Why won't my engine run??

[MMe025]

Hi,

I am having a problem getting my project 85 911 engine started. I have never heard the engine run before however I was assured by seller (a larger company) that it was rebuilt shortly before the car was t-boned and was in running condition when removed from the vehicle.
It was modified with a 3.3 liter crank before it came out of the last vehicle.
Assuming that to be true, I have performed the following checks:
· Fuel pressure is 38PSI. Fuel pressure remains when engine is shut off.
· Compression on all cylinders is between 155 to 160PSI
· I set the distributor timing by removing the intake cam cover, set the crank to Z1 and verified that the lifter can be moved slightly (not in overlap). I then installed the distributor with the finger lined up with the mark in the housing. By the way, I switched it 180 for *****s and giggles.
· I removed the fuel rail and put the injectors in bottles. Spay pattern looked good.
· I checked for spark on all cylinder (cap, rotor and cables are new). Present. All cables ohm out to 4K.
· This is a counter clockwise distributor. Cable are in the correct order 1-6-2-4-3-5
· I drained and replaced fuel with fresh gas.
· I would think that I should at least get a puff or something that resembles an ignition but..... NOTHING.
I am baffled because of the very simple principal of Suck, Squeeze, Bang, Blow.
I have spark.
I have fuel.
The timing should be on (allot of suck, squeezing and blowing).
So where is my BANG

Perhaps someone has some suggestions.
Some additional questions:
· If there is an air leak say from a disconnected vacuum hose, should the engine still start? At least sputter?
· I have tried spraying ether in the intake and still nothing. Could it be that my spark is simply not strong enough?
· Could a defective sensor cause the DME add or take away too much fuel for an incorrect mixture? If so, other than the engine temp sensor and the head temp sensor (new), what could it be? What values should you see on a cold engine (65 degrees F.)?

I would really hate to take the engine out and tear it down to recheck timing. Any thoughts of something I may have missed would be greatly appreciated.

I hope to figure this out before I end up T-boning this engine.
Matt

[AFJuvat]

NOt 100% sure what you mean by setting distributor timing with your finger. The rotor should line up with a notch or line on the housing when pointing at TDC #1.

Few other things to check.

Make sure your wiring harnesses are all connected correctly. Those two black plugs above #3 cylinder are not interchangable, if the engine cranks but will not start, try switching the plugs.

Behind #3, there is a plug on the back firewall, make sure it is plugged in.

Is your speed sensor gapped properly? (0.8mm) If the speed sensor is gapped properly, the reference sensor will already be at the proper spacing.

Check wiring harness at left side of engine compartment for proper connection

Same with grounds above #1 Intake

Is your DME\Fuelpump relay good?

Ground strap from transmission to chassis connected?

Are you sure the injectors are actually firing?

AFJuvat

[gduke]

Check spark plugs for spark, check coils. Sounds like it could be igition if tf there's plenty of fuel pres.

[MMe025]

I appreciate the responses!!

I have spark (when engine is cranked).
I have fuel. (pressure and spray patterns good and fires when the engine is cranked)

Question on what AFJuvat said...
Would you still get spark if.....
- If the plugs on the left side were switched?
- If the plug at the #3 firewall (head temp sensor) were unplugged?
- If the gap were too large on the reference senor?

My guess would be no in all cases however I am not sure....

Thanks again... Matt

P.S. When I described distributor timing above, the finger I was referring to is the distributor rotor.

[AFJuvat]

You Should get spark on all of them - however the DME will not "start" the engine.

Head temp sensor must be plugged in or DME will richen the fuel mix - DME may not "start" then engine Head temp is the white plug

Spark plugs incorrectly set - you will get spark, but the motor will run like garbage.

Speed sensor gapped incorrectly - motor will crank but will not start.

Speed and referense sensors plugged in wrong (i.e speed sensor plugged into referense sensor harness) - engine will crank, but will not start. Speed and refernnce sensors are the two black plugs below the whead temp plug.

4 prong plug on firewall behind #3 - engine will crank but not start - injectors will not open.

