Intermittent Hard starting
02-07-2018, 09:35 PM
#1
Racer
Thread Starter
Intermittent Hard starting
Hi all
I have a 2003 c2 with approx 85k miles
sometimes I am having a hard start issue where the motor cranks over but won’t fire up for several seconds
when this is happening, I notice no bounce of the tach needle
when it starts fine (99% of the time), the tach needle bounces prior to firing up
i also have a 944 and the DME relay is a known issue, to where it’s recommended you keep a spare in your glove box
when the 944 DME is acting up, you have the same symptoms with no tach bounce.
could this be a DME relay issue? Is this also a known thing on 996’s
any help from the brain trust here is appreciated
I have a 2003 c2 with approx 85k miles
sometimes I am having a hard start issue where the motor cranks over but won’t fire up for several seconds
when this is happening, I notice no bounce of the tach needle
when it starts fine (99% of the time), the tach needle bounces prior to firing up
i also have a 944 and the DME relay is a known issue, to where it’s recommended you keep a spare in your glove box
when the 944 DME is acting up, you have the same symptoms with no tach bounce.
could this be a DME relay issue? Is this also a known thing on 996’s
any help from the brain trust here is appreciated
02-09-2018, 10:26 PM
#5
Burning Brakes
Ditto the CPS (either crank or camshaft, they're the same part no.) for such symptoms. When these fail (as on other Bosch systems such as on Porsche 951 or BMW E30), it's not the sensor itself, but rather the connector plug which attaches to another cable going to the Motronic. The exterior of the cable plug may look just fine, but the internal plastic bits crack and crumble with age and thermal cycles, so don't hold the three little wires properly, so one day she won't start due to poor continuity/loose bits inside. Wiggle the wires and see if that helps to isolate the problem. If you're careful removing the little metal clip holding the plug together and don't let the bits fall out, you can repair this plug with Crazy Glue. Otherwise, check with Lindsey Racing in Oklahoma City to see if they have $40 cps cables that are the exact same as used on BMW E30, etc. instead of paying the Porsche dealer ~$180 each...
Also spank the Motronic, in case it has a hairline crack which opens and closes with temperature changes. If that works, consider reflowing the solder joints with an $8 soldering pen from Harbor Freight. The ignition trigger is another prime suspect when this symptom appears on Bosch units on BMWs, most likely the same story with Porsche... Such ignition trigger can be replaced at DigiKey or Radio Shack, for about $4 each, get the number stencilled on your unit for comparison.
Another hard start issue may result from poor residual pressure in the fuel line, due to faulty internal check valve which fails to maintain internal pressure while you run into the supermarket or go to lunch. So, since pressure falls off quickly after shutdown, it takes more cranking on restart to build fuel pressure to start the car. A check valve inserted in the return line downstream of the fuel rail fixes this, and saves undue wear on starter and fuel pump.
Also spank the Motronic, in case it has a hairline crack which opens and closes with temperature changes. If that works, consider reflowing the solder joints with an $8 soldering pen from Harbor Freight. The ignition trigger is another prime suspect when this symptom appears on Bosch units on BMWs, most likely the same story with Porsche... Such ignition trigger can be replaced at DigiKey or Radio Shack, for about $4 each, get the number stencilled on your unit for comparison.
Another hard start issue may result from poor residual pressure in the fuel line, due to faulty internal check valve which fails to maintain internal pressure while you run into the supermarket or go to lunch. So, since pressure falls off quickly after shutdown, it takes more cranking on restart to build fuel pressure to start the car. A check valve inserted in the return line downstream of the fuel rail fixes this, and saves undue wear on starter and fuel pump.
