Boiling Petrol- help
Discussion
Has any body experienced this before.
Just been on a 45 min run in the Ultima. Water stayed ok and everything was fine for the first 30 mins.
However, while coasting the revs went mad as if an ignition fault. In traffic this got worse unless constant reving. Back driving on open roads ok. But turning into the garage at home the car died.
Had a look at the carb and the fuel is boiling and forcing into the venturis. Checked the temp and the carb is at 65c.
Has anybody had this before and any suggestions before pie on the beach tomorrow.
I know it is hot but the car survived a slightly cooler Le Mans!
Just been on a 45 min run in the Ultima. Water stayed ok and everything was fine for the first 30 mins.
However, while coasting the revs went mad as if an ignition fault. In traffic this got worse unless constant reving. Back driving on open roads ok. But turning into the garage at home the car died.
Had a look at the carb and the fuel is boiling and forcing into the venturis. Checked the temp and the carb is at 65c.
Has anybody had this before and any suggestions before pie on the beach tomorrow.
I know it is hot but the car survived a slightly cooler Le Mans!
Guy
Don't know what engine or intake manifold you have, but the only way a carb can be heated is if your electric choke has a short and is acting as a heater element, you have a manifold that has a water jacket, or an exhaust jacket as used in some anti-polution set-ups. Check for problems there.
Normally, when you have air that is mixed with fuel,you have a cooling effect that helps keep the carb and the intake manifold cool.
This might be a place to start.
Many, many years ago I had a Shorrock supercharger on a racing Sprite, and the way they cooled the intake air was by having a length of aluminum tube between supercharger and the carb. When the engine was running, that tube was actually cold and acting as an inter-cooler. This fed cooled air into the charger which bolted to the cylinder head.
Jack
Don't know what engine or intake manifold you have, but the only way a carb can be heated is if your electric choke has a short and is acting as a heater element, you have a manifold that has a water jacket, or an exhaust jacket as used in some anti-polution set-ups. Check for problems there.
Normally, when you have air that is mixed with fuel,you have a cooling effect that helps keep the carb and the intake manifold cool.
This might be a place to start.
Many, many years ago I had a Shorrock supercharger on a racing Sprite, and the way they cooled the intake air was by having a length of aluminum tube between supercharger and the carb. When the engine was running, that tube was actually cold and acting as an inter-cooler. This fed cooled air into the charger which bolted to the cylinder head.
Jack
My carb was getting mega hot in london traffic making it really difficult to drive without constant revving.
I made a 1" carb spacer and i re-circulated the fuel back the to tank. (I fitted a restrictor in the renturn line to prevent too much presure loss)
This ensures a constant supply of cool fuel right up to where it enters the carb.
I also noticed an improvement in low/mid torque also.
Here's a picture of it beeing made: (no thats not me, but my dad!)
www.mez.co.uk/chevyupgradeupdates.html
I originally made an open square bore one, but that that didn't work at all well, becuase my manifold has a central web down the middle. This one matches the 4 holes on the bottom of the carb.
Eliot.
>> Edited by eliotmansfield on Sunday 10th August 19:29
I made a 1" carb spacer and i re-circulated the fuel back the to tank. (I fitted a restrictor in the renturn line to prevent too much presure loss)
This ensures a constant supply of cool fuel right up to where it enters the carb.
I also noticed an improvement in low/mid torque also.
Here's a picture of it beeing made: (no thats not me, but my dad!)
www.mez.co.uk/chevyupgradeupdates.html
I originally made an open square bore one, but that that didn't work at all well, becuase my manifold has a central web down the middle. This one matches the 4 holes on the bottom of the carb.
Eliot.
>> Edited by eliotmansfield on Sunday 10th August 19:29
Hi Paul, Andy may have allready told you about this but, while we where at Santa Pod yesterday, we both suffered with what sounded like a Missfire in 1st and 2nd gear off the line. But it cleared by the time I was in third. Talking to the pit crew for a 11 Litre 8.8 Second Calibra, they looked at my car and said that the weather ie. heat was to much for the fuel lines, And showed us there fuel recirculating system, but also said that it was mainly because the fuel was sitting in the fuel lines heating up while the engine was not being driven hard. So once we had used the fuel in the lines, then the problem would go.
