Low fuel pressure, despite new HPFP, new fuel pressure regulator, new fuel pressor sensor ?!

[qluvr]

...and here's a log file for a short crank session with lots more columns. Maybe some clues there? Some columns I don't understand. I really want to focus on the low Voltage crank problem. if that gets solved there's a chance I'm DONE with all problems. Maybe I got TWO bad OEM batteries in a row?

 

[pedroYUL]

Bad starter drawing too much juice and not spinning fast enough?

 

[qluvr]

Reminds me of a fellow here with the username "FixUntilBroke" , LOL.

I wish I had some silver bullet for you.

Any ideas on the low voltage/low rpm cranking? That's the problem I want to focus on. Everyone seems so focused on the HPFP/fuel system, but if I can get a fast crank, it's just possible that everything else works.
One suggestion was a bad starter that underperforms and draws too much current? Plausible?

 

[TurboABA]

Voltage Drop Test starter circuit... there's a connector\cable\ground\starter issue in there!

 

[qluvr]

I threw in the towel, I'm giving up on attempts to get past the low voltage crank issue to give the BH/SQ5 pump a fair trial.

I've ordered the correct 'CD' variant pump, be here Wed/TH.
Btw -Cascade German Auto Parts rocks. $1,500 instead of $1920 stealership price (or $900 direct from Bosch but they were backlogged too long)

I got a quote from a reputable local VW-centric shop to do the R&R for $1,600 labor which seems quite reasonable for this 'buried-in-V/under-turbo/rear-mounted pump'. I'll probably do that assuming they'll work on a deleted vehicle. Then if the low voltage crank thing persists after the right pump installed, the shop can figure it out with my gratitude. And I get 20+ hours of my life.

 

[oilhammer]

Wait, I must've missed a part in all your ramblings....

But, just to be clear:

You had no issue with the engine running.

You replaced a pump that didn't need to be replaced.

And you replaced it with the WRONG PUMP????

 

[TurboABA]

Affirmative (he got a pump from a 313hp BiTurbo just because why not) ..... a pump is a pump

 

[oilhammer]

Oh, Jesus....

 

[qluvr]

Wait, I must've missed a part in all your ramblings....

You had no issue with the engine running. <<< Correct, what started this odyssey was a coolant leak from the coolant valve buried in the 'V' and I asked the forum for advice on what to replace while I had the labor-intensive 'V' exposed. It was an obvious time to physical delete the EGR cooler with a Darkside kit. The Malone tune II was running great for a month before the leak happened.

You replaced a pump that didn't need to be replaced. <<< probably/mabye true. On internal inspection the original HPFP had minor pitting on the cam but perfect rollers and cylinders/pistons. Have been using a lubricity additive for 90% of the Treg's life. Would the minor pitting progress to a grenade at some future mileage? Maybe. who knows? A survey of CP4 HPFP failures showed most failing, that failed at all, around 130K ish miles, some as soon as soon as 90K (and likely others still working fine up around 200K.)

And you replaced it with the WRONG PUMP???? <<< yes I had a major stoopid moment, though in fairness I was told by someone that the trailing letter codes on the same numeric part number was just minor variants for the various ports and connectors to point in the right direction. But still. I was an idiot to follow that advice and not get the correct "CD' variant for 2.5X the price. Especially since the '13 and later HPFP is sooo labor-intensive to R&R, penny wise and pound foolish. Hope that others don't make my mistake.

Many thanks to you oilhammer for your huge contributions to the forum.

 

[PRY4SNO]

"A survey of CP4 HPFP failures showed most failing, that failed at all, around 130K ish miles, some as soon as soon as 90K (and likely others still working fine up around 200K."

What survey is this? Have a link?

 

[qluvr]

"A survey of CP4 HPFP failures showed most failing, that failed at all, around 130K ish miles, some as soon as soon as 90K (and likely others still working fine up around 200K."

What survey is this? Have a link?

i spent an hour or so doing my own survey on 3 forums and found about a dozen reports of HPFP failures at various mileages. a few graceful failures, and mostly grenades, for which stealerships wanted ~$13k to fix, which is catastrophic enough to consider freshening up the pump to prevent a low-probability event, or so I reasoned at the time. Which may have been stupid logic. The original HPFP's cam did have minor pitting though the other parts, (rollers, pistons, cylinders) were perfect. (lubricity additive used). Nobody knows if the next 100K miles or so would result in worse pitting and eventual grenade.

 

[qluvr]

Hi all, (the OP)

Our beloved Touareg LIVES! it RUNS, very well. The wife is VERY happy as it's her daily driver. Much of the engine is new and intake path is clear of fat carbon, fully deleted, should run for aother 130K miles easy.

The mystery solved by a clever mechanic who's now my hero. He found that the spline on the installed HPFP wasn't quite right. I don't quite understand the spline-sprocket geometry issue, (i.e. why the shorter spline that came already on the "BH" variant didn't let the chain slip!), but he put a longer spline on the new "CD" correct variant pump and voila. Engine started, runs great! (The theory about a sprocket-HPFP mismatch idea was sooo close, literally, to being right.) BTW - I had VW dealer mechanic torque the BH's spline nut as I didn't have the spline-holder tool and he didn't spot the diff.

