I have an ’84 12A and seem to be having a firing problem. I have done some searching on here but haven’t found my exact problem in another post.
The car runs great about half of the time. I can rev it up as high as I want and it seems to run very smooth with great power a few times….. then it seems to only fire the leading or the trailing set of plugs and of course losses a lot of power and runs rougher than normal.
If I let it idle for a second or two, I hear either a relay or solenoid click once and the idle/power/firing go back to normal.
The tach isn’t affected so it must be the other coil being told to cut out or?
It has fairly new plugs/wires/cap/rotor. I have run Sea Foam through it (I drained the tank prior to doing this) and actually still working on what’s left in the tank. The fuel filter looks fairly new but then again that doesn’t mean much.

I am reading through the tutorial now to remove the rat’s nest…could any of these solenoids running to/from the distributor cause the problem I am seeing?

Any ideas on where I should look?

PS, if anyone has a stock diff with good spider gears in it please pm me… I don’t care if it is an open rear or what…just something so I can drive this thing on the street. Since two of the four spider gears in mine were stripped and the diff housing was damaged, I just welded things together so I could drive the car a few miles to my house. I don’t like this 85hp drag car thing I got going on now..

Thanks

-Jarrod

 

i'd say replace your fuel filter, remove the rats nest, air pump, and gut the cat. This should fix your problem. If not, then I dont' know.

 

Can you be more specific in the symptoms? btw if the trailing ignition was going off and on 1) you wouldn't notice a diff in power, 2) your car would die shortly after due to no fuel and 3) you're right, you'd have no tach when it would go off. When you say you can rev up as high as you want do you mean on the road and under load or parked? does it feel like you're driving and hit a rev limiter sort of loss of power? at what rpms/speed/gear?

 

Change your fuel filter if you don't know exactly how old it is. If that doesn't correct the issue, then inspect and clean all electrical connections from the battery to the starter (positive and negative wires). How's the cap/rotor?

 

I mean the engine runs the same under load or free revving and it will rev up from idle to redline either way, but there is a difference in the rev….it takes longer to get up in rpms. It seems like the engine is firing half of the time.
Maybe it is the fuel filter….it could possibly be that after it idles a few seconds, the carb’s bowls have time to fill up with fuel, so the engine runs correctly until they are emptied??..I don’t know, I am a carb newbie.
Either way I will change it this evening.

The cap/rotor/plugs seem in decent shape but if the fuel filter doesn’t fix it, I will replace those as well.

Also, I bypassed the solenoids for the dist and went straight to the carb via a T…no difference.

Thanks again guys.

 

Yeah that's what would happen with a less than ideal fuel volume going into the carb. If changing fuel filter doesn't fix it, maybe time to replace fuel pump. Do a fuel pressure and volume test if symptoms persist.

 

Ok, new fuel filter is in...the old one was gross! The car has a fairly new fuel pump on it too.
Also new, plugs, cap & rotor. It still does it. One thing i did notice is both of the plugs in the second cylinder (closest to firewall) are fouled and smell like gas...so this cylinder (or whatever it is in rotor terms) is misfiring about half the time. The cap is on right, the wires are correct....and all this work didn't change anything, so where do i look now? It can't be a coil can it because if it were, i would have both the leading or both the trailing not firing correct?
I unplugged all of the rats nest solenoid plugs while idling and no change either...figured it wouldn't but it was easy to do.

Thanks again for any input,

-Jarrod

 

y dont u unplug one of the wires going to the coils and see if the coils are getting electricity just a thought

 

Check the float levels on both of the sight glasses on the carb. With the fuel filter being full of crap, some may have gotten into the carb. With only the rear plugs fouling, the needle/seat/float may be sticking in the rear fuel bowl.

If the fuel levels are not the same front and rear, it may be time for a carb rebuild. I would do a compression test too to make sure there isn't a problem with the rear rotor.

 

+1 on the compression test.

 

Well it's fixed!!!....in a ghetto fabulous way for now, but fixed nonetheless.
I will get pictures this evening but on the driver side of the carb there is a large vacuum line that runs to a fitting on the underside of the breather. This goes to some type of valve that looks to be hooked to control the carb in some way...possibly open/close a set of butterflies. Either way, with this plugged up, the car revs/runs great!
Can anyone tell what this valve is supposed to be doing? This is what i was hearing that was clicking like a solenoid/relay and the engines tune would change.

I will eventually do a comp check just for good measure...and the two site bowls on the carb are reading very close to eachother so i am assuming the carb/float set-up is working correctly.

As always, thanks for the input guys! Boy this thing is fun to drive...it's so light....gotta get rid of this welded up rear though...

 

Just plug that hose and you'll be fine. That was the first thing I had to do when I got mine...