Surging problems

[yellow67]

Have a 67 bronco with a 289. I recently replaced the timing chain and got it running and timed. But when I attach the vacuum advance vacuum line it starts surging badly. The vacuum advance is new but when I apply vacuumed to it I cannot get it to move the distributor plate seems very stiff and when I checked spark it was not consistent it was erratic not spark, spark but sparkedy, spark, spark, spark. Could this be a bad distributor?

 

[70_Steve]

Have a 67 bronco with a 289. I recently replaced the timing chain and got it running and timed. But when I attach the vacuum advance vacuum line it starts surging badly. The vacuum advance is new but when I apply vacuumed to it I cannot get it to move the distributor plate seems very stiff and when I checked spark it was not consistent it was erratic not spark, spark but sparkedy, spark, spark, spark. Could this be a bad distributor?

Hi! And Welcome to ClassicBroncos.com!!!

What vacuum source are you connecting the line to? Should be ported vacuum (almost no vacuum at idle) not manifold vacuum (18" vacuum at idle).

What carb?

 

[ransil]

Diaphragm in the distributor could be bad, put a vacuum pump on it and see if it leaks.

 

[yellow67]

The vacuum line comes off of the bottom of the carb, a two barrel auto lite. This vehicle is stock all the way. My dad bought it new in 67 and I just use it for hunting. I have tried sucking on the vacuum advance but cannot budge the distributor plate.

 

[yellow67]

The vacuum advance is new and seems to work. the spring tention in the distrubtor seems to be very strong. I feel like when I hook up the vacuum it has to vork very hard to move the plate the i goes all at once and ove shoots.

 

[70_Steve]

I have tried sucking on the vacuum advance but cannot budge the distributor plate.

You can't create nearly enough vacuum to get that vacuum advance to operate by sucking on the hose. You'd really need a vacuum pump. The hand operated ones are good for testing this kind of stuff.

 

[Rustytruck]

Take the cap off the distributer. twist the rotor by hand it will expand the fly weights now let go and the rotor should spring back on its own accord.
Now remove the vacuum line at the distributer and rotate the rotor again and while it is still twisted put your finger over the vacuum port on the distributer and let the rotor move it will move some and not go all the way back. now let go of you finger on the vacuum port and the rotor should turn fully back. this will test if you diaphram is still working properly. if this passes the test then the distributer is capable of working properly. with the early vacuum canisters on the 289 they were unscrewed and adjusted by adding washer like shims to adjust the vacuum advance use the later model sealed vacuum cans and most of them can be adjusted inside the vacuum port with a small allen screw if need be.

 

[yellow67]

All that seems to work okay. It is when I hook up the vacuum line the engine starts to surge badly. when I remove the vacuum line the engin smooths out and runs great.

 

[yellow67]

found the problem. I took the distrubitor plate out. It was allgummed up. i cleanded it and lubed the three contact points. Put it back in and the surging problem is gone!

 

[Justafordguy]

Good job, I'm glad it was something easy.;D