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I went thru the low power thread probably twice or three times. car has low power and zero faults. I'll give you a rundown of what I've done:
Customer said it slowly lost power over 3 days until no power. Started with the basics, verified timing and pump timing by putting plate on cam, pinning IP and verifying crank @tdc, check vacuum lines and VVT diaphram operation.*
Tested Maf, tested wires to maf for resistance, short to ground and short to power.
Verified power and ground to MAF*
Have ran some logs via VCDS and car runs no better with the Maf unplugged.*
Right now I have vacuum plumbed directly to the N75 vac port.*
Tested boost pipe from turbo to egr for leaks.*
Checked Map/iat per the Bentley.*
Vac line to booster is good and good vacuum directly to VVT
fuse 34 is good
Replace ECU with known good one, no change
109 and the power relay(in position #2) good
Snow screen is clean and right now running straight thru the maf without filter box or filter.*
Vac pump is working as I do have vac to the N75.*
Slight resistance in the fuel pickup so replaced*with new one.
In tank is clean, no algae or trash, car has not been fueled in a couple of weeks, car has never ran bio.
Fuel filter is new.
No oil in boost pipes or intercooler
swapped out injectors with some from one of my tdi's, no change.*
all cylinders >380 psi and within 10psi of each other.
Checked all wires to IP to ecu/destination for resistance, short to +)(-
Checked EGR for proper seating when closed- currently unhooked
New Turbo
Intake cleaned resently- verified by removing and installing
Cleaned grounds under the battery
Had a fault for faulty CTS, replaced
Ran vehicle on clean/new fuel with no change
Swapped out IP with known good one no change
Tested IP sensors at connector, all tested within spec to destination
verified mark on crank at pulley and flywheel the same, #1 piston also up
Fuel return valve pointing right direction
New Maf harness
just tested a new maf also, no change
Pedal has been tested via VCDS
exhaust has good pressure out the rear and loosening exhaust from turbo has no effect.
have logs also attempting to do a 3rd gear pull
 

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Discussion Starter #3
I guess I should have said, low power, no power and no faults. car will barely pull itself. log shows it is boosting up to 1900+- but maf never increases above 635. I'll attach some logs in the morning.
 

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Have you checked the camshaft and lifters for excessive wear? It's a good chance they're worn since they would cause low power and no fault codes. There's a write up in the DIY for what to look for. Is there any unusual noise like a popping or thumping sound coming from the intake and/or exhaust?

Since you've checked everything else, the only other thing I can think of is gas (petrol, not diesel) in the tank... If the customer accidently put gas in there mixing with diesel it would cause low to no power.
 

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Discussion Starter #6
yes, to add to the list I did check the cam and lifters however it is an ALH and not really prone to the PD wear problems. As stated above I have ran the car on an alternative fuel source with fresh fuel.
 

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As stated above I have ran the car on an alternative fuel source with fresh fuel.
Sorry, I seem to have missed that one on the list. Any other symptoms other than low (or no?) power? Does it start up ok? Does it rev up ok just not move?
 

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Since there are no fault codes, compression and air supply is good I would then guess fuel restriction. Have you checked fuel pressure to the IP? Maybe blockage in fuel supply line(s)?
 

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Discussion Starter #10
Since there are no fault codes, compression and air supply is good I would then guess fuel restriction. Have you checked fuel pressure to the IP? Maybe blockage in fuel supply line(s)?
I kinda ruled that out running it on a jug a fuel 3 feet from the IP
 

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Ok, that rules out blockage. Were you just revving it parked or driving it with the jug supplying fuel? I assume you had a pump in the jug when doing that test? I imagine there should be some PSI supplied to the IP...

Have you checked the VNT actuator with a vacuum pump to make sure it moves freely? If the rod is stuck or vac port blocked you could have underboost... at 2500rpm you should have plenty of boost so that could be it seeing as fuel supply is unrestricted.
 

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No, ALH has no positive fuel pressure, the pump is straight suction (although you can mod it to add the BEW in-tank lift pump). GpoJerry: can you upload the raw data or graph it? I think most people (me included) don't want to look at the raw data in an image form, it's a pain to transcribe it and it's hard to see what's going on. I don't have any good recommendations for what blocks to measure; MAF and MAP might be good, needle lift sensor might be helpful... I'd also check/verify timing via VCDS as per the timing belt howto. Sounds like a tough nut to crack.
 

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no, has no balls and does not like to rev above 2500 unless going downhill
GpoJerry, any luck diagnosing/repairing the problem? I'm really curious what the problem is/was considering no stone was unturned in troubleshooting...
 

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Discussion Starter #14
ok guys, thanks for the ideas and questions. I drive the car with a container of fresh fuel ziptied under the hood. I will graph 3, 5, 10, 11 and post them. did a couple of other things today. Since this is a non-immo car I ran it without the instrument cluster to rule out coolant intrusion like some of the beetles had. Also:
  • Quantity adjuster verified key on engine off(block 19), value in first window 0.740(spec is .50-.97), window 2 value 4.52 volts (spec 4.15-4.74)

  • N75 has battery power to the valve, tested 16.5 ohms (spec is 20-30, although a new one tested the same) (keep in mind I have vacuum going directly to the VVT right now) just verifying wiring in the engine compartment to ecu/destination

  • N18 has battery power to the valve, Tested at 15.5ohms (spec is 14-18), tested short to power and short to ground

  • IAT & MAP sensor tested within spec, wires tested to ecu and destination for continuity, short to +-

  • Remove exhaust pipe- no change

  • Removed ECU and verified no water intrusion or burnt areas

  • Hooked mechanical gauge to boost pipe, 12psi(this is a little low but the engine will not add enough fuel for full boost if there is a problem).

  • Removed instrument cluster and test drove- no change. (some beetles had the coolant transfer to the cluster problem)
thanks for the feedback, will do some graphs and likely post in the morning.
 

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Just following up. I swapped my nozzles with a used set I had from a PP520 upgrade years ago, car is now driving like normal. Prior to this, can't believe how well it started in -20 c, how it revved up in neutral. I understand it doesn't need much fuel but still. Zero smoke other than what I would consider normal startup haze then it would clear up. No smoke while driving. Boost, maf met requested, injector deviation looked fine, countless parts swapping and heachaches. Tired old injectors with almost no sign of being so, who woulda thought. Hopefully this can help someone else out one day!
 
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