944 Turbo No Start / No Tach Bounce

[944tger]

Hi everyone,

yes this is yet another no start thread, but I promise I did all the command checks but seem to have a particular stubborn case. I have also read tons of threads on multiple forums but have yet to find the solution.

Here is the case:

1985 944 Turbo does crank but no start after recent engine out rebuild (hasn't run since). No tach bounce.

Here is what I tried, measured, replaced:

- Starter is brand new and turns over good
- reference sensor and speed sensor are both new and have been gapped to 0.8mm (multiple times)
- ohm reading at the sensor and at the DME plug are within spec for both
- getting slightly over 1V between PIN 8 and 27 when cranking
- DME relays is brand new, I tried two different ones and also tried jumping it
- Power is getting to the DME Plug and the DME relays
- Coil is getting 12V
- Fuel pump runs when DME relay is jumped
- Fuel arrives at the rail and also gets injected when cranking with the DME relay jumped

Probably forgetting some more things I tried, but basically did everything according to Clarcks Garage + everything else you commonly find on threads in different forums.

Does anyone have any other idea besides the DME computer itself? I have not checked that because I am struggling to find one to replace at the moment.

Any help is greatly appreciated!

[Monkey Wrench]

there is some info on Clarks garage that might help so I'd read over that first, you need to narrow things down..

I suggest putting a small watt tst lamp across the coil wires ( primary coil not the HV outut) - the two "prongs on the coil"

crank it and see if there is an ignition pulse, the lamp should flash while cranking.

if that's ok I'd jump to the injectors, pull the fuel rail out but leave it hooked up crank engine, be careful not to start a fire.. have an extinguisher handy , do it outside be careful this will spray raw fuel, so be prepared..

put a clean cloth under the fuel rail so you can see what amount of fuel ejected.

Just crank it a second or to and look to see if all the injectors are spraying fuel or not and if they shut off after key off..

If the ignition primary coil pulse is missing, or if the fuel isn't spraying then I'd look backwards into why that is..

there might be alternate troubleshooting routines, Id do that first to uncover whether you have those two.. You can go into finding out why that is and go more complex, like into troubleshooting the engine sensors, or looking for a dead fuel pump for example, but I think this should prove all the main component of either spark or fuel system as functional or not functional by looking closer to the end result, spark or fuel being missing.

If you dont like checking the coil that way, then you can tape the button down on a timing light and put it where you can see from the key, see if it flashes when cranking.. if it does you know you have ignition coil pulses.

If you feel that spraying raw fuel fron the injectors presents a safety hazard you can check fuel pressure, you can check the leakdown time( if fuel rail holds pressure) you can connect a node light to watch for it flashing to confirm injector pulses.

you can measure fuel output to see if you have enough fuel from the pump ( filter or tank not plugged ) - again working with raw fuel and the associated fire hazards.

you can remove plugs and put one in at a time and turn engine by hand to confirm you have compression or remove all the plugs and use a compression tester, write down the compression pressure of each of the 4 cylinders, compare to see if they are similar and if the compression is reasonable.. you can put a squirt of oil in each cylinder and redo the test to see if there is a difference with the rings being wet. write that down as a second set of numbers..

if you can define that one of the three is missing, compression spark or fuel, then you are closer to you are now.

[944 Ecology]

The KLR/ecu modifies the ignition signal from the DME/ecu before it gets to the ignition coil. The input is pin number 9 and the output is pin number 16. Try jumpering those two pins as a test. If it starts, then you have a bad KLR.

If you are in the USA, you can send me your DME and your KLR, and I will test them for you in my 951 for the cost of return shipping. PM me for details.

[azbanks]

I would say to check your coil and your plugs/plug wires but the lack of a tach bounce leads me to believe that they are not the issue.