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marc69
08-12-12, 06:19 PM
My nova has started playing up when under pressure. Today I could not get past 6000 rpm in 4th gear, it misses everytime. (on a private road of course...)

Anyway, today when it did this I switched the electric fuel pump off and then the ignition as I was close to an exit. Turned off the road and then opened the carb and saw this.

http://i988.photobucket.com/albums/af5/69marc/IMAG0140.jpg
It seems not enough fuel is getting to the float chamber. This has only become a problem the last few weeks.

At home I left the pump running for 1 minute and got 5 fl or just over 100 ml. This was the same at the carb and at the exit to the pump.

I then removed all the pipes and put some wd40 through the fuel pump.

Now in 30 seconds, over 15 fl at the pump, big improvement.

After blowing through all the pipes and refitting them, I notced there is a little resistance at the carb, is this normal?

Testing now is giving 15 fl at the carb for one minute but double at the pump, is it normal to have a reduction in flow by the time it comes out the carb?

15fl is obviously 3 times the original 5 so it looks as though the pump was dirty, testing next weekend then....................
mowgli
09-12-12, 12:23 PM
the pump will always run better with no pipe on the outlet, compared to having a 2m long fuel line, but 100ml per minute will equate to 6L in an hour, which is definitely not enough. cos that is 1 1/3 gallon & at 30mpg that equals 40 miles driving, which in an hour is definitely strangling it.


do you have a filter in the line? if not, then get one.

does the pipe have some crap in it or a kink? new nylon pipe is easy to get from truck spares places (ask for stuff that is petrol proof) or you can use copper pipe from b&q (or anywhere else)
marc69
09-12-12, 02:32 PM
Thanks, glad that I've found the problem. I have fuel lines from the nova I broke in the summer, they are the plastic external ones.

The fuel line just now is in the car and is braided hose type, will it be safe enough to use the external plastic stuff in the car?
mowgli
09-12-12, 05:15 PM
check with the track day people, cos i thought they prefer the fuel lines to be external
marc69
09-12-12, 05:23 PM
For the filter before the pump (there is another one before the carb), it sits at the fuel tank and is a halfords metal job.

Will the wee plastic clear one be ok on the outside? It would ket me see being clear.
mowgli
09-12-12, 05:59 PM
ok, i'd do away with the clear one if the one near the tank is ok, its mostly there to protect the pump anyway.

i am concerned about the flow though. there must be a restriction of some sort.. in extreme cases, the inner of a rubber hose can get sucked in and it will severely limit flow.
marc69
09-12-12, 10:33 PM
That's handy, getting rid of the 2nd filter will cut the resistance a bit. I have had a few issues with these braided hoses, leaks etc. I noticed they are just rubber rolled up so will be easy to block etc. I'll be glad to get rid off them! There must be some reason why people like them?
mowgli
10-12-12, 06:26 AM
That's handy, getting rid of the 2nd filter will cut the resistance a bit. I have had a few issues with these braided hoses, leaks etc. I noticed they are just rubber rolled up so will be easy to block etc. I'll be glad to get rid off them! There must be some reason why people like them?

cos they look cool, as with a great many 'tuning' parts & accessories, they don't actually improve the working of the vehicle
marc69
11-12-12, 09:26 PM
Well this is how much braided hoses improve things, I removed them, spent a few hours fitting the original type line under the car, moved the pump to the firewall (bulkhead) that I welded in the other month.

previously even after cleaning the pump I got 300 ml in one minute, today I got 800 ml in 30 seconds. I'll hopefully test it running over the weekend and see how it goes after I tidy the wiring etc.

I ran it before with the return blocked on the carb, I did consider putting in the return pipe but as it went fine before, it should still run ok without the return?
mowgli
11-12-12, 10:36 PM
you might need a return if you get flooding issues
marc69
11-12-12, 10:39 PM
does the float not stop the ccarb from flooding?
thegingerwhinger
14-12-12, 08:06 PM
hi Marc are you sure the "metal" filter isnt designed for fuel injection use hence why its resricting the power of a low pressure carb type pump. i just use 2 inline plastic filters on my stock cars and thats fine.
mowgli
14-12-12, 08:08 PM
/\ the metal ones are high flow capacity.
marc69
14-12-12, 09:54 PM
hi Marc are you sure the "metal" filter isnt designed for fuel injection use hence why its resricting the power of a low pressure carb type pump. i just use 2 inline plastic filters on my stock cars and thats fine.
With the metal filter on it's giving 1600 mls compared to 300 mls per minute after changing from the braided hose to ordinary fuel line so the filter is not a problem, it was definately the braided fuel lines. . Of course the real tell will be the next warm track day (I'll hold my breath!)