Damaged tooth causing issues??

[frdboy]

Attempted to start a new MS3 build tonight and no matter how I adjusted the pots the tooth logger looks like junk.....put the o-scope on the crank sensor and noticed 2 teeth consistanly lower than the others. Looks like there is some damage to the teeth and I am thinking this may be causing my issues? Does anyone see anything else that could be causing the issues? Should I try and move the sensor closer? I am using a factory timing cover/sensor mount and wheel/balancer. This was running fine on MS2 with EDIS a few weeks ago.

I plan on getting a new toothed wheel before going forward.

Ford 351W, 36-1, vr cam sensor MS3/MS3X/V3.57

[DaveEFI]

Have a look at VR out (Tsel) with your scope. That is the important signal after the VR input circuit has done its job. You should see consistent level and shape pulses there.

[Edit] Sorry - just noticed it is a a V3.57 board. So make that at J1.

[billr]

Got a picture of the damaged teeth? What is the air gap? That scope trace may not be ideal, but looks good enough to me to be reliably detected, I don't think the wheel teeth is your problem.

[frdboy]

Got a picture of the damaged teeth? What is the air gap? That scope trace may not be ideal, but looks good enough to me to be reliably detected, I don't think the wheel teeth is your problem.

I tried to get a pic last night but I couldn't get a good shot........there are 2 teeth that are a little shorter than the rest....not much but maybe .040"-.060"....looks like something hit it at one time.

I didn't measure air gap yet but it looks like maybe .080" away.

It was late last night.....I will check stuff out better tonight.

[billr]

Can you tighten the gap? Less is always better, and .080" is way more than any decent crank wheel needs.

[frdboy]

Can you tighten the gap? Less is always better, and .080" is way more than any decent crank wheel needs.

Yeah I am going to remove my cooling fan so I can get to it and see if I can tighten it up some.

[billr]

I would be looking for more like .008", quite a jump from .080

[jsmcortina]

Can you repair the damaged teeth?

James

[frdboy]

Can you repair the damaged teeth?

James

I could probably weld and reshape but I think I have a line on another one so I will probably just replace it.

[frdboy]

Ok....checked gap...it was about .065", I reduced it to about .015 - .020

Still having sync issues....here are some datalogs of me trying to start it....I did try reversing the polarity of the crank sensor and that did not help.

[frdboy]

Datalog

[frdboy]

I have not replaced the toothed wheel yet.....I just wonder if that could be the problem or am I barking up the wrong tree? It is a bunch of work to replace it.

[billr]

No, I don't think that last tooth-log (the file-type that makes most sense to me) is so crappy because of the wheel. At least, not because of just two low teeth on it. Are you sure there isn't other damage, like axial run-out? How about posting a new scope trace similar to the previous, now that you have the gap tightened? Also, a trace of the output from U7A. The crank sensor is VR, correct? How are the mainboard pots set?

[frdboy]

Pots are fully counterclockwise....I have tried different settings a 1/2 turn at a time and really not seen any huge improvement. I would like to scope the output but I have not found how to do that yet.

Run-out is fine, I can re-scope it a lil later.

[billr]

Look at (scope) any of the even pins on the mainboard J1 (6-pin header). They are all connected in parallel, so any will do, no matter what position you have the jumper in there. If you have two channels, sync the scope on the cam input signal, that will give you at least one full crank rotation of the crank signal on the other trace.

[frdboy]

Look at (scope) any of the even pins on the mainboard J1 (6-pin header). They are all connected in parallel, so any will do, no matter what position you have the jumper in there. If you have two channels, sync the scope on the cam input signal, that will give you at least one full crank rotation of the crank signal on the other trace.

I will try that and report back, I will be out of town for a couple day though.

Would a hall effect sensor be less trouble? I would have no issue fabing up a bracket and buying a hall effect if it would be a better set up.

[jsmcortina]

You don't know what the problem is yet.

James

[frdboy]

You don't know what the problem is yet.

James

Right.......just wondering if VR and sync issues are more common.

I will do some more testing and report back.

Thanks!

[DaveEFI]

You don't know what the problem is yet.

James

Right.......just wondering if VR and sync issues are more common.

I will do some more testing and report back.

Thanks!

They are - but always a good reason for it. Hall effect tend to be a lot less reliable than a VR sensor, as they contain electronics which can fail if overheated. A VR sensor is little more than a coil of wire.

[jsmcortina]

The scope trace from the sensor looks generally ok, but the tooth log you posted is all over the place. This suggests to me that the VR conditioning circuit is either set wrong or defective.

Scoping the AC input and DC output from that circuit would be my next step.

James