Fuel Flow Rates

[beardy bloke]

I have a TVR which has a 1.6 Fiat Twin Cam engine , i have trouble occasionally with what appears to be lack of fuel to carb can anyone tell me what the fuel flow rate should be so i can check to see if my non standard electric pump is the problem.The problem is most apparent when going uphill so i wonder if gravity is an issue so i am planning on checking flow rate on ramp also , to see if this makes a difference as the pump might not be able to pull enough from tank ?.

[TOAD]

I don't know about the flow, but if the pump is old has its little filter been cleaned lately, and is is fitted and the correct end of the car, some pumps are pushers, other suckers or pullers,  my thinking would be a new pump in the wrong place may do it, but an old tires one my cry enough.

  Regards

       Roger.............

P.S   Pinch of the return pipe to get full flow and see if that makes a difference, could give you an indication.

[Tas131]

What size needle & seat have you got in the carb. If too small they can be a restriction, especially a problem if your float level is too low to start with.

[beardy bloke]

The pump i have is a small german electric pump , i am not sure if it is set up to push or pull , it is next to the engine so should be a pull!. I think that what i want to do is either replace the original mechanical pump, which is still on the engine or service/replace diaphram. Do you now where i could either get a replacement diaphram or a new mechanical pump. I was interested in the flow rate as i wanted to makesure if i replaced what i had then i fit something suitable. Is it easy to strip electic pump and replace / clean internal filters?.

[TOAD]

The standard pump is not the best, if the engine has been working with the electric pump and you think it is a pump problem, try a FACET Solid sate pump, its a little square one and works very well, try Ebay.   Did my 2Lty for ages until we raced it.

  But like I said, pinch the return pipe and drive it up the hill, this should show if its a flow issue as all of the fuel will be going to the engine, and not just returning to the tank.

[miro-1980]

There could be a lot of reasons ( starting from a filter to carb problem to  dirt in the tank). Too low a fuel level in the carb, a bad fuel filter, or some dirt in the cab are the immediate suspects !

1/ replace the fuel filter ( and test for performance)
2/ follow TOAD's pinching suggestion 

Re pump: I agree with TIOA facet suggestion , but if the carb requires a lot of fuel ( like two twin barrel Weber 44's and over 150 bhp ) I would recommend a Red Top Facet, but before going for a new pump DO CHECK if the pump is the issue and fix any carb filter problems if you find any.  Than get an electric pump anyway. Mechanical will always be less reliable.

By the way : use a fiat 124 fuel filter (as on spider 2.0 f.i. models). 

Miro  

PS: make sure you are using not the cheapest fuel you can find ... this a source of a problem (electric or mechanical pump alike). 

[TOAD]

Why such a big one for a single Carb ?

[miro-1980]

On a single carb - you are right a smaller will suffice!

Miro 

[beardy bloke]

I will try pinching return pipe as suggested , i assume this will force all fuel from pump into the carb. I have a single carb , 32ADF , and only a cheap inline filter this is fitted between pump and carb , would i be better off with something else and fitting one between the tank and the pump , incase dirt in tank might be fouling the pump . I only got the car last year and it had been driven very lightly in previous 8 years and not run at all inlast 3years , so i suppose everything could do with servicing/ cleaning. The reason i started to ask about flow rates was to have some idea of what i need to use if i replace the existing pump or so i can decide if it is ok to continue using the pump as it is .Looking at various pumps a good average is around 100litres per hour ,is this what you would suggest . I am not sure if solid state pump next to tank is best or pull pump near engine?.

[TOAD]

No idea, but Toad as a road car used a solid state type on a pair of fortes for some years, mounted beside the tank to push fuel to the front.  I do not drive slowly so it had to do allot of pushing.

If the car has stood for a while, a good Carb clean would seem a fair starting place, and instead of trying the hill, see if the car will pull cleanly to max revs and hold that for a while.


On the flat I expect you drive at a steady pace, on a hill you give it more throttle to pull you up, what does the engine feel like when it falters ?

[beardy bloke]

The engine pulls fine when sat on drive !. Most of the time it will pull fine on the flat and on a recent run was cruising on M4 at 4000rpm no problem, the problem on hills is not at all times but when it does in almost chokes it self . When it does this it still seems willing to rev freely in neutral but chokes when you try to drive in gear. I thought it might be crap in fuel tank or bloked jets or filters?. The engine also always sounds a bit rubbish until you get to 3000rpm and then seems almost to get quieter and engine noise evens out , i assume something must be blocked in primary and once secondary kicks in it evens out?. My Haynes manual says that there is a power jet on secondary , there is a inlet on top of my secondary but it appears to just drop into the carb body should there be another jet feeding this ?.
Any suggestions would be helpful , i am going to try to clean carb and all filters the weekend and then see if there is any change . Then service kit and possibly new jets.

[TOAD]

Try a nice new cheap baking try, 99p jobbie  some cellulose thinners and some Carb clean aerosol to blow out the passageways.

  Strip the carb in the thinners and blow it all out with the aerosol, mind your face, the aerosol stings your eyes. Get it in pieces and cleaned in the thinners bath, it will come up like new, and blow all the jets backwards as well.

  Running the engine on the drive is not the same as it's not under load like driving it. 

The more time you spend cleaning the better the job will  be.  and make sure the correct jet goes in the correct hole, and that the diaphragm go back the correct way as well, there are little holes to align. 

  Its Ganaby fun   

[beardy bloke]

I did not soak the carb in thinners as I thought it would be better to get a service kit before I did that . The carb is running a lot better at present but I have not taken it on a long run as yet . I had a lot of trouble resetting the float heights the measurements in my Haynes manual 6mm/14mm travel did not seem correct as when I did this the carb flooded with fuel .I have set these slightly larger around 7mm/ 16mm travel and seems to be ok .I assume this is vital to get right any advice as it appears to be either no fuel or too much . Also any suggestions on air filter as k+n is not suitable , at the moment I may put back a larger pancake filter , what depth was the original air box on 1.6 t/c ?.

[TOAD]

Did you check or change the needle valve that lets the fuel in?     it should have a smooth point

[beardy bloke]

No I did not change needle valve , I was going to leave that till when I get service kit as that comes with it. Could this be sticking/blocking and this could be my problem?. Car does seem ok now but I have not taken it on along run as yet .