Fuel Pump Relay Logic Question
10-06-2011, 12:45 PM
#1
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Fuel Pump "Relay Logic" Question
Hi everyone,
I have a 2001 (only owner) 1.8T which I'm having problems with. Starting the engine on the 1st try almost never happens anymore.
If the engine is off for say an hour or so, it won't start on the 1st crank like it used to. It now almost always takes two short cranks for the engine to "catch". The starter crancks engine at a good rate of speed.
So far I've changed;
-Fuel filter (after 130k miles "life time")
-Fuel pressure regulator
-Spark plugs are OK
-Throtle body cleaned - TBA done.
-Coolant temp sensor was replaced when I replaced the coolant flange a year ago or so.
The battery is fairly new and the engine is in excellent running condition. There are no "codes" or other issues...
To me it feels like the fuel system rail is not "primming at pressure" properly so as to start up on the 1st try.
Just saw this Troubleshooting Guide at http://reviews.ebay.com/VW-VOLKSWAGE...00000005382319
BTW- This is an Excellent guide
The guide says this about the FP relay "...If you open your door you hear the pump kick on, if the pump no longer kicks on...replace the fuel pump relay."
This "open door then pump kicks on" sequence makes sense from a functional point of view...
Can anyone confirm this please?
If this sequence is indeed present, it (or the lack of it) could be what is causing some of these "hard start problem" posts I found while searching.
Thank you for your inputs on this.
I have a 2001 (only owner) 1.8T which I'm having problems with. Starting the engine on the 1st try almost never happens anymore.
If the engine is off for say an hour or so, it won't start on the 1st crank like it used to. It now almost always takes two short cranks for the engine to "catch". The starter crancks engine at a good rate of speed.
So far I've changed;
-Fuel filter (after 130k miles "life time")
-Fuel pressure regulator
-Spark plugs are OK
-Throtle body cleaned - TBA done.
-Coolant temp sensor was replaced when I replaced the coolant flange a year ago or so.
The battery is fairly new and the engine is in excellent running condition. There are no "codes" or other issues...
To me it feels like the fuel system rail is not "primming at pressure" properly so as to start up on the 1st try.
Just saw this Troubleshooting Guide at http://reviews.ebay.com/VW-VOLKSWAGE...00000005382319
BTW- This is an Excellent guide
The guide says this about the FP relay "...If you open your door you hear the pump kick on, if the pump no longer kicks on...replace the fuel pump relay."
This "open door then pump kicks on" sequence makes sense from a functional point of view...
Can anyone confirm this please?
If this sequence is indeed present, it (or the lack of it) could be what is causing some of these "hard start problem" posts I found while searching.
Thank you for your inputs on this.
Last edited by Zeca; 10-06-2011 at 08:34 PM.
10-07-2011, 07:50 AM
#2
AudiWorld Super User
Listen for the pump to run briefly; my '96 doesn't' do the door-open prime, only when turning the ignition on does the pump run for a second. If your car is designed to only prime once, when the driver's door opens, and not when the ignition is switched on, maybe there is a door switch problem. Do the interior lights come one when the door is opened?
You could also manually prime in different ways; with VAG-COM, run output tests which runs the pump, then try starting. See if you get a first-try start. Another way could be to remove the knee bolster cover, remove the fuel pump relay, take the cover off, then reinstall without the plastic cover. Now you can close the relay contacts with your finger to run the pump briefly, then try to start in the normal way. You should see the contacts close as the starter begins to run.
If you have VAG-COM available, check the coolant temp reading before starting, even though the sensor isn't that old.
You could also manually prime in different ways; with VAG-COM, run output tests which runs the pump, then try starting. See if you get a first-try start. Another way could be to remove the knee bolster cover, remove the fuel pump relay, take the cover off, then reinstall without the plastic cover. Now you can close the relay contacts with your finger to run the pump briefly, then try to start in the normal way. You should see the contacts close as the starter begins to run.
If you have VAG-COM available, check the coolant temp reading before starting, even though the sensor isn't that old.
10-07-2011, 10:16 AM
#3
Sometimes a faulty crank position sensor can cause starting issues.
We have them available below.
Click HERE to order or for more information.
Let me know if you have any questions.
Jason
We have them available below.
Click HERE to order or for more information.
Let me know if you have any questions.
Jason
10-11-2011, 05:06 PM
#6
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Sad to say
The fuel pump relay wasn't it...The problem continues.
However I am certain that the fuel pump used to "kick-in" when the door was opened.
The interior lights come-on when the door is opened so whatever switch/sensor is at play sensing the door opening is still OK.
I don't have an electrical diagram /'logic block' diagram to study but I'll keep on looking.
Apreciate any and all inputs on this..
However I am certain that the fuel pump used to "kick-in" when the door was opened.
The interior lights come-on when the door is opened so whatever switch/sensor is at play sensing the door opening is still OK.
I don't have an electrical diagram /'logic block' diagram to study but I'll keep on looking.
Apreciate any and all inputs on this..
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