I suspect I may have a problem with my fuel getting too hot. I figured since I run HSR this would be the appropriate place to post this but it could apply to almost any car.
After a long run, especially in hot stop and go traffic, my car starts to run rough and stinks more. (the exhaust always smells a little of raw fuel but it gets bad at times) I have been trying about everything tuning wise to correct it and yesterday when I parked and opened my door I could hear gurgling. I thought it was the cooling system at first but it was coming from the rear of the car. I opened my gas cap and it got louder. I sounded like bubbles coming up through the fuel. Could this be causing my car to run poorly when hot?
I have full, stock metal fuel lines with adaptors up front by the power steering pump then it changes to rubber lines which route around to the back of the motor by the distributor. I have headers which are about 3-4" from the lines in the engine compartment and have routed the drivers side exhaust straight back past the trans so the front muffler (next to the trans) is 2-3" from the fuel line in that area.
I am wondering if the constant circulation of fuel and the close proximity of the exhaust/fuel lines, not to mention the fuel rails right on the manifold, may be heating up the fuel to a point where it is somehow affecting delivery. I have noticed that AFR goes up (leaner) when it gets hot and the problem seems worst.
I am considering some heat shielding of the fuel line where they are close to heat sources and possibly re-routing them all together if necessary. I don't know if there is anything I can do about the heat picked up at the fuel rails but it seems a "parallel" circuit at the rails may pick up less heat than the current "series" circuit. Any comments or ideas are welcome.
Thats funny that this happened to you yesterday. I mean "not funny, HAHA, but a coincidence. I happed to drive my 85 yeasterday. It was 98* here. I drove 20 miles to my home and the car was just running poorly. I pulled in the garage, got out and heard the same thing. Gurgling, gas smell and all. I did not here the little tank vent by the rear end making any noise. I went to take my gas cop off and it was sooo pressurized/or under vacuum, the the cap turned about 1 full turn till it started to vent. I could not get it off. I left it vent over the next hour or so and finally I was able to fully remove it. Its obvious there's a problem with my vent/and canister. Need to check that out.
There are so many threads on this. I wish this could get figured out. Good luck!
Yes, I understand the EFI can suffer from a condition similar to vapor lock in with a carb. Under normal conditions the pressure the fuel is under on the supply side keeps the fuel from boiling so it's not vapor lock in the normal sense, but if conditions are so hot the fuel in the return can boil and send some vapor back to the tank and semi-cavititate the pump. This in turn drops fuel pressure and causes fueling problems.
I think there may be other things going on too, possibly affecting how the injectors are able to control fuel.
In regard to the pressure/vacuum at the fuel tank cap, I haven't noticed this ever. I don't know if it SHOULD hold pressure in the tank under normal conditions.
So what's the solution??? I have a 49 Chev truck with an 85 Vette TPI wired to MAP of a 91 Vette. I starts and runs great. Quit once and wouldn't restart til it cooled down. Had spark and noid on injectors. I can get it to do it in my garage if I get it hot, wait about 10 minutes and then it cranks and cranks. Maybe one time acts like it'll fire then cranks and no start. Then I can spray fuel , 3 or 4 squirts of fuel from a spray bottle into the intake and it fires right up. The PROM has been set for EGR and VATS delete for a streetrod and the 9th injector cold start deleted. I have a 30GPH inline fuel pump on it and it maintains 41 at idle even when shut off for quite a while. If I bleed off the fuel rail it acts like it's boiling and bubbles like aerating. I just ordered a different pump that puts out 80 GPH and 100psi and plan to get rid of metal hoses for rubber. Sounds like quite a few guys have this problem...we need a solution? You have any? I'll post what happens next week.
I'm going to try a higher volume fuel pump and rubber hoses connected to the rail and back to the pump. I'm using an inline pump.
Otherwise it's a spray bottle of fuel and spray into PCV hose if it won't start. I hear the ethanol fuel doesn't like the heat and is like cooking corn...LOL. Any one tried good fuel ...non-ethenol? All C4 front and rear.
I'm right there with you guys. 91 MAP/Speed density TPI with emissions, vats tuned out of the prom. Excessive fuel tank pressure. Pump holds steady around 40 psi. Hard starts after it's hot...the whole 9 yards. I think it's the Ethanol. Nobody around me (Western PA) seems to sell non ethanol blended fuel anymore. If they did I'd love to try that.
I ran the non-ethanol fuel in several of my T/A's this past winter. I didn't see a problem.
