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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / August 2005No Spark 85 Caprice
Hi, I'm getting a no spark condition in my 85 Chevy Caprice. It used to only happen when the engine was warm, but now it does it cold too, and hasn't started up for 6 hours. I hooked up an inductive timing light to it, cranked the engine, and got no flashing from the light. Also took a wire and plug, held the plug against the valve cover, cranked engine, and got no spark. It has the HEI ignition. ALl my Chilton's manual tells me is that there is an "integral ignition coil" inside the top of the cap, and how to replace it. Also that there is a "module" inside the cap somewhere, and how to replace it. Doesn't say how to test them. What's the most likely cause of the no spark ? How can I test it the coil and the "module"? I have another module of some sort bracketed to the passenger side inside fender which I think might be an Electronic Spark Control module, but Chilton's doesn't mention it. I guess the rotor could simply be shot, too. I'll check that next, of course. Any help welcomed !!!! Thanks You can check the coil with a VOM. The mudule can be checked for free at many auto parts stores. That black module mounted on a small pedestal on the passenger fender well is a map sensor. (Note the vac line.) Well, it started up again, after 7.5 hours of cooling down. I did check the rotor. It was a bit rusty, and there was a little black carbon dust in there too, on top of the white part of the rotor, not much. Since the contacts don't actually pass a spark, I guess they are OK. I'm still going to be back at square 1 when the engine is warm again, though. Whatever it is, it's only happenning during starting, not running, so it's probably isolated to the starting system. Is the module only used during starting? More help appreciated ! > Well, it started up again, after 7.5 hours of cooling down. I did check > the rotor. It was a bit rusty, and there was a little black carbon dust > in there too, on top of the white part of the rotor, not much. > Since the contacts don't actually pass a spark, I guess they are OK. How's the contact "button" inside the cap? Does it still stick out, or is it worn flush with the plastic housing? MasterBlaster wrote : <<How's the contact "button" inside the cap? Does it still stick out, or is it worn flush with the plastic housing? The button is worn flat but it still sticks out a good eighth of an inch or so. The new buttons are supposed to be domed a bit, I think. On closer inspection, I noticed the rotor had a dimple worn into it where it pressed against the cap button, and also had a small rough spot inside that dimple. (It had a * LOT * of miles on it). So I bought a new rotor. The new one has a stronger tang on it. It sticks up farther, to press against the cap button. The old one had sagged lower, and maybe it was just barely connecting to the cap, and that dimpled part was def not touching the flat cap button. The car starts much faster now when cold or hot. It also starts now when warm, although sometimes it takes some playing with the gas pedal. So, I am cautiously optimistic that the new rotor solved the problem. Still more testing to do before I am sure. Thanks. > MasterBlaster wrote : <<How's the contact "button" inside the cap? > Does it still stick out, or is it worn flush with the plastic housing? > The button is worn flat but it still sticks out a good eighth of an > inch or so. The new buttons are supposed to be domed a bit, I think. > So, I am cautiously optimistic that the new rotor solved the problem. > Still more testing to do before I am sure. The button is replaceable too. Usually comes with a new cap. Back to the drawing board ! It's doing it again. No spark sometimes, when warm. It was OK for a few days with the new rotor. > Back to the drawing board ! It's doing it again. No spark sometimes, > when warm. It was OK for a few days with the new rotor. Sorry I'm late to this thread. Assume you've removed all the ignition wires and wiped them with cleaner (eg piant thinner). Did you check the ignition module (transistorized points)? If you are losing spark when warmed up it could be in the electronics of this module. You should be able to remove it and take it to a parts store for testing. Some of them will test the modules for free. If it fails the test shop around for a replacement as they can be twice as much at some locations. If it needs replacment bed the new one dialelectric heat transfer grease, $1 per packet at an electronics store (NOT Radio Shack which charges about $10). There is a description of diagnosing and replacing mine on my website (see below) under "Cars". good luck. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-FreeNet email must have "notspam" in subject or it's returned William, thanks. No, I haven't wiped down the wires. Would that actually help? They are a bit greasy. Yes, I could take out the ignition module and take it in for testing. I could bring a hair drier to heat it when they are testing it (seriously), and see if it starts to malfunction when it gets warm. Caprice85 > Hi, > [quoted text clipped - 21 lines] > > Thanks The coil is indeed mounted in the top of the distributor cap, they rarely fail. Check that you have 12v on the bat+ connection at the distributor with the key on. Under the rotor you will find the Ignition module, most autoparts stores can test it. It is also a cheap part to replace. Another common HEI problem is the pick-up coil, mounted under the rotor and surrounding the distributor shaft, The wires tend to break due to metal fatigue, from rotating with the advance plate. The distributor must come out to replace the pick-up coil.  