SAI pump starting while driving?
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Mudding
Joined: Mar 2015
Posts: 133
Likes: 12
From: Nova-Scotia, Canada
SAI pump starting while driving?
Good morning, quick question, not a major issue but I started noticing the SAI pump starts sometimes after startup. It seems even after driving a good 20 minutes, it will sometimes kick in at idle. Is this normal? It didn't do that before... no CEL and no other issues.
Thanks
David
Thanks
David
Camel Trophy
Joined: May 2016
Posts: 3,969
Likes: 859
From: Britainistan, UK
Mine does that too. The engine control module cycles the SAI pump on & off depending on emissions output during cold weather.
Google exothermic reaction.
Google exothermic reaction.
Last edited by JUKE179r; Mar 22, 2019 at 08:54 AM.
makes me feel better. I was wondering how it could figure that it needed to run the SAI after a while driving... cats cooling down somehow? weird.
Mudding
Joined: Jun 2017
Posts: 150
Likes: 13
From: Colorado Springs, CO
Happens to me in winter often. My deduction is the difference in the temp at the intake manifold and the temp at the bottom output sensor of the radiator.
TReK
Joined: May 2011
Posts: 2,768
Likes: 396
From: kitchener, canada
Anyone know what parameters makes the sai run ?
Sometimes mine comes on when driving
sometimes it comes on on the first start of the day sometimes not. It’s weird
is it based on the o2 sensors
Sometimes mine comes on when driving
sometimes it comes on on the first start of the day sometimes not. It’s weird
is it based on the o2 sensors
Pro Wrench
Joined: Apr 2018
Posts: 1,516
Likes: 442
From: SE PA
I suspect there's a problem with the SAI pump relay. Here's what the RAVE has to say.
The ECM checks the engine coolant temperature when the engine is started in addition to checking the elapsed time since the last engine start. The engine coolant temperature must be below 55°C (131°F) and the ambient temperature above 8°C (46°F) for the SAI pump to run.
There's no way your coolant is getting below 155° during normal driving. This could indicate a faulty Coolant Temp Sensor tricking the ECM into powering the relay (causing the pump to come on), but this would introduce other running problems as the mixture would be affected so my guess is that the SAI pump relay itself is faulty and causing the pump to randomly come on. Some other fault in the wiring could be shorting and causing the pump to run but the relay is triggered by the ECU itself so the relay would be my first guess. Also, in testing the pump itself by jumpering the relay it cautions not to let the pump run for more than 90 seconds:
Only allow the SAI pump to run for a maximum of 90 seconds and allow sufficient time for the pump to cool down before running again.
If it's running longer than that then that's another indication the ECM is not triggering the pump to come on.
The ECM checks the engine coolant temperature when the engine is started in addition to checking the elapsed time since the last engine start. The engine coolant temperature must be below 55°C (131°F) and the ambient temperature above 8°C (46°F) for the SAI pump to run.
There's no way your coolant is getting below 155° during normal driving. This could indicate a faulty Coolant Temp Sensor tricking the ECM into powering the relay (causing the pump to come on), but this would introduce other running problems as the mixture would be affected so my guess is that the SAI pump relay itself is faulty and causing the pump to randomly come on. Some other fault in the wiring could be shorting and causing the pump to run but the relay is triggered by the ECU itself so the relay would be my first guess. Also, in testing the pump itself by jumpering the relay it cautions not to let the pump run for more than 90 seconds:
Only allow the SAI pump to run for a maximum of 90 seconds and allow sufficient time for the pump to cool down before running again.
If it's running longer than that then that's another indication the ECM is not triggering the pump to come on.
