• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Throttle response question

Share this page

MgKid1974

MgKid1974

Senior Member
Offline
I know that throttle response for our old carbeurated MG's isnt that great in the first place but something I noticed on my B is that if I press the gas all the way down the carb lugs and the car barely accelerates. But when I let up on the gas slightly the acceleration picks up considerably. FYI I have a Weber 32/36 DGV.

Hopefully what I am explaining is clear...do you think it could be a simple air/fuel mix adjustment??

Thanks again guys,

Greg
 
When you say the engine "lugs" does that mean:
a) the engine misses and runs roughly until you back off the throttle
or
b) the engine runs smoothly, but it won't produce any power until you back off the throttle
 
The Weber has fixed jets so the mixture isn't really adjustable other than rejetting the carb. Idle mixture is your only real adjustment, which isn't going to come into play once you come off idle. It sounds like you are not getting enough fuel into the carb bowl. This could be a result of a clogged fuel filter, a weak fuel pump, trash in the fuel tank or trash in the float valve in the carb. Another option is you are getting enough fuel into the fuel bowl but the jets in the carb have some gunk in them that is partially restricting fuel flow which will lean the mixture out. As always, make sure your ignition is in good shape before chasing perceived fuel delivery problems. Has the car been sitting? If you let a car sit for a long period of time the fuel will get stale and burn poorly as well as produce a nasty varnish that will cause problems inside your fuel system (like a sticky float valve). When storing a car, it's best to put some fuel stabilizer in the fuel and then run the car for a few minutes (to ensure the treated fuel makes it into the carb). Another thought, what happens if you pull the choke out about 50% while trying to accelerate?
 
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]throttle response for our old carbeurated MG's isnt that great in the first place[/QUOTE]
Speak for yourself! /bcforum/images/%%GRAEMLIN_URL%%/wink.gif Swing by and I'll take you for a ride in a properly tuned SU setup. Can't help with the Webers since I have no experience with them, but you should not have any lag or hesitation whatsoever.
 
Agreed. SU's are as responsive as about any other induction setup.

Sounds like a fuel delivery or float setting problem.
 
The car is a daily driver...it never sits more than a day without being driven. And the fuel filter was replaced about 10,000 miles ago. Unfortunately I dont have the time until my spring break to be taking apart my carb to clean out the jets...I do have some of that carb cleaner that you add to your tank when you fuel up, hopefully that will at least help it for now. Thanks for all the advice guys.

-Greg
 
I have the same type of Weber and have noticed something similar. When I push on the pedal after the car has been idling for a moment, there is hesitation before the revs come up. I've attributed this to the nature of the carb itself, and hadn't thought that I might have a fuel delivery problem. I suppose I could get a fuel pressure gauge, though I haven't seen a relatively cheap one of those.

What should the fuel pressure at the end of the fuel filter be?
 
2.5~4 pounds. Four would be a bit on the high side. look to float level and needle/seat issues. That carb has a "pump" for accelerator jets. The orifi are very small and can plug up if old fuel sits in it.
 
Look down the throat of the carb ( engine off ) and see what is happening.........accelerator pump should be squirting in fuel. Do both butterflies open fully? Thats the progressive carb right? Hard to trouble shoot over the internet, but could be a gunked up jet problem.
I ran a DGV on a 1500 spitfire for a couple of years until i found a good set of used S.U's and they were easier to work on, cheaper to fix and unless you are racing the car hard, SU's are the way to go!
But, good luck with the webber..........
 
heliguy wrote:
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]I ran a DGV on a 1500 spitfire for a couple of years until i found a good set of used S.U's and they were easier to work on, cheaper to fix and unless you are racing the car hard, SU's are the way to go! [/QUOTE]

Yup. Why try to swim upstream!?!

...as I look out at the "fleet" equipped with DCOE Webers...

/bcforum/images/%%GRAEMLIN_URL%%/smirk.gif
 
What year MG? What ignition system ie Lucas points, Lucas electronic etc. Most of us agree that most fuel problems can be fixed by fixing the ignition first.

Guinn
 
DrEntropy said:
That carb has a "pump" for accelerator jets. The orifi are very small and can plug up if old fuel sits in it.
Click to expand...
iagree.gif

BTW...I don't really like DGVs
I prefer SU but, DCOEs are nice also.

DGVs are really sensitive to float adjustment & check your auxiliary venturi for looseness.
 
I was trying to figure this out as well.

Your Jet needs to be changed out for another.

A friend of mine with an MGA and DGV setup almost went back to SU's until he changed the JET to a leaner one.

Now when he stomps on it, it goes without hesitation.

The stock jet in the dgv is too rich.

I have my replacement (a .15 i think) and will be installing it in a few weeks.
 
Back
Top