Jshprd

Hey peoples,

So i recently replaced my clutch and flywheel on my 1985.5 944 NA after my stock clutch pretty much the teeth or fingers on the clutch fell off. so i bought a replacement SACH brand clutch and flywheel ( had to replace the flywheel the broken clutch scored and damaged the flywheel) Im a DIY dude and began the process not know how lengthy and tedious this replacement is. its not for the faint of heart but i guess if you got this car you should know what your getting yourself into. After 3 weekends of work and making sure i torque everything down to spec the moment of truth comes. I set the car to TDC, made sure the speed and ref sensors are in place and in the right order, plug the battery up. When i turn the ignition the car cranks but doesnt start. I checked and made sure the sensors where in the right order check to see if i missed anything but again crank and no start. One time it turned on for about 30 seconds then the car died out. im at a lost cause all the part ive bought for this car are brand new and replaced. im not sure what it could i wanna say it come be the spark plugs and change those but i havent driven the car far or put some heavy mile on it? Could the sensors have gone bad? IDK what to do and any help would be greatly appreciated.

Van

The ref sensor set screw is in the flywheel?

Does the tach bounce?

Does it have fuel?

Why did you set the engine to TDC? Did you do something with the timing belts?

odonnell

PerryB

Wow, it's deja vu all over again!!

I strongly suggest that you adopt a methodical, step-by-step approach using the factory diagnosis procedure. Get a digital volt-ohm meter and test the various sensors and components as called for in the Porsche factory service manual.

Good Luck!

Perry

Jshprd

Van - I dont notice a tach bounce and it has about half a tank of gas. I set it to TDC to be safe to make sure it was at full reset when i finish the job.

Van

Tach bounce is an indicator that the DME is receiving an RPM pulse from the speed sensor.

If the DME doesn't receive a speed signal, it won't turn on the fuel pump or fire the spark plugs.

Jshprd

So the issue could rely on a bad DME relay?

Van

It's possible. But it's more likely that it's related to the items you actually touched while changing the clutch.

Think Occam's Razor.

Jshprd

okay imma check out the sensors first cause those had to be removed when installing the clutch. ill try gaping them too if this solves the issue. Thanks

divil

Here's a bit of info that might help: the DME relay has 2 relays inside it. One powers the fuel pump, the other powers the DME, idle stabilizer, injectors, and on turbo cars, the KLR. If that one isn't working, then you get no power the DME and therefore no tach bounce. However all you have to do to verify that is pull the DME connector and check with a volt meter. If you have battery voltage at pin 35, then that part of the relay must be working and it can't be the cause of no tach bounce.

Jshprd

Update -

I checked the DME relay and test out fine got new sensors and still doesnt start but i feel im getting close because now the tach jumps to 7k rpm then bounces around 2-3k rpm but still no start. And i went back and checked all the steps needed to change the clutch and flywheel.

odonnell

That's not normal, it sounds like a dme issue, it's not correctly interpreting the speed sensor signal into a digital waveform.

Van

Take a spark plug out and with it wired up, ground it on the engine and verify it's sparking.

If you have spark, I'd pull the fuel rail, with injectors connected, and turn the key to start the engine - if you see puffs of fuel, then that's good too. (don't worry, you won't blow up)