pump not crank jumped a tooth

12MPGHWY

Veteran Member
Joined
Mar 28, 2008
Location
el California
TDI
none
Recently about 15k into the last timing belt I pulled up to a gas station, fueled up and went to start the car.

No start condition with slight firing.

Towed the car home and after checking several things I locked the camshaft and lined up the crank with its marker and low and behold the pump, not the crank had jumped a tooth.

That is the cam was still timed to the crank, but the pump was one tooth back.

How in the world could this happen?

The tensioner and belt still looked good, but I changed them anyways, and have seen another 1k miles without problems.
 

Lug_Nut

TDIClub Enthusiast, Pre-Forum Veteran Member
Joined
Jun 20, 1998
Location
Sterling, Massachusetts. USA
TDI
idi: 1988 Bolens DGT1700H, the other oil burner: 1967 Saab Sonett II two stroke
12MPGHWY said:
...I locked the camshaft and lined up the crank with its marker and low and behold the pump, not the crank had jumped a tooth.
Please elaborate.


Did you loosen the cam sprocket fit the lock bar, and THEN line up the crank? As in "locked the camshaft and lined up the crank"
or was it possible to fit the cam lock before loosening the cam sprocket and the crank coincidentally also lined up? As in "locked the camshaft and the crank lined up"
BIG difference.

If you loosened the cam sprocket, lined up the cam, and then had to rotate the crank to line it up, then the cam and crank might not have been aligned to each other before you started. They may well have been lined up, but now there's no way to state that for sure.

Only if the crank was lined up and the cam lock fit BEFORE the cam sprocket was loosened, can you can state that only the pump is out of time.
 

Lug_Nut

TDIClub Enthusiast, Pre-Forum Veteran Member
Joined
Jun 20, 1998
Location
Sterling, Massachusetts. USA
TDI
idi: 1988 Bolens DGT1700H, the other oil burner: 1967 Saab Sonett II two stroke
Here's a far-fetched, but possible cause:
Car is rolls backward, engine off, in gear. Is the car parked nose up on a hill without the parking brake? It might start fine when cold but not once warmed up (different timing related to engine temp).
The crank is turning backward, pulls all the tension out of the tensioner making the belt loose as it tries to "push" the pump backward.
The belt is still 'pulling' on the cam (through the tensioner) so the cam doesn't jump, just the pump.

The belt pulls under tension, it can't push worth a crap. This is why I do not rotate the engine backward.



But... that scenario moves the belt back (pump sprocket forward), not what you described.
 
Last edited:

12MPGHWY

Veteran Member
Joined
Mar 28, 2008
Location
el California
TDI
none
Of course I didn't loosten the cam sprocket before locking it and then claim that the cam was still timed to the crank.

When I say I locked the cam, what that means is I turned the engine forward in gear until I could slip the cam lock through and the crank was also lined up which is no coincidence it means that the crank and cam were timed together.

Moreover I use this cheap cam lock tool which I find to be much better than the non cheap cam lock. It is a machined flat piece of bar stock that is just thick enough to fit in the cams slot. So thick infact that it is impossible to get feeler gauges in there with it, which means its used without them.

The engine never roled back on a hill, and the pump was exactly one tooth off and yet was running great minutes before not running.

This is just wierd


Lug_Nut said:
Please elaborate.


Did you loosen the cam sprocket fit the lock bar, and THEN line up the crank? As in "locked the camshaft and lined up the crank"
or was it possible to fit the cam lock before loosening the cam sprocket and the crank coincidentally also lined up? As in "locked the camshaft and the crank lined up"
BIG difference.

If you loosened the cam sprocket, lined up the cam, and then had to rotate the crank to line it up, then the cam and crank might not have been aligned to each other before you started. They may well have been lined up, but now there's no way to state that for sure.

Only if the crank was lined up and the cam lock fit BEFORE the cam sprocket was loosened, can you can state that only the pump is out of time.
 

