Hello, Can someone explain to me if the TDC sensor has direct relation to the flywheel? This is, the sensor does the reading on the flywheel movement or the crankshaft movement directly? Problem is that the car has been running extremely rough with a lot of pops and explosions. Checked almost everything. It has new spark-plugs, new extenders, new wires (Magnecor), new distributor caps, new rotors, coils are fine, WUR seems fine, TDC sensor and velocity sensor seem fine (around 700ohms) and fuel pump and acumulator are OK. There seems to be no vacuum leaks also. The blue connector in the fuel distributor was cleaned and works fine. This way, I thought on the possibility that the flywheel isn't installed correctly. This would make sense if the sensor reading is processed directlly with flywheel movement.. There aren't PM1-4 marks because the flywheel has been lightned and the marks disappeared so it's difficult to know if it's instelled correctly. But I have put manually the engine in PM with the help of a stick through the valve hole in cilinder number 1 and the camshafts seem correctly aligned so it's not a timing problem. What do you guys think?? Thanks in advance. André
The mounting holes on the 308 flywheel will only allow the flywheel to be installed correcty. I would assume the 328 is the same way.
Where is the piece of metal (bump or lump?) that the sensor "reads" located? Is it a part of the flywheel or is it part of the ring gear (teeth for the starter motor)? Was any material at all removed from this lump/bump? The gap is pretty critical on something like that. If the gap became bigger for some reason you could have problems. If the lump/bump is part of the ring gear I am wondering if they removed the ring gear and re-installed a little bit off. Can't imagine why they would have removed it but.....
I believe that the ring gear you're talking about is in the other side of the engine. I think that the reading will be in the flywheel itself or the crankshaft (if this is possible). I don't know if the bump/lump was changed. I'll have to disassemble the flywheel section to see that. What is strange is that with the engine in TDC there's no sign of flywheel marking (but remember it was lightned). There seems to be a PMI mark in another place and it doesn't match with TDC engine position. Don't know if it's PMI or PM1... and the rest has disappeared. If it was really the old PM1-4 mark it's not in the right place. Could this be the problem???
Yes. (The 328 OM/SPC/WSM documentation isn't very clear, but) I think that there a 2 pins pressed into the frontside of the 328 flywheel that pass sideways by the nose of the TDC sensor as it rotates, so the relationship between these two pins and true PM1-4 is very important (you might try removing the TDC sensor and look down the hole as you manually rotate the crankshaft and see what passes by). I would suggest that you go back and mechanically establish piston #1 being at TDC and the end of its compression stroke and make your own PM1-4 mark. Since you have something like ~140 teeth on the ring gear, each tooth represents roughly ~2.5 deg so the firing point for cyl #1 at idle should be about 3~4 teeth in front of your "new" PM1-4 mark (call this the cyl #1 firing mark). If you run the engine at a ~1000 RPM idle and a timing light shows that cyl #1 is not firing when pointer is near the cyl #1 firing mark, you know you have big trouble that needs to be addressed. Also, you can use the timing light on any/every cylinder and just shine it on the pressure plate -- if it isn't a stable/repeatable image that advances smoothly as you increase RPM, this would also show that you have something seriously wrong. Good luck, but I don't see how you could do a proper reassembly without having the PM1-4 mark in the "stock" location.
