73 ignition + MFI problems HELP PLEASE !!!

[herman maire]

I know this is pretty boring but I would really apreciate some help on this....

I just put the motor back in my 73S and wired EVERYTHING up the way it was when it was running 6 months ago.... everything looks good but the + on the coil is dead = no spark.

Heres a few things I checked-
1-The ignition box has power ( 12V )

2-Yellow/Blue wire that goes to the + coil from the ignition box that should have 12V for the coil with key ON is DEAD.

3- All grounds are perfect.

4- 2 wires that go to the distributer - 1st purple/black wire that goes to the distributer 2nd- black wire that connect to the same terminal as the purple/black wire on the distributer.

What else can I check??? I dont see why the ignition box would have power but its not sending power to the coil with the BLUE/YELLOW wire



MFI PROBLEMS-
Quick history.... The pump injector lines were unbolted on the top of the pump to tension the belt. I have cranked the motor alot but the spark plugs remain dry ( NO GAS SMELL) Does MFI system have to bleed the air out when the lines have been opened ( Like a diesel) ? I dont understand why the injectors are NOT spraying gas. The MFI pump is getting fuel in the inlet and is returning to the fuel filter console.... so its getting fuel fine.

HELP PLEASE

[Grady Clay]

Ok,

The ignition transformer “coil” doesn’t have 12V at the + terminal. When the CDI fires, the + terminal gets a 300V pulse from a charged capacitor – be very careful around this terminal.

So, the CDI has 12V. Is the CDI “singing” – a high pitch whine? If not, we need to suspect the connector or something internal.

The most likely suspect is the ignition points in the distributor. Take the two wires off the distributor and connect the leads from a multimeter in the “continuity” or “Ohms” function. Turn the engine clockwise (CW) by wrench. The points should open and close three times per revolution.

For reference, the black wire at the distributor should be the lead to the CDI (many are shielded) and the black/violate wire is the signal to the “RPM transducer” for the MFI and to the tach.


On to MFI.

Do you have gas? Is the electric pump running? Is there fuel pressure at the fuel filter console fitting closest to the rear of the 911?


Yes, you need to get the air out of the steel high pressure pipes. Disable power to the CDI while doing this. Do this outside with a fire extinguisher handy.

Loosen the fittings between the pipes and the nozzles. Remove the rubber cover for the “main rack access.” This is the rubber boot just above the MFI pump drive pulley. An angled scribe works well to get it off – don’t drop it down the belt (it is far harder to get it off than to reinstall it). Use a long M4 screw and screw it into the end of the rack a few turns. It does not have to be tight. Pulling on the screw (toward the front of the car) gently to the stop makes the MFI full rich while cranking. Use this to purge the air. When you release the screw, it should snap back to the stop.

For those with a ’69 pump, you can simply apply power to the lower solenoid to make the pump full rich.

(Did you fill the MFI pump with oil?)

Tighten the fittings at the nozzles. Repeat cranking to purge the remaining air. This should result in some fuel in the engine. Check that there aren’t any fuel leaks between the pipe fittings and the pump or nozzles.

Remove the M4 screw and replace the rubber boot. (If you ever find the boot seeping oil, a fix is 2-3 turns of safety wire.)

Reconnect the CDI. The engine should be ready to start. Is there oil in the tank and cranking oil pressure?

Best,
Grady

[herman maire]

Grady,
I was counting on you but I thought I was out of luck because of the weekend, boy am I happy .

I think I got the spark taken care of.... Since you say the + on the ignition transformer "coil" is not suposed to have 12V then it looks OK. I had my brother crank the motor over with the plug grounded and it had a nice spark, it looks like my problem is the MFI.


I started working on the MFI ( I am really surprised that the system has to be purged of air like a diesel....It makes running out of fuel all that more of a pain) .

I unbolted the #4 (cyl) hard line , oh , and I also pulled the spark plugs to help spin the motor faster. There is no fuel at all coming out .

A few thing you should know...
1- the electric pump is pumping perfectly
2- I checked on the MFI pump INLET by pulling the fuel line then running the electric pump and the fuel flow is VERY good. When I put the inlet fuel line back on, the fuel returns to the fuel filter console by the OUTLET on the MFI pump.

3- The line feeding the fuel filter console passes throught the frame rail to the TOP of the fuel filter console. The return line passes on the outside of the frame rail.

Do you think the fuel shut off selenoid on the MFI pump could be stuck? Is there any way to check it???

I am going to buy a M4 bolt right now.... how long of a bolt should I get?

Thanks again Grady for helping me out.... I really apreciate it

You should put a PAYPAL address beside your price list.... you never know

[Jim Richards]

Herman, is your MFI injection pump drive belt installed? Did you time (in the ballpark) your injection pump per CMA?

[herman maire]

Originally posted by Jim Richards
Herman, is your MFI injection pump drive belt installed? Did you time (in the ballpark) your injection pump per CMA?

The pump belt is installed and tensioned.... the timing never changed so I never felt the need to check the timing. FWIW the motor ran B E A U T I F U L ..... I just wish I could get it to fire faster.

Thanks Jim for the reply.

I am still blown away the MFI system has to be purged of air.... what a bummer, I probably would have not unbolted the lines.

Thanks again

[Grady Clay]

Check your fuel plumbing at the filter console against this thread: MFI Problems. The only thing on the TOP of the console should be the cold start enrichment solenoid.

The bolt length for the rack is about 4 cm. Get M3 and M5 also, I’m not absolutely sure of the size (it has only been 20 years ).

I suppose the over-run solenoid could be stuck on (either mechanically or electrically) but I have never heard of that. An easy check is to take it off the MFI pump. Be careful with the gasket.

With the thermostat cold, the engine will eventually purge the air from the steel pipes. Moving the rack just speeds the process.

BTW, there are two “dimples” in each cam housing, partially under the fan shroud, that can collect spilled fuel. Use compressed air to blow those dry. You are not to have a fire!

I got paid for this with Rennenhaus all those 18/7 years. Now I just give back; you can thank Pelicans rs911t and pwd911S. I went to the Pueblo NASA event on Saturday and was asked to become an instructor. (The little Camry got 56 mpg – must be the GT3 CUP license plate keeps it scared.) Today was “sleep in.”

Best,
Grady