tii re-setting itself??

[classicman]

Hi

I have been struggling with my tii setup for some time now. I have gone through all the checks and the timing is right (set on the flywheel ball at 2,400rpm), the linkage lengths are correct, the warm up valve cone rises it's 10mm, etc, etc. When I set the CO's (5.8% at 4,000 rpm and 2.5% at idle) it runs beautifully for a while. The first problem I had was when accelerating hard, it would quickly start running rough, until I realized that the stop on the accelerator pedal was not synchronized to the stop on the pump, so the clamp bolt under the Tuna can would shift. I rectified this and thought that all would be OK.

Yesterday I took my car out for a photo-shoot for an article in an upcoming BMWCar magazine. On the way there she ran nicely (120km/h on the freeway), but when I stopped en-route and switched her off, she ran on as though she had pre-ignition. She also fluffed at about 5,000rpm, as though she was running out of fuel. After cranking for quite some time, she started again and ran ok, but the fluffing problem then started to happen at about 4,000rpm. I had to start her and switch her off numerous times during the photo-shoot and she started easily, but the idle was a bit erratic at 1,000rpm and she "pre-ignited" almost every time I switched her off. On the way home, the fluffing started at around 3,000rpm and I started to worry about making it home. I have checked the linkages again and she has not reset herself and the timing is still in.

I really am frustrated and stumped by this. I know the mixture is a bit rich at 5.8%, but surely this isn't the problem? Any help will be appreciated. I am running a pertronix, new Bosch plugs, new 8mm silicone wires and a new flamethrower coil. When I built the motor I put in a new thermostat that is 5deg colder than standard. The temp gauge runs midway between the blue mark and the halfway mark. I have been wondering if she is not running too cold and therefore too rich, but the cone rises to it's 10mm.

[c.d.iesel]

test the fuel pressure

test the fuel delivery volume - measure

how much fuel delivered in 30 sec.

make both tests T -ing into the hose at

the cold start injector report back

hint:

bad fuel pump

bad fuel pick up in tank - with crud

bad fuel filter

bad strainer at injection pump

[jgerock]

Check fuel pressure but do not rule out electrical gremlins.

Pertronix

Coil

Plug wires

Easy test - remove Pertronix and try good old points and condensor.

[JsnPpp]

Check that the magnetic ring in the distributor is not able to twist - if it is loose in any way the car will behave as you describe.

You may have to add a bit of tape or something to firm it up a bit.

Or this may not be at all. Keep at it, you sound like you are making progress! 5.8% sounds a bit rich yes.

~Jason

[PaulTWinterton]

I had similar issues at high rpm because the gas tank filter was almost totally clogged and anytime there was a high demand for fuel, the engine would cut out. Would run fine at lower rpms.

Also, because the filter is so clogged, fuel pressure is low, making it difficult to set fuel/air mixture properly. Rich/lean/unburnt fuel. All causing flooding, runon, hard starting.........

Check your fuel pressure (s/b 28.5psi min) and filters. You may be pleasantly surprised to find blockage that is easily remedied with inexpensive filters.

Oh yeah. Check your dwell if you haven't lately. Makes a difference.

[wegweiser]

Make sure your distributor is advancing and retarding through the rpm range. it should max out at / near 32 deg BTDC at 3200-3500 rpm. I had a wonky distributor cause all kinds of issues...and eventually a blown head gasket!

Two failures were present on mine:

a) vertical play in distributor shaft allowed the rotor to BUMP the ignition points and tweak them / damage them

advance curve was all over the map, causing detonation and / or lean mis / high combustion chamber temps. I'd check it and it would be fine at one rpm and wayyyy off at another.

I had the unit re-curved at Advanced Distributors in MN and it's flawless now.

Check your ignition points and / or condenser first!

[jgerry2002]

+1 for a worn distributor. I had run-on problems/weird idle/weird idle mixture as well with my distributor prior to rebuild.

[codigoRojo]

With dieseling (engine run-on after ignition switched off) I would suspect air-fuel problems before ignition. Plus he described recent work on the fuel system linkages resulting in a change (improvement) in engine behavior. I suppose if his ignition was too advanced he could be getting hot combustion chambers which might lead to dieseling, but that probably wouldn't cause stalling at 4-5K rpm. I'm not a tii guy, but I'd guess there are two problems: fuel supply blockage and fuel linkage problems. -Rojo

edit: with such terrible fuel mixture, you're probably killing spark plugs, which would result in erratic/low power at speed under load. Throw a new set in and I bet you can reproduce the initial improvement, and after driving a while, a gradual decrease in performance. Not sure how this would contribute to dieseling.

[classicman]

Thanks for the feedback guys.

I will check the fuel delivery rate / pressure this evening. I suspect that there may be clogging as I had the tank cleaned (sandblasted) and it stood empty for a few years before I put gas in it. The fuel lines are brand new as are the filters, but the main filter may be clogged with rust / dirt.

The magnetic collar on the Pertronix is a tight fit. How do you check maximum advance on the distributor?

Plugs and leads are new.

[pilotnbr1]

Perhaps the intermediate shaft is out of round at the clamp and it is shifting... Intermediate shafts are cheap- $30. Get one before its nla and scratch one possible problem from your list. Dont forget the socket bushing it sits on.

[JsnPpp]

Is this the car with A4 injection in it? If yes, you can also verify butterfly sync . While this shouldn't shift over time it is essential to the proper running of the car.

~Jason

[classicman]

Is this the car with A4 injection in it? If yes, you can also verify butterfly sync . While this shouldn't shift over time it is essential to the proper running of the car.

~Jason

Nope. A4 pump but std intake.

[classicman]

test the fuel pressure

test the fuel delivery volume - measure

how much fuel delivered in 30 sec.

make both tests T -ing into the hose at

the cold start injector report back

hint:

bad fuel pump

bad fuel pick up in tank - with crud

bad fuel filter

bad strainer at injection pump

Tested at both the cold start valve and the return line at the gas tank - 1L in 30 seconds, so that means that my fuel lines are OK, right?

[classicman]

I have checked my plug and they look quite rich. I was expecting this as my CO's are on the rich side. I'm running an A4 pump which would give the motor more fuel up the rev range I would assume. Possible that my rich mixture is too much for the plugs to burn up the rev range?

Something else struck me though. My car was set up with an external ballast resistor on the old coil ('74tii). I have changed to Pertonix and a Flame Thrower coil and left the resistor disconnected. Could this be the problem?

lastly, how do I check that my mechanical advance is working correctly? How do I check maximum advance on my distributor?