Thanks Jack Riffle - problem finally found - long
06-14-2006, 03:21 PM
#1
Racer
Thread Starter
Join Date: Aug 2001
Location: Attleboro, MA
Posts: 470
Likes: 0
Received 0 Likes
on
0 Posts
Thanks Jack Riffle - problem finally found - long
My 81 has had some intermittent non start issues. but everytime I'd go to trouble shoot it, I would find nothing substantial, just something questionable like weak spark or questionable vacuum lines or, for some strange reason, it would just fire and run great as if nothing ever happened. I'm always on top of maintence and have even replaced the coil, fuel pump and fuel pump relay just to be sure.
This monday - she fired right up after a long winter slumber and for the first time in 16 years - died on the road. No sputter, no hicup - just dead- traveling 40 MPH as if someone turned off the key. Popped the hood to find good fuel pressure and spark- but despite numerous cranking attempts (normal sounding)
- she wouldn't even begin to catch. She got a piggyback ride home and after work and searching the list - I dove into her.
The timing belt was replaced about a year ago, properly tensioned - driven for 1K mi and retensioned but, I had noticed over the winter that when I warmed her up - if I rev'd the engine and shut her down quick, I could hear an idler bearing still spinning - coasting down. I had planned on rechecking the tension but forgot in my haste to drive her in the sun. I had hoped the TB wasn't the problem but remebered the spinning idler when she died and prepared for the worst. I get home and for giggles tried to start her. To my surprise, she started, but ran god awful -like the timing skipped! Not what I wanted. Pulled the covers and the TB is like new and the tension is fine. Now I'm a little stumped.
Then I remembered a post by Jack Riffle about the AFC relay and the 2 #87 terminals. I pulled the relay and sniffed it - sure enough it smelled toasted. I checked the coil and it was a dead open. I opened up the case to find that the coil winding must have been getting hot for some time becuase the insulated ends were so warped, the moving contact could barely engage (likely my intermittent no start). I think the coil just finally burnt out and thats what killed her. A fashioned a quick 3 way jumper and she fired instantly and ran fantastic. The neat thing is that I was able to take a standard 30 amp general purpose relay I had laying around and after insulating one lead and shorting the 87 & 87a terminals together internally - it worked great. The GP relay does not have a surge suppression diode on the coil (like the original) but I'm wondering how critical that is since i believe it's energized by the Key switch?
Anyway - Jack - Thanks for your insight and sorry for the long post.
This monday - she fired right up after a long winter slumber and for the first time in 16 years - died on the road. No sputter, no hicup - just dead- traveling 40 MPH as if someone turned off the key. Popped the hood to find good fuel pressure and spark- but despite numerous cranking attempts (normal sounding)
- she wouldn't even begin to catch. She got a piggyback ride home and after work and searching the list - I dove into her.
The timing belt was replaced about a year ago, properly tensioned - driven for 1K mi and retensioned but, I had noticed over the winter that when I warmed her up - if I rev'd the engine and shut her down quick, I could hear an idler bearing still spinning - coasting down. I had planned on rechecking the tension but forgot in my haste to drive her in the sun. I had hoped the TB wasn't the problem but remebered the spinning idler when she died and prepared for the worst. I get home and for giggles tried to start her. To my surprise, she started, but ran god awful -like the timing skipped! Not what I wanted. Pulled the covers and the TB is like new and the tension is fine. Now I'm a little stumped.
Then I remembered a post by Jack Riffle about the AFC relay and the 2 #87 terminals. I pulled the relay and sniffed it - sure enough it smelled toasted. I checked the coil and it was a dead open. I opened up the case to find that the coil winding must have been getting hot for some time becuase the insulated ends were so warped, the moving contact could barely engage (likely my intermittent no start). I think the coil just finally burnt out and thats what killed her. A fashioned a quick 3 way jumper and she fired instantly and ran fantastic. The neat thing is that I was able to take a standard 30 amp general purpose relay I had laying around and after insulating one lead and shorting the 87 & 87a terminals together internally - it worked great. The GP relay does not have a surge suppression diode on the coil (like the original) but I'm wondering how critical that is since i believe it's energized by the Key switch?
Anyway - Jack - Thanks for your insight and sorry for the long post.
06-14-2006, 04:29 PM
#2
Chronic Tool Dropper
Lifetime Rennlist
Member
Lifetime Rennlist
Member
You can easily add the diode insiode the relay case. It cuts way down on contact arcing in the ignition switch. IMHO, it's easier to add a diode now than it is to diagnose another intermittent some time later, when the ignition switch starts to go south. You could easily buy the correct dual-contact relay too. The ones that have two 87 terminals usually have two sets of contacts, so adapting a GP single-contact relay for the duty is a temporary solution anyway.
By the way-- great job on the diagnosis. Intermittent stuff is the toughest to troubleshoot. I usually get stuck in some far-off point in a bad neighborhood, and have to recruit gang members and a crew of homeless guys to help get the car to safety.
By the way-- great job on the diagnosis. Intermittent stuff is the toughest to troubleshoot. I usually get stuck in some far-off point in a bad neighborhood, and have to recruit gang members and a crew of homeless guys to help get the car to safety.
06-14-2006, 05:02 PM
#3
Racer
Thread Starter
Join Date: Aug 2001
Location: Attleboro, MA
Posts: 470
Likes: 0
Received 0 Likes
on
0 Posts
Bob,
actually, the original AFC relay is not a dual contact relay (inside). In fact, what would be the normally closed contact (in a GP relay) is still in there, it just has a plastic cap over it so that in the de-engergized state, no contact is made. The 2 # 87 lugs are just bussed inside.
Good call on the key switch - I hadn't considered the arching and given the recent rash of key switch problems.. I think I will order a new relay. Adding the diode to mine looks like bear...and I hate working with the coil windings... fat fingers and all.
actually, the original AFC relay is not a dual contact relay (inside). In fact, what would be the normally closed contact (in a GP relay) is still in there, it just has a plastic cap over it so that in the de-engergized state, no contact is made. The 2 # 87 lugs are just bussed inside.
Good call on the key switch - I hadn't considered the arching and given the recent rash of key switch problems.. I think I will order a new relay. Adding the diode to mine looks like bear...and I hate working with the coil windings... fat fingers and all.
06-15-2006, 08:28 PM
#5
Addict
Rennlist Member
Rennlist Member
Originally Posted by Fogey1
Dumb question - Which is the AFC relay? What does AFC stand for?
06-15-2006, 10:51 PM
#6
Drifting
John, glad my long ago post helped you. Always nice to know that someone else benefited from one of my experiences. That's what makes Rennlist so great. Anyway, enjoy the shark, and always carry a few spare relays and jumpers in the glovebox. May save a flatbed ride home next time.
