3.2 911 not starting
 

I know there have been many threads on this and I have read lots of them but I am still not able to figure my car out.

Ran fine 2 weeks ago. Was going to drive it yesterday and it started to start for about 1 sec then died. Since that initial start attempt it does nothing but crank.

Battery voltage is good.

38psi when I testing at the driver side fuel rail.

At least spark plug 1 is getting spark with a spark tester

Idle control is humming

Pin 87 of the DME relay do show good voltage with the key on.

Pin 87b show good voltage under while cranking. (jumped out pin and can hear the full pump running)

Metered resistance on the 2 black plugs on drivers side intake manifold. From my reading these are the reference and crank position sensors. Both metered at 996 ohms.

Car cranks fine but never sputters or does anything other than make the garage smell like gas.

I have not pulled a plug yet to see if they are wet. Going to do that soon.

Please show me the error in my ways or what I am missing. And of course what I should check next if I haven't missed anything obvious.

Thank you.
Foster

Check head temp sensor. If it goes open, engine will run very rich to the point of flooding and not running (and will smell like gas).

Start with basics: Compression, fuel, spark.

Compression: Assume that's good because the car ran fine until 2 weeks ago, and suddenly had this problem. Loss of compression is not an instant problem, nor does it affect all cylinders at the same time.

First test: Spray starter fluid in the intake. See if it fires. If it does, and then dies, that indicates you have spark but loss of fuel to the injectors, or injectors not operating. I know you used a spark tester, so you "should" have spark. If so, then it "should" fire on starting spray.

Fuel. If it doesn't fire on starting fluid, pull a spark plug and see if it's wet. If so, then it may have flooded. Often, just removing the plugs and cranking the engine will clear it (Disconnect the two wires to the coil when cranking without the spark plugs installed).

Spark: Pull a spark plug and connect it to its wire and against the engine or other ground. Have someone crank the engine while you check that it is sparking regularly. if you have consistent spark and it's still not firing, try the starting spray again.

Even if the engine is not firing, you should not smell fuel in the garage. That shouldn't happen in normal starting. That makes me think the engine was flooded. If so, then you will have to figure out why.

Report your results. Then we can narrow down the possible sources of the problem.

I had the same problem you did. I went through the whole gamut of diagnoses, and got to the point where it seemed that the Motronic unit was the culprit. Sent it off to Scarceller and he confirmed that the soldering had failed at multiple points. He fixed the issues, upgraded my 24-pin to 28-pin, and the car is now running like nothing ever happened.

I appreciate the post as I was just going to start one on the same subject. Don't mean to hijack the original post from flee27. Ran fine a week ago, battery is good and the engine cranks, but will not fire. No gas smell whatsoever.

Will go the starting fluid route. I have an aftermarket intake with cone filter ..... remove the filter and spray right into the intake while cranking?

Typical no-spark, three bad connections on the coil-driver TO-3, a simple three minute repair!

Yes, remove the filter and spray into the intake. If the filter is a paper filter, you can spray the filter. If it's something like a K&N oil/gauze unit, spraying the filter will flush off the oil.

Thank you all for the suggestions. I have been out of town for the past 3 weeks. back now and ready to figure this out. Recap of the problem. Drove car one weekend and everything was good. Next weekend no start. Engine turns over fine without any odd noises. Zero indication of trying to actually run. No pops, sputters, changes in rpm while starting.

Today I have confirmed I have good spark with a spark plug tester and with the plugs pulled and grounded. Very bright and consistent spark.

I don't think I am getting fuel but do have fuel pressure at the rail. All plugs were dry when pulled after some failed starting attempts.

Where I am confused is after pulling the air filter and spraying starter fluid into the intake I get nothing. Not a sputter. I have compression, tested with compression tester and did a leak down test again this morning. Also verified distributor cap and button look good.

I feel like I am over looking something simple and hoping those with more experience can help. Battery is charged and even hooked up a jump box to ensure voltage stays up during my testing. How could I have spark and compression and get nothing with starter fluid? Not possible right.

Thanks for the help,
Foster

Take the AFM off the intake and make sure no one built a home in there.

You have spark and fuel pressure, but not firing when starter fluid is used. Air flow is the last ingredient.

Before that however, clean that stack of grounds that attach to the left side of the intake manifold.

air passage is good. added fuel directly to #3 cylinder and still no hint of firing off. But have spark. Wondering about timing of spark...

Tested reference and speed sensor at DME.

Speed, pins 8 & 27-2.19 volts ac, 1.009k ohms
reference, pins 25 & 26- .39 volts ac, 1.009k ohms

From my research shows these are good. The hunt continues.

Foster

The speed & ref sensors may have gotten reversed, e.g. a timing problem?
Check the distributor rotor.

mysocal911. I did swap the 2 plugs in the engine bay early today just in case. (even though nothing was done to the car from running one week to not running the next).

rotor button and cap look good.

I know I keep saying that I have checked the various things and they check out but obviously something is wrong. So I appreciate all the suggestions and will double check all things.

Starting to wonder if the DME could have a problem. With compression, spark, air, fuel ( I introduced) Is should get something. Could a problem with the DME make the spark timing wrong? Is there a way to verify the spark is happening at the right time?

Thanks again everyone for the help.
Foster

I would test the fuel pump. Mine went bad, and I chased ghosts for several weeks (all the ones you've already checked) before I tested the pump and discovered that's all it was. You can wire up a switch to the DME plug under the driver's seat that will let you power the pump while the car is off. If you can't hear it running, there's your problem. I know you said you have pressure, but I would think the system can hold some pressure regardless of whether the pump is working. Here's how to make and hook up a test switch:

http://forums.pelicanparts.com/porsche-911-technical-forum/916075-broken-down-near-pt-reyes-ca-2.html#post9139291

Tested and passed

Use a timing light and check cyl #1 while cranking for TDC.

Please clarify. Looking into the engine on the left side rear there is a mount for 3 plugs. These are the cylinder head temp, TDC, crank speed sensors. The side of the harness that has all 3 sensor leads going into one harness is the DME side. The lead pointing towards the middle of the engine are the sensor sides.

Metering the CHT sensor it shows open. I do have 2 pins in that plug. I metered between the 2 pins and each to ground. All readings show open. This would indicate the CHT sensor is bad correct?

Form research some say this can cause a no start situation. Fingers crossed.

Best
Foster

it should not be open, it’s a thermistor inside. The resistance values are in the shop manual.
if you want to see some pics from when I replaced mine, they’re here: (so you can make newer and better mistakes!). https://www.joepampel.com/post/replace-your-cylinder-head-temperature-sensor

Looks like my no start issue is the cylinder head temp sensor. This evening I jump a resistor (1800 ohms) across the pins and the car started immediately. I have ordered the new sensor and will install it in a few days.

Thanks for all the opinions and suggestions.

Best
Foster

As zuch said to check.

Write that one down guys, I'm never right :-)