If you all will recall, my tachometer wouldn’t register rpms and, through
the use of a voltmeter, discovered the tach generator was the problem. I
removed the tach generator and through the use of a mirror and touch could
see/feel the drive dog. I went ahead and purchased a tach generator, but
decided to play it safe and order a new drive dog, which I didn’t install.
Finally managed to install the new tach generator after too much time
fussing with the Allen screws and got a good reading on the tachometer.
This meant that the old drive dog was O.K. The lesson here is to make use
of a mirror before deciding the drive dog is the problem. But why did the
engineers decide to use Allen screws in such a tight work area? Regular
bolts with lock washers would have done the job, I think. And they would be
so much easier to handle than trying to get an Allen wrench to insert and
hold in an area that is truly finger-tight.
Bob
64 E-type 3.8 FHC
Gee, It wasn’t finger tight when they assembled the engine on the
line. I feel that as fit punishment, every engineer should be forced to
work on the car they design.
Robert J. Richardson wrote:>
If you all will recall, my tachometer wouldn’t register rpms and, through
the use of a voltmeter, discovered the tach generator was the problem. I
removed the tach generator and through the use of a mirror and touch could
see/feel the drive dog. I went ahead and purchased a tach generator, but
decided to play it safe and order a new drive dog, which I didn’t install.
Finally managed to install the new tach generator after too much time
fussing with the Allen screws and got a good reading on the tachometer.
This meant that the old drive dog was O.K. The lesson here is to make use
of a mirror before deciding the drive dog is the problem. But why did the
engineers decide to use Allen screws in such a tight work area? Regular
bolts with lock washers would have done the job, I think. And they would be
so much easier to handle than trying to get an Allen wrench to insert and
hold in an area that is truly finger-tight.
Bob
64 E-type 3.8 FHC
Gee, It wasn’t finger tight when they assembled the engine on the
line. I feel that as fit punishment, every engineer should be forced to
work on the car they design.Robert J. Richardson wrote:
If you all will recall, my tachometer wouldn’t register rpms and, through
the use of a voltmeter, discovered the tach generator was the problem. I
removed the tach generator and through the use of a mirror and touch
could
see/feel the drive dog. I went ahead and purchased a tach generator, but
decided to play it safe and order a new drive dog, which I didn’t
install.
Finally managed to install the new tach generator after too much time
fussing with the Allen screws and got a good reading on the tachometer.
This meant that the old drive dog was O.K. The lesson here is to make use
of a mirror before deciding the drive dog is the problem. But why did the
engineers decide to use Allen screws in such a tight work area? Regular
bolts with lock washers would have done the job, I think. And they would
be
so much easier to handle than trying to get an Allen wrench to insert
and
hold in an area that is truly finger-tight.
Bob
64 E-type 3.8 FHC
I figured they did it so that you could “offer up” the bolt and washer on
the end of the allen head. I f it were a plain old bolt you couldn’t do
that.
Bill B-----Original Message-----
From: John Franklin jwf@ibm.net
To: e-type@jag-lovers.org e-type@jag-lovers.org
Date: Saturday, August 22, 1998 4:05 PM
Subject: Re: [E-Type] Tach generator
I am reassembling my 61 MK II motor and I have the tach generator out.
There is nothing wrong with it but I wonder if I should open it up,
clean it etc. Is there an o-ring inside that should be replaced? Does
anyone have any experience with it??
Dennis 61 MK II
Dennis - It’s easy enough to get to, if it needs attention in the future.
If it ain’t broke, don’t fix it! I believe there’s an O-ring on the
outside of the unit that SHOULD be replaced. Clean it externally and refit
with confidence! All it is is a permanent-magnet generator (a motor with
the rotor driven, outputting a variable voltage, instead of the other way
'round). If you really want to pull it apart, I guess you could re-grease
(or replace) the bearings.
Good luck with your engine rebuild!
Larry Schear
Twin Cam, Inc.
At 05:18 PM 6/30/99 -0700, you wrote:>I am reassembling my 61 MK II motor and I have the tach generator out.
There is nothing wrong with it but I wonder if I should open it up,
clean it etc. Is there an o-ring inside that should be replaced? Does
anyone have any experience with it??Dennis 61 MK II
Larry,
Mine does not have and outside o-ring. The unit bolts to the back of the
cam cover. I suspect there is an o-ring inside the generator to stop oil
leaking into it.
Has anyone worked on one like this before?
Dennis
Larry Schear wrote:>
Dennis - It’s easy enough to get to, if it needs attention in the future.
If it ain’t broke, don’t fix it! I believe there’s an O-ring on the
outside of the unit that SHOULD be replaced. Clean it externally and refit
with confidence! All it is is a permanent-magnet generator (a motor with
the rotor driven, outputting a variable voltage, instead of the other way
'round). If you really want to pull it apart, I guess you could re-grease
(or replace) the bearings.Good luck with your engine rebuild!
