2001
New member
Hi all,
Seeking some input on issues with my 2001 TDI.
Short summary - has anyone found a connection between tired/collapsing lifters and hard starts, or solved a hard starting concern with fresh lifters?
Background - Since I have had the car it has exhibited an intermittent long crank when started after sitting overnight. Usually this is relatively minor, Every now and then it will take an especially long time to start, and once in a while there will be no delay at all, it'll start up in the morning like it was just shut down. Harder starts will be accompanied by some smoke and a couple of stumbles. Seems slightly more exaggerated in colder weather but this is probably only due to slower cranking. Generally it seems to be affected by sitting for an overnight duration rather than by temperature. Once it starts, shutting it right back down, it'll start again immediately.
Another symptom that has been present is a very light but consistent mechanical tap in the engine. This is subtle enough that it is not audible under the hood, but noticeable inside the car with the doors closed, particularly at highway speed. Tracks engine RPM but is not dependent on load, it'll be there at any throttle position or on overrun, not temperature dependent. Suspect this is probably a separate issue but occasionally I wonder if the two problems are related.
New fuel filter and tank pickup, injectors refreshed in the past year with new Bosch nozzles, no air visible in the clear line or evidence of supply restriction. Injection pump is believed original. Glow plugs and harness are recent and in good condition. TB is about 15k miles old, IP timing set slightly advanced from baseline spec. These symptoms were unchanged by replacing the belt or by any of the work that has been done. ASV works fine and does not stick, intake is clean, Runs excellent other than these two issues, plenty of power.
Oil is either 5W40 or (currently) 0W40 synthetic.
What else I notice:
Sometimes, when it takes an extra few revolutions to start, it acts it has one or more cylinders that are down on compression, uneven cranking speed, like there's a collapsed lifter or two?
What I want to believe is that after 325k miles, the lifters are tired and are causing both the tap and the hard start and I will fix both by putting a fresh set in. But I found one other discovery that suggests there's something else going on which I can't wrap my head around yet:
The only way I can get the engine tap to go away is by running the engine with the anti-shudder valve closed. The test works like this: if I coast the car downhill, at low speed, and shut the key off with the car coasting in gear so that the engine continues to spin, the anti-shudder valve closes, and the mechanical noise disappears. The engine keeps "running" with no noise, coasting with no fuel injection, until I step on the clutch and the engine stops.
If I repeat the same test but first unplug the anti shudder valve solenoid, deactivating the valve, it will coast in gear down the hill, with no fuel injected, but with the anti shudder valve open rather than closed. In this configuration, the mechanical noise continues and remains noticeable.
In other words, having the valve closed, and the intake throttled, is the only time this noise does not occur.
Conclusions from this -- having vacuum in the intake manifold stops the noise. I can't see how the noise could be caused by a lifter in this case, seems like it would have to be a wrist pin or other effect in the rotating assembly. Other views, something I'm missing?
Tempting to throw a set of lifters at it, esp since after 300k plus they're probably justifiable regardless, but what I observe makes me think this may not be the direction it needs to go to solve the issues. This is a spare car so it will wait until good weather for the next round of repairs, but current next steps intended to be:
- used oil analysis - check for possible evidence of a mechanical cause for the audible noise
- compression test - hard to believe it'll be anything less than great given how it runs, but should cover it
- oil pressure check - ditto, it should have blown up already if it's low since I've put thousands of miles on with these issues evident, but should have the numbers
- static test of lifters
- ?
Other ideas? I'm more or less at a loss on the starting if the lifters aren't the cause, unless it's a tired IP; there's no air ingress even though it acts just like that's the issue, and timing and glow system are all as they should be. I'd suspect cylinder compression but the issue is too inconsistent for that. IP head/rotor getting tired??
Thanks.
Seeking some input on issues with my 2001 TDI.
Short summary - has anyone found a connection between tired/collapsing lifters and hard starts, or solved a hard starting concern with fresh lifters?
Background - Since I have had the car it has exhibited an intermittent long crank when started after sitting overnight. Usually this is relatively minor, Every now and then it will take an especially long time to start, and once in a while there will be no delay at all, it'll start up in the morning like it was just shut down. Harder starts will be accompanied by some smoke and a couple of stumbles. Seems slightly more exaggerated in colder weather but this is probably only due to slower cranking. Generally it seems to be affected by sitting for an overnight duration rather than by temperature. Once it starts, shutting it right back down, it'll start again immediately.
Another symptom that has been present is a very light but consistent mechanical tap in the engine. This is subtle enough that it is not audible under the hood, but noticeable inside the car with the doors closed, particularly at highway speed. Tracks engine RPM but is not dependent on load, it'll be there at any throttle position or on overrun, not temperature dependent. Suspect this is probably a separate issue but occasionally I wonder if the two problems are related.
New fuel filter and tank pickup, injectors refreshed in the past year with new Bosch nozzles, no air visible in the clear line or evidence of supply restriction. Injection pump is believed original. Glow plugs and harness are recent and in good condition. TB is about 15k miles old, IP timing set slightly advanced from baseline spec. These symptoms were unchanged by replacing the belt or by any of the work that has been done. ASV works fine and does not stick, intake is clean, Runs excellent other than these two issues, plenty of power.
Oil is either 5W40 or (currently) 0W40 synthetic.
What else I notice:
Sometimes, when it takes an extra few revolutions to start, it acts it has one or more cylinders that are down on compression, uneven cranking speed, like there's a collapsed lifter or two?
What I want to believe is that after 325k miles, the lifters are tired and are causing both the tap and the hard start and I will fix both by putting a fresh set in. But I found one other discovery that suggests there's something else going on which I can't wrap my head around yet:
The only way I can get the engine tap to go away is by running the engine with the anti-shudder valve closed. The test works like this: if I coast the car downhill, at low speed, and shut the key off with the car coasting in gear so that the engine continues to spin, the anti-shudder valve closes, and the mechanical noise disappears. The engine keeps "running" with no noise, coasting with no fuel injection, until I step on the clutch and the engine stops.
If I repeat the same test but first unplug the anti shudder valve solenoid, deactivating the valve, it will coast in gear down the hill, with no fuel injected, but with the anti shudder valve open rather than closed. In this configuration, the mechanical noise continues and remains noticeable.
In other words, having the valve closed, and the intake throttled, is the only time this noise does not occur.
Conclusions from this -- having vacuum in the intake manifold stops the noise. I can't see how the noise could be caused by a lifter in this case, seems like it would have to be a wrist pin or other effect in the rotating assembly. Other views, something I'm missing?
Tempting to throw a set of lifters at it, esp since after 300k plus they're probably justifiable regardless, but what I observe makes me think this may not be the direction it needs to go to solve the issues. This is a spare car so it will wait until good weather for the next round of repairs, but current next steps intended to be:
- used oil analysis - check for possible evidence of a mechanical cause for the audible noise
- compression test - hard to believe it'll be anything less than great given how it runs, but should cover it
- oil pressure check - ditto, it should have blown up already if it's low since I've put thousands of miles on with these issues evident, but should have the numbers
- static test of lifters
- ?
Other ideas? I'm more or less at a loss on the starting if the lifters aren't the cause, unless it's a tired IP; there's no air ingress even though it acts just like that's the issue, and timing and glow system are all as they should be. I'd suspect cylinder compression but the issue is too inconsistent for that. IP head/rotor getting tired??
Thanks.
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