Have you check compression?
Not a great weekend. I finally got the car running pretty good yesterday. The only issue O had was that it was idling at about 1800 RPM and when I tried to dial it down it would drop to 600 and run rough. I decided to leave it at 1800 and take it out for a spin to see if it drove ok other than that. My wife and I took it to dinner. It ran great. Very smooth and normal power. On the way home at 60 MPH, it just turned off. It sounded like there was a weird sound from the back, but I don’t know what it was. It had the sound of a belt breaking, but maybe it was just I burnt fuel popping in the exhaust. We went back on the road and did not see any parts. I tried to restart the car, and it just cranks. No attempt to fire at all. No weird noises. I had to have it towed home. Now I have a whole new problem and once again I have no idea what the issue is. Really frustrated at this point.
Welcome to keeping a ~40 year-old car sorted . Nothing else you can do except start chewing on the ignition system until you get spark on both banks during starter motor cranking. To begin with: 1. Verify that you have +9~12V DC on the coil(s) terminal 15 (the yellow wires) relative to ground when the key is "on" (Pos II) and during starting (Pos III). If OK, 2. Measure the AC voltage between the two wires of the flywheel RPM sensor (aka the engine speed pick-up) during starter motor cranking -- should be something like ~2V AC during starter motor cranking. See page 74 in your 248/82 OM for the wiring to the Diagnostic Socket where you can make this AC voltage measurement. If you get nothing (like less than 0.1V AC), measure the resistance of the unplugged flywheel RPM sensor itself = it should be ~700 Ohm. If infinite Ohms, you can buy a new one without regret. Image Unavailable, Please Login
Thanks Steve. I confirmed voltage at the coils last night. It’s good. I am traveling today, but will check the other sensor when I get back to the garage.
I would just be so happy to see no sparks. Electrical may be harder to track down but invariably cheaper than mechanical. Be grateful for the little things— at least that’s what I tell my wife
Such a good point…. Unless I find out no sparks are because the rotors in the dizzy are not turning because of broken cam belts. [emoji846]
Such a good point…. Unless I find out no sparks are because the rotors in the dizzy are not turning because of broken cam belts. [emoji846]
I confirmed positively no spark during cranking. I am suspicious that there may be no fuel when cranking either, because there is no fuel smell, even after trying to start multiple times. I did confirm the pump runs when touching the air flow plate or pulling the safety plug. Is there anything that could cause both fuel and spark to not work on both banks? I have not yet figured out how or where to test that RPM sensor, but I can say the tach never even wiggles during cranking. Not sure if that is an indicator or not. I did check all fuses and relays and did not find any issues. I am running out of swear words to use. I see now why the Weber cars are worth so much.
Seems your problem keep changing. Was a problem with no spark on #4, then spark on all but maybe weak. Now no spark anywhere. No spark on either bank would be odd since each bank is totally independent. Thus, maybe power to the Digiplex which is supplied from the ignition switch, unfused. Check pin #8 on the Digiplex for 12 V with ignition in the "Run" position.
Yeah. Some of it was symptoms changing, and some of it was just me doing diagnostics and figuring out more info. After another long night thinking about this issue, I have a bad feeling in the pit of my stomach that I suspect what is going on now. I think the issue now is much worse. I suspect that I may have a cam belt that just broke. Looking back I am starting to put the pieces together. 1. When I would start the car there was always a slight squeak in the engine. I thought it was an idler pulley or something, but couldn’t pin it down ….it was likely a cam belt tensioner or bearing. 2. As I drove the car, it always seemed it ran great when cold but it felt that performance got a little worse when the engine warmed up. Hard to explain, but felt the engine had a little resistance on it when hot and didn’t feel as peppy. It felt like a brake caliper was dragging or something. This was likely a cam bearing seizing up. 3. All the weird issues I have been having lately, I think the belt was starting to fail and possibly had cam misalignment, and finally leading to major failure the other night. I hope I am wrong. I will try to get to the garage today to confirm. I have only had the car 6 months. A major service was done 2 years/2000 miles ago prior to my ownership. I suspect whoever did it made a mistake somewhere. I think that mistake is going to cost me a lot money.