I looked at the stock sensor arrangement a while back, just to see what the Marelli is doing. (I was trying to work out how to run individual plug-mounted stick coils off the stock sensors.) The sensors pick off the flywheel, as far as I can tell. I can't say how the pickups are triggered, exactly, but what I got was that the "rpm" sensor is about 144 pulses per flywheel rev and the "TDC" pickup produces *two* pulses per flywheel rev -- so it's not really TDC of cyl #1, but once every 180 degrees of flywheel (TDC of 1-4 *or* 2-3 on a flat crank). (That's all that's needed to ping-pong between the two coils (banks), leaving it to the two cam mounted distribs to pick which of the four plugs fires.) So that gives the computer one signal every 180 degrees, and one signal every 2.5 degrees (144*2.5=360). But if you look at the tech specs, the ignition map shown couldn't possibly be implemented with a rough 2.5 degrees of resolution. So I have to presume some kind of phase locked loop arrangement inside the computer. But, with a flat crank, this also means that the cams can be installed out of phase and still work. With CIS, there's no injection timing involved. So as long as the cam mounted distrib puts the spark on the compression cylinder, the cylinder will fire. With the distrib on the cam, it's in the same phase as the cam, even if that's the wrong phase. So your bank can be 1-3-4-2 or 4-2-1-3 and will work either way. And the front and rear banks are independent of each other. The two coils just fire 90 degrees apart, twice per flywheel rev. (It also means you can't run individual stick coils off the stock ignition sensors alone. You'd need to convert the distros to some kind of cam position sensors. Or install a separate TDC#1 sensor and run a "wasted spark" setup.) But you say you checked your cams. When you say "the coils are fine", did you check the amp modules too? I'm told a lot of ignition issues are the coil amps. Another thing to check is vacuum advance. For no adequately explored reason, Marelli put the vacuum sensor inside the computer box itself. There's a long hose that runs from the plenum to the computer (off the left side of the plenum, on US edition cars). I gather that the vac advance sensor isn't working on many of these cars, either because of a clogged or crimped hose, or because the sensor inside the computer has gone off.
Thank you guys for all your help and technical knowledge. I'm always learning!!! I'll ficus on these three items by this order: Flywheel position and lumbs/bumps (will make the test with timing light and probably will disassemble it). I have great doubts that it's fitted correctly; Coil amps; Vacuum; The only test I made to the coils was turn each red wire off with engine running and see if it made a difference. It did. The engine started to run from rough to very, very rough and eventually would go off. So, I thought it should be OK. Buy the way, is there an easy way to test this?? I have a friend that checked the vacuum hoses and they seemd OK. About the sensor inside the ECU I have no idea but will leave this for last. Thank you very much. André
Yeah, but a lot of what you got so far isn't quite right ....and I might be giving you more There are 2 pins on the back of the flywheel 180 degrees apart. There are also 2 sensors mounted 90 degrees apart, one for each distributor. The engine runs like 2 4 cylinder engines which fire every 180. The two 4 cylinder banks are 90 degrees apart which is why there are 2 sensors mounted 90 degrees apart. There is also a vacuum line that Tees and runs to both ignitions for load sensing. There is a 3rd sensor that reads the teeth on the flywheel but I'm pretty sure it's not connected in anyway to the ignition. I think it goes to the lambda computer for your CIS As already stated the bolt pattern in the flywheel will not allow it to be installed wrong. Check your cam timing. The cams can be timed wrong and will create the symptoms you describe.
forgot. The crank sensors are for crank position sensing, not TDC sensing. I don't believe they they are at TDC, there is not reson why they would be and quite a few reasons why they wouldn't. I would expect them to be about 40-50 degrees before TDC but I never checked them. Edit: Actually, yes I did check them because I used one of them on my aftermarket EFI install and it worked, so they are at least 40 degrees BTDC, I'd have to pull out my note to give you the exact number.
Is it possible to get the car to a garage where they can connect an oscilliscope to the test points in the engine compartment (the socket with the rubber cap on the left side). I believe you can look at the output waveform for either of the two sensors reading the flywheel signals. Of course you'll need to know which pins to connect to and what the waveform should look like (from the technical manual) under normal circumstances. I believe that if you disconnect the coil from one bank of cylinders the car should still idle fairly well and run okay with much reduced power. But.... since you're already starting with an engine that is not running well I can see why it would stall running on only one bank of cylinders. Maybe you already know but it's basically two 4-cylinder engines sharing a common crankshaft. That's why you should be able to still drive it (not that it would be a good idea!) if you have one good bank running normally. PS. can you send a nice Fino my way? Just kidding...
Mark -- this is for a 308i or 308QV ignition -- not a 328 ignition (and there is only 1 ignition ECU on a 328 so only one vacuum line for load sensing). But agree with you that the pins on the flywheel are most like advanced by more than the maximum ignition advance (so that the pulse recovered by the TDC sensor always occurs before any igntion event needs to occur).
