Jingkun

iTrader: (4)

Well on my way to work today, and I'm getting on the highway, I suddenly seem to loose compression on 1 rotor. Its making the chug sound that says lack of ignition, but it idled fine on the side of the highway. After a couple minutes seeing if it was going to right itself I decide to pull off the highway and into a parking lot. It dies at the light and I wind up having to push her to the parking spot she's in now. Now I try to start her and I can hear the starter kick against the flywheel and then nothing. Just stops. So the engine is locked.

Can anyone offer any insight on what just happened here? Was it a seal? Did I spin a bearing? Whats going on?

t_g_farrell

iTrader: (1)

Sounds like a dead battery to me. Check that first. Could be the alternator is gone and you were
running on battery alone.

Or it could be your ignition is starting to fail, like the leading ignitor but that doesn't explain the starter issue.

I'm sticking with low battery charge at this point.

Jingkun

iTrader: (4)

I'd love for it to be the battery but I just bought that back in October. Battery reading is about 12 volts steady and I've been running the GM ignitor mod for about 2 years now. Is it possible that I spun a bearing and now the rotor is sitting funny and jamming the engine movement? Or even possible that if I did throw a seal that it is jamming on that. Like I said (least i think i said) the starter is engaging with the flywheel gear just fine, it doesn't disengage from the gearing until I let off the key.

ray green

iTrader: (14)

Tim is being hopeful, and certainly you need to rule out the little stuff first, like the battery. Easy check there is to see if your headlights turn on and are nice and bright, if so, battery is fine.

Other optimistic outcomes would be a bad leading igniter, to test that just swap your leading and trailing electrical connections to the igniters on the dizzy. If the problem goes away you have a bad igniter, which because it's now powering your trailing ignition is not compromising engine output. (note, if you've put in some of Tim's GM ignition parts you will need to check with him about how to diagnose the igniters).

Fuel is another obvious possibility, to check that disconnect the feedline at the carb, put it in a 1 gallon plastic jug to collect the fuel output and turn the engine on, being careful to collect the fuel being pumped through the system. As I recall you should get about a half gallon per minute at 1200 or so rpms, but if you want the exact spec it's in the FSM. There should be enough fuel in the carb bowls to run the test.

If all these fail, you will need to starting thinking about the possibility that you've lost an apex seal and are losing compression in one rotor, most likely the rear. This would explain why the engine is seized, you have a hunk of apex seal wedged between the rotor and housing.

But check on this too, you can put a spark plug wrench on the eshaft pulley and try to turn the engine over. If it does, the engine isn't seized, but if it doesn't budge, time to start getting depressed. I had a 12A fail that way, with symptoms exactly as you describe.

t_g_farrell

iTrader: (1)

Can you turn the engine by hand with a wrench on the eccentric nut on the front of the engine?
if you can't turn it by hand then its definitely locked up.

Oops didn't see Rays last sentence. I guess great minds think alike

Jingkun

iTrader: (4)

I haven't been able to get a wrench on it since I still had to get to work. But if Ray says that he had a 12a that failed in much the same way then I've gotta look to that. I know the starter is trying to push the motor but can't and the starter is definitely good. I just hope that when I lost the compression that the seal didn't tear up the housing too bad (read "at all"). Either way as much as this depresses me I'm gonna turn it into a good thing. I hear a dremel calling my name.

So Ray, if I'm understanding correctly I should only need the "Closing kit" from atkins right?

t_g_farrell

iTrader: (1)

If it is a stuck seal, you will have housing damage more than likely. I wouldn't order rebuild bits
until you take it apart and verify all your existing parts.

I hope you are lucky and theres no damage. Keep us posted on how it turns out.

ray green

iTrader: (14)

Hi Jingkun, well don't give up without a fight. Put a wrench on there first, if it turns over say a prayer to the Rotary Gods and go on to the next step.

But if it's seized it's not good, chances are almost 100% there is damage to a housing or rotor or both, maybe even the eshaft if there are bearings involved. You really won't know the full extent of the damage until you pull the engine and tear it down, so the rebuild costs are only a guess at this point.

Depending on the damage, you may be able to rebuild (hope so, I hate to see another 12A go to the graveyard) but the costs add up quickly, as I'm sure you are aware just looking at the kits from Atkins. Decent 12A housings and rotors are out there, but you need to do some serious hunting and shopping to find good ones at a decent price. Eshafts aren't a problem, they are in excess because of all the 12As that have been torn down and not rebuilt.

You are correct, for the rebuild parts the Closing Kit makes sense unless you really want to skimp and try to reuse parts like apex seals, side seals and springs. But if you're going to the trouble and expense of a rebuild I wouldn't cut corners at that point, the best part about rebuilding is you have a new engine with known provenance so you don't want to be worrying about any weak links after that.

Alternatives are to find a good used 12A (not many out there and buyer beware) or you may want to think about the 13B "upgrade" (I happen to like 12A's better, but that's just my opinion). At least 13B's are easier to find and parts in the future will easier to find.

Let us know how it goes, you're either going to get lucky and have an easy fix or you're about to begin a most excellent adventure, can't lose either way.

P.S. Tim and I are on the same mental telepathy channel, so sorry for the redundancy.

Jeff20B

iTrader: (13)

If you can't find any 12A stuff, Nikki carbs work really well on 13Bs. I wouldn't have it any other way.