How to Change the Ferrari 328 Crank Sensors

Closure of this thread:
https://www.ferrarichat.com/forum/308-328-sponsored-yellow-compass-group/154250-328-cranking-but-not-starting.html


1. The Ferrari 328 has two sensors located on the bellhousing area on the driver’s side. One reads the TDC/crank position (front one) and the other provides information to the tachometer (rear one). These differ from the 308, which has three total sensors: one tachometer, and a TDC one each for each bank.
2. One sensor will tell the computer that the engine is turning for spark, and one will provide tachometer readings. A failed or malfunctioning sensor can cause no reading on the tachometer or no spark and a no-start condition. The sensors may also be blocked or covered in oil/dirt/grime and not be able to transmit its signal. They seem to fail intermittently and give the symptoms above, before a total failure.
3. Both of the sensors are originally installed on the motor before it goes in the car, so hoses, pipes, and other parts are now in the way of an easy swap. This will also lead to difficulty removing the old sensors, since they are routed around other parts, and will not slide out. The sensor on one end and the connector on the other end may be too big to pass through the wire’s route.
4. On the 328, the same part number is used for both sensors, though one needs to be modified to fit. Ferrari part number is 119052 (angular speed sensor). 119052 became the part number for both sensors, though the front used to be 128364 (TDC sensor).
5. Both sensor wires go to the top of the engine bay on the left side and connect to two connectors that are tied together between the coils and the oil filter. Though the sensors are the same, they are not interchangeable at the top connection, so do one at a time to avoid reversing them.

Though the mechanical difficulty in changing these is fairly straightforward and easy, the accessibility and frustration factor can be pretty high. This would be a good fix to do during a major service or other work with a dealer or independent. If you have to do it yourself, here are some directions.

1. Most of the work will be from the rear left wheel well and underneath just ahead of it. You will still need to access the top engine bay to connect the sensors. For accessibility, lift the car and remove the left rear wheel. Then remove the inner wheel liner (2 pieces). 10mm bolts and Philips screws.
2. The rear sensor is on the block at about 4 o’clock as you look into the wheel well. It is easy to see and not too hard to get to. There are two threaded posts sticking out to the rear, almost parallel to the ground. Each post has a small washer and 8mm nut. Remove the nuts and washers, and wiggle the sensor out. I put a rag beneath it to catch anything. An open end 8mm wrench seems to work better than a socket, due to some metal lines. The wire for this sensor goes up under the rear distributor and under the base near the oil filter to the connector. It should be obvious at the top connectors which wire goes front and which one goes back. Disconnect the one going to the rear. It can be difficult to reach the connectors due to being between other hoses and a long reach in from the top left under the deck lid. A pair of long needle nose pliers helps hold one end.
3. The old rear sensor will be hard to remove from the car due to its routing. You can’t seem to pull it out from beneath or pull it out from above. After installing the new sensor in the block with the washers and 8mm nuts, you can easily route the wire up around the hoses to the connector. You will not be able to go the exact same route, because the path is too narrow for the connector end. Clean/inspect the connectors and connect the new sensor wire on top. Again, you may need some long needle nose pliers to hold one end, because the reach is awkward. At this point my only choice was to cut the old wire on the old sensor to get it out, and pulled the top half out on top, and the bottom half out from below.
4. The front sensor is installed the same way, but more difficult to do. Most of this is blind, with a mirror on a stick between steps to see if it was correct. The sensor is about 10 o’clock on the block (looking from the left rear wheel well) beneath the front distributor. Its wire is doubled over, since the distance is much shorter.
5. From beneath the car, reach up near the fuel pump and try to find where the wire goes. Just in-board and below the front distributor cap. I could feel the wire and sensor, but could not see it. The threaded posts on this sensor point up about 45 degrees, which means you have to “attack” it from below, but get your wrench higher and come down on it. I used a small ¼ socket wrench with a deep 8mm socket for reach. I also used the mirror on a stick to see what it looked like.
6. I could get the socket on the nuts blindly and was able to loosen both. However, the nuts and washers were out of reach by hand by an inch or two, so once they were fully loosened, they could fall anywhere. I put a little grease in the socket, and luckily both bolts stuck in the socket and defied gravity. One washer stuck to the bolt, but the other stayed on the threads. I used a long magnet on a stick and the mirror to get it. Magnetic socket would be helpful.
7. Once you have two bolts and two washers out and accounted for, the sensor will wiggle out. Unplug it from above, and it easily slides out.
8. The old front and rear sensors look the same, but the front sensor threaded posts are closer together. The new front sensor will fit in the hole, but the threaded posts will not go through the sensor flange holes. Both mounting holes on the flange need to be slotted in for the narrower width. A Dremel or drill will work, but be cautious not to be too aggressive and hit the sensor. The sensor is magnetic and will attract all the filings, too. This is a “test and repeat” to get the right width. I was told that this difference was only on the 308, but it was on my 328, too.
9. After a few tries slotting the holes a little at a time, the new sensor fit on. I had to hold it by the wire and manipulate it into the hole and over the posts, since it was still out of reach. I used the mirror again to see that both posts were coming through the holes.
10. Here is where you need to figure out how to come down on the threaded posts with nuts and washers without dropping them. They are out of reach by hand to start the nuts. I took the washer and nut and glued them on top of each other, and let them dry. I then stuffed the deep socket so that the nut would go in only its own depth. I then taped the nut into the socket and poked a small hole in the center of the nut. This would hold the washer/nut in the socket, but would tear out once on the threads. There may be a smarter way to do this; maybe a magnetic socket.
11. From below with the nut in the socket, reach up, then come down 45 degrees and hit or miss until you get the nut on the threads. I used just the socket without the wrench to get it started. Do each side and check with the mirror that washers and nuts are on.
12. The wire for the front sensor is easily routed up to the connectors. Clean/inspect the connectors and connect the new sensor wire on top.
13. Account for all your tools, re-attach the wheel well liners and left rear wheel, and start the car. My car was flooded from previous attempts without spark, so it took a little extra cranking to get going.

