Crank trigger sensor

[mike]

can someone give me any idea why ive had 2 crank triggers give out in 3000 miles?
its a hassle cause when it goes out ur done....tow truck time.
basically i have a 427 sb, with twm fuel injection controlled by Big Stuff ecu. after it happened the first time my tech told me he moved other electronic stuff as far away from the crank trigger as possible.
abt 1k miles later it just happened again. driving along, a little hiccup/backfire and its done.

anyone know what might cause this and what might prevent it from happened in the future?
im abt ready to just go carb just to have peace of mind.

 

[Jack Houpe]

Mike, crank triggers are very sensitive to shock, is the trigger wheel bumping it? Is it a secure mount? When the trigger wheel rotates is it true?

Mike Trusty and I have a solid week of experimenting with triggers and found that the trigger wheel had been manufactured incorrectly causing the problem. The space where two teeth are missing was not cut properly and the signal to the ECU was inconsistent.

The best one to purchase is the trigger used for ABS system on mid to late 90s GM cars that are front wheel drive. It puts out 2.5 V peak to peak verse .35 V peak to peak of the normal ones. It also has a chisel tooth pick up so it can be a little further away from the trigger wheel. How many tooth wheel are you using and was it made by electromotive?

I do not think electrical transmission from other devices is your problem.

All this being said I have had 2 failures on another car I have.

 

[mike]

Mike, crank triggers are very sensitive to shock, is the trigger wheel bumping it? Is it a secure mount? When the trigger wheel rotates is it true?

Mike Trusty and I have a solid week of experimenting with triggers and found that the trigger wheel had been manufactured incorrectly causing the problem. The space where two teeth are missing was not cut properly and the signal to the ECU was inconsistent.

The best one to purchase is the trigger used for ABS system on mid to late 90s GM cars that are front wheel drive. It puts out 2.5 V peak to peak verse .35 V peak to peak of the normal ones. It also has a chisel tooth pick up so it can be a little further away from the trigger wheel. How many tooth wheel are you using and was it made by electromotive?

I do not think electrical transmission from other devices is your problem.

All this being said I have had 2 failures on another car I have.

wow, thanks jack.
i agree abt electrical pulses not being the prob, but the tech said it COULD be a factor.
would you have a part number of your preferred sensor?
thanks much
mike

 

[Jack Houpe]

When the car back fired and quit running did it ever fire again or just totally dead? If it tried to fire then its not the sensor, its the computer that came out of time with the trigger wheel and threw a fault signal shutting the ECU down. If your trigger wheel is electromotive 60 -2 (58 tooth) tooth wheel then it could be one of the units that was improperly cut. Its hard to explain till you see what happens on an O scope when the trigger wheel is spinning. Mike Trusty and I spent hundreds of hours combined working on his car before Road America. I kept telling him it was the crank sensor and he agreed, but it wasn't! The night before we left for RA we were in my garage and I took a trigger wheel I had cut with my waterjet and looked at the pattern on my O scope when spinning on my mill, then looked at what he was getting on his crank trigger output and it was different when it passed the area where the 2 teeth are missing. I told him to grind that area down so there would be more of a collapse of the trigger coil like I seen on the wheel I made. He did and the second full revolution of the engine it fired and ran perfect. I am an electronic tech and knew that the little coils just cant open up as they are nothing more than an micro alternator and there is really no voltage feeding them BUT they can become magnetized and the signal will fall after a period of running the engine. Thats why I started looking at different sensors and the voltage output of them. I got the sensors from a guy I lease some garage space to who works on GM cars only. I will get with him tomorrow and get a part number for you. I would also look at that trigger wheel if I were you.

Hope this make some sense to you. You are welcome to call me if you want. 479-787-6299

Jack

 

[Roger]

It might be worth checking that the trigger wheel is not magnetized. Has somebody fogoten to demag the crank of trigger wheel after crack testing?

 

[Ron Earp]

Hi Mike,

Jeff and I spent a lot of time working with a mag pickup similar as you describe that was recently fitted to his TR8. After a lot of time with the o-scope we were able to figure out when it was dropping pulses and causing the engine to run poorly.

More investigation found that the sensor that was fitted was impedance mismatched to the Haltech ECU. Turns out the fellow that put the system together used a VW (Bosch) wheel speed sensor to pickup the tooth signal. This particular wheel speed sensor was happy with frequency counts in the 0-8000 per minute range but it was definitely not happy with counts up to 35000 per minute the system would produce when the motor ran at redline.