But....it wasn't 95* out either. I'm gonna run a series of tests over the next couple of weeks and see if I can make a correlation. IDK.
I ran the non-ethanol fuel in several of my T/A's this past winter. I didn't see a problem.
But....it wasn't 95* out either. I'm gonna run a series of tests over the next couple of weeks and see if I can make a correlation. IDK.
I had the same issue in traffic when very hot in So Cal. I use my car for Time Trials on road courses and it never happened under full throttle track use but the fuel would get so hot if I drove it home, it would lose all pressure from boiling and stall. I have a 383 with Mini Ram, headers, and 3.5 inch exhaust. I wrapped muffler and exhaust over axle, insulated fuel lines, cut stock lines at back of engine to go directly to mini ram fuel rail so it does not pick up engine heat, went to a Bosch 44 fuel pump, and took check valve out of line to charcoal canister. The Walbro pumps pump so much fuel it gets hot doing all the circulating so the Bosch pumps less and supports my 400 hp at wheels. Without check valve on canister it allows fuel tank to breathe and less pressure is less heat and it will not hiss when gas cap is cracked. This works and I have not lost fuel pressuse since.
Forgot to mention if you can not do everything I did, carry one gallon of fuel with you in the car and dump it into tank when hot fuel issue happens. One gallon is all it takes to cool fuel in tank enough to start. Then run at heavy throttle until you get to a gas station and top off tank with cooler fuel. Heavy throttle will use more fuel vs. circulating it which allows it to not get as hot.
I suspect I may have a problem with my fuel getting too hot. I figured since I run HSR this would be the appropriate place to post this but it could apply to almost any car.
After a long run, especially in hot stop and go traffic, my car starts to run rough and stinks more. (the exhaust always smells a little of raw fuel but it gets bad at times) I have been trying about everything tuning wise to correct it and yesterday when I parked and opened my door I could hear gurgling. I thought it was the cooling system at first but it was coming from the rear of the car. I opened my gas cap and it got louder. I sounded like bubbles coming up through the fuel. Could this be causing my car to run poorly when hot?
I have full, stock metal fuel lines with adaptors up front by the power steering pump then it changes to rubber lines which route around to the back of the motor by the distributor. I have headers which are about 3-4" from the lines in the engine compartment and have routed the drivers side exhaust straight back past the trans so the front muffler (next to the trans) is 2-3" from the fuel line in that area.
I am wondering if the constant circulation of fuel and the close proximity of the exhaust/fuel lines, not to mention the fuel rails right on the manifold, may be heating up the fuel to a point where it is somehow affecting delivery. I have noticed that AFR goes up (leaner) when it gets hot and the problem seems worst.
I am considering some heat shielding of the fuel line where they are close to heat sources and possibly re-routing them all together if necessary. I don't know if there is anything I can do about the heat picked up at the fuel rails but it seems a "parallel" circuit at the rails may pick up less heat than the current "series" circuit. Any comments or ideas are welcome.
I spoke with an engineer at Aeromotive. He said the fuel filters can get gunked up from the ethanol and cause enough restriction that it is heating up the fuel. I plan to change the filters soon. My fuel is boiling, too.
There are a few things you can do to fix this problem. One, don't run a cheap Chinese fuel pump (these are the ones with the painted body and colored caps). Two, don't run an external pump if you can avoid it. These are both very susceptible to the effects of hot fuel, really touchy. The best pump you can run is a Walbro DCSS pump, like the F90000262 or 267, for example. These deal with hot fuel WAY better than anything on the market, hands down.
The other thing you must avoid is running your fuel pressure regulator "after" the fuel rails. This is the single biggest contributor to fuel heating on a car with an aluminum intake. LSX cars with plastic intakes don't have this problem. Run your supply into the regulator, then out of the regulator to the rails, either parallel or series, and plug the end(s). The return line would come out of the bottom of the regulator and go back to the tank then.
The best place to run the regulator in terms of fuel heat is to just put it as close to the fuel tank as possible. That way you are only circulating fuel through a short circuit and back into the tank so there's not much heat picked up. If you need to boost-reference the FPR make sure you don't use rubber hose since it's such a long run. Run a 1/8" nylon tubing, for example.
Last edited by realsquash; 09-27-2016 at 10:58 AM.
