ajh Posted September 1, 2011 Share Posted September 1, 2011 Other than the fuel lift pump; what tuning / parts can cause a high-rpm stutter that feels like fuel starvation on a 200 TDI? At the same time, does anyone know what the fuel loop pressure and flow rate should be on a healthy lift-pump? Quote Link to comment Share on other sites More sharing options...
stuck Posted September 1, 2011 Share Posted September 1, 2011 Without wishing to state the obvious, fuel filter? Quote Link to comment Share on other sites More sharing options...
ajh Posted September 3, 2011 Author Share Posted September 3, 2011 Without wishing to state the obvious, fuel filter? Nope, and I've tried two different mechanical lift-pumps as well as the 12V pump I used when I had my lift-pump die while on the road. I've found a number of problems; none of which seem to correct the hesitation at high-rpm... In the interest of full disclosure here's what I've done this week and the symptoms. I changed the timing belt, the cam sprocket mark was on it in such a way that it couldn't line up 100%, it had to be half a tooth forward or back of the mark, I elected for forward. I've been micro-adjusting the timing since to try to get things running as smoothly as possible and I feel I have a good sense of what too advanced and too retarded feel like now and in general the engine is running very strong, fairly cool, and quieter than ever so I believe the timing is good. The symptoms are; I start the vehicle, drive to the highway 1km away, engine runs very strong throughout the RPM range, in fact when it's working it is the first time I've been nearly happy with the performance. I even hit 130kph going up about a 4% grade on the highway; that's about the minimum level of performance I'm shooting for. Then within a minute I start getting fuel starvation symptoms at full throttle, if I back-off or shift up it goes away briefly until I get back to full throttle again. Am I correct in my deduction that the only thing left at this point is the high-pressure injection pump? Quote Link to comment Share on other sites More sharing options...
ajh Posted September 3, 2011 Author Share Posted September 3, 2011 Anyone? This is getting really frustrating and the next step is stripping the FIP from the other 200 I have here and swapping it in; but that means no sleep. Quote Link to comment Share on other sites More sharing options...
Roverdrive Posted September 3, 2011 Share Posted September 3, 2011 So many things it could be. Has it only happened since changing the timing belt? Could it be drawing air in on the suction side of the lift pump, either at the pump or the tank? Are the leak off pipes on the injectors secure and leak free? ( Going from memory here as it is a while since I have laid hands on a 200 Tdi ) Blocked vent on the fuel tank? Will put the thinking cap on Quote Link to comment Share on other sites More sharing options...
ajh Posted September 3, 2011 Author Share Posted September 3, 2011 I know, I found a number of things that could contribute but fixing them doesn't seem to change much, and yes since changing the timing belt, power before sucked and was running higher EGT than normal and topping out at 110kph... it's running smoothly, except once the fuel starvation starts... I'm fairly convinced it's either the FIP or air getting into things somewhere, the leak-off seems good, I changed the hoses on them about 5 months ago, I tried with the filler cap off the fuel tank and got the same symptoms. The closest I've seen to the behavior was on my Fireblade when the fuel vent pipe got pinched, would run but then starve and stall. This only stalled once when I was stopped and rev'ed it up. Tomorrow I'll focus on air and looking for any holes worn in the fuel line but after that I'm stumped. Quote Link to comment Share on other sites More sharing options...
Roverdrive Posted September 3, 2011 Share Posted September 3, 2011 Is it possible to put a piece of clear plastic pipe in the fuel line to the HP pump? You would be able to see air bubbles then. Should be visible when reving the engine, despite not affecting the engine, as the bleed off back to tank should get rid of the air, ( could always put the clear pipe here as well )as less fuel is required for the engine - if that makes sense? Do you still have to drive the 1km to notice the problem if the engine has been stopped but it still warm? Quote Link to comment Share on other sites More sharing options...
ajh Posted September 3, 2011 Author Share Posted September 3, 2011 I did some more troubleshooting. The problem occurs when the fuel filter empties, so there must be an obstruction in the feed-line that's preventing it from getting fuel quickly enough. Even with just the electric pump running and the bleed screw removed it took about a minute (engine off) for the filter to fill up again. At least this feels like progress My believe now is it must be between the tank and the filter which narrows it down significantly to either something lodged in the feed line, the sedimentor, or the fuel pickup. However it's now almost 10pm and I'm getting tired of smelling of diesel so I'll check all that in the morning. With this info, do you thing it could be anything else? Quote Link to comment Share on other sites More sharing options...
Roverdrive Posted September 3, 2011 Share Posted September 3, 2011 Sorry, but very rusty on the Tdi! As standard is it just a mechanical lift pump on the side of the block? Is this where you have fitted the electrical pump? If so, try drawing fuel from a 5l can rather than the tank, and time how long the filter takes to fill. If there is no change try connecting a new pipe on the suction side of the pump and repeat. Might give you a clue as to the location of the restriction. Quote Link to comment Share on other sites More sharing options...
western Posted September 3, 2011 Share Posted September 3, 2011 Maybe the electric pump is not able to provide the flow/pressure the mechanical lift pump can & thereby causing a fuel feed/stravation problem, there should be no need for a extra lift pump electric or mechanical, do a search for the diesel fault diagnosis chart. Quote Link to comment Share on other sites More sharing options...
ajh Posted September 3, 2011 Author Share Posted September 3, 2011 No, the electric is significantly better than the mechanical. I'm going to go make sure the pipes are clear in a few minutes. Quote Link to comment Share on other sites More sharing options...
ajh Posted September 3, 2011 Author Share Posted September 3, 2011 OK, problem fixed and it looks like everything else done has had an improvement over how it was when it got it. Cruising at 130kph with a top-speed of 137kph right now (with a little smoke, now that the other stuff is working I can get the pump dialed in properly finally. The problem was something had lodged in the fuel pickup pipe, a blast of air and it shot across the room like an airsoft bb and now it gets the fuel it should and with the new timing is running at 200F on the highway under full load and 190F on side streets which is cooler than before too and the more advanced timing dropped the EGT quite a bit except under full load (since right now it's clearly overfueling).. so yay! Quote Link to comment Share on other sites More sharing options...
Roverdrive Posted September 3, 2011 Share Posted September 3, 2011 Nice one! Sometimes it pays to go back to basics and work through methodically. Glad you got it sorted Quote Link to comment Share on other sites More sharing options...
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