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I have a rather long winded story about a hard start problem on my 2002 Jetta. Several years back, when I hot rodded my Jetta, I bought an 11mm injection pump for $100 from a forum member who said in his ad that the salvage yard cut the connector and he thought it was probably unusable. When I pulled it out of the box to see if I could rewire it, I was pleasantly surprised to see the salvage yard had cut the wires before the connector for the IP so it was perfectly fine. 
I installed the pump after a preventive reseal and ran it hard for 200k miles.
Fast forward to this past winter, I was traveling for work and ended up in Milwaukee and Peoria on days when the temp was 20 below F with wind chills in the -30's and had some very long crank starts. I do carry an extension cord, but neither hotel I stayed in those days had a place for me to plug in
After spring hit, I noticed some longer crank times when cold, and progressively worse long crank times when hot. 5-6 seconds cold and 10-15 seconds hot. No DTC's were set and the car ran perfectly once started. I have actually been getting 50-56 mpg on every tank since my new low rolling resistance tires were installed and the car seemed to have decent power.
I did notice a feeling during hard acceleration that felt like worn inner CV joints, figured they were probably coming due soon.
I decided to dig into my hard start problem while at the shop today, I started by checking compression, close to 500 on all 4. Verified proper cranking RPM with VCDS. Verified relay 109 was functioning properly. I then removed the case pressure relief valve, and sure enough it had come apart completely. I put it back together and still had hard starts I checked fuel flow with a spare injector and during cranking I couldn't see any fuel flowing until the car started sputtering to a start after the usual 15 second warm start cranking.
A-Hah.
Case pressure must be too low from excessive wear from the sub 20 degree starts. Earlier the summer, my daughter's Golf was due for injectors, and she isn't a power junkie, so when I installed the Sprint 520's in her car I also swapped her 11mm injection pump with a 10mm pump I resealed so she wouldn't notice any power increase. (Her car came with an 01m but is now sporting an 02J) I saved her pump for a rainy day.
After installing the spare 11mm pump and priming and bleeding injectors, the car started like it used to, nearly immediately. Cold or hot, it busts right off. And my acceleration vibration is gone, so I'll be getting more miles from my inner CV joints.
I thought I would share this in case it will help anyone in the future.
I installed the pump after a preventive reseal and ran it hard for 200k miles.
Fast forward to this past winter, I was traveling for work and ended up in Milwaukee and Peoria on days when the temp was 20 below F with wind chills in the -30's and had some very long crank starts. I do carry an extension cord, but neither hotel I stayed in those days had a place for me to plug in
After spring hit, I noticed some longer crank times when cold, and progressively worse long crank times when hot. 5-6 seconds cold and 10-15 seconds hot. No DTC's were set and the car ran perfectly once started. I have actually been getting 50-56 mpg on every tank since my new low rolling resistance tires were installed and the car seemed to have decent power.
I did notice a feeling during hard acceleration that felt like worn inner CV joints, figured they were probably coming due soon.
I decided to dig into my hard start problem while at the shop today, I started by checking compression, close to 500 on all 4. Verified proper cranking RPM with VCDS. Verified relay 109 was functioning properly. I then removed the case pressure relief valve, and sure enough it had come apart completely. I put it back together and still had hard starts
I checked fuel flow with a spare injector and during cranking I couldn't see any fuel flowing until the car started sputtering to a start after the usual 15 second warm start cranking. A-Hah.
Case pressure must be too low from excessive wear from the sub 20 degree starts. Earlier the summer, my daughter's Golf was due for injectors, and she isn't a power junkie, so when I installed the Sprint 520's in her car I also swapped her 11mm injection pump with a 10mm pump I resealed so she wouldn't notice any power increase. (Her car came with an 01m but is now sporting an 02J) I saved her pump for a rainy day.
After installing the spare 11mm pump and priming and bleeding injectors, the car started like it used to, nearly immediately. Cold or hot, it busts right off. And my acceleration vibration is gone, so I'll be getting more miles from my inner CV joints.
I thought I would share this in case it will help anyone in the future.
