I am trying to understand my AAZ injection pump . It has two solenoids. One is the shut-off of course and the other one... situated at the bottom of the pump is described in Bentley as the injection start positioner. My local VW dealer could not find this one in their files. My pump rebuilder thinks that this part is not important. Before puting the whole idea to rest I would like to hear opinions from this forum.

Thanks.

Haybayian.

if so you don't need it.  it retards timing at idle to reduce NOx pollution.

You do however need to wire it to get 12V whenever the engine is on... usually by connecting it to the fuel shutoff solenoid.

Otherwise your timing will stay retarded and performance will suffer slightly.

Here's a few more details with some pictures:

http://vwdiesel.net/phpBB/viewtopic.php?t=579

Quote from: "jtanguay"

if so you don't need it.  it retards timing at idle to reduce NOx pollution.

You do however need to wire it to get 12V whenever the engine is on... usually by connecting it to the fuel shutoff solenoid.

Otherwise your timing will stay retarded and performance will suffer slightly.

Here's a few more details with some pictures:

http://vwdiesel.net/phpBB/viewtopic.php?t=579

Thanks Jtanguay and Vince (and the others)

Yes what I have on my pump is  what he pictures above are suggesting and  is called "start positioner" in the Bentley manual (23a-5). Here is what  Bentley says:
"The IP is equipped with load-dependent timing and boost pressure enrichement. The load dependent timing function retards pump timing during low engine loads for better fuel economy and exhaust emisssions. In order for the boost pressure enrichment to function, load dependent timing must be turned off during high boost \load situations. The test below checks this switching off function....etc" end of quote.

The question seems to be: if the solenoid in question is not  energized the load dependant timing (retards) function should not be activated and appart from higher emissions and worse fuel consumption performance should not be affected.

Am I right or am I wrong?


Now  since the solenoid in question is disfunctional on my engine , what I need to know is how to order  a new one ( what to call it). Is it...the same solenoid as the shut-off control, does anyone here knows?

Thanks again for your help.

Haybayian

can't you just delete that solenoid though?  like.. remove it so you don't need to give it 12v?  might need to frankenstyle it by taking parts from another pump, but still...

the retarded timing will give you poor performance, and possibly poor economy due to the poor performance.  your idle economy should go up with retarded timing, but thats about it...

I have re-read the testing procedure suggested by Bentley. I think now that the pump is designed to retard timing when light load is present...however the solenoid in question seems to be activated at 3000+ rpm. The absence of solenoid may translate into a slower response throttle.
Thanks.

Haybayian

This solenoid does not retarded the timing at any RPM, the 12V come at around 2800-2900RPM only, and when the 12V is applied on this solenoid, the timing is advanced, but, when you floor the accelerator, the effect is the same, at WOT this solenoid is useless.

If you removes the wire on this solenoid, this pump will work like a 1.6TD pump, thats all.

Merci Tintin

What you are saying seems to coroborate the story I heard from the shop that rebuilt my IP. I will put this issue to rest.
Take care.
Haybayian.