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MG TD TF 1500 - Front carb issue
|More work today has improved things but not much.|
When I turn the key to engage the fuel pump, it clicks away and then slows or stops for a minute, showing, I think, that the bowls are full. But then it begins clicking again and fuel gushes out of the overflow pipe on the front carb.
Today I put in a set of needles in the float bowls which I had found as spare parts; that made the problem worse, both bowls overflowed. I returned to the original needles and it improved, but still a problem, after a minute on the front float.
Should the fuel pump cease clicking once the lines and bowls are full? Or is there enough pressure on the fuel pump end to overfill the bowls if you don't engage the starter and get the system running?
Thanks for all answers.
|G M Baker|
|Your floats should cut off the fuel, make pressure in the line and stop the pump?|
|Invest in a "new" set of needles, or better yet Grose Jets. Also check for minute particles in the fuel that will stick the jets. Also, see this tech article by Dave DuBois:|
|Thanks, engine seems to be running fine, no leaks so long as the engine is running. Someone else suggested that the fuel pump is capable of overflowing the floats if left running without the engine turning over... as soon as the engine was turning over the problem disappeared...|
|G M Baker|
|The float levers must shut off the fuel when the engine is not running. There is no time limit to start the engine to avoid overflow. The test for proper fuel shutoff is done with the ignition on and the engine off.|
|Remove the float and make sure it doesn't slosh. Or you may have grit/rust/trash in the fuel and may need to install an inline filter.|
|Also, make sure your floats "float!" See if they float above the fuel level, then remove them and shake to see if they are taking on any fuel causing them to sit lower in the bowl.|
|The pump shouldn't pump when the bowls are filled, even if the engine isn't running...something is preventing the needles from closing?|
|I think the first question we should ask is are you using a stock SU fuel pump? They are very low pressure jobs and if your using just about anything else the pressure will excede the capabilities of the floats.|
|OK, it's running fine now. The fuel pump will stop pumping when the floats fill and I have no leaks. Combination of a bent float fork and not having the banjos tight enough, I think!|
On to the next issue... black smoke - too rich. New thread time!
|G M Baker|
|Geoff - First of all, I have to take exception with Larry's recommendation to use Gross jets. they used to be the best type of needle valve available, but in recent years they are not any good - company was sold or something. Second, if you experience the overflow again after the car has set long enough for the fuel in the float bowls to evaporate out, then you have excessive float lever drop, which can be corrected by following the instructions in the link that Larry provided. |
"Or is there enough pressure on the fuel pump end to overfill the bowls if you don't engage the starter and get the system running?"
The answer to this is no, if you have a proper SU fuel pump, there is no way it can develop enough pressure to overcome a float that is not flooded and is adjusted properly (not even a 'high pressure' SU fuel pump develops sufficient pressure to overcome the float).
"Someone else suggested that the fuel pump is capable of overflowing the floats if left running without the engine turning over... as soon as the engine was turning over the problem disappeared..."
That someone is wrong, unless you have an after market pump in of the SU fuel pump. The fact that the overflow ceases after the engine is started points to a float lever drop mis-adjustment that is being cleared by the vibration of the engine running.
"The test for proper fuel shutoff is done with the ignition on and the engine off."
If you are going to do this test, be sure to disconnect the white wire from the coil so it isn't damaged by having power applied for too long without the engine running. Cheers - Dave
|Oops... I put in new Grosse jets when we did the 1 1/2s.. they really looked high quality...(of course I like anything polished brass)... came with three shims (am told the thinnest one usually is the one)|
Seemed like a great concept...!!
|Gordon - "Seemed like a great concept...!!"|
It is a great concept and the original Gross Jets were wonderful. But like all good things, the company was sold and the ones sold since then have not lived up to the original reputation. I put a set in our daughter's car and in a very short time, they were sticking closed. Maybe they have fixed the problem since then, but I will wait to hear from someone else who has tried them. Cheers - Dave
|I will let you know... am going to put the new head/valves together with the old carbs to get it running...then when everything is ok, will do the carb swap...(don't like to make too many changes at one time...hard to diagnose problems)|
This thread was discussed between 21/11/2009 and 23/11/2009
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