Banzask Posted March 2, 2023 Share Posted March 2, 2023 Hi All my first post on here i'm hoping some on is able to assist me Last week I had the coil light flashing at me with code P0087 Fuel rail pressure too low, at 1.5/2k rpm in 4th, after clearing it would come on again similar revs and gear cruising country lanes If accelerating hard coil light would not come on. I changed the fuel filter, fuel was clear in the housing. Now the coil light will come on anytime randomly when driving steady or harsh. What has me puzzled is that if when trying to drive hard the fuel can successfully be supplied can this be a pump issue? The only common scenario is it seems to come on when on rough road i've noticed, never on the 15 mile daily stretch of dual carriage way If someone could assist would be greatly appreciated Quote Link to comment Share on other sites More sharing options...
Stevey Y Posted March 2, 2023 Share Posted March 2, 2023 2 hours ago, Banzask said: Hi All my first post on here i'm hoping some on is able to assist me Last week I had the coil light flashing at me with code P0087 Fuel rail pressure too low, at 1.5/2k rpm in 4th, after clearing it would come on again similar revs and gear cruising country lanes If accelerating hard coil light would not come on. I changed the fuel filter, fuel was clear in the housing. Now the coil light will come on anytime randomly when driving steady or harsh. What has me puzzled is that if when trying to drive hard the fuel can successfully be supplied can this be a pump issue? The only common scenario is it seems to come on when on rough road i've noticed, never on the 15 mile daily stretch of dual carriage way If someone could assist would be greatly appreciated Hi most of the time its one of the two lift pumps under the back seat, I don't know which code reader you used but if its VCDS that should tell you which one is misbehaving, yours is classic symptoms of a lift pump degrading the question, is it the main pump or the assisting pump, my guess is the assist pump which is on the n/s rear of the seat pan, you could be lucky and its a corroded connector which is a common problem. Steve. Quote Link to comment Share on other sites More sharing options...
Banzask Posted March 3, 2023 Author Share Posted March 3, 2023 16 hours ago, Stevey Y said: Hi most of the time its one of the two lift pumps under the back seat, I don't know which code reader you used but if its VCDS that should tell you which one is misbehaving, yours is classic symptoms of a lift pump degrading the question, is it the main pump or the assisting pump, my guess is the assist pump which is on the n/s rear of the seat pan, you could be lucky and its a corroded connector which is a common problem. Steve. Thank you Steve I will take a look at the connector after work. Quote Link to comment Share on other sites More sharing options...
Banzask Posted March 4, 2023 Author Share Posted March 4, 2023 On 3/2/2023 at 6:54 PM, Stevey Y said: Hi most of the time its one of the two lift pumps under the back seat, I don't know which code reader you used but if its VCDS that should tell you which one is misbehaving, yours is classic symptoms of a lift pump degrading the question, is it the main pump or the assisting pump, my guess is the assist pump which is on the n/s rear of the seat pan, you could be lucky and its a corroded connector which is a common problem. Steve. Hi Steve, the assisting pump you refer to there is no panel on the n/s rear seat pan only on the o/s for the main lift pump, would this mean there isn’t an assisting pump? what I have noticed, I’ve tried turning the ignition on for 10 seconds and off and only can hear the pump every so often not each time the ignition is on. I’d except to hear it kick in each time or am I wrong? Many Thanks Joe Quote Link to comment Share on other sites More sharing options...
Stevey Y Posted March 5, 2023 Share Posted March 5, 2023 On 3/4/2023 at 4:37 PM, Banzask said: Hi Steve, the assisting pump you refer to there is no panel on the n/s rear seat pan only on the o/s for the main lift pump, would this mean there isn’t an assisting pump? what I have noticed, I’ve tried turning the ignition on for 10 seconds and off and only can hear the pump every so often not each time the ignition is on. I’d except to hear it kick in each time or am I wrong? Many Thanks Joe Hi Joe you have the earlier mono pump type and yes you should hear the pump every time even for a couple of seconds as it takes up the air space in the fuel line, easiest way is leave over night and then try the ignition on and see what the duration of the pump run is a worn pump will run for some time indicating that the pressure is being lost, but a healthy pump will run for about 5 seconds as its not loosing as much pressure, easy way to check pump flow is ok is disconnect the in feed from the filter hosing and put it in an old litre coke bottle, turn on the ignition and if it fills in record time its not the pump, therefore the only other culprit would be the fuel rail pressure sensor on the inlet side of the rail [screws into the rail end] and this is easy to change just let the pressure in the rail dissipate overnight before you change the unit. Steve. Quote Link to comment Share on other sites More sharing options...