Lug_Nut

TDIClub Enthusiast, Pre-Forum Veteran Member
Joined
Jun 20, 1998
Location
Sterling, Massachusetts. USA
TDI
idi: 1988 Bolens DGT1700H, the other oil burner: 1967 Saab Sonett II two stroke
12MPGHWY, then I haven't a clue.
Actually I do have another theory, but the tone I perceive indicates that you're probably not interested.
You're on your own.

Graham, The IP timing is accomplished by rotating the pump body relative to the sprocket, but the sprocket lock pin bore would still line up. I believe the issue is that sprocket didn't line up. The pump body could (if the slots were long enough) be timed correctly with the sprocket anywhere, but the sprocket shouldn't move relative to the pin bore in the block/head.
 

12MPGHWY

Veteran Member
Joined
Mar 28, 2008
Location
el California
TDI
none
Should I have put it in italic green to denote sarcasm?

A master mechanic of 50 years I am not, but on a non sarcastic note, this is frankly the easiest timing belt I have ever done.

A few other engines I have done belts on such as my old Mitsubishi truck, are interference engines and yet have no method of locking the cam or crank.

yesterday I got curious and compared the removed belt tensioned with the one I pulled 20xxx miles ago when I bought the car and the spring in the replacement is extremely weak.

Also I was going to make the same comment to Graham, in-fact when I have adjusted timing on the pump, a couple of times I did it with the locking pin in-place, I don't like doing it with the car running obviously.

In case it wasn't clear from my original post the car is already back together, was on the same day the problem occurred.

Lug_Nut said:
12MPGHWY, then I haven't a clue.
Actually I do have another theory, but the tone I perceive indicates that you're probably not interested.
You're on your own.

Graham, The IP timing is accomplished by rotating the pump body relative to the sprocket, but the sprocket lock pin bore would still line up. I believe the issue is that sprocket didn't line up. The pump body could (if the slots were long enough) be timed correctly with the sprocket anywhere, but the sprocket shouldn't move relative to the pin bore in the block/head.
 
Last edited:

Crispy_8V

Well-known member
Joined
Apr 26, 2005
Location
Mersyside, UK
TDI
Mk1/A1 Golf GTTDI, Mk4 GTDI & Corrado TDI
Right folks, any theory behind this one?

I've just had the same thing, the pump timing is one notch anti clock wise!

this happened to me during a motorway/freeway run - under pushing it
popped/lost power, but still drove home with a more lighter smoke

I've not fixed it yet, we come across a reason why it might happen?
 

TonyJetta

Top Post Dawg
Joined
Sep 15, 2005
Location
Tucson, Az
TDI
'15 Jetta TDI SE / '06 Jetta TDI DSG Pkg0 / '96 Passat TDI
Crispy, how many miles since you replace the timing belt, tensioner, and roller? Did you buy top name parts?

Tony
 

paramedick

TDIClub Enthusiast, Vendor
Joined
Jul 29, 2001
Location
Versailles, Kentucky
TDI
2015 Audi Q5 TDI
Easy to have happen if there is ANY slack between the IP the the crank. I've had it happen a few times before I learned this trick.

When stretching the belt from the crank to the IP, push down on the IP lock pin to rotate the IP sprocket a bit. Then engage the teeth of the belt on the IP sprocket and release the pin. It will pull out the bit of slop that normally exists if you don't do this.

Never had it happen after I started doing this tweak.
 

Crispy_8V

Well-known member
Joined
Apr 26, 2005
Location
Mersyside, UK
TDI
Mk1/A1 Golf GTTDI, Mk4 GTDI & Corrado TDI
zero slack at all chaps, all part are VW bits done last year, less than 4000 Miles ago!

as it turns out the pump (which had a 12mm Mann head upgrade) put back to correct notch still wouldn't start

It looks like internal timing of the pump has also altered as when turning the pump on it's own, you can feel the rock of the cam not near the locking tool position ,but 30' further. still firing on all 4 injectors in sync!
put on a spare 10mm pump and starts fine.....

pity I'm heading over the Nurburgring, germany in a couple of weeks
Thanks for the help
 
Top