Bottom line is make sure your components are matched and suited for the job. But, you might have a complete kit with properly selected components and my observations might be mote in your instance.

In any event, you're going to need an o-scope to figure this out, preferably a dual channel so you can monitor input and output. Used that feature on the TR8 during throughout the ECU fiasco and it was handy, but that is a different story.

 

[JohnC]

Cherry Corp make very high quality speed & direction sensors that are ruggedised, have Delphi Metri-pack connections and are good up to 12kHz.

 

[Ron Earp]

Hi Mike,

Jack Houpe pointed out to me that I've used the wrong term with impedance in describing my situation in hopes that it might help you a bit. My apologies there if it has caused some confusion as the term is incorrect.

What I was trying to convey is that the system I worked on is a batch fire mode Haltech deal that is using a trigger wheel that gives four signals per crankshaft revolution. Yes, I know, stone age but it is what it is.

In any event, over time the pickup sensor would start to fail as the RPM's increased. It'd get worse and worse and eventually the sensor would be "broken". Replacement of the sensor would start the cycle over - working, working, not working well, and then not working at all.

As I wrote, we eventually learned that our sensor was mismatched for our expected frequency range and turned out to be some sort of wheel speed or driveshaft speed sensor from a Bosch truck system. We took the sensor out of the system, found one that had the appropriate response range and all has been good.

I sort of doubt you've got this issue but I didn't think we had this issue either until I'd spent many hours finding it out.

Ron

 

[Jack Houpe]

DORMAN Part # 970010

{OE Solutions}

This is the sensor I described in an earlier post. Its $29 and can be found at most auto parts stores. Its off a 2000 S-10 blazer 4 wheel drive unit and is the speed sensor for the ABS system. Remember the sensor puts out an ac signal but still has a polarity as it is pulsed at 0 potential. So if you hook the two wires up wrong it will not work, but all you have to do is switch them around and it will trigger the ECU.

Ron I don't think your far off in your explanation but what I think was your issue was the collapse of the coil which is important, perhaps not impedance but inductive reactance.

Don't confuse a hall effect sensor with a trigger unit. Hall effect have generally 3 wires with shield, trigger sensors have 2 with shield and sometime without a shield.

 

[mike]

thanks much for the help guys...
ill report back when we take a look at things.

 

[mike]

Re: Crank trigger sensor...UPDATE

ok my friends....
the problem isnt with the crank trigger going, the problem is for some reason i keep chewing up distributor gears and that in turn blows out the crank trigger.
the problm is chewing up the distributor gear.
ive broken 2 distributor gears in under 3k miles.

im at a bit of a loss as to why.
any ideas??
thanks

 

[Dave Wharran]

Mike,
A couple of causes for fast wear or chewed up dist. gears on C engines are:
high volume oil pumps (excessive torque to turn pump)

Cast iron dist gear run on a steel roller crank (dissimilar materials cause a high rate of wear on the cast iron gear. Must use a steel or brass dist. gear on a roller camshaft.

Not enough end play on distributor when inserted in block. If the gear is pinned to low on the distributor shaft, when the distributor is installed, the gear will bottom out on the lower bearing boss when the distributor is locked down. Result is high torque to turn the distributor/oil pump and a quickly worn dist gear.
I caught this issue on my engine during assembly and had to fabricate a shim to go between the upper distributor housing and block to get the correct end play on the distributor shaft.

 

[mike]

Mike,
A couple of causes for fast wear or chewed up dist. gears on C engines are:
high volume oil pumps (excessive torque to turn pump)

Cast iron dist gear run on a steel roller crank (dissimilar materials cause a high rate of wear on the cast iron gear. Must use a steel or brass dist. gear on a roller camshaft.

