Engine won't shut off

Need some advice.
Problem: 74 246gts - - engine does not stop when key is moved to the full off position. All other electrics go off normally. Engine idles and runs at speed fine.

What I've done so far:
1. Tried the John Corbani solution of taking apart the ignition switch on the back of the key cylinder and re-building. Didn't help.
2. Bought and installed a new ignition switch (www.bavauto.com - - same part as the BMW 2002 assembly - - $125 +S&H). Didn't help.
3. Thought the key cylinder assembly might be causing a problem, so I held the new ignition switch in my hand and operated the switch manually, isolated from the key assembly. Didn't help.
4. Thought the MSD might be having a problem. Replaced it with the new Dinoplex I had on the shelf. Didn't help.

Obviously the ignition system is getting power through a contact that is not "breaking" when I turn the ignition system off. I don't see a relay in the schematic. Is this a charging system problem . . . alternator is not being "disconnected" at the voltage regulator(?) due to a stuck contact or similar?

Appreciate any ideas

Bill

 

My vote would be for a bad diode in the alternator letting it feed power back to the ignition switch. I had a similar issue with my Mondial. An easy test would be to disconnect the alternator belt and crank up the car, if it now shuts off pull the alternator and head to the rebuild shop.
Paul

 

Paul - if you believe that a bad diode is the culprit, an easier test would be to simply remove the fuse on the firewall in the engine bay.

However, according to the schmatic, power to the Dinoplex ignition unit comes from the switched side of the ignition switch. It does not appear that the alternator could provide power to the ignition if the switch is off.

I suspect that someone in the past has modified his system, or plugged the main electrical bus on to the wrong spade on the ignition switch.

Spade #15 on the ignition switch is normally open, and only has voltage when the key is on.

Bill - if you want more help, send a private e-mail.

Jim S.

 

It sounds like the primary wiring on the coil is still getting 12V even when the ignition switch is turned off. So I would guess the problem is somewhere between the ignition switch and the primary wire to the coil.

 

Paul & Jim,

Thank you both for your assistance on this. Paul, a local competent Ferrari repair shop also suspected (over the phone) something in the charging circuitry and recommended getting the voltage regulator out of the circuit to see if that fixes the problem. They suspect a contact in the VR is sticking closed even though the ignition switch is fully off. However, the story continues . . .

Jim, first let me say that I've read many of your posts and really respect and appreciate the education you give us on the theory and practical aspects of these relatively simple but troublesome DC circuits. My 3 semesters of EE over 40 years ago are but a vague memory. That said, your comment about the Dinoplex being hooked to the #15 terminal set off an alarm. When I removed the MSD, which is connected directly to the battery, I re-installed the Dinoplex to the same power line, i.e., directly to the battery. The instructions didn't say to connect to a switched source so I assumed (bad word) that it was just like the MSD which has been on the car since 1981. Wrongo! It needs to go to Terminal 15 and that may solve the problem. On the other hand, why did I have the same problem when the MSD was on the system. MSD failure maybe. It's old! In any case, I won't get to do any troubleshooting until the weekend so please standby and I'll post results then.

Many thanks,

Bill

 

Bill - I recently installed an MSD in my restored Dino. Yes, the instructions say to go directly to the battery, but this did not make sense. Hence, I connected the MSD to the switched terminal.

I suspect that your ignition is on all of the time. I might suggest that you disconnect your ground lead during the time it takes to figure this out. Have you noticed that your battery goes dead between drives? Perhaps your amp meter reveals large charging currents during the first few minutes of a drive.

Anyway, don't hesitate to pm me and perhaps a phone call or two can lead to resolution. Happy to help. Oh, and by the way, the first thing I learned after leaving school is that you get what you pay for, and this consultation is free.

Jim S.

 

Did you buy it with this condition or did it suddenly start?

 

Jim S. & Dignini,

Jim, luckily I've had the sense to always keep the ground disconnected since this problem first occurred. Dodged that bullet! Your FREE advice may do the trick!

Dignini,

The Dinoplex is new from Superformance. I've owned this Dino for 29 years, and, except for the engine and tranny rebuild at 53,000 miles (10 years of FCA track events up and down the East Coast), I've done all the maintenance myself. So, I have no one to blame but the driver and mechanic. The rebuild was prompted by two cylinders that were low on compression and bleed-down . . . some worn valve guides and two slightly worn cam lobes, tranny was excellent except for near-microscopic pitting on two bearing races (metallurgy problem?), no synchros needed. To me this was a testament to the strength of the Dino engine / tranny combo . . . well engineered and relatively easy to maintain. The engine had noticeable power improvements on the track after the engine rebuild. The transmission shifts very smoothly since I made a small modification to the shifter box -- added a couple grease grooves to the holes in the box that act as the bearing surfaces for the shift rod. Hardened steel sliding on cast aluminum is not a good combo.

Hmm . . . long answer to your short question. Sorry!

