• Hi Guest! Being a Paying Supporter is NOT a requirement to participate at BCF. However, subscribing will help ensure we can continue to serve the LBC community for years to come. If you enjoy BCF and find our forum a useful resource...Please consider supporting us by **Upgrading**
    (PS: Subscribers don't see this banner)
Tips
Tips

Wedge TR7 carb seeping fuel

johnrip

Jedi Hopeful
Country flag
Offline
I have some gas seeping on the bottom of my bowl in the front carburetor. When I took off the K/N airfilter, there was gasoline in the carb, as shown in picture. This is while the car has sat 24hrs. Is this normal? The car runs very well, but I have smelled gas for a while....
 

Attachments

  • IMG_20170613_165621.jpg
    IMG_20170613_165621.jpg
    66.2 KB · Views: 27

Merlin63Tr4

Jedi Trainee
Country flag
Offline
Not normal.
Either the fuel level is set too high on that carb or you have a leaking/stuck float valve.

M.
 

poolboy

Yoda
Country flag
Offline
I agree with "Merlin"...but between the 2, I'd be betting on the float chamber needle valve.
And it would be a good idea to check your oil...if you smell gas on the dipstick, don't start the engine until you fix the problem and have changed oil and filter.
 
OP
johnrip

johnrip

Jedi Hopeful
Country flag
Offline
I now have noticed the second carb is doing the same thing. I had previously checked the float valve, they seemed to be working. What would make both carbs do that?
 

poolboy

Yoda
Country flag
Offline
You say the needle valves seemed to be working...does that mean they shut off the flow of fuel when the floats rise ?
It sure doesn't sound like it.
 
OP
johnrip

johnrip

Jedi Hopeful
Country flag
Offline
I am not sure. It just seems odd that it would be both carbs. It seemed to refill after I cleaaned it out overnight, with out running the car. Could there be some sort of a siphoning effect going on? Perhaps with the emissions hosing?
 

poolboy

Yoda
Country flag
Offline
It could be the siphoning effect...I had that problem when the gas tank was full and the car sat overnight..I put a fuel cut off valve after that happened a couple of times.
Have you checked for the smell of gas on your dipstick oil ?
 
OP
johnrip

johnrip

Jedi Hopeful
Country flag
Offline
I don't smell gas now....but it had plenty in the oil after it sat for the winter. I was thinking of the shutoff valve. Do you close yours whenever the car sits ..all the time?
 

poolboy

Yoda
Country flag
Offline
Not for short periods of time, but if it's a few hours or overnight then yes, I use the valve...But the only time I've experienced flooding in the past was if the gas tank was full or nearly so.... I don't trust needle valves (Grose jets even less) so to avoid breaking the habit, I raise the bonnet and close the valve regardless of the fuel level... I attribute all that to hydraulic head, once the head is lower, the pressure is reduced
I think you can see the valve here with a red knob:
 
OP
johnrip

johnrip

Jedi Hopeful
Country flag
Offline
What do you mean "the head is lower". I noticed that when I turned off my car, my fuel filter was 2/3 full. Then I clamped the line, above the filter, and the filter was full 5 hrs later. It seems there is syphon pressure, even with a clamp on the line. Is this a gas tank issue (I am 2/3 full), or could it be from the EGR or emissions stuff? PS thanks for your help!
 

poolboy

Yoda
Country flag
Offline
Hydraulic Head "The force exerted by a column of liquid expressed by the height of the liquid above the point at which the pressure is measured. Although head refers to a distance or height, it is used to express pressure, since the force of the liquid column is directly proportional to its height. Also called head or hydrostatic head."
It's my theory, John, and maybe that's all it is but I can't think of any thing else that would cause my carbs float chambers to over flow when the gas level in the fuel tank is about maximum..that plus I don't believe that the float chamber needle valves are real good at acting as cut off valves and I don't trust them to. They function more like a valve that regulates the fuel level within the float chamber.
Anyway, regardless of the underlying cause of my carbs flooding under certain conditions, a cut off valve (and using it) put an end to it.
 