Solutions:-
1. Insulate fuel lines in engine bay.
2. Change fuel pump for larger GPH, and install constant fuel bleed back to tanks.
3. Or don't drive slowly.
Solutions:-
1. Insulate fuel lines in engine bay.
2. Change fuel pump for larger GPH, and install constant fuel bleed back to tanks.
3. Or don't drive slowly.
This is exactly why i recirculate my fuel. My chevy is in a 4x4, which makes it even worse, becuase most work is done driving very slowly. The fuel pipes come up up on the bulkhead right next to the headers, then over the top of the engine. So at tickover, hardly any fuel is used, hence the fuel is red hot before it even enters the carb.
When its sat in traffic, the fuel return pipe is atcually quite hot.
Eliot.
When its sat in traffic, the fuel return pipe is atcually quite hot.
Eliot.
A word of caution about carb spacers.
Jet sizing is important factor that has to be changed when adding a spacer. Larger jets are required with a spacer. One jet larger for a spacer with four holes is typical if not more. An open spacer generally needs an even larger size.
I think the recirculation of fuel could be a good thing, but heat soak into the carb has been identified before, so spacers can't be bad.
Jet sizing is important factor that has to be changed when adding a spacer. Larger jets are required with a spacer. One jet larger for a spacer with four holes is typical if not more. An open spacer generally needs an even larger size.
I think the recirculation of fuel could be a good thing, but heat soak into the carb has been identified before, so spacers can't be bad.
I think part of the problem may have been down to the octain booster... Guy mentioned that he was using this and I know Clive was trying this as well (and had problems from the first run).
My car however was running with just super unleaded and I only had the problem on the 3rd run when the car had had to sit for a hour waiting to go back on the track so under canopy heat was extremelly high and the lines were untouchably hot.
Incidentally.... I noticed that the engine bay temp was over 60c at one point and was even sitting at over 50c whilst driving home from pie on the beach... and thats with huge side scoops and exhaust wrap.
Anyone else have a temp guage in the engine bay?
My car however was running with just super unleaded and I only had the problem on the 3rd run when the car had had to sit for a hour waiting to go back on the track so under canopy heat was extremelly high and the lines were untouchably hot.
Incidentally.... I noticed that the engine bay temp was over 60c at one point and was even sitting at over 50c whilst driving home from pie on the beach... and thats with huge side scoops and exhaust wrap.
Anyone else have a temp guage in the engine bay?
Reliant Scimitar's have a fuel boiling problem as well. Not sure how relevant this is but it might be worth saying.
Scimitar's have a mechanical fuel pump and the fuel boils in the pump resulting in pumping only bubbles into the carb. Fine under cruising, but as soon as try to overtake you get on the wrong side of the road, fully comit to the overtake and then the float chamber gets sucked dry. Really hairy!
Standard fix is to fit an electrical fuel pump.
Scimitar's have a mechanical fuel pump and the fuel boils in the pump resulting in pumping only bubbles into the carb. Fine under cruising, but as soon as try to overtake you get on the wrong side of the road, fully comit to the overtake and then the float chamber gets sucked dry. Really hairy!
Standard fix is to fit an electrical fuel pump.
I also blame the Carter pumps. An SPA fuel pressure guage is fitted and when cold, 6psi is easy to obtain. When hot however this can drop to 3psi and with the car under load I saw 2psi... Fitted a Holley pump and regulator to Pump 1 (Left), the backup Carter is in Pump 2 (Right). The Holley pump maintains 6psi under all conditions - the fuel lines have roll-over one way valves so don't recirculate but I don't have the heat problem and yes, I was on the road yesterday (green house effect very present in the cabin) !
Cheers,
Dave
Cheers,
Dave
The reformulated Fuel sold in large cities in the US has a much lower boiling point than in the past.
Higher octane fuel is actually less volatile and a higher boiling point since it is designed to burn slower for high compression applications.
This is exactly why I went with an EFI LS6.
Higher octane fuel is actually less volatile and a higher boiling point since it is designed to burn slower for high compression applications.
This is exactly why I went with an EFI LS6.
Dave... both me and clive run holley blue fuel pumps so it wasn't that.
Your unlikelly to recreate the circumstances that caused my brief stutter on the road (I still did a 12.4!) and I did over 500miles this weekend and never had even the remotest issue (except that one time on the strip obviously) so I'm not that concerned.
I think the answer is to not use octain booster on hot days in an Ultima!
Your unlikelly to recreate the circumstances that caused my brief stutter on the road (I still did a 12.4!) and I did over 500miles this weekend and never had even the remotest issue (except that one time on the strip obviously) so I'm not that concerned.
I think the answer is to not use octain booster on hot days in an Ultima!
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