# Plunger sticking?



## CALLAWAY TURBO (Aug 27, 2005)

So I have what is suppose to be a relative newly rebuilt dizzy.
I have a wide band in the car.

So occasionally it will spontaneously go lean while I'm driving.
Car will be running rich around 12.0 (where I set it) and then be 15.0 or worse.
I think it only happens as I slow down in gear but I'm not certain about this.

If I turn the engine off and restart it goes back to running rich (12.0) where I set it.

This only happens occasionally (the spontaneously going lean). 

I'm thinking its the old plunger sticking issue and I need to give it a good cleaning. 
Thoughts? 

(I've buzzed out this system pretty thoroughly in the past)


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## Butcher (Jan 31, 2001)

I doubt if the plunger is sticking. On decel, it's possible that the mixture will be leaner. In my opinion, 12 is way too rich for a steady state cruise mixture, heck, it's too rich for idle too. 

So, what warm up regulator do you have? Does it have vacuum/boost lines to it? Does it have lambda? Do you have a way to watch the control pressure while driving?


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## CALLAWAY TURBO (Aug 27, 2005)

Butcher said:


> I doubt if the plunger is sticking. On decel, it's possible that the mixture will be leaner. In my opinion, 12 is way too rich for a steady state cruise mixture, heck, it's too rich for idle too.
> 
> So, what warm up regulator do you have? Does it have vacuum/boost lines to it? Does it have lambda? Do you have a way to watch the control pressure while driving?


I'm running it rich because of the spontaneous lean thing that happens.
If I ran it "normal" the car would die when it spazs.

Normal WUR for an '82, no vac / boost lines. 
lambda is not connected. 

No way to watch the control pressure. 

Flakey WUR? 

When it flakes I can adjust the mixture up to get the idle to a better A/F
but you know when I start to run up the rpm's it goes lean again. 
Weird.


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## Butcher (Jan 31, 2001)

'Lambda not hooked up' means what?

The lambda system is hooked up and working but there is no O2 sensor installed?
The lambda system is not even installed in the car [and it should]?
The lambda system is installed but the frequency valve in not buzzing [ie not plugged in, module not plugged in, etc]?

Sorry for the questions but it matters. 

With a complete mechanical system [no frequency valve installed] then it could be the fuel distributor or the warm up regulator. It has been my experience that when either one goes bad, they are bad all the time, not intermittent. If I had to guess [which I hate doing] I would pick the warm up regulator.

If the system has electronic [working lambda/buzzing frequency valve] I would lean on that portion of the system. I have never seen a frequency valve go bad. Usually if they are buzzing, then it's working. Usually they are not buzzing or the buzz is not correct. The right buzz allows for the proper fuel mixture. Simple installation of a frequency tester would tell you if the buzzing changed when the fuel system is leaning out.

If the system suppose to have lambda and it's not working at all, the system will not work properly but it will not be intermittent. I will not be working properly all the time. It's possible that you can get it running by changing the idle mixture so rich but at higher RPM's it will run lean. You could change the control pressure to enrichen the system so it will be running fairly good but the pressures will not be close to factory specs.

I hope that makes sense because it does in my head but it rarely comes out that way thru my fingers.

If you do not have a CIS pressure tester, you should have one. If you want to purchase one, I like this one. It's small, it can be left under the hood while doing tests, and it works.
https://unwiredtools.com/utcis-cpgauge.asp


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## CALLAWAY TURBO (Aug 27, 2005)

Butcher said:


> 'Lambda not hooked up' means what?
> 
> The lambda system is hooked up and working but there is no O2 sensor installed?
> The lambda system is not even installed in the car [and it should]?
> ...


lambda is installed however the O2 sensor is disconnected from the control module and left floating ... which always struck me as a possible problem. 
(This is how I got the car so its one of those weird things I left as is) Perhaps it should be grounded or pulled up or left connected.
Guess I'll try reconnecting it and see what happens.
Hard to believe it could swing the mixture that much but who knows. 
It is something that could be weirdly intermittent


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## Butcher (Jan 31, 2001)

With the lambda hooked up, then the most likely fuel mixture change is from the electronics. The way that system works is that there is a temperature switch that tells the lambda module that the engine is hot enough to start to work. Having that switch AND the O2 sensor working will allow the system to do it's job. If you bypassed the temperature switch so it reads cold all the time [it's either shorting or unplugging] then the lambda probe wire should be ignored. 

