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Hard Start and LPFP

M

madelinot

Ready to race!
Location
Ottawa, ON
Hi all,

I’m having an issue where my 2016 R is hard to start, especially when cold. Sometimes, between 4-8 seconds to start. Here are my pertinent mods:
  • APR EFR7163 Stage 3 kit with custom electronic wastegate actuator
  • Eurodyne Maestro Stage 3 ECU tuned by Moose
  • Walbro 525 Hellcat Low Pressure Fuel Pump
  • Torqbyte PM4 fuel pump controller module
  • Precision RaceWorks 1300cc MPI
  • APR Red Top Ignition Coils
  • NGK 4656 {#R74389} Racing Plugs
  • Intake ports divider removed
The hard start situation seems to have slowly degraded over the last several months. I think this issue has to do with fuel. On the low-pressure side, I am seeing pressure of about 3.2 bars with ignition on. Most people seem to think that should be at least 5 bars with ignition on (engine off). VW does not publish a spec for this. What are people seeing? What pressure level should I see with engine off and ignition on? What should be the LP pressure at cranking?

Here is what was done to try to pinpoint the issue, without any improvement:
  • Replaced all plugs and coils
  • Replaced LPFP with a new one (525)
  • Replaced the PM4 with the OEM controller
Increasing the duty of the LPFP while cranking seems to help a bit, but the car was not exhibiting this behavior previously, so I think something is going on.

I’m still using the original OEM battery and it tested okay at the dealership. Most people I talked to don’t seem to think it’s related to a faulty battery. The car seems to crank the same as before, just longer.

I did remove the intake port divider to help with the DI spray pattern. Has anyone seen this causing hard start issues?

Other than the hard starts, the car runs great and I have enough fuel at WOT. I'm not getting any code.

Any insight as what the issue could be?

Thanks!
 
M

madelinot

Ready to race!
Location
Ottawa, ON
One thing that I'm thinking now.... could I have a leaking port injector (or maybe more than one) that is flooding one cylinder making it harder to start? I guess I could test that too with a gauge...
 
Last edited:
JerseyDrew77

JerseyDrew77

Autocross Champion
Location
Virginia & NC
Car(s)
2016 TR GTI S 6MT
madelinot said:
Thanks! I guess you mean the DI injectors. That's a good idea. Wouldn't they misfire if that was the case?
Click to expand...

Yes, the DI injectors and for the most part, they would misfire if they are only spraying a little. You can first try different cleaners like Seafoam, Red Line, Chevron, etc... before pulling them and cleaning them out or replacing them.
 
M

madelinot

Ready to race!
Location
Ottawa, ON
Right now, e50. And I know it's normal to be harder to start on a blend. Last summer, I was also running e50-e70 and it was NOT that hard to start. The thing is that it was also hard to start a few weeks ago running regular 94 pump gas. I do adjust the tune to consider the ethanol blend.
 
M

madelinot

Ready to race!
Location
Ottawa, ON
I can see in VCDS that the car is requesting 5 bars, but I'm only getting 3.2 to 3.6 bars with ignition on. I think that's the issue, but I can't understand what the source could possibly be. I would also expect the ECU to throw some codes over this. I have a low pressure gauge kit, I will do some tests over the weekend.
 
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