Larry Schear
Twin Cam, Inc.At 05:18 PM 6/30/99 -0700, you wrote:
I am reassembling my 61 MK II motor and I have the tach generator out.
There is nothing wrong with it but I wonder if I should open it up,
clean it etc. Is there an o-ring inside that should be replaced? Does
anyone have any experience with it??Dennis 61 MK II
Gurus,
Every year or two my tach generator drive dog decides to get lazy and it
backs out of the coupling at the back of the cam. I’ve replaced the
coupling, so that’s new but yesterday was the day it decided to do it
again. Every time this happens I pull it back out and peen the thing
with a punch but this apparently is not a permanent fix because it now
has punch marks all over the place and it slid out very easily. I’ve
read that others have had this problem too. What has been your,
hopefully better fix?
pauls 67ots
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Paul,
You’re talking about the bush slipping back inside the housing right?
What I did was unpeen the back cover and remove it so I could
disassemble the thing. Pressed out the bush and then glued it back in.
I forget now what glue I used, maybe just silicone. This actually did
two things for me, first stopped it from moving, and second cured and
oil leak that I had thought was coming from the oil feed pipe but was
instead coming from around that bush.
Ultimately the best solution was when a brand new one came up on Ebay
for $100. I’ve seen them go by a number of times
Eric
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Eric,
That’s exactly the problem. I wondered what would happen if I were to
try to take the back off. I hate removing covers that are crimped on.
Anything in there pose a problem or is it straight forward? I think
the usuals get about $160 for them, when they have them 
I’m not
totally against spending $160 but this one works fine and I see what the
problem is. Discarding it is a problem, for me anyway.
pauls 67ots>>>>>>>>>
From: “Eric MaLossi” emalossi@austin.rr.com
Subject: RE: [E-Type] Tach generator
Paul,
You’re talking about the bush slipping back inside the housing right?
What I did was unpeen the back cover and remove it so I could
disassemble the thing. Pressed out the bush and then glued it back in.
I forget now what glue I used, maybe just silicone. This actually did
two things for me, first stopped it from moving, and second cured and
oil leak that I had thought was coming from the oil feed pipe but was
instead coming from around that bush.
Ultimately the best solution was when a brand new one came up on Ebay
for $100. I’ve seen them go by a number of times
Eric
<<<<<<<<<<<
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Nope it’s totally obvious once you get it off. Just tap gently on the
swages with a straight screwdriver to loosen up the cover. Remove the
c-clip that holds the thing together, and tap back on the shaft gently
to drive the cover off. The only thing you have to be careful of is
that the coil doesn’t move about and break the leads off, but if I’m
recalling correctly that’s held in by a large clip on the back side, so
there’s not much risk there.
Press the bush out with a bench vice and some sockets and then glue it
up and press it back in. Most likely all of you peens have knocked the
hole a bit out of round and that’s why it keeps loosening up on you.
Eric
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Eric,
Thanks, then I’m going to give this a go. In the mean time I had another generator lying around here with broken leads/contact. Yesterday I successfully soldered the lead back, hooked it up to a drill and it works. Stefan Roundy says he has new contacts so I’m ordering one from him. Once I get the newly repaird generator assembled and installed I’m going to disassemble the old one for a permanent fix. I agree the old housing is probably now getting weakened from all the peening. I knew it was time to find another fix.
pauls 67ots
Nope it’s totally obvious once you get it off. Just tap gently on the
swages with a straight screwdriver to loosen up the cover. Remove the
c-clip that holds the thing together, and tap back on the shaft gently
to drive the cover off. The only thing you have to be careful of is
that the coil doesn’t move about and break the leads off, but if I’m
recalling correctly that’s held in by a large clip on the back side, so
there’s not much risk there.
Press the bush out with a bench vice and some sockets and then glue it
up and press it back in. Most likely all of you peens have knocked the
hole a bit out of round and that’s why it keeps loosening up on you.
Eric
<<<<<<<<
Search the archives & forums - http://search.jag-lovers.org/
Subscription changes - http://www.jag-lovers.com/cgi-bin/majordomoFrom: “Eric MaLossi” emalossi@austin.rr.com
Subject: RE: [E-Type] Tach generator
My tach generator finally died for good and I just received
the new replacement. It is missing the thin washer that forms
the groove for the o-ring seal. I removed the washer from the
old one, is it just the interference fit over the the shoulder
of the new casing that holds it on? Should I deform the
shoulder with a punch or something to make sure it doesn’t
slip off the next time it needs to come off?
Thanks,
Jim–
Jim Horvath, '67 OTS, 1E13653
San Jose/CA, United States
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In reply to a message from Jim Horvath sent Wed 16 Apr 2014:
It depends how snug it is though when you press it on but
you might want to punch it lightly a couple times. You
don’t want it falling off inside there.–
Erica Madison Moss 64 3.8 OTS
Austin,TX, United States
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In reply to a message from Jim Horvath sent Wed 16 Apr 2014:
Oh also, if it’s new, it’s probably never been pinned. The
bronze bushing has a really nasty habit of backing into the
housing carrying the rotor with it. This disengages it from
the drive dog and your tach falls to zero. If you’re even
more unlucky it will break up the drive dog in the process.