Good luck. Again, step 1 should be “let someone else do it if you can.” Thanks to Maranello Motorworks in Denver, Ferrari of Denver, and my friend Bob for the parts and guidance.

 

Just about to do this on my Mondial QV 308. Very useful!
Thanks!
Peter

 

great write up, thank you !

 

Under Ferrari Chat advanced search, select the 308/328 section and search for "crank sensor". There are many more threads which will help, also.

Good luck, Peter and Michael!

 

I replaced both crank sensors on my 328 (1988.5) both purchased at Eurospares. To my surprise is the new TDC sensor clearly longer than the old one. The new Tacho meter sensor is same length as the old one and same length as the old TDC sensor. See pics:

Does anybody experienced this? I do not know what effect the longer length of the TDC sensor might have.

I more than welcome any input. Thanks in advance
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Do not install the longer one -- it will hit the pins on the flywheel. (It can't be the correct part if the old one worked.)

 

Steve, you are 100% correct. Unfortunately I was impatient and after checking the Eurospares site and pics I thought it must be right. So I installed it and it............broke as the pic shows. Yes, I was absolutely stupid but now I guess I must open the bell housing to collect the scrap of the sensor as it will otherwise create damage.

I certainly contact Eurospares and let know how that will go.
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wow, never seen that before

how long - ähm short - was your drive ?

 

No drive as no start. Engine just cranked few rotations on the starter motor.

I do not know if or what damage I migh have as result of the broken sensor.

Congrats with the beautifull victory of your fellow German Ferrari pilot in Australia. Sebastiaan was great and real cool.

 

This type of passive reluctance type sensor have a gap tolerance of around 0.1mm.

That looks more like 10mm!

The magnet in the sensor seems to have gone so will be stuck to the flywheel. This might cause whats known in technical terms as "unpredictable results"

 

yes, unpredictable and opening the bellhousing....

I have no choice and whilst being there better do the clutch.

 

FWIW the sensor is a common part to many vehicles. I recall purchasing a couple of spares for less than $30 ea.

 

Menno,
Sorry to hear the problem you had. I hope you get it all sorted on back on the road soon. Best of luck!

 

thanks all. It might take more than a week before I am in the bell housing but let it know here

 

The maximum amount the flywheel could turn before the inevitable "crunch" is just 1/2 a revolution. They improved the flywheel design configuration on other, and later, models where it is impossible to install a "too long" sensor (which is not the case on the "pin" configuration models).

I'd be tempted to go a little stoogie on the fix (seeing how effective the pin was at crunching the sensor housing) -- if it cranks without any concerning noises, and fires up without any concerning noises (after you get the correct sensor), I'd just let the bits eventually fall out the bottom . JMO.

If it won't fire up with the correct sensor in place, give a shout, and we (meaning you ) could maybe do some electrical measurements to see (without any disassembly) if the pin(s) did get damaged and/or dislodged.

 

thanks Steve, I appreciate some - possible - good news.

Still, I guess that this is the time to combine opening up the bellhousing with a clutch service. The 328 is in 2 months 29 years and still has the Original plate after 75.000 km.

regards, Menno