emaxxowns

Hey guys, been reading around here and i just have a question as i bought a 944 that seems to be some electrical issue causing it not to start. when i use a multimeter to check the resistance on the sensors themselves i get good readings, but when i try to measure it from where the DME is on the wiring harness, i dont seem to get any readings really. would this indicate that the wiring harness is at fault somehow? if i need to replace that do i just pull it up through the engine bay?

emaxxowns

i've actually since looked at the connectors on the harness side and it appears the one for the speed sensor was not getting a good connection as it pulled off from the wires with little effort. i can solder them back into place with heat shrink, does anybody know the which color cables go to which pins?

peanut

do you have a workshop manual ? there should be electrical diagrams on the forum somewhere if you do a search

alternatively do a Google search for 944 electrical diagrams and you'll find loads to download
https://www.pelicanparts.com/944/ele...l_diagrams.htm

emaxxowns

so i replaced my reference sensor harness with one from lindsey racing after seeing the previous one was damaged. the car started after that but ran really rough and i turned it off and it hasnt been able to start since. i checked the sensors again and they read good at the sensor and at the dme at about 900 ohms. i checked for spark at the plugs and got nothing, checked at the coil and also got nothing so that explains but it wont start and probably why it was rough before, any ideas what else could be the issue now?

peanut

When you crank the engine ....do you see a tiny bounce of the rev counter needle as it is cranking ? Its very small about 1/4" or less but you should see it .

If you have no spark when cranking then the problem probably lies with the DME relay. Ignition spark comes from the ECU which is powered by the DME relay .

Replace the DME relay with a 3x wire bypass joining DME relay base terminals terminals 87, 87b and 30 and see if the engine starts.
For bypass seePelican Parts
https://www.pelicanparts.com/techart...leshooting.htm

emaxxowns

i will try that as soon as i can, also i do not have tach bounce, i should have specified that earlier. thank you for the reply

emaxxowns

so i got my dme relay in the mail today and it turns out there wasnt even a dme in the fusebox to begin with, which is odd because that would mean that i got it to start without a dme relay at all about a week ago. with the new relay in, still no start, still no tach bounce. pins 25 and 26, and 27 and 8 are reading about 950 ohms each so i dont think that would be an issue. any other ideas?

peanut

yes ... see my suggestion post #5 have you tried a 3x wire bypass yet ?

emaxxowns

i tried the 3 wire bypass using 14 gauge wire and same thing, still no tach bounce as well

emaxxowns

i tried to bypass the alarm to see if that may be an issue but that one looks like it can be ruled out also. what options would seem to make sense that it was able to start once once before and once after changing the harness? bad sensor even though the resistance is reading good? is it worth getting a coil/ignition switch/dme to see if it may be one of those?

boerge

Does your car have the ignition module at the headlights, like the S2 has?

emaxxowns

it appears that it does not, that looks to be integrated into the dme for my year car

peanut

Fitting the 3x wire bypass in place of the DME relay should power your fuel pump ECU and injectors etc.

Do you hear the fuel pump running with the 3x wire bypass fitted and the ignition off. ?
Tell us which terminal numbers you are connecting on the DME relay base with the bypass. Its amazing how many get the connections wrong

emaxxowns

i do hear the fuel pump running when i use the bypass with ignition off, i am connecting terminals 87 87b and 30.

peanut

if you still have no tach needle bounce then that has to be the first thing to tackle.
Its a very tiny movement of the tach needle. You have to look closely to see it ...probably around 1/8"
The ECU will not function until it sees 200+rpm cranking speed from the crank speed sensor. (CSS) so you'll get no spark or fuel.

Make sure that your engine cranking speed is more than 200rpm.... Crank the engine and time the revolutions over 5 seconds and multiply by 12 should give you a good idea.

I believe that you have tested the speed sensor and the resistance is within spec.

Are you certain that you wired the replacement sensor wires the right way round ?