AltaKnight

Jedi Knight
Offline
Both my carbs on my TR6 suddenly sprung leaks from the large plug in the bottom of the fuel bowl, put new seal rings in and it now doesn't smell of gas.
 

George_H

Jedi Trainee
Country flag
Offline
Are you running a stock fuel pump? or electric aftermarket? If you have a electric, you may have to put in a pressure regulator.
 

Hasbeen

Freshman Member
Offline
The above question is important. Your carbs can not handle more than 2 PSI. Over 2 PSI will cause flooding, from a little to a lot depending on pressure. Most electric pumps are set at 4 PSI, so are not suitable for your carbs, without a regulator.


The mechanical pump on the 7 can produce more than 2 PSI if the pump with the long arm is fitted, & the 3/16" spacer is missing from between the pump & the engine block. The closer to the block the pump, the higher the pressure.


Old needle & seats in the float bowl are not good as shut off valves. When the engine is stopped there will be some residual pressure in the hoses from the pump to the carbs. This will slowly leak into the float chamber causing an overhigh float level. The excess fuel will run just by gravity through the carb jet, & lie in the carb throat, as in your photo. This clears when the car is started, & the carb will not flood while the engine is running. It uses more fuel than will leak past the needle& seat.


The fuel pump should not pass fuel when stopped. However if there is dirt or silt in the valves a very full fuel tank can cause some fuel to pass them to the carbs, & cause the same flooding. This is not common.


To test any of this, next time you run the car, immediately you stop the engine, remove a fuel hose from one carb. A small amount of fuel will squirt out as you do, reliving the residual fuel pressure. Refit the hose, & check a few hours later. You should not find any fuel in the carb throat. If so, you now know why it's been getting there. If this is all it is, it really doesn't matter, unless it makes the car hard to start. It will clear as soon as you start the engine.
 

poolboy

Yoda
Country flag
Offline
Both my carbs on my TR6 suddenly sprung leaks from the large plug in the bottom of the fuel bowl, put new seal rings in and it now doesn't smell of gas.
That's a simple gravity leak thru the O-ring seal, but John is experiencing something different in that a full float chamber is overflowing into the carbs' mixing chamber...when there is no more room in the float chamber the incoming gas is using the 0.10 opening in the fuel jet to escape the float chamber.
Residual fuel pressure, or hydrostatic head when the engine is not running...a cut off valve puts an end the overflow.
Too much fuel pressure from the pump should have shown up when the engine is IDLING...overflow, flooding or fouled spark plugs at the very least.
 
Last edited:
OP
johnrip

johnrip

Jedi Hopeful
Country flag
Offline
I have a mechanical fuel pump. I see fuel after the car sits for a few hours. I am going to reset float level, but I am thinking there is a certain syphon issue. I will install a fuel **** off, but still would like to know why there is the syphon. again, thanks for all the help offered!
 

poolboy

Yoda
Country flag
Offline
If it turns out that you have Grose jets instead of needle valves, get rid of them and put in the original type needle valves.
Grose jet for ZS 175 carbs on far right:
 

AltaKnight

Jedi Knight
Offline
Seems to me that fuel pooling in the carb when parked requires two things, first a fuel bowl jet that is "passing" (leaking), second it needs residual pressure in the fuel line to the carbs. on the TR6 the fuel line between the mech fuel pump and the carbs is routed across the top of the engine (above the water pump and higher than the fuel level in the gas tank) which would probably break any "siphon" effect but I'm not sure how this is set up on the TR7.
 
OP
johnrip

johnrip

Jedi Hopeful
Country flag
Offline
I think I have original needle jet...I will check. I have an appointment with my mechanic in ten days. I clamped the fuel line, so that I don't flood the engine while it sits, and over the last 12 hours, it is still drawing fuel slowly. All with the line clamped! I assume it will stop soon...
As per the fuel lines are routed under the carbs on the tr7.
I tried with gas cap off, and it made no difference.
I am going to get the float level adjusted, and fuel turn off installed, but I am shocked that it continues with line clamped (at inlet to fuel pump).
 
