1930 Ford Backfiring

[COL Tom]

My 1930 Ford has a problem that I cannot seem to figure out.  She idles fine.  When I take her out, she runs smoothly for about 5-10 minutes, but then begins to backfire constantly.  I have changed the condenser and the points.  The gap is good.  The timing is good.  I have checked the fuel mixture to ensure its not too lean.  I have loosened the gas tank to ensure there is no air vacuum.  I have changed carburetors. Nothing seems to work.

 

Again, she seems to run fine initially (and also when idling, even when warmed up), but once she warms up, the backfiring begins when you are driving around. 

 

Does anyone have any other ideas?

[Bhigdog]

Distributor cap................Bob

[60FlatTop]

Test it with a condenser from a car that doesn't backfire.

[46 woodie]

Most of the condensers that are available today are junk. As 60 recommends, I would replace yours with a known good one, only two screws to remove it. Several articles in the Model A club magazines about condensers and the lack of finding good ones. A company called Echlin, available from NAPA and some others are decent from what I have read. Sounds like something is breaking down in the electrical system when it gets hot.

[John348]

Coil????

[Real Steel]

I have a '30 Ford 'A' also.  I like the folks here on the AACA forum and they have helped me several times...and I can see that some folks have chimed in already to help you.  I've also received help here

https://www.vintagefordforum.com/forum/model-a

 

[Povertycove]

In a condition like this, the third thing I do is to replace the spark plugs. With air cooled engines its the first thing I do.

[JACK M]

Valve adjust?

[old car fan]

Could be a fuel problem even though it is a gravity system

[Pete O]

Backfiring out of the carb or out of the exhaust?  

[Guest]

That was going to be my question is it "backfiring" through the carb (usually means lean mixture, a sticking valve or an intake manifold leak), or "after firing" in the muffler (usually means rich mixture and/or a sticking valve or late timing).

[Real Steel]

12 minutes ago, Tinindian said:

That was going to be my question is it "backfiring" through the carb (usually means lean mixture, a sticking valve or an intake manifold leak), or "after firing" in the muffler (usually means rich mixture and/or a sticking valve or late timing).

 

Its been many years since I've heard someone use the terms "backfire" and "after-fire" correctly. 

 

[Guest]

14 minutes ago, Real Steel said:

Its been many years since I've heard someone use the terms "backfire" and "after-fire" correctly

When I worked in a GM dealership (1959-1973) I saw "service salesmen" chased out of the  building by "tune up mechanics" because they were unable to use proper descriptions.  The mechanics were paid piece work and did not appreciate looking for something when it was really something else.

On the other hand I have seen (in four trips)  the replacement of a left axle bearing, a right axle bearing, pinion bearings and finally a front inner wheel bearing on the same Vauxhall Viva.  The customer complained of a noise, the service writer road tested the car three times and said it needed each of the first three parts replaced.  Each time the mechanic argued with the service writer when he heard the car drive into his stall.  The fourth time the mechanic replaced what had been wrong all the time.

No doubt the real problem always is communication and terminology.

 

Edited June 4, 2018 by Guest (see edit history)

[mcdarrunt]

Weak coil runs good cold; runs bad hot.

[JACK M]

40 minutes ago, mcdarrunt said:

Weak coil runs good cold; runs bad hot.

 

Or condenser.

[pmhowe]

6 hours ago, JACK M said:

 

Or condenser.

 

My recollection is that, when a condenser fails, it fails catastrophically.  Not true?

[cahartley]

Not true......it acts exactly like a coil going bad which is what makes trouble shooting so much fun....... 

A failing condenser can make an engine sound like it's not going to make it....... LOL

[60FlatTop]

I think there are support groups for those in condenser denial. But it is a simple, two step program.

[Grimy]

I'm a believer in trying the easiest, least invasive, parts substitutions first.  To that end, I carry two known-good condensers and one known-good coil in my "supplies" bag which accompanies my Traveling Tool Bag in a vintage car if I'm venturing more than 25 miles from home.  Without removing the distributor cap, you can add a supplemental condenser by attaching the pigtail to the low tension coil terminal which supplies power to the points, BUT you must ground the condenser body with the jumper wire, an essential item in your Traveling Tool Bag.

 

I've also substituted a coil on the side of the road by taping it to a radiator steady rod or other place within reach of the low tension and high tension wires.  It's a good idea to pre-plan for this in the comfort of your garage, to determine whether you may need to add extension low tension and/or high tension wires to your kit for roadside installation.

[JACK M]

Grimy,

You know the old saying, "if you bring it you wont need it."

[Grimy]

Jack M, that's why I carry so much stuff!  In the last 20 years of touring, I've done one condenser substitution, one coil substitution, and one rotor replacement (latter on another guy's car) on the side of the road.

 

On my dual point distributor cars (Pierce 8s) where you can't see to reset slipped-adjustment points without removing the distributor head, I carry a spare dist head with pre-synchronized points, which can be swapped out in 5 minutes.  Began to do that AFTER one instance of spending an hour trying to get a decent-enough point adjustment without pulling the dist head.  And these spare parts also keep the tigers away!