I have a vortech HSR with a kirban FPR, and i had this problem last year when i first swapped from carb to EFI. In ma, i dont need emissions so the line out of the tank i had capped off and was getting lots of pressure. Pressure is gonna be normal from the fuel heating up. The valve on the tank is there to prevent a over pressure event of the gas tank - So it doesnt become essentialy a explosive. On a properly operating system, it should naturally vent from the charcoal canister vent. My evap line was capped off, and i fixed it with a filter, You guys might have a clogged charcoal canister or a bad vent valve if your building pressure in the system. Asfar as fuel boil, i run nylon lines covered in heat wrap and dont have any problems - Even running longtubes and a custom y pipe - The only issue i have is when the tank gets lower than 1/4, the AFR's start to lean, but i belive thats because im not running a EFI tank, and the fuel is getting airated.
Last edited by 86CamaroDan; 09-08-2016 at 07:41 AM.
I suspect I may have a problem with my fuel getting too hot. I figured since I run HSR this would be the appropriate place to post this but it could apply to almost any car.
After a long run, especially in hot stop and go traffic, my car starts to run rough and stinks more. (the exhaust always smells a little of raw fuel but it gets bad at times) I have been trying about everything tuning wise to correct it and yesterday when I parked and opened my door I could hear gurgling. I thought it was the cooling system at first but it was coming from the rear of the car. I opened my gas cap and it got louder. I sounded like bubbles coming up through the fuel. Could this be causing my car to run poorly when hot?
I have full, stock metal fuel lines with adaptors up front by the power steering pump then it changes to rubber lines which route around to the back of the motor by the distributor. I have headers which are about 3-4" from the lines in the engine compartment and have routed the drivers side exhaust straight back past the trans so the front muffler (next to the trans) is 2-3" from the fuel line in that area.
I am wondering if the constant circulation of fuel and the close proximity of the exhaust/fuel lines, not to mention the fuel rails right on the manifold, may be heating up the fuel to a point where it is somehow affecting delivery. I have noticed that AFR goes up (leaner) when it gets hot and the problem seems worst.
I am considering some heat shielding of the fuel line where they are close to heat sources and possibly re-routing them all together if necessary. I don't know if there is anything I can do about the heat picked up at the fuel rails but it seems a "parallel" circuit at the rails may pick up less heat than the current "series" circuit. Any comments or ideas are welcome.
I'm in the same situation with my GTA, If I run the AC its even worse. So far I have shielded the fuel lines any where they get close to the header or exhaust, vented gas cap, run ethanol free gas.. still the fuel will over heat and cause the car to start stalling.
I'm in the process of installing a Walbro pump, I'm hoping it will be less sensitive to the fuel temperature.
If that doesn't work I will be changing over to a LSI tank and pump assembly.
I'm in the same situation with my GTA, If I run the AC its even worse. So far I have shielded the fuel lines any where they get close to the header or exhaust, vented gas cap, run ethanol free gas.. still the fuel will over heat and cause the car to start stalling.
I'm in the process of installing a Walbro pump, I'm hoping it will be less sensitive to the fuel temperature.
If that doesn't work I will be changing over to a LSI tank and pump assembly.
How are your rails plumbed? Changing tanks is completely not needed!
The plastic Ls1 tank is superior in sump design and less susceptible to heat transfer from the exhaust, those things alone make it worth the upgrade to me.
The plastic Ls1 tank is superior in sump design and less susceptible to heat transfer from the exhaust, those things alone make it worth the upgrade to me.
You have a miniram on this car? So the FPR is technically "before" the rails, so to say? Or does it run into the rails first, then returns out of the regulator?
There are a few things you can do to fix this problem. One, don't run a cheap Chinese fuel pump (these are the ones with the painted body and colored caps). Two, don't run an external pump if you can avoid it. These are both very susceptible to the effects of hot fuel, really touchy. The best pump you can run is a Walbro DCSS pump, like the F90000262 or 267, for example. These deal with hot fuel WAY better than anything on the market, hands down.
The other thing you must avoid is running your fuel pressure regulator "after" the fuel rails. This is the single biggest contributor to fuel heating on a car with an aluminum intake. LSX cars with plastic intakes don't have this problem. Run your supply into the regulator, then out of the regulator to the rails, either parallel or series, and plug the end(s). The return line would come out of the bottom of the regulator and go back to the tank then.
The best place to run the regulator in terms of fuel heat is to just put it as close to the fuel tank as possible. That way you are only circulating fuel through a short circuit and back into the tank so there's not much fuel picked up. If you need to boost-reference the FPR make sure you don't use rubber hose since it's such a long run. Run a 1/8" nylon tubing, for example.
