Can cranking the engine with no spark flood the engine?
 

Simple question. I haven’t been able to start my car and I’ve cranked it quite a few times while diagnosing.

I know I’m getting fuel through the fuel lines into the MFI pump.

Is fuel accumulating inside the pump/ engine every time I crank the car?

Sorry for the stupid question but I’m a newbie.

Last thing I would want is blowing something up with a ton of fuel accumulation, and has me slightly concerned once it finally fires up

Yes, pull the spark plugs and take a look at them to see if they are wet. Leave out overnight to let fuel evaporate from the cylinders.
Also will contaminate the oil.
Watch YouTube to see how to check for spark using a plug held against the engine case.
Check your points are opening and closing.
From your PM, determining if you have spark is first on your list.

I picked up a spark plug tester light this afternoon.
I pulled the middle plug off the distributor and shoved the tester in there.
No light when cranking.
I also put the tester against the other end of the wire that comes off the coil and no light either.

I’m not entirely sure if I did this correctly.

I measured 12V on all of 3 fuses (both sides) in the back of the engine bay so there is power.

I’ll try to pull the spark plugs tomorrow. I’ve been dreading it because I’m terrified they’re going to break.

Does fuel accumulate in the cylinders pretty quickly?
I just changed the oil so I’d hate to have to change it again. (Not cheap)

You need to verify the basics. Fuel, air, spark.

Lots of threads on this topic.

*** edit *** just saw your other post. Sounds like you are getting fuel. As Timmy2 says, most likely ignition.

Open distributor and check your points to be sure they are opening and closing when you crank.

To get a spark to the spark plug in the engine. Several things need to happen. First, you need power to the CDI. Next you need to have a way to trigger the CDI (the points do this by opening and closing). Then the CDI will then send a pulse to the coil which will increase the voltage and send it through the high tension lead to the rotor and to the selected spark plug. You need to verify that each step in this chain is working.

1) Verify that the CDI is getting power.

2) Verify that the CDI is producing power to make a spark. You can do this with a "telegraph" test. Take the high tension lead off of the center of the distributor and put a spark plug on it. Ground the threaded part. With your plug attached to the center lead, open the distributor, remove the rotor, place your key in the run position, and manually open and close the points. Each time you cycle, you should see a spark from the plug. If you do not, you may have a bad CDI. Or Coil.

3) Verify that the coil gets a signal when you crank. Replace the rotor and distributor cap. Leave the plug on the center high tension lead. Crank the engine. Do you see a spark? If so, you are getting spark to the distributor. If not, your point gap may be off or there is some other problem with the connections.

4) Verify that the spark goes to the spark plug wires. Reattach the center lead to the distributor. Attach you spark plug to one of the leads going to the cylinder spark plugs and ground. Crank engine. If you see a spark you may have a timing problem. If no spark, you have a problem with your rotor or distributor cap or your wires are improperly seated.

Do a search here as there are many threads on this topic. Look especially for the ones by early_s_man. Warren (RIP) left a great deal of knowledge on troubleshooting this problem.

If you need to check fuel:

Is MFI pump belt still in place? Assume so if engine sputters.

Do you smell fuel in the tail pipe? If so, you got fuel. If not:

Pull sender and check for clean fuel tank. Possible fuel filter sock clogged and no fuel flow.

Pull fuel supply line after engine filter to MFI pump and check flow into catch bottle. This will verify fuel pump still working. Fuel pump should be always on with key. If you can, check flow into engine bay filter and out of filter into injection pump. This will isolate clogged filter.

I assume you grounded the other side of the tester.

Good

They should not break. If you have the factory tool kit, the sparkplug wrench they provide works great.

It can. As noted above pull the plugs and let the cylinders air out. FWIW, the cost of new oil is trivial to the cost of rebuilding your motor due to damaged bearings.

Do you know how to check points operation?
Can you confirm the CDI is working (permadoom)
Have you watched videos on how to use your spark tester?
This forum has tons of information on doing all the basic checks.
Start by learning how to use the advanced title search.
Click search this forum and then advanced search.
Look for posts from 10 years ago and further back by Early_S_man.
Read, read, read…
Here are some things to read:
https://forums.pelicanparts.com/search.php?searchid=23661676

Thank you for that info Harry.
I remember reading through that on another thread.
The only thing I do not understand from that write out is how to “manually close the points in the distributor”

I’m not entirely sure what this means or how to do it.

Im getting fuel yes, the cold start solenoid system is not working but shouldn’t keep the car from running.

I did not ground the spark plug tester light.
As @Timmy2 said, I should’ve done more reading on how to use it. I was just too excited to figure out if I was getting spark or not (lol)

I’ll redo the testing tomorrow and update.
I really appreciate your help and I apologize if I’m asking for questions that have already been answered.
I’ve been doing a TON of reading on this forum, but there are some terms that im not familiar with so it’s harder to understand.

It is all about how you ask the question. Demonstrating you’ve been researching and asking for more info or guidance will always get better responses. :)
Detailed photos of what you are asking about help a lot too.

Can cranking the engine with no spark flood the engine?
 