Ciao,

Bill

 

So it was after the rebuild that this condition appeared.....

Also more details on the grease mod please, what prompted you to make the modification in the first place?

 

Bill,

I have the superformance unit in my car, if you need any wiring assistance, I can take some pix for you.

BTW, works great, looks right, all in all, a great solution to my personal ignition issues.

Dave

 

dignini,

The rebuild was completed about 2 1/2 yrs ago. Current problem started about 4 weeks ago. During the last 3 weeks I tried solutions as outlind in my first post. With luck and spare time to work on the Dino, I'll have a solution this weekend.

Dave,
Did you hook-up the new Dinoplex using the original Dinoplex connectors so you have the back-up capability of switching to the Kettering points system? If so, I'd love to know how you did that (in great detail). The instructions that came from Superformance are pretty simple and worked well for me EXCEPT it doesn't tell you to go to the switched terminal on the ignition switch. It just shows a wire labeled "12V DC" or similar. I know, I should've known but . . . dah!

Bill

 

I suppose in microsoft speak, what was the last known working configuration? Did anything happen or did anyone do anything that might have caused it. Did it happen after a rain storm or after you hit a bump? If it ran for over two years its unlikely to be the way it was wired..........good luck with your search

 

Good question. Thanks for making me review this whole scenario in my mind.

I started my troubleshooting based on the initial failure which was . . . out for a Saturday drive with a car-crazy friend on a bright, clear day. Configuration: overall, the same as it has been since engine rebuild completed couple years ago, i.e., MSD ignition system which was first installed upon Dinoplex failure in about 1980. The failure during that Sat drive was strange. After about 3 miles of moderate speed driving, I noted a bit of stumbling in the engine for about 5 seconds and then gradual decline of power over 5 seconds while coasting with the clutch disengaged. Pulled to the side of the road. Tried restarting. Starter worked fine but no engine start, not even a sputter. Total 3 attempts, no luck. Hmm . . .fuel starvation? Check the fuel pump. I could hear it running. Took the fuel line off where it exits the carbuerator manifold -- plenty of fuel. Check the spark. Pulled the wire off #3 and cranked. Not only did I have spark but the engine started! Drove the 3 miles back home, all was well but on shutdown I noted the engine ran for about 5 seconds after the key was off. Also, during this whole episode, I'm noticing that the key is not operating smoothly in the key cylinder . . . it's hard to turn clockwise out of the full "Off" position, also a "rough" spot moving counter-clockwise out of the "On," engine running position. But it's a new key. Back home I check my old key and it's better but still not quite right. I'm suspicious that there might be a ignition switch problem.

Fast forward to the next weekend and I test drive the car to see if I can repeat the failure. All is well except I get longer periods of engine run-on, maybe 10 to 30 seconds and then it dies on its own! Very strange. I search FerrariChat and decide to do the "John Corbani Ignition Switch Rebuild" (w/ diode insertion to prevent future contact burning). I do that but it doesn't help this problem - - still have run-on for short period At this point, I decide it might be the MSD, and since I've been wanting to go back to original everything on this Dino, I decide to use the Dinoplex that's been on the shelf for 6 months to eliminate the possibility of MSD failure. I make the switch, engine runs great and everything seems fine except now the engine doesn't quit unless I stop it with the clutch. Put in a NEW ignition switch and no change. I eliminate the key cylinder assembly by operating the ignition switch separated from the assembly. Now, thanks to jselevan, I know the Dinoplex is definitely one of the problems since I have it hot wired to the battery (just like the MSD instructions say . . . Dummy!) Sunday I will rewire the Dinoplex and see if the combo of properly wired Dinoplex and new ignition switch have solved the problem.

Thanks for your patience and standby for a progress report.

Bill

 

Well it seems you have plan all my only advice is: Do one thing at a time, confirm or eliminate it and move on to the next.

 

dignini,

Excellent advice. Wish me luck. Hopefully this will be resolved by Monday, on day late for our FCA event in Annapolis, MD

Bill

 

Yep! Switched the power source for the new Dinoplex to the ignition terminal that goes "hot" when you turn the ignition switch to the "On" position. It had been connected directly to the battery as is done with the MSD that I was replacing. The engine started fine from cold as it always has. All okay. It stops running now when the ignition switch is moved to "Off." BUT took a 25 mile test drive and, at the end, discovered it doesn't start nearly as quickly now when the engine is hot compared to when I used an MSD . . . and please believe me I know how to start a hot Dino. Any number of things I could check (plugs, dwell, timing, point resistance, coil output), but I was mostly curious about voltage that the Dinoplex sees now that it's hooked to the battery through the ignition switch vs. MSD hooks directly to the battery.

With the battery fully charged (12.8 volts), I measured 11.0 volts at the ballast resistor where the Dinoplex gets it's "juice" in the trunk. For the MSD, I still have the line that goes from the battery to the trunk where I used to plug into the MSD. It reads 12.6 volts. Is it possible that the 1.6 volt difference multiplied many times through the coil could make the noticeable difference in hot starting characteristics and, maybe, overall performance?

