pos
Well-Known Member
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- 3,685
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- West Yorkshire
Hello,
Anyone who has been following my threads with regards to the lumpy idle problem on my 200tdi, or who has been experiencing similar problems themselves, may benefit from trying out a few things that I have found to be successful in ultimately curing my erratic idle and blue / white smoking problem. This should also help cure similar symptoms on a 300tdi engine. A lot of credit goes to CharlesY, who has been helping me out behind the scenes, with ideas and suggestions as well as the fundamental workings of the Bosch VE injection pump
The problem in my case, can be narrowed down to three things:
1) An improperly installed fuel line that was allowing a small amount of air to be drawn into the system
2) A restriction in the fuel return line between the injection pump and the fuel tank
3) My fuel injection timing
Let's start with the fuel line allowing air to be drawn in. I had replaced various parts of my fuel line with 8mm rubber hose, sleeved over 8mm metal unions to try and irradiate the air problem a few months back, but to no effect. There has evidently been a leak somewhere between the fuel pickup pipe and the fuel lift pump (only two unions), the only part of the fuel line which is under vacuum. Air can be drawn in here, but fuel does not necessarily have to leak out. I decided to completely strip out the entire fuel line system in my 90, and replaced it with 8mm nylon fuel line (3 metres gave me plenty to play with), joined with compression fittings that tightened down onto the nylon fuel line, reenforced with brass tube supports. No where have I used a jubilee clip, or any other form of fuel clip. The system is solely nylon pipe, compression fittings and hollow fuel line bolts with olives. I now have an air-leak-free fuel line, and the flow of diesel to the injection pump is completely uninterrupted.
Secondly, I had to cut through the existing nylon injection pump return line, in order to fit the 200tdi engine in place of my old 2.5N/A (12J). I then made the old nylon return line, fit the return setup on the 200tdi injection pump by sleeving 8mm rubber hose over the nylon pipes, securing them in place with jubilee clips. The problem here, being that the jubilee clips had to be fairly tight to avoid a diesel leak and tightening the jubilee clips to the extent that prevented a leak, meant that the nylon pipes were crushed, significantly restricting the diesel from free-flowing back to the tank. This Inevitably created pressure buildup in the fuel return line, which effects the governing of the injection pump. The Bosch VE utilises a calibrated return (banjo bolt with a small hole) to maintain internal pump pressures. The cold start advance / idle advance / retard mechanism internal to the pump, is in a state of balance, and is controlled by internal fuel pressure. Restricting the return line had thrown the mechanism out of kilter, and the engine would not idle correctly.
Finally, with regards to the White / blue smoke problems that I had been having from a cold start (notably worse in the colder weather), I believe this is down to a combination of the restricted fuel return line and the ever so slightly advanced injection timing that I set up for better high end power. The injection pump would naturally try to advance the injection timing from a cold start, but the restriction in the return line was effecting the internal fuel pressure balance, throwing the timing too advance, or too retarded (I'm not sure which way it would hamper). This, coupled with slightly increased fuelling by a means of adjusting the boost diaphragm eccentric cone so that the pump injects more fuel at 0 boost, meant that there was more fuel being injected on the cold start. More fuel, more smoke, Incorrect idle / cold start timing; quite simple really.
All in all, starting from scratch with the fuel lines, and doing them properly with compression fittings and no cause for sleeving joints, has solved the problem and I now have a steady idle. I used SSL Diesel Parts (SSL Diesel Parts - Low Cost diesel fuel Parts.) for everything that I bought, including a new fuel filter head. It cost me £30 including VAT & delivery, so a bargain really considering Land Rover charge a similar price for one nylon pipe alone
I'm glad I finally found a fix, and thanks to everyone who helped along the way. I know there had been a lot of people wanting answers to this problem - so there you have it, at least in my case anyway.
-Tom
Anyone who has been following my threads with regards to the lumpy idle problem on my 200tdi, or who has been experiencing similar problems themselves, may benefit from trying out a few things that I have found to be successful in ultimately curing my erratic idle and blue / white smoking problem. This should also help cure similar symptoms on a 300tdi engine. A lot of credit goes to CharlesY, who has been helping me out behind the scenes, with ideas and suggestions as well as the fundamental workings of the Bosch VE injection pump
The problem in my case, can be narrowed down to three things:
1) An improperly installed fuel line that was allowing a small amount of air to be drawn into the system
2) A restriction in the fuel return line between the injection pump and the fuel tank
3) My fuel injection timing
Let's start with the fuel line allowing air to be drawn in. I had replaced various parts of my fuel line with 8mm rubber hose, sleeved over 8mm metal unions to try and irradiate the air problem a few months back, but to no effect. There has evidently been a leak somewhere between the fuel pickup pipe and the fuel lift pump (only two unions), the only part of the fuel line which is under vacuum. Air can be drawn in here, but fuel does not necessarily have to leak out. I decided to completely strip out the entire fuel line system in my 90, and replaced it with 8mm nylon fuel line (3 metres gave me plenty to play with), joined with compression fittings that tightened down onto the nylon fuel line, reenforced with brass tube supports. No where have I used a jubilee clip, or any other form of fuel clip. The system is solely nylon pipe, compression fittings and hollow fuel line bolts with olives. I now have an air-leak-free fuel line, and the flow of diesel to the injection pump is completely uninterrupted.
Secondly, I had to cut through the existing nylon injection pump return line, in order to fit the 200tdi engine in place of my old 2.5N/A (12J). I then made the old nylon return line, fit the return setup on the 200tdi injection pump by sleeving 8mm rubber hose over the nylon pipes, securing them in place with jubilee clips. The problem here, being that the jubilee clips had to be fairly tight to avoid a diesel leak and tightening the jubilee clips to the extent that prevented a leak, meant that the nylon pipes were crushed, significantly restricting the diesel from free-flowing back to the tank. This Inevitably created pressure buildup in the fuel return line, which effects the governing of the injection pump. The Bosch VE utilises a calibrated return (banjo bolt with a small hole) to maintain internal pump pressures. The cold start advance / idle advance / retard mechanism internal to the pump, is in a state of balance, and is controlled by internal fuel pressure. Restricting the return line had thrown the mechanism out of kilter, and the engine would not idle correctly.
Finally, with regards to the White / blue smoke problems that I had been having from a cold start (notably worse in the colder weather), I believe this is down to a combination of the restricted fuel return line and the ever so slightly advanced injection timing that I set up for better high end power. The injection pump would naturally try to advance the injection timing from a cold start, but the restriction in the return line was effecting the internal fuel pressure balance, throwing the timing too advance, or too retarded (I'm not sure which way it would hamper). This, coupled with slightly increased fuelling by a means of adjusting the boost diaphragm eccentric cone so that the pump injects more fuel at 0 boost, meant that there was more fuel being injected on the cold start. More fuel, more smoke, Incorrect idle / cold start timing; quite simple really.
All in all, starting from scratch with the fuel lines, and doing them properly with compression fittings and no cause for sleeving joints, has solved the problem and I now have a steady idle. I used SSL Diesel Parts (SSL Diesel Parts - Low Cost diesel fuel Parts.) for everything that I bought, including a new fuel filter head. It cost me £30 including VAT & delivery, so a bargain really considering Land Rover charge a similar price for one nylon pipe alone
I'm glad I finally found a fix, and thanks to everyone who helped along the way. I know there had been a lot of people wanting answers to this problem - so there you have it, at least in my case anyway.
-Tom
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