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Hi,
I have an 86 944 turbo and was hoping for some help on this...
My understanding is that I should be hearing the electric pump turn on for about 30 seconds to cool down the turbo after shutting the car down? My fuses seem to all be OK - how do you suggest I go about troubleshooting this? Is there a spot I should be checking for voltage/current upon shutting down the car (which I am assuming would stay on for a specific period of time)? What voltage reading should I be getting?
Any guidance would be greatly appreciated!
Thanks!
There is a relay in the fuse box that controls that turbo pump. Check relay #22 on the top right corner (when viewed from above).
You can remove and check for voltage. You can also they bypass the relay and send power straight to the pump.
Odds are, the relay is stuck/bad. If not, the pump is either bad or has a bad contact.
Thanks for the info!
Would you know which points on the relay I should be measuring for voltage and when they are active? (12V??)
I'm not sure the best way to troubleshoot...is the pump always on when the car is running (in addition to the 30 sec shutdown period) or only when the car reaches a specific temperature?
Lastly, is there a test procedure for the relay?
Thanks!
Mike
Thanks again for the info and links. I read through them all and did the following tests...still not sure what the issue is.
Before I explain, I should mention that my turbo temp sensor is brand new, OEM part bought from the dealer and used about 100miles - so I am assuming the sensor is fine.
Here is what I tried:
When I disconnect the turbo sensor wire and ground it out, the pump turns on.
When I disconnect the wire to the pump and ground out the turbo sensor wire, I will get 12V when measuring the disconnected pump wire. This was expected, however, I kept it grounding out for about a minute and the voltage never dropped back to 0 as I was expecting? I was expecting the relay to shut down the voltage after 30sec.
After driving the car with the turbo sensor connected, but with the pump disconnected, I shut the car and immediately checked the voltage at the pump and it was showing 0.1-0.2V
It seems as though my turbo sensor is never grounding out the wire and therefore, never running the pump. If this is accurate, what would be causing that to occur?
I am on the fence if the relay is bad since it sent 12 V to the pump and made it operate when I manually shorted the temp sensor wire.
The turbo temp sensor wire looks like it has seen better days, but since it worked when I grounded it out, my gut says something is up with the actual sensor.
When I ground out my thermoswitch, I hear the pump motor circulating water. I kept it grounded for more than 30 seconds and it just keeps running. Would this confirm that the relay is the problem? If not, how do I go about testing the relay to confirm it is the problem? I opened the relay and all the solder joints look fine and coil seems perfect too - but didn't test the capacitors etc...
If you read the first link from Husteric you will see that the pump will run continuously if you ground the turbo sensor as this is the over temp condition which will continue until the temperature drops.
Back to the relay and its connections...
A quick test for the relay is to turn the ignition on without starting, then turn it off. The pump should run for 30 seconds. If not, the relay is 99 percent bad.
As CliveB states above, short the sensor circuit ti ground and the pump shoud run continuously, then, when you remove the ground the pump should stop.
Thanks all for the guidance! @931guru I tried the test mentioned above and nothing happened with the pump.
Although I am quite certain at this point that the issue is with the relay I would like to rule out the connections. How do I go about testing the connections and making sure the correct voltage is arriving at the relay?
Secondly, is there a way to test the internals of the relay to ensure that is the issue? Is there a common fail point on these relays that can potentially be fixed?
Thanks all for the guidance! @931guru I tried the test mentioned above and nothing happened with the pump.
Although I am quite certain at this point that the issue is with the relay I would like to rule out the connections. How do I go about testing the connections and making sure the correct voltage is arriving at the relay?
Secondly, is there a way to test the internals of the relay to ensure that is the issue? Is there a common fail point on these relays that can potentially be fixed?
Mike, a multimeter and a wiring diagram are your friends..
You can bench test most relays, but, since this has an electronic component, you may not be able to test the relay. Test the inputs to the relay first, then the outputs.
Hi all, just wanted to post an update in the event it helps someone else. After doing all the testing, my relay was the problem. Replacing the timer IC with a standard 555 timer IC solved the problem. Soldering the chip on is straightforward and took a few minutes. Thanks to everyone for helping out and credit to the creator of the following thread who figured out the replacement IC! http://forums.pelicanparts.com/porsc...mp-fixits.html
07-07-2022, 11:43 PM
Turbo - not cooling down when car is shut off