Not enough end play on distributor when inserted in block. If the gear is pinned to low on the distributor shaft, when the distributor is installed, the gear will bottom out on the lower bearing boss when the distributor is locked down. Result is high torque to turn the distributor/oil pump and a quickly worn dist gear.
I caught this issue on my engine during assembly and had to fabricate a shim to go between the upper distributor housing and block to get the correct end play on the distributor shaft.

we did consider the high volume oil pump, as that is what i have. what would the solution be? swap it out with a "regular" volume oil pump??

if the distributor sits too low, can i fashion like a thick gasket to add space, or do i have to fabricate a shim?

the first distributor was a normal distributor gear that everyone runs and the crank is forged. when that gear broke we used a carbon fiber distributor gear and that one lasted abt 450 miles.
i believe if we fix A and B above, the gear material maybe wont be a factor.

question....might the cam grind have anything to do with this issue, and is the only way to tell if the problem is fixed is if the car DOESNT break down??

its a real hassle breaking down in these things.

thanks

 

[Dave Wharran]

Like many topics, the viewpoints of standard vs high volume pumps, at least in C engines, differs. I run a high volume pump in my engine and have not had gear issues with 25K miles on the engine. Others run a standard pump with a stronger spring in it.

On the C engine, there is an oil gallery plug just behind the distributor gear/cam gear mesh point. I read somewhere that a small hole drilled in the center of the plug in this gallery will allow a steady stream of oil to squirt directly onto the gear. I made this mod when I built my engine. Does this help? Don't know, but with 25K miles on the engine, it hasn't hurt! I'm running a Crane steel gear on a Crane hydraulic roller cam.

While a thick gasket under the distributor flange may increase the end play, it wouldn't be as positive as I'd like to see. A shim is not compressable and as such is much more positive and won't change over time.

The cam grind should have nothing to do with breaking or chewing up distributor gears. Camshaft material and distributor gear material does and they must be compatible with each other. Some use brass distributor gears but from what I read, they also wear and are more or less a sacrificial gear that protects the cam gear at the expense of the distributor gear. It may be difficult, but I'd suggest trying to get a look at the gear on the camshaft to see if it is chewed up as well. If it is damaged, it will in turn damage any new distributor gear that is meshed with it.

While not easy to do, you should probably pull the distributor every 300-400 miles to have a look at the gear until you're confident the problem has been solved. As you note, it isn't very nice breaking down in any vehicle let alone a GT40.

 

[mike]

Like many topics, the viewpoints of standard vs high volume pumps, at least in C engines, differs. I run a high volume pump in my engine and have not had gear issues with 25K miles on the engine. Others run a standard pump with a stronger spring in it.

On the C engine, there is an oil gallery plug just behind the distributor gear/cam gear mesh point. I read somewhere that a small hole drilled in the center of the plug in this gallery will allow a steady stream of oil to squirt directly onto the gear. I made this mod when I built my engine. Does this help? Don't know, but with 25K miles on the engine, it hasn't hurt! I'm running a Crane steel gear on a Crane hydraulic roller cam.

While a thick gasket under the distributor flange may increase the end play, it wouldn't be as positive as I'd like to see. A shim is not compressable and as such is much more positive and won't change over time.

The cam grind should have nothing to do with breaking or chewing up distributor gears. Camshaft material and distributor gear material does and they must be compatible with each other. Some use brass distributor gears but from what I read, they also wear and are more or less a sacrificial gear that protects the cam gear at the expense of the distributor gear. It may be difficult, but I'd suggest trying to get a look at the gear on the camshaft to see if it is chewed up as well. If it is damaged, it will in turn damage any new distributor gear that is meshed with it.

While not easy to do, you should probably pull the distributor every 300-400 miles to have a look at the gear until you're confident the problem has been solved. As you note, it isn't very nice breaking down in any vehicle let alone a GT40.

thanks, good point abt the distributor shim.

 

[Jack Houpe]

Dave is your trigger unit mounted in a distributor housing?

 

[mike]

one more thing that might be related to the high volume oil pump and the torque it takes to turn it....
i have a dual oil filter set up. not sure if that could be a mitigating factor...

 

[Dave Wharran]

Dave is your trigger unit mounted in a distributor housing?

Jack,
No, my trigger and home signals come via a special Haltech Hall switch that looks at magnets embedded in the flywheel. One magnet is orientated so the switch sees a south pole, the other three magnets are orientated as north poles. The Hall switch has two outputs. Trigger comes on at every magnet. Home only comes on with the south pole magnet. The home magnet is set in the flywheel at about 70 degrees BTDC. The other 3 are all set 90 degrees from each other. Static and dynamic (curve) timing are set in the computer.

My distributor has been cut down and an aluminum top put on it. I'ts purpose in life is to drive the oil pump.