Just drill a tiny hole though the housing and into the
bushing and tap it for a small set screw. Don’t drill all
the way through. Then loctite in the screw. Don’t ask me
why they didn’t come with this already done. It’s happened
to two of mine and one was brand new.–
Erica Madison Moss 64 3.8 OTS
Austin,TX, United States
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In reply to a message from Erica Moss sent Thu 17 Apr 2014:
Erica,
Thanks, it is a pretty snug fit, I had to put it in the
freezer and heat up the washer to get it on but I’ll give it a
little hit with a punch just to be safe. And yes I will pin
it like I did to my old one. Or maybe a set screw as you
suggest, a dog point would work quite well there.
Thanks,
Jim–
The original message included these comments:
Oh also, if it’s new, it’s probably never been pinned. The
bronze bushing has a really nasty habit of backing into the
housing carrying the rotor with it. This disengages it from
the drive dog and your tach falls to zero. If you’re even
more unlucky it will break up the drive dog in the process.
Just drill a tiny hole though the housing and into the
bushing and tap it for a small set screw. Don’t drill all
the way through. Then loctite in the screw. Don’t ask me
why they didn’t come with this already done. It’s happened
to two of mine and one was brand new.
–
Jim Horvath, '67 OTS, 1E13653
San Jose/CA, United States
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Someone mentioned the tach generator recently…just saw this on ebay
Les…'68 S1.5 2+2
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I tested my tach generator last night and got no output.
I see Terry’s has a “top portion” for around $30, and a complete
assembly for around $300.
I haven’t taken it apart, but just curious if there’s any chance it’s
usually the top that fails, or if it’s more likely to be in the guts
of the generator?
Kind of a surprise as this generator was put in when we rebuilt the
engine around 2003… not terribly old.
B Shriver
http://www.xkdata.com/cars/detail/?car=S810189______________________________________________________
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In reply to a message from Brandon Shriver sent Wed 29 Jul 2015:
Brandon,
How did you test it? Was it on the car or on the bench? I
think the top section just refers to the plastic part that
carries the contacts and has some springs under it. It
doesn’t fail unless the plastic falls apart. The most
common failure with these is that the bushing in which the
shaft rotates gets pushed back into the unit carrying the
shaft with it. Eventually it goes back far enough that it
can no longer engage with the drive dog.
The fix is to remove the back cover, and push the spinny
part and the bushing back out to the operational position,
then secure the bushing there so it can’t happen again. You
can glue it (maybe) or drill and pin it. I used a teeny
grub screw to fix mine in place. You obviously don’t want
the pin to penetrate into the center where the shaft
rotates. Another possibility is that the drive dog has failed.
I’m not sure what to suggest if you are testing it on the
bench. I guess it’s possible that it is the contacts in
that case.–
Erica Madison Moss 64 3.8 OTS
Austin,TX, United States
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Thanks for the response… it was tested in the car, with a multimeter.
I don’t suppose anyone has any pictures of the portion you’re trying
to pin into place.
Thanks!
B Shriver
XK Data - The Cars - Jaguar XK120, XK140, XK150 information, articles, photos and register Wed, Jul 29, 2015 at 12:32 PM, Erica Moss erica.m.moss@hotmail.com wrote:
In reply to a message from Brandon Shriver sent Wed 29 Jul 2015:
Brandon,
How did you test it? Was it on the car or on the bench? I
think the top section just refers to the plastic part that
carries the contacts and has some springs under it. It
doesn’t fail unless the plastic falls apart. The most
common failure with these is that the bushing in which the
shaft rotates gets pushed back into the unit carrying the
shaft with it. Eventually it goes back far enough that it
can no longer engage with the drive dog.The fix is to remove the back cover, and push the spinny
part and the bushing back out to the operational position,
then secure the bushing there so it can’t happen again. You
can glue it (maybe) or drill and pin it. I used a teeny
grub screw to fix mine in place. You obviously don’t want
the pin to penetrate into the center where the shaft
rotates. Another possibility is that the drive dog has failed.I’m not sure what to suggest if you are testing it on the
bench. I guess it’s possible that it is the contacts in
that case.Erica Madison Moss 64 3.8 OTS
Austin,TX, United States
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In reply to a message from Brandon Shriver sent Wed 29 Jul 2015:
Howdy,
I bought just the top from Terry becasue the spades on my original
were broken. I removed the generator and swapped it in;I get
appropriate RPM dependent output when I put a meter on the spades
with the motor running. I still don’t have tach but that’s a
different story, the generator seems to be doing it’s job
Best,
Steve–
Wuttin
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