Howdy, Stranger!
It looks like you're new here. If you want to get involved, click one of these buttons!
Categories
- All Discussions27,030
- Orphaned Marques
- ↳ Hudson21,102
- ↳ Street Rods807
- ↳ Off Topic573
- ↳ American Motors148
- ↳ Kaiser - Frazer70
- ↳ Nash70
- ↳ Packard163
- ↳ Studebaker122
- Classic American Cars
- ↳ Ford Motor Company956
- ↳ Chrysler Corporation477
- ↳ GM Corporation1,396
- ↳ Post War Chevrolets75
- ↳ Pontiac Forum119
- General
- ↳ All makes1,958
- ↳ Poll Discussions24
- Swapmeets & Events
- ↳ Events130
- ↳ Swapmeets108
- Hot Rod Corner
- ↳ Ford Rods90
- ↳ Lead Sleds67
- Special Interest Groups
- ↳ The Flathead Forum139
- European marques
- ↳ MG Car Company2
- ↳ Mercedes-Benz2
Vacuum advance Diagnosis
-
What is the proper way to check vacuum advance. My '53 superwasp has a hestitation when accelerating and I want to rule out the vacuum advance. I discontected the vacuum line and put a vacuum pump with gauge on it. If I pump it up to 20 in of vaccum the advance moves, but the pressure slowly bleeds down to zero. Is this normal?
Rich -
Testing in your car, utilize a dwell and vacuum gauge.
1. Make sure the point and valve timing are correct. I.e. Point Gap and Distributor mechanical timing.
2. Start and warm the car to normal operating temp.
3. Connect the dwell meter and observe the dwell.
Use the specifications found at ALEX BURR or KEN CATES Websites
www.freewebs.com/hudsontech/
members.aol.com/stepdown53/STEPDOWNPG.html
Slowly advance the engine speed while observing the dwell meter... the dwell should smoothly increase as engine RPMs smoothly increase.
4. If the hesitation is still present... stop engine and disconnect the advance vacuum line to the advance canister. Cap the vacuum line. Attach a hand operated vacuum pump to the vacuum canister and restart the engine.
5. While observing the dwell meter increase the vacuum with the hand pump ... use the vacuum gauge to set the amount of vacuum to that found in the tune up spec. Changes in the vacuum should cause the dwell to change. If not the vacuum canister is not working properly.
Other issues. The distributor has a mechanical advance comprised of weights and springs. If there is dirt or other debris in the advance mechanism it will not operate smoothly. Broken springs are possible as well as corrosion. You have to take the distributor out of the car and remove the point plate to access these pieces.
Hesitation can be caused by other things, some suggestions:
Bad Gas
Failing or Failed Carb Accelerator pump
Plug fouling and gap
Valves and timing
Fuel delivery
Dirt in the carb
Vacuum leaks at the intake or to the distributor, at the Wipers
Hope this will assist you -
ratlee2 wrote:What is the proper way to check vacuum advance. My '53 superwasp has a hestitation when accelerating and I want to rule out the vacuum advance. I discontected the vacuum line and put a vacuum pump with gauge on it. If I pump it up to 20 in of vaccum the advance moves, but the pressure slowly bleeds down to zero. Is this normal?
Rich
To answer your question, and assuming that you're using a hand held vacuum pump, the vacuum advance should respond quickly and not bleed down. It sounds like the rubber diaphragm in your advance is failing.
If replacing your advance unit doesn't help to eliminate hesitation, follow the other good advice offered above. -
Thanks for the responses. I replaced the failed vacuum advance and capped the line going from my dual action fuel pump to my wiper (leaks as well). The idle improved, but still have the hestitation. I hestitation is present at from start to about 40 miles a hour. So I will look at the accelerator pump and mechanical advance next.
Rich