This is an interesting suggestion, seems it would have a profound impact on fuel heating and make plumbing a bit easier in some cases. The only concern is "dead heading" the system. I thought the reason the fuel passed over all the injectors was to ensure air was purged out. If that isn't a problem then it may work. One other observation, although bypassing before the rails would keep the fuel in the tank from heating up wouldn't it in turn make the fuel in the rails hotter? Since the rails don't get the cooling effect of the fuel passing through it?
I did change some of my fuel lines out. I shortened the factory steel lines back to just in front of the tranny cross member. From there I ran nylon braided lines with AN ends. I followed the factory route to just under the steering column and up the fire wall to the back of the intake. I wrapped all the lines in foil covered insulation and made aluminum heat shields where it came close to the exhaust. This seems to have helped although I am still running all the fuel through the rails. I like the idea of moving the regulator.
This is an interesting suggestion, seems it would have a profound impact on fuel heating and make plumbing a bit easier in some cases. The only concern is "dead heading" the system. I thought the reason the fuel passed over all the injectors was to ensure air was purged out. If that isn't a problem then it may work. One other observation, although bypassing before the rails would keep the fuel in the tank from heating up wouldn't it in turn make the fuel in the rails hotter? Since the rails don't get the cooling effect of the fuel passing through it?
I did change some of my fuel lines out. I shortened the factory steel lines back to just in front of the tranny cross member. From there I ran nylon braided lines with AN ends. I followed the factory route to just under the steering column and up the fire wall to the back of the intake. I wrapped all the lines in foil covered insulation and made aluminum heat shields where it came close to the exhaust. This seems to have helped although I am still running all the fuel through the rails. I like the idea of moving the regulator.
Dead heading is not a problem, the air is purged out of the system through the injectors the first time you start the car. As long as you have a working check valve in the fuel system (in the fuel pump in the case of these cars) you will never have to worry about air in the system.
The temperature of the fuel has nearly zero impact on AFR and the fuel injectors, so really hot fuel in the rails isn't an issue. The impact is much greater to the fuel pump, however. It doesn't take much to get some of these aftermarket pumps to cavitate with minimally heated fuel. OEM pumps (and Walbro DCSS pumps) are much better in this regard. DCSS due to the impeller design and OEM pumps because they don't spin the hell out of them like the Aeromotive, etc, to get the flow rates.
In order to validate things you should really measure the temp of the fuel in the tank, or draw off a cupful and measure its temp. You might be really surprised at the results!
Dead heading is not a problem, the air is purged out of the system through the injectors the first time you start the car. As long as you have a working check valve in the fuel system (in the fuel pump in the case of these cars) you will never have to worry about air in the system.
The temperature of the fuel has nearly zero impact on AFR and the fuel injectors, so really hot fuel in the rails isn't an issue. The impact is much greater to the fuel pump, however. It doesn't take much to get some of these aftermarket pumps to cavitate with minimally heated fuel. OEM pumps (and Walbro DCSS pumps) are much better in this regard. DCSS due to the impeller design and OEM pumps because they don't spin the hell out of them like the Aeromotive, etc, to get the flow rates.
In order to validate things you should really measure the temp of the fuel in the tank, or draw off a cupful and measure its temp. You might be really surprised at the results!
Ok your points make sense. I'm sure you are right about the fuel temp. Even just touching the steel lines back at the filter they are hot to the touch which puts them at least 140'F range, probably more.
I have been planning a regulator change. I'm still running the Holley on rail regulator which seems to be working but I would have more confidence in an Aeromotive or other unit mounted on the firewall. I also want to install a pressure transducer to monitor fuel pressure and this would be a good time to do all of these mods.
One other related subject is venting and CCP. I have removed the CCP canister and capped the line near the steering box. I am expecting the tank vent will take care relieving pressure/letting air in. Is this correct and what other considerations should I make for the elimination of the purge system?
One other related subject is venting and CCP. I have removed the CCP canister and capped the line near the steering box. I am expecting the tank vent will take care relieving pressure/letting air in. Is this correct and what other considerations should I make for the elimination of the purge system?
If you remove the evap stuff you just have to make sure the tank is vented to the atmosphere. Also know that your vent has to flow at least as much air as the volume of gasoline at fillup time or it will take forever. I believe the tanks on these cars has a shutoff valve in the tank where the filler neck connects to the tank. Also, put a fuel filter or something else on the vent tube to keep road grime out of the tank.
Check your fuel line location. Mine is a 1982 Trans Am, and I never knew the line was this close to the header until I pulled the A/C box off the firewall.
It never really had issues in the 1990's, but the 10% alcohol in the gas today seems to make a world of difference.
07-26-2016, 07:37 AM
