| Author | Message | ||
     John Beech Grand Master Username: jbeech Post Number: 403 Registered: 10-2016 |
Tootsie, my 1969 Silver Shadow (SRX6816) has an ignition miss that's driving me nuts. Background info may help. Purchased her a few months back and at the time futzed around with an ignition problem that manifested thusly; the engine would start instantly (hot or cold) and would happily rev freely whilst in neutral but in drive, it wouldn't accelerate the car (e.g. under load). The solution turned out to be the coil wires had been reversed. The theory is a malicious previous looker had done it because the seller would have no clue (or reason) to do this. There had been a prior deal for the car whereby the prospective buyer had been to see/drive it several times. The fellow had free access to the car as they got to know him and thought he was going to make the purchase. The deal fell apart (obviously) and I ended up with the car, instead. Resolving this this took several weeks of off and on effort (plus a lot of head scratching). Along the way I installed a new condenser plus new spark plugs (the car has only 16,000 miles but an occasional backfire had me thinking it could be a condenser issue). That made no difference and the old spark plugs, while a little sooty, really didn't look too bad. Anyway, while the advice was to use Champion N12YC (or 14YC, I don't recall) I felt like using NGK Iridium plugs, instead. These were obtained and on the advice of NGK, I left the preset gap alone (0.040") and installed them since the usual 0.035" gap didn't present a huge difference. I figured the coil should fire them just fine. Anyway, the car ran great . . . for about 50 miles whereupon her engine's begun to miss again! In fact, the power is way down (about like it's running on 5 cylinders) and overall, Tootsie's not a happy girl. Me neither. Meanwhile, I discovered the twin point distributor actually calls for a plug gap of 0.025" versus 0.035" I had assumed - oops! While I wasn't worried about an extra 5-thousandths, an extra 15 thousandths is a ig difference. Remember, however, NGK advises against regapping the plugs. What to do? Wondering if the coil might be weak, and not (yet) having a coil tester beyond a VOM (volt-ohm meter) for measuring resistance, I set about checking the coil. This is simple as I merely disconnected the coil and measured resistance between the primary winding (+/-) and secondary coil winding (+ terminal and output terminal). I obtain a reading of 2.5 ohms between the primary winding and about 8k ohms on the secondary winding. This seems about right but it's nearly 50 years old and doesn't own me anything. Since along the way I had purchased a Pertronix electronic conversion (plus their recommended coil), and concerned about the excessive plug gap, because Pertronix has said their system will fire a 40-thou gap I install the system (plus their coil). This last was a mother f*%&er of a job because there's minimal space between the engine and firewall. Anyway, I fire it up and hmmm, it's running worse! What's more, the timing is advanced in comparison because the engine will barely turn over compression before starting (classic symptom of overly advanced timing). That's also when I realized the coil they'd sent was 1.5-ohm instead of 3-ohms. So the other day I made up a 4" long jumper wire and crimped male-spades on each end. I used this to bypass the ballast resistor because that's a heck of a lot easier than R&Ring that darned coil again, believe me! In any case, bypassing the ballast resistor means one less thing to fail. OK, car runs better. Still need to retard the timing a little bit (it pings under acceleration so I have to drive with a light foot), but it's also still missing (maybe running on 5-cylinders). Oh, and Pertronix have advised me against using the stock solid core spark plug wires. This, putatively because of EMI, which may damage their module. No mention of this in the instructions but that's where I am right now. Basically, I'm going to buy a set of 7 mm universal plus wires with straight boots and angled distributor boots. I'm undecided if I'm going to rob the screw-on ends from the stock plug wires where they fit the distributor cap or just live with the press-fit rubber boots (kind of want to keep the stock wires complete for the someone who care about a completely original car). Similarly, I still have the stock starter although it's been fitted with one of those lightweight geared starters (which works wonderfully). Anyway, while I've looked closely at the rotor button and the distributor cap for a crack or a trace, because it ran great for about 50 miles following the new spark plugs, I'm leaning against a new rotor button and cap (remember, the car only has 16,000 miles). Basically, I believe the issue relates to an excessive plug gap. Unfortunately, since I've made two changes at once, I also have to contend with replacement plug wires. Grrr. Frankly, I'd just as soon install new plug wires despite having ohmed out the originals because despite the fact the continuity is perfect and the jackets remains perfectly soft and pliable, since Pertronix advise using resister-type leads, I figure to just go along with them. Thoughts? -- John, who remains open to advice other than pull the Iridium plugs and reinstall the original plugs before proceeding. | ||
| Mark Aldridge Grand Master Username: mark_aldridge Post Number: 436 Registered: 10-2008 |
John, with such a little used car, perhaps a compression test may be useful (Sticky valves or rings), likewise the use of a "Crypton type "engine analyser. May save hours of searching. Mark | ||
| zohan92 Unregistered guest Posted From: 86.121.187.185 |
Hello guys, I have slightly the same problem with my 1970 Silver Shadow. I thought to upgrade to electronic ignition kit. What do you think? (Message approved by david_gore) | ||
| John Beech Grand Master Username: jbeech Post Number: 423 Registered: 10-2016 |
I tried the electronic ignition. Didn't resolve the issue and worse, it failed quickly. Pertronix replaced it but in the meantime I have decided to stick with the points and leave well enough alone. In fact, I've not even opened the box Pertronic mailed me. Make me a fair offer for a brand new system and it's yours. -- John, who has been so busy Tootsie is getting short shrift. | ||
| zohan92 Unregistered guest Posted From: 86.121.187.185 |
I see...so how you are going to fix the problem? I live in Europe...the shipping cost will be a bit high, I think. Where are you located? (Message approved by david_gore) | ||
| John Beech Grand Master Username: jbeech Post Number: 427 Registered: 10-2016 |
Fix the problem? Not sure. Put the points back in, and regapped the plugs to 0.025 per the book, and the points to 0.016. Engine's running better. May just lack exercise. As for shipping to Europe, advise of your address and I can calculate it. Send an email to me at: info AT genesishobby DOT com. -- John, for whom being busy means business is good! |