I do not know how to check the points of operation, or how to manually close the points. May need some guidance on that.

I got 12V from the middle pin of the CDI plug. I put the negative lead of the multimeter on the nut the CDI ground ribbon was hooked up to, so I believe it’s getting power.

Thanks for the feedback. This forum has been around for a long time so I’m still trying to get better at searching for specific topics to narrow the results.

Like I said earlier, I’ll redo the testing with the spark plug tester by using it correctly this time

You are welcome. We are here to help each other.

With the distributor cap off, after you pull off the rotor (just pull it up), you will see the points. Looks like this under the rotor:
http://forums.pelicanparts.com/uploa...1641281157.jpg

The thing on the bottom are the points. You can move them with your finger or a popsicle stick. To do the test, be sure the points are not on the high point of the lobe.

You will note the shaft in the middle. It has a lobe on it that is not round. The one shown has 4 high spots (it is for a 4 cylinder motor). Yours will have 6. When it turns, the high point of each lobe pushes the points open and once past, they close. This video is informative :https://youtu.be/BXkp9olrFWM

Lets be sure you are getting spark before addressing the cold start issue.

Timmy2 is very good. Just keep reading, and, listening and trying.

Not a problem. We were all newbies once and needed help. No dumb questions.

Also, add your location to your profile. You may have someone local who can help you.

I saw on one of your other threads that you may have a Permatune CDI unit. Permatunes do fail and this could also be your problem. Step 2 of the tests I listed above will help determine that.

Did the car ever run?

Good suggestion, I added more details to my profile.

Yes the car ran 2 years ago and died because of bad fuel (car sat for 10-15 years in climate controlled garage).
So I replaced all the hoses and the fuel tank.
But I heard it running for about 2 minutes before it died

You may need to flush and clean your entire fuel system. MFI cars do not like crap in the fuel.

As noted in the other post, focus on getting the car running. Then be sure you have brakes and steering.

While the folks at https://www.early911sregistry.org/forums/forum.php can be brutal at times, they have a wealth on information on early cars.

A common problem is that the fuel lines to the MFI Filter canister are improperly routed.

Check line routing against this picture:
http://forums.pelicanparts.com/uploa...1641331244.jpg

A quick diagnostic check is to crank the motor with the key on immediately after you (or, better, a helper) squirted some starter fluid (ether, typically) into the air intake. If the engine starts, or at least tries to, then dies, chances are you have spark, but have a fueling issue. If it doesn't do anything, then spark (ignition system) is first on the list.

Historically, in the days of carburetors, one always started with the ignition, as it was the most likely culprit. But both are part of the diagnostic tree.

Okay so here are my findings:

1) 12V on all 3 fuses (both sides)

2) Coil resistance is 0. (with multimeter, I put negative lead on negative nut, and positive lead on the nut the green wire attaches to.)

3) Checked resistance on CDI plug between pins 7 (red) and pin 31d (green wire).
With multimeter:
I put positive lead on 7 and negative lead on ground. Resistance WAS ZERO
I put positive lead on 31d and negative lead on ground. Resistance WAS ZERO
I put positive lead on 31d and negative lead on pin 7. Resistance WAS ZERO
I think this means the green wire is bad because it is supposed to be around 600 ohms. Please correct me if I'm wrong.

4) No spark at the lead wire from the coil. I attached sparkplug tester light to end of lead wire with an alligator clip, then grounded the other end of tester to the chassis.
No light when cranking.

5) Got 12 Volts at CDI box plug. (with multimeter, I put positive in pin 7 (red wire) and grounded the negative)

In conclusion, does it sound like the green wire that runs from the coil to the CDI box is bad?
Please advise.

Confused. How many pins does your CDI box have? 3 or 8? Does your distributor have points or an electronic pick up? Please post pictures.

The resistance between the two studs on your coil (low voltage side) should be around 0.7 Ohms. On the secondary side around 6000 ohms.

Be sure your multimeter is ranged correctly.

Can cranking the engine with no spark flood the engine?
 

3 pins, and the distributor has points.

I edited my original reply if you would like to re-read it

https://uploads.tapatalk-cdn.com/202...2e3d202cd9.jpg

https://uploads.tapatalk-cdn.com/202...402485ecd0.jpg

Got about 1.2 K ohms, which should be about 1200 ohms checking secondary
https://uploads.tapatalk-cdn.com/202...d1c4b4ec34.jpg

so maybe the coil is bad. 1.2k ohms seems really low if it's supposed to be 6,000 ohms

OK. Based on the two recent reports.

I checked my known good spare coil. 6 ohms between the two studs and 700 between the center and either stud.

Your numbers are for a 6 pin CDI. This is how a 3 pin one is wired:

http://forums.pelicanparts.com/uploa...1641355984.jpg

With the plug pulled from the CDI box, key on, you will have 12 v at the center (red) terminal.

On one side of the plug is a wire to the primary terminal of the coil.

On the other side of the plug is a wire to the points in the distributor.

Lastly, there is a braided ground.

This is the troubleshooting advice from Permatune for the box itself.

http://forums.pelicanparts.com/uploa...1641355938.jpg

Also, When you test your coil resistance, disconnect all there connections to test the coil itself.

