"you mentioned how you checked the residual fuel pressure"

Why is all this effort and discussion being wasted on a potential fuel issue when the engine
won't even run with carb cleaner nor starting fluid? Check here under 'No-Start' for
more info; Diagnostic

+1.....Thanks Loren......that's what i have been trying to say.

regards,
al

Tony,

I think you misunderstood my post. I am aware that residual pressure is tested with the valve open.

I wanted to see what happened with the valve closed so that I could see if the fuel pump check valve was holding.

I'm not disagreeing, maybe it is an ignition issue.

I also appreciate the link, but "check for spark at the coil and at the plugs" - I've done that. I have spark at the coil. I have spark at each of the plugs. I even put in brand new plugs. I've set the static timing and rechecked it several times. I even set the static timing out 180 degrees just in case I was crazy. This resulted in a massive backfire from the exhaust (sounded like a gunshot).

I have done the following:

- Checked spark at the coil
- Checked spark at each plug
- Replaced the distributor cap (I had an extra one)
- Replaced each spark plug (and set gap)
- Tested the Pertronix ignitor unit via the test procedure they have on their website.
- Set the static timing for the distributor using the Z1 mark.
- varied the timing by the adjustment amount on the distributor.

I honestly haven't put a huge amount of time into trying to start the car with starting fluid. Maybe I'll try that again and see if I can get the car to fire.

Just a WAG, but could your compression be down from fuel washing onto cylinder walls?

Wouldn't cause an issue in a healthy engine, but perhaps your engine is worn?

Okay, so I ran a bunch of tests today.

Started out with simply trying to get the engine to fire using starting fluid. It was sort of trying to fire for a minute or two, but it wouldn't catch. Then it went back to simply not firing at all. I went back to pulling plugs and checking spark.

This time I noticed something... odd. The spark wasn't consistent. It actually appeared random - it would fire three quick sparks, and then one spark, and then spark, spark, spark...

So... my thought was that the pertronix ignitor was acting up somehow. I had tested it as described on the pertronix website and it seemed fine, but something was clearly wrong.

So I pulled out the pertronix and reinstalled the original points. The spark is now consistent. A steady flashing.

Unfortunately, the car -still- won't fire.

One question - the pertronix setup had a white wire running to the negative and 12v power running to the positive. The white wire that ran to the negative (and is now running to the points) has a second wire with a ring connector. Anyone know where this goes?

- Damion

More updates.

The car was firing this evening with starting fluid. However, it sort of came and went - sometimes it would fire (and a few times it actually made a rotation or two) and at other times it didn't fire at all.

One thing I noticed - sometimes the tach would register around 800-900 rpm when the car was cranking, sometimes it would stay at zero.

It only fired when the tach was registering some rpms.

Is this a sign of something? Some weird electrical gremlin that could be the source of my problems, perhaps?

Time for some methodical troubleshooting. Record your results and seek guidance for each step if you need help analyzing the results.

1. Ignition:
Pull all 6 spark plugs, find a way to ground them all to the engine metal,
(wire them to each other and then to engine case with stranded copper wire wrapped around the threads works)
Pull your fuel pump relay.
Have someone crank the engine while you watch for a strong consistent spark from each plug.
Strong sparks means your ignition is working.
(this method eliminatesCDI, plugs, wires, cap, rotor etc from the equation)

Timing: TDC cylinder 1 on compression stroke and z1 mark lined up while rotor points to cylinder 1 and points open at correct time.

vacuum advance or retard: are the hoses to distributor routed correctly, if swapped accidentally you are advancing when you should be retarding and vice versa?

While you're there:
Compression test: check compression while spark plugs are out.

All above is good, move on to...

2. Fuel:
Install fuel pump relay, disconnect cold start injector wire,(you said you proved it works)
Pull injectors, put them in 6 jars and measure the volume of fuel is equal when cranking engine and is within specs as published in manual for your car. Observe spray pattern is good.
Fuel delivery equal and in spec, your fuel delivery is working.

Fuel and spark and compression good?

