no start questions??

[joet4143]

very exciting time , finally got motor back in car . cranks but no start .

1 i recall a noise at turn of the key that is missing kinda a high pitched noise . it think it was the ignition . but the noise is no longer there .

2 have the distributor set at static time , and can smell fuel at the exhaust . naturally i only tried cranking a few times to not do any damage (fuel wash cylinders )

3 the cd box is it supposed to make that noise that i was speaking of in question 1

4 how can i trace power to the ignition by the way the car is a 1971 911 e

5 hope these questions dont sound stupid as the car has sat for many years and i am trying to be very cautious with every move and dont remember all the details ...

[Rot 911]

Ok, lets keep it simple. What you need is air,fuel and spark to get that engine running. First double check to make sure the leading edge of the rotor is lined up with the notch on the distributor when the Z1 (or TDC) mark is lined up with the line on the fan housing. You can smell fuel so it sounds like you are getting gas. Pull your #1 plug wire and attach a spark plug to it. Lay it somewhere so the tip of the spark plug is close to some exposed metal on the engine or body. Have someone turn the engine over and see if you are getting a spark at the plug. Should be nice and blue-white. You may not get a spark as you are stating you no longer hear a whine from the CDI box. Let us know what the results of your test are.

[Lorenfb]

Check out this web site (www.systemsc.com) on the Diagnostics page under
"No Start". It should be helpful troubleshooting your problem.

[joet4143]

no power at coil ?? even when cranking , any suggestions

[Lorenfb]

I'm sure your car has a CDI. They DON'T have power at the coil.

[joet4143]

ok this might sound funny but i am searching for the reason i dont get any spark from the coil wire . nothing not even a twitch . just getting frustrated .

[joet4143]

also corrected the power cable to the cdi loose . no spark from coil wire though nor #1 plug wire naturally . any suggestions?

[Superman]

Good description. My fear is your CD box died. It would likely have died if it did not have an adequate ground. Make sure the grounds are all good. I think there is a ground wire to the coil, and a ground wire to the CD box. German ground wires are nearly always brown. I've never seen one that isn't. A bad coil can ruin a CD box too. Look for ignition problem quick tests, as it does sound like ignition is your problem.

[joet4143]

I have previously gone through all the grounds and wire brushed them and re-connected prior to this post as the car had sat in the garage almost 20 years . the cd unit has a three prong connector and a ground the red wire connection was loose (my bad ) so i did not hear anything from the box but now it has that typical buzzing (good) sound . I am not very experienced with this system so i am looking for some ways to test it . and see what should be my next step . i do have access to a msd box and might go that route if the stock box is no good but would really like to weather this one out and source my problem and correctly fix it...

[joet4143]

ok ready to look at my alternatives . msd , crane in your opinion what combo works best . would love to get back on the road...

[Lorenfb]

Sounds like you gave up "throwing darts" at the problem and want to spend
money that's "burning a hole" in your pocket.

1. The CDI should buzz (a Bosch).
2. The points must be clean (use a test light at +12 to check for points ground).
3. Check the spark at the coil first. It should jump 25mm to engine case.
4. Find a test coil.

If you have lots of money, give up the troubleshooting and take it to a shop.
It might be cheaper in the long run.

[joet4143]

ok now were getting somewhere

please be patient as i am not stupid just a little inexperienced in this system.

i think i got it . the cd box gets power . also sends power at the wire connecting to the distributor . so the points ground and fire the coil ?

[Slider79SC]

Not sure if the 71 has the same setup as a 79 but I just went through this same thing.

The dang "green wire" (signal wire) coming out of the distributor that provides a signal to the CD box was shorting out.

This is a coax wire, the inside carries the signal and the outside shielding provides a ground. I replaced the wire with a new one (Pelican carries them) and it fired right up.

[Lorenfb]

Almost -

The CDI makes a high voltage from the power applied to the center pin.
When the points open (no more ground) the CDI applies the high voltage
(a pulse about 400 volts) to the coil. The time of the pulse is in nanoseconds.

[dhoward]

Milliseconds.
Moot if you're not on a scope.

[Early_S_Man]

joet,

I suggest removing the electrical panel on the left side of the engine and doing some cleaning ... remove the CDI unit and clean the ground location -- bare metal under one of the CDI mounting lugs, then clean the ground tab by removing screw and burnishing the tab and case with Scotchbrite or ink eraser. Clean the three tabs inside the phenolic connector housing ... vinegar on Q-tips, followed by distilled water, then isopropyl alcohol. Remove coil from enginine and clean the treminal studs and cround wire ... set up a bench test with new wiring, per the following Bosch Test Instuction sheet ...

Wire up a test jig with all new wiring, yourself. And, when the test jig is ready, monitor the output from coil with a new spark plug and cable as a load on the coil, look at the spark quality.

With a car that has been in extended storage ... there is likely to be oxidation or corrosion on most of the electrical connections! Hence, my suggestion to test the CDI unit and coil off the engine with new wiring.

[joet4143]

I must say thank you all for the support and direction . I just needed someone to give me some clues the trigger wire was the culprit as well as gap on points and connectins (corrosion ) car starts and runs great! just have some oil leaks to address and adjust the valves noisy and #6 pops back through the stack occasionally . only let it run for about 3 minutes will address other problems first . but once again thanks to all !!!

[Lorenfb]

Milliseconds? Get your scope calibrated or you're reading the time base wrong.

Actually, it's about 100 microseconds with a rise/fall time in the nanoseconds.

Pulsewidth (1/2 cycle) = pi x sq root (C X L) where C is the capacitor in the
CDI and L is the ignition coil inductance.