l_c
Veteran Member
Got me again
It has been four years since my prior experience with this.
And instinctively I told myself that whatever happened last time is probably not what's happening this time.
For several, several months now, almost every morning my pump has lost prime and I have to pull fuel
( using the mity vac ) through the return path, before it will crank up and start in a cranky, stuttering way.
Later in the day, until the next morning it will start all right ... then on first cold start in the morning, again no prime.
Last week, it finally got worse and I could not leave work in the evening, took almost 1/2 hour to prime it successfully.
During all of this, the battery and starter take a beating.
So I had presumed my IP head seal was the culprit, since the last time I had installed the Viton gasket
( purchased from Dieselgeek ) was 6 years / 120k miles back, and I thought that I've noticed fuel dripping, more recently. ( I also did the middle & top seals 5-1/2 years back, after the original middle seal began leaking. )
It's hard to see clearly because the area under my IP has become embarrassingly messy, eaten-away wire insulation and all.
Last Saturday, I finally disassembled the IP stack and replaced all three seals (again), plus the fuel temperature sensor.
Afterward, to my chagrin the loss of prime actually became a lot worse. I accused myself of roughly handling the head seal, during re-seating of the distributor head ... i.e. you have to tighten the screws oh so gradually and evenly, but maybe I tightened one corner too abruptly, something like that.
( On the good side, my IP is running so nicely now, I think the last positioning of my QA was better than last time, so it runs very happily. Haven't yet tuned IQ using VCDS, and I should check my timing since haven't looked at it in ages. )
Sunday morning, I replaced the fuel filter and the Tee valve O-rings ( but not the valve itself ).
The vehicle started up fine afterward, but I waited until Monday morning's cold start to judge the situation.
Monday morning, a perfect start, and has been perfect for another day after. At this point, no more loss of prime.
My guess : I was losing prime through the return path again. And it's most likely those little doggone o-rings on the thermostatic tee valve. I haven't had them on there for four years, well maybe I did ... that must have been the occasion when I bought an entire new valve. ( I had posted http://forums.tdiclub.com/showthread.php?p=2396740&post2396740, and a couple of other entries in that thread at the time. )
Another guess would be fuel dripping from the bottom (exit spigot) of the fuel filter. But that's a little less likely, and after removing the filter I had it sitting full of fuel for a while and didn't see any leakage, so I don't think so.
What I really want to see, and I would buy this aftermarket since I am lazy at this point ...
give us a two-line connector assembly to go between the filter and the IP, which has clear tubing
not only on the incoming path, but on the outgoing (return) path as well.
I have had this general issue, with air getting into the return side, before, and I think it could be spotted (visually) earlier.
My clear portion of the inlet tube doesn't always show obvious air, when there's air at the spill side.
If this is merely causing a dry condition at the injectors, that could make sense but
I still don't really understand how the usual priming (at the pipe from the banjo) is able to improve the situation.
Then again, that basic priming doesn't make it immediately start; it gives the engine a chance of starting, after a few tries.
EDIT: Is it possible that ambient air entering at the tee valve causes more of an issue than air entering the spill path ... or are they effectively the same part of the system ??
Sorry for the rambling post now.
Larry
It has been four years since my prior experience with this.
And instinctively I told myself that whatever happened last time is probably not what's happening this time.
For several, several months now, almost every morning my pump has lost prime and I have to pull fuel
( using the mity vac ) through the return path, before it will crank up and start in a cranky, stuttering way.
Later in the day, until the next morning it will start all right ... then on first cold start in the morning, again no prime.
Last week, it finally got worse and I could not leave work in the evening, took almost 1/2 hour to prime it successfully.
During all of this, the battery and starter take a beating.
So I had presumed my IP head seal was the culprit, since the last time I had installed the Viton gasket
( purchased from Dieselgeek ) was 6 years / 120k miles back, and I thought that I've noticed fuel dripping, more recently. ( I also did the middle & top seals 5-1/2 years back, after the original middle seal began leaking. )
It's hard to see clearly because the area under my IP has become embarrassingly messy, eaten-away wire insulation and all.
Last Saturday, I finally disassembled the IP stack and replaced all three seals (again), plus the fuel temperature sensor.
Afterward, to my chagrin the loss of prime actually became a lot worse. I accused myself of roughly handling the head seal, during re-seating of the distributor head ... i.e. you have to tighten the screws oh so gradually and evenly, but maybe I tightened one corner too abruptly, something like that.
( On the good side, my IP is running so nicely now, I think the last positioning of my QA was better than last time, so it runs very happily. Haven't yet tuned IQ using VCDS, and I should check my timing since haven't looked at it in ages. )
Sunday morning, I replaced the fuel filter and the Tee valve O-rings ( but not the valve itself ).
The vehicle started up fine afterward, but I waited until Monday morning's cold start to judge the situation.
Monday morning, a perfect start, and has been perfect for another day after. At this point, no more loss of prime.
My guess : I was losing prime through the return path again. And it's most likely those little doggone o-rings on the thermostatic tee valve. I haven't had them on there for four years, well maybe I did ... that must have been the occasion when I bought an entire new valve. ( I had posted http://forums.tdiclub.com/showthread.php?p=2396740&post2396740, and a couple of other entries in that thread at the time. )
Another guess would be fuel dripping from the bottom (exit spigot) of the fuel filter. But that's a little less likely, and after removing the filter I had it sitting full of fuel for a while and didn't see any leakage, so I don't think so.
What I really want to see, and I would buy this aftermarket since I am lazy at this point ...
give us a two-line connector assembly to go between the filter and the IP, which has clear tubing
not only on the incoming path, but on the outgoing (return) path as well.
I have had this general issue, with air getting into the return side, before, and I think it could be spotted (visually) earlier.
My clear portion of the inlet tube doesn't always show obvious air, when there's air at the spill side.
If this is merely causing a dry condition at the injectors, that could make sense but
I still don't really understand how the usual priming (at the pipe from the banjo) is able to improve the situation.
Then again, that basic priming doesn't make it immediately start; it gives the engine a chance of starting, after a few tries.
EDIT: Is it possible that ambient air entering at the tee valve causes more of an issue than air entering the spill path ... or are they effectively the same part of the system ??
Sorry for the rambling post now.
Larry
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