Similar threads
Thread starter Title Forum Replies Date
johnrip Wedge TR7 fuel in carbon canister-twin carb model Triumph 10
D Wedge TR7 Needle in Spitfire Carb! Triumph 1
E Wedge quad carb tr7??? Triumph 8
johnrip Wedge tr7 carb mounts Triumph 2
johnrip Wedge TR7 Carb adjustment? Triumph 9
S Wedge Carb-ed vs. Injected TR7 Spider Triumph 24
F Wedge 1980 TR7 ZS Carb rebuild advice [need some] Triumph 5
Hegg Wedge SU Carb and Intake acuqisition for Federal TR7 Triumph 1
S Wedge TR7 Carb base mounts/gaskets Triumph 7
S Wedge TR7 rubber carb mounts Triumph 3
johnrip Wedge tr7 tires Triumph 1
T Wedge Canadian TR7 catalytic converter when new? Triumph 0
Got_All_4 Wedge An issue with trying to start my TR7 Triumph 9
Obtong WANTED: TR7 (Olympia/Seattle Area) Triumph Classifieds 0
T Wedge TR7 brake hard and flex lines - fittings Triumph 12
T Wedge TR7 4 speed wheel cylinders on 5 speed (locating pin) Triumph 0
Sherlock 1982 Ford F150 stepside vs 1975 Triumph TR7 Other Cars 4
humanoid For Sale - Haynes Trimumph TR7 (1975-1981) Automotive Repair Manual Triumph Classifieds 0
humanoid For Sale - Haynes Triumph TR7 (1975-1979) Owners Workshop Manual Triumph Classifieds 0
johnrip Wedge Tires for TR7 stock alloy wheels Triumph 1
johnrip Wedge TR7 LED Tail lights from Wedge Shop Triumph 1
T Wedge TR7 engine, need help identifying part. Triumph 5
S Wedge tr7/8 quick release steering wheel Triumph 0
S Wedge TR7 fuse panel Triumph 8
Got_All_4 Wedge 1980 TR7 FI linkage Problem Triumph 2
johnrip Wedge TR7 led light conversion question Triumph 1
S TR2/3/3A Tr7 and a little extra Triumph 2
P Wedge Florida TR7 Triumph 0
S For Sale Weber Conversion Kit for TR7 Triumph Classifieds 0
1 Wedge Which Parts to get from an '80/81 TR7? Triumph 1
T For Sale Group 44 Replica TR7 V8 Twin Turbo Project - $25,000 Triumph Classifieds 0
M_Pied_Lourd Wedge TR7 Roadkill Extra... Triumph 0
J For Sale TR7 stripped shell and parts Triumph Classifieds 0
J For Sale 1981 Triumph TR7 convertible fuel injected TR 7 Triumph Classifieds 0
C For Sale TR7/8 Group 44 tribute race car for sale Triumph Classifieds 6
johnrip Wedge tr7 electric fuel pump Triumph 2
johnrip Wedge TR7 fuel pump Triumph 0
A Wedge Looking at a '80 TR7 ...... Triumph 4
TRopic6 For Sale TR7 Gearshift UKC 3248 Triumph Classifieds 0
Got_All_4 Wedge TR7 drive train torquing Triumph 2
GTP1960 Wedge "TR7 End of an Era" Hemmings article Triumph 11
N Wedge '80 TR7 Alternator Options Triumph 2
johnrip Wedge TR7 Brake squeal Triumph 1
johnrip Wedge TR7 Brake squeal Triumph 1
tomshobby TR7 in TV show Spotted 2
johnrip Wedge TR7 had replaced rotors, now I have a noise and vibration-Wheel Bearing? Triumph 4
JamesH Wedge new to me TR7, need some basic info. thanks. Triumph 2
bcbennett Wedge TR7 FASD vs. Manual Triumph 0
Got_All_4 Wedge Tr7 windshield factory windshield wires Triumph 3
K Wedge TR7 Project Triumph 10

Similar threads

Top