MFI Problem
 

I have a 1968 911 with a 1972 Motor. Car sat for 6 years or so. All gas lines and tank cleaned. New fuel filter and pump. 14psi going to MSI.
Upgraded to MSD, Pertronics and Flamethrower coil, removed resistor. Cannot crank, Tries to no avail.
Had it running, rough but running with Points, original coil and MSD. Thought new pertronics inginitor would help smooth out(gapped at 38) . Gapped plugs @ 28.
I called Petronics tech support and they told me I have to have the flamethrower coil to get 3 or above ohms to use the MSD. I have a blaster coil which has not been used in the box.

On another post, the moderator stated: if you have a pertronix ignitor with the flamethrower coil, you can ditch one or the other-- you can use the pertronix to trigger the MSD, and use and MSD high vibration blaster II coil, or use the pertronix with the flamethrower and ditch the MSD. The primary resistance of the flamethrower coil is too high for a CDI system.

Need help from the ‘Experts’ that have made this conversion. I have to be missing something small.
Maybe send injectors off to be cleaned and tested? Motor tries to start with starter fluid down the throat.

BTW, I did search around first. Too much conflicting information for me at this time until I learn more.
Help…

Did you try moving the distributor around to find a more advantageous initial timing? The Pertronix will change the timing from your points until reset dynamically with a light.

my head is spinning, the MSD with the MSD blasterII coil, there made for each other. pertronix to trigger should be good to go.

I have not tried moving the dist around. I'll try to do this tonight. Currently, I have the flamethrower coil attached. Sounds like I need to go back to the blaster II.
I really appreciate all the advice.

Here the plan for this weekend. Remove the flamethrower coil and reinstall the MSD Blaster II coil. Check the Petronics gap to ensure it is indeed set at 38. Get new plugs and Gap the plugs @ 28. Try to start again. If no, loosen Dist bolt and move it around a bit to see if it’s a timing issue.
Any other ideas? I’ll post results.
My thanks…

got a timing light? that will help to figure out if there is spark, and works to set timing also.

Wes,

Thanks for the shout-out above.

Let me explain what's going on and that should help you.

Let's start with the Pertronix Igniter. This replaces the points with a magnetic sensor, a magnetic trigger wheel mounted on the distributor shaft, and a solid-state switch which alternatively grounds and ungrounds the coil, allowing it to charge.

In the old days, our cars used points, and the amount of current that could go through the points was about four amps before they would burn up. So the original coils used a primary resistance of about 2.1 ohms, together with a 0.9 ohm ballast resistor, for a total of three ohms resistance. 12 Volts / 3 ohms = four amps. Pretty simple.

All right, here's where it gets fun. When the Pertronix and other solid-state switches for the coil were invented, somebody figured out that they could carry a LOT more than four amps. In fact, from seven to ten amps can flow through one of these. This allows you to use a coil with lower primary resistance, so it will charge faster. The rate that the coil charges and stores its energy is proportional to the amperage that flows through the primary windings.

So if you can put 10 amps through the switch, then your coil can have a lower primary resistance, in this case, 1.2 ohms. And in fact, the Flamethrower has either 1.5 or 3.0 ohms primary resistance. 1.5 ohms gives you 8 amps, maybe not quite that much due to resistance in the wires, but not bad.

Just to round out that thought, the reason you want faster coil charging is because at high RPM, a six-cylinder engine doesn't leave enough time for the coil to charge and then discharge before the next cylinder comes up for firing. So in effect what happens is you end up with reduced ignition energy-- if you drop below about 30mJ you don't have enough to light the fire.

All right, now comes the MSD. The MSD is a capacitive discharge system. This means that rather than storing energy in the coil like an inductive system, the MSD (and Bosch CDI, and others) store energy in a capacitor, which then uses a very high-speed switch called an SCR to dump all that energy into the coil when the points open.

In a CDI system, the coil is not responsible for storing energy-- it's responsible for transforming the approximately 350V output from the capacitor into ignition voltage. As such, you don't want high primary resistance in the coil, because that will just slow down the buildup of high voltage in the secondary and the firing of the spark. So the MSD HVB coil, for example, has a primary resistance of .7 ohms. The Bosch CDI coil, according to my own measurements, is only 0.2 ohms.

Are you with me so far? So the coil's resistance among other things is chosen by the product engineers to match the type of ignition system. This is a very long way of saying, use the coil that matches the thing it connects to-- if an MSD CDI is driving your coil, use the MSD coil. If you are only using the Pertronix to drive the coil, then use the Flamethrower.

Hope this helps, trying to not to give you a math/physics lesson but I find it helpful to explain what's going on, it makes it easier to make a decision, and be confident in that decision.

Excellent info.
Clear what I need to do at this point.
I'll be busy this weekend trying these variables (coil, timing etc...). I'll post back results.

Update... reinstalled MSD Blaster II coil.. Loosened dist bolt... Moved a bit..... Car runs..... Congrats to all..... Had another beer......
Car is running on 5 cylinders..... Narrowed it down to No 4 cylinder... I'll post pics. Pulled stacks the noticed the throat is full of fuel. (Thought I stripped the butterfly valves. Car sat for years.. Took a while to break loose the linkage)
Question: does this mean the injector is bad? Does not appear to fire. ( see pics)
Wanted to post progress before I dive any deeper. I do know V8's inside and out but this car and mechanics is new.

Asking help from the 'Experts'

BTW, if your anywhere around Paris Mountain in SC... Beers and Steaks on me. (Or a good single malt scotch)
Thanks in advance...
Wes

ok.... How do I post the pics..... Dont want to upload to website to post. What is the secret code to post from local harddrive?

click go advanced, and click upload picture, select where picture is and upload. mechanical fuel injection i presume?

Should I pull the Injector? Soak for a while? There is a good thread on servicing the injectors I can try or send off for service. Not sure if the injector is the problem or not

http://forums.pelicanparts.com/uploa...1362188966.jpg
http://forums.pelicanparts.com/uploa...1362189057.jpg

Thanks James... Yes MFI... 68 911 with a 72 engine... Barn find with 69000 MI....

check the butterflies to make sure they all open at the same time with the throttle. If that one is stuck closed (hard to have one stuck) and the rest open, fuel will flow into the cylinder but no air. long shot but it is something to rule out. the valves are opening and closing when turning the engine over? another thing to check. MFI guys should chime in soon, change the title of this thread to MFI problems

Butterfly valves are consistent. Will change... My thanks...

James, is there a link to change this thread to MFI or CCP into new thread?
Wes

select edit and go advance at the top (scroll up), you can change the name or you can start a new thread about your MFI. See if you can swap the injectors around and see if the problem moves.

MFI Problem
 

Any help appreciated.
Wes

Good idea on swapping injectors... Will try first thing in the am... Cannot seem to change the title.