See, I said there was a lot of 1/2 true info Are there still 2 pins on the flywheel or just 1? I can't figure out how they could determine which distributor to fire with 2 pins??? And the rpm sensor connected to the ingintion ECU....although I guess you still wouldn't need it?
Yes, there are still only two pins on the 328 flywheel. The 328 ignition ECU is a lot smarter and controls both coils -- so it "knows" to fire the other coil 1/2 way inbetween the first coil's firing events. TR have a very similar ignition architecture with 3 notches on the flywheel detected by the TDC sensor and one ignition ECU driving two coils -- in fact, in the euro 328 OMs, they messed up and wrongly show the TR's 3 notches on the flywheel in the ignition schematics (but they fixed this in the US 328 OMs and correctly show the two pins).
ahh....that right. At 180 they are both the same coil and the distributor is dealing with the TDC issue any way.......now it comes clear
Ican confirm that 328's only have one crank sensor and one rpm sensor. The crank sensor is located in the front of the engine. There is also only one ignition module. There is no lambda, it's a euro version. There are no cats and air injection, too. Less things to go wrong is better Just to be absolutely sure, piston nº1 is the one at the rear bank on the right side, correct ? I believe that was the one that Oporto328 has used to check crank position. I am right, André ?
My bad...I have a QV/328 suppliment manual and assumed it was complete #1 is the rear bank on the right side. I still very much doubt the crank sensor is at TDC and you can not assemble the cars wrong it cause it to move unless you've re-machined stuff.
I can't say on installing the flywheel, but on a flat crank, cyls 1&4 hit TDC at the same time, and 2&3 hit TDC together. Which cyl is on compression or exhaust at TDC is determined by the belt-driven camshafts. Which cyl on that bank gets spark is determined by the distrib -- mounted on the camshaft. So you can put the cams in upside down and it will still run, as long as you have both the cams on that bank the same way.
Plus unlike the flywheel the cams can be installed in ANY orientation, I'm thinking check the cams. Be carful getting the degree wheel on right.
Yes, I think you are right about the crank sensor not being at TDC, there are a few references in the forum. Problem is that the flywheel has been machined, it is much thinner than the stock one. That's why we wonder if it was incorrectly reassembled ... Maybe Oporto328 can post a picture to be more specific ....
The only update so far is that the cams are all correct if you position cylinder 1 on TDC, so the timing should be ok. In that position the PM mark on the flywheel is WAY off: you can't even see it from the opening on the bellhousing, so we're pretty sure that the flywheel is in fact out of place. Could there be any other possibility ?
Have you verified that the PM position is still on the flywheel? I thought you mentioned some markings were missing because of the machining. Cylinder #1 is on the rear bank, right side, closest to the air filter box/radio antenna etc. That's what you're using as #1 correct? Have you confirmed that when you are making the TDC measurement that all four valves on cylinder #1 are closed? I suppose you would need to remove the valve cover to verify but at this point maybe it's worth it. At some point, if nothing else works and you don't check the TDC and RPM sensors on an o-scope I think you'll have to try replacing them. If I'm not mistaken they are the same part # (it's a 328 right?) so you should only have to buy one and try it in the different locations (unlikey both would go bad unless they were struck/damaged by the flywheel for some reason). Did you disconnect, clean and reconnect the sensor connectors? I know you've probably checked all these things a number of times so they probably sound like stupid questions but......
That is so true ... and according to my friend André problems started after a clutch change ... hummm ...
Yes, the PM position is still visible on the flywheel, but hardly. The machining has removed about half of it's height Correct We have checked using the visible opening through the oil filler and the markings on the cams (on the outside). On the 328 there are black pointers attached to the head that point to a mark on the cam close to the cam wheel. Not a accurate method to check timing but a good reference to see if it is roughly in place. All seems to be right, but I do know that the correct and precise way to do it is remove the covers and check. We're looking for the problem and trying not to fix something that doesn't need to be fixed ... It is a 328. That is a good ideia (buying one and checking). We will try using a strobe light to check the marks on the flywheel. Since the sensors are both out, we will clean them before reinstalling. "There are no stupid questions, just stupid answers" - Carl Sagan Thanks for your help. These are all good suggestions !
