Pipkim Posted January 4, 2015 Share Posted January 4, 2015 Our 2006 Knaus motorhome is based on a Renault Master 2.5 ltr diesel engine. We have a re-occuring problem with an apparent air leak in the fuel line but we do not appear to be able to identify the cause. On cold start up, after being left a few days, the engine will run for about 5 seconds and then stall. There is a manual fuel priming “bladder” within the engine bulkhead and the fuel lines leaving to & from it are clear so it is very evident that there is air within the pipes. By squeezing the bladder [which is normally empty by now], fuel is introduced to the bladder and is soon “firm” and thus the line is now “primed”.. On restarting the engine all is well and it continues to run smoothly. There are no starting issues if the engine is still warm. It thus seems that fuel is draining back into the fuel tank after standing for a day or two and perhaps drawing air in from the fuel filter. Is that a possibility? My local garage has investigated the issue, checked the sender unit on the fuel tank, traced all the fuel lines but have been stumped by this problem. They are saying that if the van was in daily use, the issue would probably not be noticed. At the moment, every time I go to start the van, I have my “heart in my mouth” wondering if it is going to start properly. I do “prime” the fuel line using the bladder beforehand but that isn’t always 100% successful. Has anyone else come across this engine malady before? PilgrimPhil Link to comment Share on other sites More sharing options...
mgnbuk Posted January 4, 2015 Share Posted January 4, 2015 Many years ago I had a similar problem with a Citroen BX turbo diesel car - the Citroen agent finally found a problem with the fuel pre-heater. This was a cast aluminium chamber bolted into the block in contact with the coolant - fuel on it's way from the tank passed through the chamber & was heated (presumably to ensure no wax problems in cold weather ?), The problem turned out to be with the short brass pipes in the block that the flexible fuel hoses were attached to - these were bonded into the casting & one had come loose, allowing air in & the system drained down overnight leading to starting problems the next day. With a new pre-heater block fitted, normal starting returned. The leak must have been very slight, as there were no fuel puddles under the car. The cold starting problem also came on very quickly, not a gradual "starting getting a bit worse" situation. HTH Link to comment Share on other sites More sharing options...
George Collings Posted January 6, 2015 Share Posted January 6, 2015 I am not sure about the 2006 Master but on some vehicles the problem is air leakage due to poor sealing of the spill pipes from the injector back to the filter. Hardening of the rubber can be involved. Its very difficult to find but the pipes are often just push on and the hose is very cheap. Link to comment Share on other sites More sharing options...
Flyinghigh Posted January 7, 2015 Share Posted January 7, 2015 There are no spill pipes on the master, it's a high pressure fuel rail, I would remove the fuel filter complete and pressure test it, change filter and all rubber seals and pay particular attention to the quick release connectors going to the filter Link to comment Share on other sites More sharing options...
lennyhb Posted January 8, 2015 Share Posted January 8, 2015 Had a Kia Sedona with the same problem never could find the leak, trouble is it only needs to be a minute leak enough to let air in but too small to let fuel out. The Sedona was OK in the summer just needed a bit more turning over to start unless it had been left a few days. In the winter I used to pop the bonnet and give the bladder a couple of squeezes and it would start and run perfectly. You will probably have to take it to a diesel specialist theses type of leaks as near impossible to find yourself. Link to comment Share on other sites More sharing options...
Pipkim Posted January 17, 2015 Author Share Posted January 17, 2015 Touching wood, we seem to have resolved this engine/fuelling issue. After the van refused to start last weekend, it was impossible to get any pressure in the fuel line using the hand pump bladder. My garage came out with a substitute bladder and connected it “in line” with the existing one, and the fuel line pressurised after a few hand pumps. Thus confirming that the existing bladder was at fault. A new Renault bladder and associated fuel line was £30 + VAT, which was far less than we were expecting, so it was ordered. In order to start the van to get it to the garage, the old one was disconnected from the filter and the pipe cut. The temporary/substitute bladder was then connected using jubilee clips and the van fired up straight away. On closer inspection it was apparent that there were two splits around the moulded pipe entry which must have been admitting air into the system. It looked like the rigid rubber moulding had perished and there was also evidence of a split about to start on the actual bladder itself. 90 minutes later the van was back on our driveway and our wallets were £130 lighter but it seems to have worked! Once on the garage ramp, the half full fuel tank had to be released & lowered to connect the fuel pipe to the top of the tank and the piping threaded through the suspension & steering rack. The van was left for two days and this morning [cold & frosty] it fired up straight away. So I am hopeful that this specific issue has now been resolved. Next job – to change the battery in the Cobra alarm remote key fob! PilgrimPhil Link to comment Share on other sites More sharing options...
lennyhb Posted January 17, 2015 Share Posted January 17, 2015 Good news, it's nice when people report back on the forum letting us know you have solved the problem. Link to comment Share on other sites More sharing options...
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