Ok here it goes.
With key on (fuel pump running)
From that diagram:

A to B

https://uploads.tapatalk-cdn.com/202...6d1f3e7da2.jpg

C(green wire) to ground

https://uploads.tapatalk-cdn.com/202...e602499437.jpg

D to B
https://uploads.tapatalk-cdn.com/202...b5bda6ce19.jpg


mounting flange to pin D : Zero

You are supposed to check the terminals on the permatune box, not the harness that connects to it….

Your readings do not make sense. On the connectors, you are checking for continuity end to end.

Test 1-Measure voltage in center pin. Key on should be 12v
trun key off.
Test 2-Measure resistance from Pin A to ungrounded wire on coil (remove wire from coil). should read about 0 ohms.
Test 3-Measure resistance from Pin C to lead connected to points (remove wire from points connector). Should read about 0 ohms.

These three tests will verify power to the permatune box and continuity to the coil and distributor.

Do the tests listed on the Permatune sheet posted above to check Permatune unit.

Round 2. I really appreciate the patience, but I’m learning a lot.
Test 1: https://uploads.tapatalk-cdn.com/202...61e7cb6207.jpg


Test 2:
https://uploads.tapatalk-cdn.com/202...258f028d20.jpg


Test3:

https://uploads.tapatalk-cdn.com/202...a875947a4f.jpg


Secondary on Coil with key off shows 1.6 kohms (1600 ohms). Not good

Did I get it right this time?

Looks good. Did you do the tests on the Permatune box?

Secondary coil resistance looks high. Did you measure directly on the coil? Or did you use the center lead? What is the resistance of the primary side?

Can cranking the engine with no spark flood the engine?
 

From permatune tests:

Pin A to D: 3375 ohms
Pin B to C: 99.2 ohms
Pin D to Mounting flange: 0
Pin D to pin B: see pic. Not sure if this is right:
https://uploads.tapatalk-cdn.com/202...1c9e9e0258.jpg


Primary side of coil is 0.5 ohms
Secondary is 0.6 kohms so 600 ohms from inside the coil to ground

Looks like all appears ok. Making progress.

Next steps are to reattach everything. Go to post 4 and start at step 2. Report findings.

Please post a picture of your distributor internals with the cap and rotor removed.

If you have a helper, with cap and rotor off, have them crank car and see if points are opening and closing.

Harry, I couldn’t thank you enough for all the help.
I’ll take the rotor apart tomorrow and will update with the results

No, the cylinder will not fill with gasoline. There is less than a 'drop' of vaporized (not liquid) fuel in a cylinder when the engine is being cranked. If this mixture of fuel vapor and air is not ignited, it is expelled by the exhaust stroke of the piston into the exhaust system.

I see progress on your troubleshooting and your confidence already! Keep at it.

You can use a timing light to check for spark in one fell swoop without taking anything apart. If you do find you have spark, no need to fiddle with points and coils and plugs and CDI boxes. If you don't have spark, no need to mess with fuel questions until you do.

Also, I don't think the fuses in the back do anything for engine running. Rear defrost and heater blower for SCs, if I recall correctly.

And, Alex12 answered your original question, no you don't need to worry about your cylinders filling with fuel. I wouldn't take the plugs out.

Maybe I missed it, but what year 911 are we talking about? Put that in your sig and you'll make life just that much easier.

72 mfi

@Winter911

I don't want to be killjoy, but it seems that you're new to car electrics. Please be aware because of the high voltages coming out of the CDI up to 500 volts, these are life dangerous!! Those voltages going into the coil and will be transformed up to 40.000volts! If you do not know what you're doing, please go to a shop!

Nevertheless - one question: Is it possible that one ignition wire dropped of the spark plug while cranking? In that case the spark cannot flow off against ground and instead hits back into the CDI box, already the first spark will destroy the CDI box! So this happened accidentially to mine as well and the box died immediately...

Thomas

Can cranking the engine with no spark flood the engine?
 

EDITED:

Okay here are my findings. TLDR, GOT SPARK

Grounded the spark plug threads to a bolt on the chassis and attached other end of spark plug to lead wire off the coil using alligator clips.
I tested the spark plug and it’s working fine.
With key on, I pushed the “arm” with a piece of wood to close the points (is this right?)

Cranked the motor to see if the points were closing and the arm seemed to be moving.
Spark plug also sparked when cranking motor

https://uploads.tapatalk-cdn.com/202...8335e7e88d.jpg
https://uploads.tapatalk-cdn.com/202...3470b9bc61.jpg

https://uploads.tapatalk-cdn.com/202...11f38e6972.jpg

Great news. Next is steps 3 and 4. Be sure spark is getting to the plugs.

Also for ga-ha’s check for continuity between the motor ad the car chassis. Just checking that the motor has its ground strap intact.

If 3&4 is successful, As Walt Fricke suggested a shot of starting fluid when you crank Will verify if you got spark.

Got spark at plugs.
I’ll get some starting fluid this afternoon.
I’m starting to think fuel might be a problem.