Attention to all people who are having hard start issues when car is warm
Posted: Sat Feb 22, 2020 4:55 pm
Hi guys, i have read few topics regarding numerous people having issues when starting their RS6/7 & S8’s. I also experience this problem on my RS6 which I always thought its the map I have and the ghost immobiliser conflicts with each other. Just to confirm, during this week I had an S8 2017 turn up to my workshop with the same issue so I thought it must be a common issue since others are also having the same problem. Car normally hesitates to start leaving it to rest after getting to operating temperature. You would need to try once or two to get it going, or apply a bit of throttle to fire it up. Also when it does start, it would misfire for a second or two till it builds up the revs.
We have dealer level diagnostics and access to all the technical information on the VAG group. Therefore I have carried out a series of test. I can certainly confirm that the issue relies to the High Pressure Fuel Pumps. What happens is that the pump starts leaking fuel internally, which then loses pressure. To build up the pressure it takes longer for the fuel to get into the system and bleed itself. During the test, it asks to measure the fuel pressure drop in 5mins, 10mins, 15 & 20mins. This then determines leaky HPFP. On our engines there are two of them, however when you look at the TPI via Audi, it states both pumps need replacing regardless. Unfortunately, if you are experiencing this issue you’ll need to replace your oil and filter as your oil would be contaminated with excess fuel.
Faulty injector is also another possibility, however very unlikely as they are not very common for replacement. For people who are in the region of South East, we can carry these checks are and diagnose which one it is, or you can get your local dealer to have a look at it. However knowing dealers, they do not like customers approaching them to tell them what checks to carry out. I’ve read some who had their exhaust valves blamed at, some with their remap. So it may be tricky to get your dealer to diagnose it.
New HPFP’s are about £254 +VAT each, retail. Easy enough to replace, and do not need coding or adapting. It will just work out the box. Once you remove the old pump, you can look at the spring in the middle which would have slight rust marks on it. This indicated that its been leaking. Sorry for the long write up, but I thought i’ll share my findings as there are numerous people having the same issue. Hope this helps guys
We have dealer level diagnostics and access to all the technical information on the VAG group. Therefore I have carried out a series of test. I can certainly confirm that the issue relies to the High Pressure Fuel Pumps. What happens is that the pump starts leaking fuel internally, which then loses pressure. To build up the pressure it takes longer for the fuel to get into the system and bleed itself. During the test, it asks to measure the fuel pressure drop in 5mins, 10mins, 15 & 20mins. This then determines leaky HPFP. On our engines there are two of them, however when you look at the TPI via Audi, it states both pumps need replacing regardless. Unfortunately, if you are experiencing this issue you’ll need to replace your oil and filter as your oil would be contaminated with excess fuel.
Faulty injector is also another possibility, however very unlikely as they are not very common for replacement. For people who are in the region of South East, we can carry these checks are and diagnose which one it is, or you can get your local dealer to have a look at it. However knowing dealers, they do not like customers approaching them to tell them what checks to carry out. I’ve read some who had their exhaust valves blamed at, some with their remap. So it may be tricky to get your dealer to diagnose it.
New HPFP’s are about £254 +VAT each, retail. Easy enough to replace, and do not need coding or adapting. It will just work out the box. Once you remove the old pump, you can look at the spring in the middle which would have slight rust marks on it. This indicated that its been leaking. Sorry for the long write up, but I thought i’ll share my findings as there are numerous people having the same issue. Hope this helps guys