Next:

3. Have fuel and spark within normal range?
Possibly a vacuum leak.....
Pull your intake off the car as you have done a leak test that found nothing...
Pressure test the airbox with all devices removed, if that passes...Replace the cracked rubber boots on your intake runners that you mentioned earlier.
Replace injector o-rings,throttle body o-ring, cold start o-rings, and the injector guides/sleeves and o-rings, inspect/replace every air supply system hose and fitting and vacuum lines of the intake system while it's out.
Prove there are no leaks of any kind...Install new intake gaskets.

Then....

Put it all back together knowing everything is within spec. Should fire up.

In addition to excellent advice above, I had a 74 with intermittent spark that turned out to be wire from points to CDI. It was shorting to the shielding braid.

And you can unplug the extra wire that goes to tach(usually purple/black IIRC) to take it out of equation since if tach wire is grounding,........ no spark.

Okay... how do I determine whether the spark is "strong"?

In a perfect world I would have checked spark when the car was running so I would have something to compare, but I never did that...

I don't know if a picture of a strong spark would help or not... ?

Totally unrelated to this thread, but I'm researching some issues and noticed this statement. My pump(s) come on with the ignition, but you indicate this is not correct. When *should* they come on, and why would it be this way?

I have a 73 (or 73.5?) 911T. Other older cars I've dealt with (Jaguar) have FP on with ignition and like the Jag with the old points fired fuel pump, in the Porsche I can "hear" when pressure is built and thus the engine will start. I've never thought much of it because it was the same thing I was used to with the 1955 Jag, but if it is wrong perhaps I should add that to my "to do" list.

Thanks!

Your car, a 73, was designed for the pump to come on with the ignition--it's working as it should. The change came with later CIS that had an air flow sensor in the intake.

Thanks for clearing that up! I'm trying to make some general reliability improvements on my 73, and getting an overload of CIS stuff on here!

Again, the engine needs to run by spraying carb/brake cleaner continuously
before one changes focus from the ignition and other mechanical problems
to potential fuel system problems.

Bottom line: Too much mis-directed efforts!!!!!!!!!!!!!!

Including yours.....
 

In all the years that I have spent tinkering SC engines, I never used starting fluid to make the engine starts. I have been very successful in all my attempts by simply checking fuel pressures, injectors spray patterns, air/vacuum leaks/s, ignition timing and sparks. They are very easy to start even after a complete tear down. BTW, I use starting fluid for my lawn mower and snow blower both carburated systems.

When was the last time you work on SC engines? Bottom line.....people are doing guess-work troubleshooting. Test and verify. There is nothing difficult making a CIS engine come to life.

Here is my challenge: Give me an SC engine with decent compression and I'll make it run!!!!! If I fail to deliver my promise, I'll pay for the shipping costs (two-ways) or send the engine to above expert.

Tony

Strong spark is easily visible in bright sunshine, if you have to look for it then it is weak. Nice bright spark in the shade.
Hard to describe, if you have another good running engine, lawnmower, whatever, do the same test to get an idea of what you want to see.

Okay. I have strong spark, then.

The car is firing on starting fluid now... I think I may be getting somewhere.

Okay - question for everyone:

Does your tach move when you are cranking the car?

I'm noticing that the tach does not move when the battery is fully charged. However, once the voltage in the battery drops down (from continued cranking) the tach moves and shows around 1k rpm.

It also seems like the car only fires when the tach is registering RPM.

Does this mean anything to anyone? Or am I finally losing my mind?

Look at your wiring schematic to see where your tach signal is coming from. This is a big clue.
Tach signal if I remember correctly is from coil signal source. If coil is not firing, signal is not sent.
Others please correct me if I'm wrong, this is from memory of installing a tach on my '75 rabbit in 1980... :)
Coil faulty if I am correct, or signal from CDI intermittently bad? One or the other or both?
EDIT: Could be a wiring problem and not the devices.
Does your distributor have the famous "green wire" coming out of it ? (could be brown with age now)

My '78 tach signal comes from the "high tension ignition unit" (CDI in other words) so if it is the same, then I would suspect the CDI unit as not sending a consistant signal.

CDI signal or feedback signal from coil?

Loren is an expert in this arena, so I would ask for his opinion.