Chasing down tii running problems... Coil dying?

[Einspritz]

34 minutes ago, saaron said:

I do have an old Roundel article where they talk about tuning a tii's AFR without the data from an AFR gauge.  I'll be curious to see what Einspritzer says about that.  

 

If that is the article from Jim Rowe and Jim Blanton, I don't have that in electronic form to post. It has a few good nuggets, particularly noting that weak distributor springs (it advances too soon) can wreak havoc on the idle. I agree.

 

It really does not address full throttle / full load settings, and I guess that is left up to relying on the pump being correct. The inference is that you set the idle and at 3000 RPM and that should be it. But that doesn't address the WOT setting.

 

I advocate tuning first at WOT then mid-range, and the idle last. Perusing my notes, I see that a setting of 4.5% CO at idle is OK, so you don't have to try incessantly to get that leaner, though you can follow the "Jim's" direction to get close, or whatever setting works for your engine.

 

41 minutes ago, saaron said:

Big picture, I view it as eliminating variables.

 

Very much so.

 

41 minutes ago, saaron said:

I notice my tii runs a little different in summer and winter - I theorize it is the blend of the fuel, or the ambient temps, or a combination of both?  I don't know that for sure, of course.  

 

That is correct. Modern gas is not just gasoline any longer, there are Summer and Winter blends and the injection system is that sensitive. I noted a gas mileage change of about +/- 2 MPG and re-tune twice a year.

 

Note that the Kugelfischer system runs on fuel density which is the amount of energy in any given amount of fuel. So that will change with the composition of the fuel. Also the system was designed for 100 Octane which is more dense and has a slower flame front. You will be amazed at how well (and fun) the engine runs on that fuel.

 

It is THAT precise.

 

Remember too that the throttle body will allow the maximum amount of air at anything above ~85% opening; the rest of WOT is additional fuel provided by the pump following the P4 curve.

 

AND the nature of the plenum design allows for "sonic" tuning providing resonant air pressure above atmospheric pressure into the cylinders (15.5 psi vs. 14.5 psi) at about 4500 RPM. Try THAT with your dual sidedrafts.

 

48 minutes ago, saaron said:

I have not heard about that gauge of wire issue in regards to the fuel pump.  Totally makes sense.  Very interesting. 

 

In researching (making) a wiring harness, I measured all of the wires and then calculated the loads vs. wire gauge vs. resistance and found the wire to the fuel pump was insufficient for the published requirements of the pump, particularly if it was a Turbo at WOT. Incidentally, the replacement pump from Bosch is technically insufficient too......

 

 

54 minutes ago, saaron said:

I did have an idle hunt that cropped up - I was able to adjust the screw inside the tuna can a tiny bit to eliminate it.  I made it a little richer and that cured it.  Really want that AFR gauge...

 

Perfect!

[saaron]

Here are the two articles I have, just to share them with the other tii owners.  

 

The "Jim's" article referenced above, and a more thorough article which goes through adjusting the valves, ignition system, syncing the pump and throttle body, etc.  It does not cover adjusting the AFR via gauges or anything like that.  

 

When I was in college, about 5 miles from campus there was a Sunoco station that had racing gas - I think it was 105 octane.  The tii LOVED that gas.  It was amazing.  

 

At least we have 93 around here.  Not too bad.  

 

Scott

Fuel Air Ratio Adj tii.pdf TechBMWProceduretiiFI.pdf

[jgerock]

My 73tii recently started having starting problems when hot.  Drive for 1 or more hours, shut it off then if I tried re-starting it, it would crank until you could smell gas from the cold start valve (but it wouldn't start). I'd have to wait a while to let the gas evaporate in the intake.  This happened AFTER I did the 2600 mile trip to Arkansas.  I'm running standard points and condenser inside my rebuilt dizzy from Advanced Distributors.  Examination of cap/rotor/points and condenser didn't reveal any "gotchas", so I swapped the condenser with another old one (I recall Terry Sayther mentioning this during the Tech Session at Mid America).   Car starts OK but I haven't driven it enough to know if it solved my hot re-start problem.

 

I've got a new cap/rotor/points and condenser ready to install.

[rstclark]

Have you checked to see if the cold start valve is spraying any gas on a hot start up ?

Thats the typical problem when the cold start box fails and sprays gas at every start hot or cold 

[Einspritz]

18 hours ago, rstclark said:

Have you checked to see if the cold start valve is spraying any gas on a hot start up ?

Thats the typical problem when the cold start box fails and sprays gas at every start hot or cold

 

Perhaps it is just leaking when the fuel system is energized, and you don't notice it during regular running but manifests problems upon hot start.

 

An easy check by removal, energizing the fuel pump, and seeing if it leaks when hot.

 

If not also check the temp / time switch (cold and hot) as the electronic box only serves to change the amount of time at those temperatures.