Scrap the Dinoplex and buy another MSD? Too hell with originality!

Any thoughts would be appreciated.

Bill

 

Bill.

My car with the Dinoplex is also a little more difficult to start HOT than it used to be.

There's a thread on here somewhere about it, but, it's not impossible to start, just a little tougher.

I've also found the car harder to start hot as a result (my mechanic thinks) of the ethanol content in the reformulated summer gas. IT may be the winter mix works better. I'll let you know in about a month.

Dave

 

There are probably many members who could explain to me the changes gas mixture entering the combustion chamber goes through and the difference between hard starting after a run; or after the car has sat in the heat for a while. In my case, all these issues were resolved when I got rid of the Orinal Dinoplex and points. From that moment no matter what the conditions, the car started. I know John Corbani feels it is un necessary to get rid of them and obviously it works for him, as for myself, I don't see any point in keeping them. One thing that I always have done, is to wait a 5 to 10 seconds for the fuel pumps to do their stuff, before engaging the starter.

 

Bill - what are you referring to when you say that you have hooked the Dinoplex to the ballast resistor in the trunk? You mention 11.0 volts versus 12.6 when tested at the line directly to the switch (formerly used for the MSD). When cranking, the 11.0 volts will drop below this.

Did you not mention that the Dinoplex had been gutted and Permatune electronics now populate the box, or am I mistaken?

Anyway, there should be no resistor in line with the power source for the Dinoplex. The Dinoplex should receive main bus voltage (12.8) when switched on. Finally, it is possible that the MSD was more efficient at generating higher voltage to the coil than the current state of affairs in the Dinoplex. Hence, difficulty in starting.

Jim S.

 

Dave, good point about the ethanol. This summer we went up one grade of gas on our two vehicles that use "regular" because they were running crappy with the ehthanol blend. Solved the problem immediately. Tried regular a couple weeks ago (cool weather) and it reverted to crappy on both cars.

Diginini, I'm leaning your way, also. First, I'll do a minor tune-up just to check some of those other factors I mentioned. I've got all the parts on the shelf and I'll be totally retired in 2 weeks so it sounds like a great weekend project.

Thanks for your feedback.

Bill

 

I've run my Dino 7,000 km over the last year and haven't fouled the plugs with the MSD. I'm using Bosch platinums and am actually thinking of Corbani's recommendation on Iridiums.

It is far better for the internal health of your engine to have the more complete combustion that the MSD offers.

 

I carried a spare coil and points and condensor before I went pointless. I attached a photo of what's in my distributor. The only thing missing is the infrared send/receive unit which is mounted on that little bracket. That's it. No points to adjust, no points bounce to worry about. easy start easy go!
Image Unavailable, Please Login

 

Jim, yes the line from the ignition switch goes to a terminal on the ballast resistor BUT it's a 3 prong terminal and the line from the Dinoplex goes to one of the other prongs. In effect, the Dinoplex has a direct connection to the ignition switch. I was a bit surprised at the drop from 12.8v to 11.0v from the battery to the ignition switch to the Dinoplex. Do you suppose that's due to corroded grounds in that path? I'll have to play with that possibility. On the otherhand, it started hard under hot engine conditions even though it was incorrectly wired directly to the battery (12.6v). Strange. Another possibility is that when the starter gets hot it has a much larger resistance than when cool. Consequently, it's drawing more amps during cranking which lowers voltage to the Dinoplex which makes for a hard start. Is that correct EE thinking?

Btw, the Dinoplex is from Superformance. I don't know who does their conversions.

Bill

 

Whew! That's impressive. Very simple. Thanks for sharing.

synchro, do you have the optical distributor, also? You're right about not fouling plugs with the MSD. I put two MSDs on my 330GT 2+2 and that solved all fouling problems.

Bill

 

Bill - yes, the drop in voltage may be owing to significant contact resistance in the male/female spade connector in the 3-prong housing. They are difficult to clean, but I would consider trying. A test would be to turn on the ignition, and after a few moments hold the 3-prong housing in the palm of your hand. Is it warm???? The Dinoplex (Dynatune) will likely pull 4 amps or more. Given a few Ohms resistance in the contact, you should feel some heat. If excessive, then that is your culprit.

Does the starter sound as though it is laboring??? A hot starter should crank the same as a cold starter. Wet sparkplugs following engine shutdown will require adequate voltage to spark, and if the system bus voltage is down during cranking, or due to contact resistance, then you may not be getting sufficient voltage for a healthy spark.

I have found that since converting to optical pickup and MSD ignition that my car starts better. I suspect that modern electronics (which you have in your converted Dinoplex) are superior to the stock system. I certainly feel as though the engine has more power, which may be an additional advantage of modern systems.

Jim S.