If the cam belt or belts is broken, yes, it is going to cost a lot of money to replace bent valves and maybe damaged pistons. But something else was causing your ignition (spark) issue since the cam belts were definitely NOT broken initially. TBH, it's hard for me to imagine the cam belts are broken now but it's possible, I guess. But cam bearings don't usually cause problems - there isn't really much load on them and the cam spins at 1/2 crankshaft speed. I don't recall ever seeing/hearing of a cam bearing seizing. NOT saying it can't happen but it has to be pretty rare. It will be interesting to hear the ongoing saga... Good Luck!
Same deal. One broken belt won't result in no spark on both banks. More likely a broken belt would prevent the engine from cranking at all.
I hope you guys are right. Will try to check it tonight. I thought maybe there cere can position sensors that would shut down the digiplex units if they are out of sync. Fingers crossed.
Happy to report I was wrong. The belts are intact. I don’t know what the issue is, but I know what the issue is not, and that is a huge step in the right direction. I still have no spark on any cylinder, so still trying to chase.
Good news re cam belts! Of course it could be in the crank sensor system. The 328 Microplex has one TDC sensor and if it fails there is no spark. If I recall correctly, the 308 Digiplex has two - one for each bank. It seems unlikely that both would fail but something common between them could... There are threads on testing the sensors; do a search on "Crankshaft Sensor" and I'm sure you will find the necessary info.
Steve mentioned the Vehicle Speed Sensor as a component that is shared between the two banks. I did find one other thread with someone that had no spark that this was the issue. That is where my focus is next. I was just going to order one so when I tore into it I could just replace it, but it looks like they are over $300 so I am going to test first. [emoji846]
Does that year 308 have the flywheel/RPM sensor(s) pass through a connector mounted on the oil cooler duct in the left rear wheelwell like my 328 does? If that connector comes loose, you'd lose all spark. I have seen people report problems with that in the past so it's worth checking. On my 328, there was a lot of interference between the oil cooler duct, wheelwell liner, and the mounting bracket for the connectors (there are two -- one for main engine harness, one for the sensors). I felt like that was a dumb place for Ferrari to put such important connectors, and took extra care to clean them both and reinstall them very carefully (probably better than original). If you haven't already, pull that left rear wheelwell liner and check out those connectors.
I don’t know. Thank you for this! This may also be a good place to rest the sensor without having to go in too deep.
I checked the speed sensor at the white connector, and it measures out at 732 ohms, so I think that’s ok. Is there a way to test this at the destination? For instance, if this sensor runs to the digiplex, can I test it there to ensure the signal is making it all the way there? There are some connections in the wheel well, but they are larger 6+ wire plugs. Not sure if that was what you were talking about or not.
Yes, you can measure its output during cranking where it connects to the Digiplex ECU, but measuring at the Diagnostic Socket would be more convenient. Alternatively, if you have the early-style "bullet" 2-pin connector, you should be able to partially unplug it so the RPM sensor is still electrically connected but enough of the metal pins are exposed to touch/connect the AC voltmeter leads. See Fig 58 on page 75 of your 248/82 OM for the location of the "socket for diagnosis", a.k.a., Diagnostic Socket. (And please confirm/deny if you have one present.)
I do have the diagnostic socket, but I don’t have a diagram of the pin out to know what is what. Does that exist anywhere?
The sensors are used on other European cars of similar vintage, and can be found for much less - Superformance in the UK sells the Flywheel Pulse Unit/Crank Sensor (part number 119052 supersedes 128364, 128365) for £45.55 (under $60 USD) - scroll down to the Trigger Impulse section on the Superformance 308 Ignition section
Yes, Fig 56 on page 74 of your 248/82 OM (which will also show what pins to measure at the Digiplex ECUs if you want to do the measurement there).
Forgot to add that sometimes they show connectors on schematics like you are looking at the unplugged front side and sometimes like you are looking thru them where the wires enter at the backside -- keep that in mind when trying to figure out who's who.
