crankshaft position sensor
05-10-2014, 01:31 PM
#1
4th Gear
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crankshaft position sensor
Anyone have any problems with a crankshaft position sensor? I have checked the fuses and relays in my 1985 928s. All of which are good. It will crank but not start. I am thinking it is the crankshaft position sensor but wanted to check to see if anyone else had to replace theirs and if it fixed the
problem before I spend the money to buy one. Thanks for any help.
1985 red 5 speed
problem before I spend the money to buy one. Thanks for any help.
1985 red 5 speed
05-10-2014, 01:50 PM
#2
Nordschleife Master
Before I would look at the CPS, I would look for a more common culprit on the fuel side. You crank, but won't fire. When you turn on ignition can you hear fuel pump operating ? If not, you can 'jump' the fuel pump relay (XX - 20) by bridging the 87 and 30 leads. If you get fuel and hence some form of ignition you know the relay was not supplying current to the pump. This is a starting point before jumping down the line.
05-10-2014, 02:49 PM
#3
Failures of the CPS are common, mostly due to age.
05-10-2014, 03:41 PM
#4
Chronic Tool Dropper
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And it seems the connector is a very common failure point, followed by the wiring to the sensor.
Does the tach bounce when you crank the starter? It triggers off the CPS IIRC. That also triggers the fuel pump circuit, so there's a little bit of sleuthing for you to do.
Does the tach bounce when you crank the starter? It triggers off the CPS IIRC. That also triggers the fuel pump circuit, so there's a little bit of sleuthing for you to do.
05-11-2014, 03:19 AM
#6
Drifting
hmmm, may be that is part of my issue, I will driving and then the tach with bounce and engine die, attempt to restart and the tach will bounce a couple of times, spit and sputter and then start to run...really wierd.....
05-11-2014, 12:18 PM
#7
Rennlist Member
Could be a number of issues. I would start by jumping the LH and EFF relays. It is unlikely that it is the LH relay as it shouldn't have as direct an effect on the tach, so I'd start with the EZF relay.
I fought with a similar problem on my 85 for quite some time. I'd gone through all relays, power and ground connections, with ultimately no success. I finally had it running (idling) at the house an reached over and smacked the LH computer, at which point it promptly died. Turned out to be a bad solder joint in the board of the LH where the 25 pin connects. You may want to try wiggling the LH harness connector with it running and see if it has any effect. I opened the LH and re-wet 4 or 5 suspect joints, which seems to have cured my issues.
I fought with a similar problem on my 85 for quite some time. I'd gone through all relays, power and ground connections, with ultimately no success. I finally had it running (idling) at the house an reached over and smacked the LH computer, at which point it promptly died. Turned out to be a bad solder joint in the board of the LH where the 25 pin connects. You may want to try wiggling the LH harness connector with it running and see if it has any effect. I opened the LH and re-wet 4 or 5 suspect joints, which seems to have cured my issues.