It should be fairly easy to figure the switch out and you may have to tweak the fuel mixture again. Then go on a road test to see if the mixture changes again.

The lambda probe wire is very sensitive and when shorted, tells the lambda module it is running lean. The lambda module will adjust the frequency valve so it richen the mixture up. Left shorted to ground, it will richen it up a lot. It is possible that the sensitivity of this wire could pick up stray voltage and cause the system to lean out. 

Anyway, back on your original question, I do not think the plunger is causing your issue. I now think it's electrical and once the lambda system is hooked up completely, it will work fine.


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## CALLAWAY TURBO (Aug 27, 2005)

Ok ... rehooked the lambda ... I could hear the frequency valve going ... however its super hot here
and the fan kicked on and I couldn't hear it anymore. 

It did flake again with the lambda connected however I couldn't hear anything over the fan so I'll have to try 
this tomorrow. 

Oh, and prior to that it had flaked and I gave the dizzy a few whacks with 
a rubber hammer and that didn't change anything.


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## CALLAWAY TURBO (Aug 27, 2005)

Too hot outside again to do diagnostics again.

I'm wondering if this could be a mechanical thing with the airflow sensor.
Maybe something with the spring? 

I'll have to take the air flow sensor apart and give it a going over.


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## CALLAWAY TURBO (Aug 27, 2005)

Ok, pulled out the gauges ...

system presssure 5.75 Bar ... a smidge high for that year Scirocco CIS Lambda.

control pressure 3.9 Bar (Warm).


Humph.


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## CALLAWAY TURBO (Aug 27, 2005)

Ok, took the dizzy off.

In the course of doing that I noticed that there is a HUGE amount of play in the hinge.
The plate can slide up/down along the hinge by many millimeters so there's something wrong
with the air handler.


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## Butcher (Jan 31, 2001)

If the pressures are the same when the problem happens, it's probably not fuel related. The pressures should not change [much, if any] once the engine is at operating temperature. If the control pressure is manipulated with vacuum, then of course it would change under load. What you are looking for is a pattern of the fuel pressure changing when the problem is occurring. 

As you mentioned, the air flow housing must be in top shape for it to balance the right air flow with fuel flow. It sounds like you are going down the right path now.

Building a strong foundation while diagnosing allows for a better decision on what to do next. I doubt if the plunger could be intermittently sticking. Usually they are binding [and not running] or they are 'good enough'. I have never seen an air flow housing worn out, but with these older cars, anything that moves can wear out. The pivot assembly should have no play what so ever at the fulcrum.


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## CALLAWAY TURBO (Aug 27, 2005)

Its definitely something wrong with the hinge of the air handler. 
I wish I could get a good picture of it.
But basically it slides up and down the hinge way too much (in a way it shouldn't). 

I'll have to replace the air handler with a good unit and perhaps
take the old one apart to see what the failure was. 

It fits the failure. The plate could get misaligned with the cone and kinda jam somewhat open. 
When airflow reduced it lead to a lean condition that persisted.
If I turn the engine off it must of jogged it enough so it would settle back into an aligned position.


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## Butcher (Jan 31, 2001)

CALLAWAY TURBO said:


> It fits the failure.


Yeah it does. Good for you to figure it out.:beer:


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## CALLAWAY TURBO (Aug 27, 2005)

Not to beat a dead horse but I took apart the air handler specifically the hinge part.
Wish it were easier to post pictures here!

So at some point in the past someone took it apart and left out one of the two springs that center
the plate. I know this is hard to visualize ... but there is a hinge with a ball bearing and a spring 
on each end held in by a plate and circular clip. 

It amazes me that this worked as well as it did for as long as it did.
I have no idea who did this ... some previous mechanic decades ago at this point.

Putting in the new donor air handler. 
Now the gasket I got from MK1 autoparts that goes between the air handle and its case is too loose. 
Its NOT cork like the old one. I ordered what I hope is a cork one from ECS Tuning and we'll see how that works out.


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## Butcher (Jan 31, 2001)

I can only assume that the previous mechanic removed the spring so more fuel will be delivered. Not understanding how CIS works is the biggest issue with that system. That and old gas.

Glad to have an update.


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