Banzask Posted March 6, 2023 Author Share Posted March 6, 2023 22 hours ago, Stevey Y said: Hi Joe you have the earlier mono pump type and yes you should hear the pump every time even for a couple of seconds as it takes up the air space in the fuel line, easiest way is leave over night and then try the ignition on and see what the duration of the pump run is a worn pump will run for some time indicating that the pressure is being lost, but a healthy pump will run for about 5 seconds as its not loosing as much pressure, easy way to check pump flow is ok is disconnect the in feed from the filter hosing and put it in an old litre coke bottle, turn on the ignition and if it fills in record time its not the pump, therefore the only other culprit would be the fuel rail pressure sensor on the inlet side of the rail [screws into the rail end] and this is easy to change just let the pressure in the rail dissipate overnight before you change the unit. Steve. Thank you! I will try this in the morning Joe Quote Link to comment Share on other sites More sharing options...
Banzask Posted March 8, 2023 Author Share Posted March 8, 2023 On 3/5/2023 at 7:10 PM, Stevey Y said: Hi Joe you have the earlier mono pump type and yes you should hear the pump every time even for a couple of seconds as it takes up the air space in the fuel line, easiest way is leave over night and then try the ignition on and see what the duration of the pump run is a worn pump will run for some time indicating that the pressure is being lost, but a healthy pump will run for about 5 seconds as its not loosing as much pressure, easy way to check pump flow is ok is disconnect the in feed from the filter hosing and put it in an old litre coke bottle, turn on the ignition and if it fills in record time its not the pump, therefore the only other culprit would be the fuel rail pressure sensor on the inlet side of the rail [screws into the rail end] and this is easy to change just let the pressure in the rail dissipate overnight before you change the unit. Steve. Hi Steve thanks again for your advice So I tried as you suggested, took the feed pipe off the outer housing turned the ignition on, absolutely nothing. Tried this multiple times. Put the pipe back on remove the bench seat and access panel to the filter, tried turning the car on to see if I could hear the pump. Every time I turn the key past ignition to start, I can hear the pump for a second before engine turns over and for a second after engine is turned off. I’m confused now, does this mean the pump is being told not to prime the system or does it mean it doesn’t actually prime on just ignition? Joe Quote Link to comment Share on other sites More sharing options...
Stevey Y Posted March 8, 2023 Share Posted March 8, 2023 5 hours ago, Banzask said: Hi Steve thanks again for your advice So I tried as you suggested, took the feed pipe off the outer housing turned the ignition on, absolutely nothing. Tried this multiple times. Put the pipe back on remove the bench seat and access panel to the filter, tried turning the car on to see if I could hear the pump. Every time I turn the key past ignition to start, I can hear the pump for a second before engine turns over and for a second after engine is turned off. I’m confused now, does this mean the pump is being told not to prime the system or does it mean it doesn’t actually prime on just ignition? Joe Hi Joe, sounds like the pump is ok as the pump operating for a second after shut down is what its supposed to do to take up any air in the system and if its only running for the same time on start up thats ideal, which brings me back to the rail pressure regulator which is a spring loaded device that is solenoid controlled but it can have a tendency to stick when worn as they are not individually monitored by the ECU they generally throw up a code for rail pressure the clue could be that the car only does it on rough roads, they don't like being rattled around when worn, the reason for the effect not happening when accelerating hard is because it will use a part of the valve stem in the unit that is infrequently used, once the valve is worn they can stick and starve the rail of pressure as it is slow on reacting to the opening pulse. Steve. 1 Quote Link to comment Share on other sites More sharing options...
Banzask Posted March 21, 2023 Author Share Posted March 21, 2023 On 3/8/2023 at 7:15 PM, Stevey Y said: Hi Joe, sounds like the pump is ok as the pump operating for a second after shut down is what its supposed to do to take up any air in the system and if its only running for the same time on start up thats ideal, which brings me back to the rail pressure regulator which is a spring loaded device that is solenoid controlled but it can have a tendency to stick when worn as they are not individually monitored by the ECU they generally throw up a code for rail pressure the clue could be that the car only does it on rough roads, they don't like being rattled around when worn, the reason for the effect not happening when accelerating hard is because it will use a part of the valve stem in the unit that is infrequently used, once the valve is worn they can stick and starve the rail of pressure as it is slow on reacting to the opening pulse. Steve. Thank you Steve, I will have a look at this in two weeks time currently away with work 1 Quote Link to comment Share on other sites More sharing options...
a6blacked007 Posted November 30, 2023 Share Posted November 30, 2023 Did you solve this have same sort of issue with our a1 1.6 tdi Starts fine drives fine up until about 50mph then coil light flashes and limp mode changed fuel filter still same .. Thanks mark Quote Link to comment Share on other sites More sharing options...
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