Car running -very- lean under boost

[Yale]

Anyone else ever deal with this situation?

 

it is 10% rich at idle so we are looking at an injection pump issue. 

[Einspritz]

Yes.

 

What is very lean under boost? %CO would be best for me.

 

Is that full throttle, full boost?.....and at what level of boost?

 

And of course, when was the pump calibrated and do you  have data proof of its output curves?

 

10% rich at idle in what units?

 

Thanks

[Einspritz]

Check the pressure regulator on the back of the pump.

 

Remove the nut to see if the chamber has oil in it, if it does, then the rear seal of the pump has failed, and if there is a lot, you may be experiencing a hydro-lock situation where the enrichment under boost is prevented from doing so.

[Preyupy]

Also make sure you don't have a kink or a blockage in the hose from the injection pump to the Altitude Compensator. 

 

Has the pump been rebuilt or do you know if it has ever run properly?  I have found a few pumps where the "Verboten Screw" had to be adjusted because no matter what you did you could not get it rich enough under full load.  Once you move that you have to go back and completely readjust the idle mixture.  On the Dyno I have found you need to get the full throttle mixture set 1st then you set the idle mixture. 

 

Obviously you have to get it to run well enough so you can drive it.  Don't spend a ton of time on idle and mid range mixture as it is much easier to lean it out than it is to richen it up.  Make it run, then make your full throttle mixture adjustments, THEN work on the idle and mid range mixture. 

Edited December 17, 2018 by Preyupy

[Einspritz]

5 hours ago, Preyupy said:

Also make sure you don't have a kink or a blockage in the hose from the injection pump to the Altitude Compensator

 

I think that  would only be an issue under vacuum. Under boost, the air flow would go from the plenum to the pressure regulator on the back of the pump, through the hole in the piston, to the altitude compensator.....where any adjustment at the bellows really has no effect.

 

Now, if you have the hoses hooked up incorrectly, that would mess up the works; the piston would move in the wrong direction and NOT enrich the mixture under boost. Perhaps that is your problem.

 

Ibid on Byron's comment about the pump, and setting WOT first, then mid range under boost, then mid range under vacuum, then idle.

 

Don't be too fussy on getting the idle %CO perfect unless everything else is good and proper.

[Preyupy]

56 minutes ago, Einspritz said:

 

where any adjustment at the bellows really has no effect

 The Bellows does not have any effect because under boost the air lifts the small plate against the spring holding it down.  If the hose is kinked the airflow is restricted and the pressure on opposite sides of the piston in the pressure regulator tries to equalize.  This causes the piston to move back towards the middle of the travel causing it to go lean under boost.   

[Einspritz]

Good point, duly noted.

 

I use the booster hose that has the internal wire (it came that way) so I have never experienced that, but have had the rear seal fail filling the chamber at the bottom, hydrolocking the system.

 

so Yale?

[Preyupy]

I have not seen the oil leak issue.  Good information to keep in mind.  Thanks

[Yale]

Sorry I have not come back to this post. It turns out when my alternator was rebuilt they replaced the voltage regulator with a new one from the same company as the original....but....it wasn't the same and was putting out 17 volts when on  the gas! So the exhaust gas reading equipment was compromised. Luckily they didn't throw the old one and I had them put it back in. Now I have to wait for better weather to go through the exhaust gas readings again.

[Einspritz]

Are you using the OE voltage regulator or have you installed a late model alternator with the regulator on the unit?

 

If the former consider something like this:

http://www.240turbo.com/AdjustableVoltage.html#vw

 

If the latter consider adding a resistor to jack up the voltage; I can send you an article on how to do that.

 

There is also a unit that has a screw adjustable transistor, but I can't find the page.

 

17V is a bit high unless you are reconditioning the battery, better to be at 14.5V on the battery, or at least 13V with all your accessories turned on, depending on the amperage of the alternator.

 

HTH

 

 

 

[Einspritz]

or this:

 

http://vwparts.aircooled.net/Adjustable-Voltage-Regulator-1980-91-VW-Vanagon-p/adjustable-voltage-regulator.htm