AFJuvat

[aigel]

I just wanted to add, that if you have a big a$$ vacuum leak, the engine will not even puff. The CIS is quite a bit different, but a good example: My toilet seat (pop off valve) stays open sometimes when it backfires on a cold morning. It is because it was installed 180 degrees rotated and hangs op open on the air filter... anyway, with the pop off valve open, the car won't even bog. While I think the 3.2 motronic doesn't rely as heavily on a working intake vacuum, I am positive it still won't even puff if you have a big vacuum leak.

FI ist great when it works. If not, oh well...

Good Luck. I think you have done a great job troubleshooting and there isn't much that I can add. I'd check all electrical connections (again) and vacuum connections. Do you have a friend with a similar engine that can come over so you can put them next to each other and follow every lead on the system? That often helps!

George

[MMe025]

Is there a good way of testing the Head temp sensor?

It seems to me that this is the best direction to go in because of the rich mixture.

To expand on that, I do not have an O2 sensor in the car. Would that cause the engine to run richer right away?

The plugs are new but I will check the gap anyway.

One further question. There are several marks on the pulley. I know what Z1 (TDC Cylinder 1) means. Do you know what the "FE" mark and the "30/35" marks mean?

"Es ist nicht wie schnell man fahrt sondern ab der Motor startet vor den Rennen"

Noch mal vielen Dank!! Matt

[aigel]

Es ist nicht wie schnell man faehrt, sondern ob der Motor startet, vor dem Rennen

[ChrisBennet]

Originally posted by MMe025
Is there a good way of testing the Head temp sensor?

It seems to me that this is the best direction to go in because of the rich mixture.

The head temp sensor has a resistance of around 3000ohm cold and 300 ohms hot. You can use a a 2.2-3.3K ohm resistor to temporarily replace the sensor, if it starts and runs fine you'll know the sensor was at fault. (Bend the leads of the resistor back on themselves and shove them in the female connector. Put a bit of tape over it to hold it in place.)
As the car warms up it will be too rich with this setup so switch to a smaller resistance if you want to keep testing with a warm motor.
The head temp sensor is the one with the white connector in the gang of 3.
-Chris

[84toy]

Hook up a timing light while you are trying to crank it over and confirm that it is firing about TDC. This will at least confirm that the sensor has picked up and the ignition is firing at the correct location.

[power]

Originally posted by AFJuvat

Speed sensor gapped incorrectly - motor will crank but will not start.

Speed and referense sensors plugged in wrong (i.e speed sensor plugged into referense sensor harness) - engine will crank, but will not start. Speed and refernnce sensors are the two black plugs below the whead temp plug.
AFJuvat

This gets my vote.

I don't have a Porsche with Bosch DME so I am only guessing, but I have a BMW with almost same Bosch DME. I had very similar experiecnce to what you describe after I did some work on the transmission. Of course I knew I had removed the speed and reference sensors so it was easier for me to trace. Now knowing that these have to be lined up correctly to start the car I would always check them first if you already have spark, fuel, timing.

[MMe025]

Thank you all again for your suggestions.
I spent the entire day today checking that all connectors are correctly plugged in and Ohmed the wires to the DME for proper routing. In addition to that, I removed the intake and the exhaust to check for air leaks. I checked and double checked that everything is properly connected. When I removed the cat, there was an excessive amount of fuel present. I am sure this was caused from the multiple times I was cranking the engine.
The head temp sensor has 3KOhms.
Just for kicks, I switched the 2 black connectors (speed and reference) on the left side of the engine. I do not get spark when they are switched.
After removing the intake and exhaust, I also removed the spark plugs to clean them off and blew compressed air in the cylinders to blow-out and residual gases.

This may not be the best test but I disconnected the injectors and sprayed ether in the engine to see if I at least get a sputter.....still nothing!!

Here are my thoughts:
1. Although I do have a spark, I am not convinced that it is strong enough. Any thoughts on how to test the intensity of the spark. (gaps are correct).
2. Whoever set up the engine did it incorrectly. (I really don’t want to take the engine out again)
3. For whatever reason I am getting way too much fuel. ???

Matt

[84toy]

From your first message it sounds like you have done some spark plug wire work. Are you sure the distributer is in the correct spot and that the #1 cylinder is on the compression stroke and not the exhaust stroke? I don't know anything about a counterclockwise distributer but mine is clockwise if I recall.

Also, recheck the big wiring plug on the firewall behind the manifold. Pull it off and double check it. Mine would not start for 2 weeks because of a plug problem there