Help starting 69 911e MFI

TC911e · 05-03-2009, 01:03 PM

I need help with the next steps in getting my 69 911e project to start (it sat for 15+ years with the PO). It appears to be getting spark, but not fuel. What should I be checking before I pull the MFI pump off and send it to someone? The tank has been refurbished, the lines flushed, the MFI pump soaked/flushed with B-12 until the rack seems to move freely. Pump timing was set when I changed the pump drive belt while the engine was out of the car.

Now I'm trying to get it to start, but there's not been even a hint of life. There is fuel pressure and flow to the MFI pump, butno "squirts" from the distributor fittings with the tube disconnected.

I've done a good bit of reading in the MFI threads, but I'm not sure what my next step should be.
Thanks,
Tim

Flieger · Flieger's Garage

Is the shutoff solonoid on the back of the pump stuck in the extended position? It pushes the rack past idle setting, to a shut off fuel volume position, when activated by the microswitch connected to the speed switch says the car is above 1500 rpm.

Just a thought

jcge · 04:46 PM

Did you depress the throttle lever while turning the engine over ?

Do you get a 2 second pulse at the cold start solenoid ?

Rack movement will count for nothing if the pistons (in the MFI pump) are stuck at TDC due to fuel gum or rust/dirt. Usually if you can move the rack, the pistons are free to rise/fall under spring pressure, but not always...

You can check by removing a side cover from the MFI pump and observing the springs compress and extend while turing the pump over. If they are gummed up, the springs will compress only (and remain compressed with the pistons stuck at TDC).

If they are stuck/gummed up, you will need to try more chemtool in to the fuel inlet - soak, rotate pump, soak etc.

In the picture below, the spring on the LHS is "compressed" TDC and the other two (middle and RHS) ere extended BDC.

TC911e · 05-03-2009, 04:48 PM

Thanks, I'll pull the side cover and take another look. I gave it a pretty good flush while the engine was out and I'm pretty sure had them moving, but I'll double check it.
Tim

TC911e · 05-04-2009, 05:00 PM

Well the springs are compressing and releasing. I pulled the cover off and cranked it through a couple of strokes. Shouldn't I be able to see something of a "squirt" with the tubes off and cranking on the starter, or is the volume of the squirt so small it's not really noticeable?
Tim

jcge · 05-04-2009, 05:31 PM

Glad to hear the pistons are moving OK
The squirt will be noticeable, esp at full throttle !! But be very careful squirting fuel around the engine bay!!
Did you check the cold start and stop solenoids ?

jluetjen · jluetjen's Garage

Try shorting the cold start solenoid on the pump to 12V. This should peg the rack to full rich. It's virtually impossible to start a cold engine without doing this.

TC911e · 05-04-2009, 07:34 PM

The cold start solenoid may be the answer. Giving it 12v directly does drive the rack all the way forward, but I don't think it's actuating when I try to start it. At the moment I've got all the plugs out to do a compression check (which yielded a 0 psi reading on #6), or I'd give it another shot right away. The shutoff solenoid does appear to functioning correctly and will pull the rack in when it's given 12v.
Thanks for the clues,
tomorrow we try again.
Tim

jcge · 05-04-2009, 08:32 PM

If your cold start solenoid isn't automatically coming in, you may have a problem with the thermo time switch.

jluetjen · jluetjen's Garage

By the way, The 69's are unique in that it's easy to make a cold-start feature that works better then the factory's "trickle of gas down the stacks" approach. Find the 12V wire from the ignition switch that drives the starter. Splice a new wire onto that wire at a convenient location. The best place to connect into this is under the dash near the ignition switch. Run this new wire to a switch on the dash-board and then connect it to the cold start solenoid on the MFI pump. When you start the engine for the first time, close the switch so that 12V goes to the solenoid as long as the starter is being cranked. As soon as the engine fires up and you release the key, the rack will return to it's "normal" position. Flip open the switch and you won't need it for the rest of the day. If by chance you try to start a warm engine with the switch closed, you'll be too rich and the car won't start. But as soon as you open the switch the engine will fire right off again. Driving around with the switch closed shouldn't be an issue since it won't be getting 12V as long as the starter is not being cranked.

Unfortunately Porsche did away with the cold start solenoids starting with the 1970 MFI pumps, and so you can't use this arrangement on the latter cars.

69911e · 05-05-2009, 05:06 AM

Start with a shot of starting fluid in each stack to make sure all is in working order. I would place the metal air filter cover back on before attempting to start in case of a backfire. It should run for a couple of seconds and may get the engine going.

TC911e · 05-05-2009, 06:43 PM

Actuating the cold start solenoid was the answer. (I'd made it a bit more difficult by disconnecting the signal from the key to the starter solenoid when I plugged in a remote starter switch so I could crank it while standing over the engine.) With the wiring connected as it should have been the solenoid actuates per the book and it started right up (on 5 cylinders anyway). Wonder of wonders.

Thanks for the help. Now I can, at least for the moment, move beyond my fear of MFI and ignition mysteries, and focus on things like stuck valves, brakes that won't release, and the other things you might expect on a car that hadn't moved for 15 years.
Thanks,
Tim