Crank Position Sensor

[billyb]

My 1996 Cali 1100i has developed a problem. It will run sweet for about 20 minutes, then start to cough and violently backfire before stopping completely. If I let it sit for about 20 minutes, it will start again and maybe run for another few miles before repeating the backfiring and then quitting. Coils and plugs and fuel supply all seem to be ok.
Could this be a faulty Crank Position sensor? Do they effectively heat up in operation which may cause the fault and the engine to quit, and then cool down again allowing me to restart the engine?

Any help appreciated.

[pressureangle]

Exactly so, yes.

[jrt]

When the CPS died on my Cali, it also died when hot- but it didn't sputter, it just died.  I started a thread on the topic sometime last summer.  Kiwi Roy suggested connecting an LED from the fuse to the fuel pump to ground and from the fuse to the ignition (coils) to ground.  It gives you an indication of what's happening- the fuel pump should cycle ~3 sec when you turn the key on, then turn off, then turn on again when the bike is running.  The coils should energize.  Keeping the coils energized (when motor is spinning) is dependent on getting a signal from the CPS. 
At least- that's what I have from memory.  Do a search for thread started by me, and there is a diagram for wiring and a lot of discussion.   I ended up replacing mine and had to source a CPS from Latvia, of all places. 
There are different versions of the CPS- some when on the flywheel, some on the timing chest.  Some were two-wire, later ones were three wire.  If you have the one on the timing chest, I can loan you the tool I made to measure the depth from the mount to the timing gears.

[billyb]

Thank you

[pehayes]

Sounds like fuel vacuum starvation.  When it stops, can you remove the fuel cap?  Or does vacuum hold it tight in place?  Vacuum develops as the fuel level drops.  It is not safe, but maybe consider a ride with the fuel cap loose to prevent vacuum.
Have  you done anything about fuel filter?  There are two and people commonly neglect the more important one.
There is a huge filter under the center tunnel of the tank.  Guzzi recommends a short interval of perhaps 12K miles.  I have run them many more miles at 40K.
However, there is also a small, pencil-sized filter inside the tank on the input line of the petcock.  Debris gathers inside the tank and gets stuck onto that filter while running.  When  you stop and the fuel flow stops, t hat debris gradually falls off the pencil filter until you start running again.  Consider removing the tank, removing the petcock, and doing a good interior flush of the tank.

Patrick Hayes
Fremont CA

[Rolf Halvorsen]

I believe the article number for this sensor is 29721660 and this is the 2 pin version.
(01721600 is the 3 pin version for the V11 series.)

Rolf

[Tom]

Like Pat says check both filters.     Especially for your year of Cal.  The sensor can be checked easily.  You start with the basic fuel delivery first.

[Tkelly]

I had those fail on 2 different bikes,once they failed you could crank the bike forever and it wouldn’t fire up.

[Speedfrog]

Is there an easy way to check if the CPS is faulty?

[nc43bsa]

Check for continuity with an ohmmeter.

[pressureangle]

Is there an easy way to check if the CPS is faulty?

Yes and no. This unit can fail...as a Brit. That is it can work when cold and fail when hot. When I bought my '97 Sport-i the sensor was bad; the first ride I got 3 miles, ten minutes later struggled home. The next day, started perfectly and I let it warm up before going out- made it about 1 mile. Back again the following day after a bunch of ignorant new-owner checks, same good start but didn't make the end of the block and pushed it back. I think that's when I found this forum. I tested the CPS in situ cold and it checked fine. Once more, let it get warm and when the block reached about 150* it started to sputter. I pulled the CPS and bench tested it multiple times with a heat gun and it consistently failed about 160*. New sensor, no problem. So yes you can ohm it in place but you have to ohm it in place *during failure* and hot to be certain it's failing.

[JoeB]

Went through this on my 98EV a few years back. Quite a few posts on it over the years.
Found this one off the bat: https://wildguzzi.com/forum/index.php?topic=85714.0
In my case measuring resistance of the sensors led me to an ez fix.

[Wayne Orwig]

You say it backfires. To me that sounds like the injectors are still hosing in fuel. Which means the crank sensor is still working, just that the spark is poor.

Have you tried relays?

But that has two sensors and it is not clear to me what happens when one sensor goes whacky, so it could be that.

[Vagrant]

Have you ever replaced the TPS?