SignatureAlan Gallacher Born to Tinker! > > Hi, > > [quoted text clipped - 38 lines] > Alan Gallacher > Born to Tinker! Good advice from Anumber1. This pickup coil that he mentions is often the source of *intermittent* operation, whereas the module seems to be more of a go-nogo-component. It has tiny wires, which when broken from the metal fatigue he refers to, can make in one position & break at a slightly different position--or even make and break from heat expansion/contraction. Bet he's got your problem pin-pointed. s <snip> > The wires tend to break due to metal fatigue, from rotating with the advance > plate. The distributor must come out to replace the pick-up coil. There is no rotating advance plate on a 1985 Chevrolet Caprice, the timing advance is totally computer controlled. The core magnets in the pick-up coil however are prone to cracking and causing all manner of problems. Went out this morning, when the engine was nice and cold. It wouldn't start! Probably no spark again, but this time when it was cold ! It used to always start when cold. Dang. Twice now I have gotten the spark back after removing the air cleaner, and tapping on the various electrical components and connectors (or it could just be coincidence). I'll have the gf get in the car and turn the key while I tap different components, and hope for the best, so I can possibly diagnose it. Also going to check for 12 Volts at the battery connection the the distrib. Sould I check for 12 V during cranking or just with "key on", or both? Don't want to destroy my voltmeter, if the volts are too high during starting. I know I have a loose connection at the alternator plug-in connector; wiggling it changes the revs a little, but it's never caused this before. Maybe it got worse. Just one more thing to check. I'm still wondering why the car can start up sometimes, and run just fine for through the cold, warm, and hot phases, with spark, then get no spark only during starting. Thanks for the replies. They help. Keep them coming, if anyone has an idea ! "Caprice85" <user132384@aol.com> wrote in news:1124632912.613802.155640 @z14g2000cwz.googlegroups.com: > Went out this morning, when the engine was nice and cold. It wouldn't > start! Probably no spark again, but this time when it was cold ! It [quoted text clipped - 21 lines] > Thanks for the replies. They help. Keep them coming, if anyone has an > idea ! the B+ at dist. (large pink wire) should be B+ in ON and CRANK. no worries about VOM when testing this circuit, volts cant exceed battery voltage. i just foung this NG so am not intune to entire thread. i hope you are indead chasing an ignition prob. as far as your alt. wiring prob, i cant see where it SHOULD cause a problem w/starting but obvious probs could show up while driving as the field collapses in alt. if it is a weak enuff contact at plugin...........kjun Kjun, Thanks. Does B+ stand for Battery positive (12v) ? I went out to test it, thinking the car would not start, but this time it started, and that was without touching a thing since it last failed to start. However..... I heard the fan belt on the alternator making a slight squeal now and then, like something was drawing current now and then. Or maybe it was just recharging the batt from all the cranking I had been doing. The alt got warm after only a minute of idling, and after 4 minutes it was downright hot. It was putting out 13 volts as measured across the battery posts. It's at least 8 years old. I could make the alt belt squeal or not squeal by moving the wiring connector to it. That's been a characteristic of this car for years, though. But the fact that the alt got hot so fast has me thinking the brushes are worn out, or maybe something is drawing a lot of current. Maybe the alt has nothing to do with the no spark on startup. Maybe it's a separate problem. Does anyone know if a looseness in the alternator wiring connections, or worn out diodes, or voltage regulator, or something else, could cause a "no spark" condition on startup? I know I'm asking a million questions, and I appreciate the responses. I'm out under the hood of this car every day with my neighbors watching me. I'm trying my best ! Luckily I have another car to drive until I get this one figured out. Thanks "Caprice85" <user132384@aol.com> wrote in news:1124643259.980126.29920 @g47g2000cwa.googlegroups.com: > Kjun, > [quoted text clipped - 27 lines] > > Thanks dont let the neighbors worry you..yes B+ means battery positive voltage. if it were me i would get a QUALITY rebuilt alt. and replace the pigtail on the harness (if its the connectors in the harness causing wiggle room) but i still cant see the parallel between alt. noise and cranks but wont start conditions. again, if it were me, next time it cranks but wont start i would give it a blast of starting fluid in the air intake unless your ABSOLUTLY sure its a no spark prob........kjun.. ps...if you open up the large loom by the brake booster coming out of firewall you will find a large purple wire (solenoid engagement circuit). if you tap into it with a switched B+ signal you can be under the hood while trying to start it. turn ignition switch to run before trying to start and make SURE veh. in park. this bypasses ign. switch and neutral safty switch for engagement. > Hi, > [quoted text clipped - 21 lines] > > Thanks One thing seems to be highly likely the problem: the pickup coil. Why not replace it & eliminate that as a possibility--and probably correct your problem? They aren't expensive. s One thing seems to be highly likely the problem: the pickup coil. Why not replace it & eliminate that as a possibility--and probably correct your problem? They aren't expensive. s << Basically, because the distributor has to come out in order to replace the pickup coil, something I'm not comfortable doing. I'm hoping the problem is something else. But you're right. I should try the most likely solutions first, whether I do it myself or take it to a mech (assuming it will start again). >Basically, because the distributor has to come out in order to replace >the pickup coil, something I'm not comfortable doing. Even if that is the case, you should be able to test it for open/short and correct impedance without removing the distributor. I replaced my pickup coil a while back because the plastic plug had broken and rotted off, allowing the wires to dangle. Replacing it involved removing and disassembling the distributor, but testing it only involved unplugging the plug and using a ohm meter across the two wires. > >Basically, because the distributor has to come out in order to replace > >the pickup coil, something I'm not comfortable doing. [quoted text clipped - 5 lines] > distributor, but testing it only involved unplugging the plug and using a ohm > meter across the two wires. I've seen a couple of instances (one a Chevy, one a Volvo) where the ohmmeter showed continuity UNTIL I bent/repositioned the wires slightly. Obviously, these 2 were broken inside the insulation, but ends were so close, they'd make and break at times, apparently from heat-expansion(?). If it is continuously open, this would not be necessary. s
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