Post-mortem on the orignal HPFP: the rollers, cylinders and pistons were perfect, however the cam showed early stage pitting, which could eventually cause a grenade I suppose. Not soon but eventually. I used main brand fuel and a good lubricity additive most tankfuls, after purchase from the original owner at 45K miles. Now at 130K miles.

(The seller of the incorrect BH pump gave me a full refund.)

I forgot to ask him about the low-voltage crank resolutionn I was so elated, but will soon and report back.

BTW - as I suggested to him, once he undid the turbo-manifold, turbo-manifold bolts, he was able to gently pry up the turbo and remove the rest of the bolts to R&R the HPFP, which avoided a lot of cramped labor and aggravation. Remember that on '13 and later Tregs the HPFP is buried in the back of the 'V', as opposed to right up front on earlier years.

Many thanks to all, esp VW-for-life and SavageSoot. What a great forum and members. (I even enjoyed the occasional abuse with good humor.)

 

[oilhammer]

Thanks for reporting back.

So, the issue in a nutshell: you took off a perfectly good correct pump, put on a new wrong pump, and the engine wouldn't start. Put the correct pump back on, and it runs again. That about sums it up?

Like I said, I must have missed the part where you said you installed the wrong pump. I would have called that out right away had I known.

 

[TurboABA]

Like I said, I must have missed the part where you said you installed the wrong pump. I would have called that out right away had I known.

Unfortunately (for him), he didn't really disclose that in a timely manner.... unless you followed both posts (over 200 reply discussion on CT), on both forums, you wouldn't know....
It's great he finally has a functioning vehicle.... tough lesson for sure, but hopefully he did learn something.

 

[oilhammer]

We have (had?) a user here with the name "fix until broke".... seems fitting in this instance.

The other phrase that comes to mind:

"If it is working, take it apart and find out why!"

 

[d2freeman]

My original cp4 is still purring along with close to 420k miles, I bought a spare a long time back but it will probably never be used.

 

[TurboABA]

My original cp4 is still purring along with close to 420k miles, I bought a spare a long time back but it will probably never be used.

Depends on lots of factors.... quality fuel and proper maintenance is a thing.... so is "tuned" and stressed, overfuelled, etc.... 4.1 vs 4.2, yaddi yadda...

 

[qluvr]

Our Treg is back to life and running great. The problem was a donor HPFP spline that was a bit short. Longer spline and everything works.

 

[qluvr]

My original cp4 is still purring along with close to 420k miles, I bought a spare a long time back but it will probably never be used.

The orignal pump I pulled out had pitting on the cam, not a good sign for lasting another 130K miles!

 

[PRY4SNO]

The orignal pump I pulled out had pitting on the cam, not a good sign for lasting another 130K miles!

How much pitting?

Have any photos?

Is this normal wear and tear or something signalling imminent doom and catastrophic failure?

What's the spec for wear tolerance?

Genuinely curious, as I have the same pump, but don't have any plans to change it anytime soon (absent any external indicators like codes, etc).

 

[qluvr]

How much pitting?

Have any photos?

Is this normal wear and tear or something signalling imminent doom and catastrophic failure?

What's the spec for wear tolerance?

Genuinely curious, as I have the same pump, but don't have any plans to change it anytime soon (absent any external indicators like codes, etc).

photos of the pitting are hard, as the cam is way down in a narrow cylinder at least phone pics. I'd do a macro shot with my big Canon and a macro zoom lens but the camera body died.
There's no real 'spec' AFAIK. pitting is likely the main failure cause for HPFP grenades.
In lieu of a photo, I'd describe the pitting on the cam as minor but who knows how it would progress. My one data point is not that useful anyway. MANY people have long life with the CP4 generation pump, but I spent an hour scanning two Treg/TDI forums to find a number of grenade style reports, and a very few 'graceful failures'. Grenade events varied from roughly 70K miles to 150K miles. My calculus, which has been criticized "if it aint broke don't fix it" -- is that I _had to expose the 'V' which is a long, difficult, tedious job to replace a leaking coolant valve next to the HPFP, so after doing that not very scientific grendae survey I decided to get a fresh pump to lower the odds of a grenade long term, and hopefully avoid $13K dealer quote for fixing a grenade event. It's a judgement call, but realize that on '13 and later Tregs the HPFP is quite buried in the back of the V and it's a damn tough and tedious job to replace it. If you do get into the 'V', be sure to replace the plastic coolant valve next to the pump, it's a known leaker. I did an EGR physical delete using a Darkside kit as long as I had the V exposed, as the cooler is another known leaker at high mileage.

If you have an older Treg with the HPFP right up front, not buried in back, the labor is a small fraction of hours and difficulty, so the bar is lower to replace the pump. However Pro mechanics on the forums don't like PM for HPFPs.

 

[PRY4SNO]

Didn't know about the plastic coolant valve, do you have a PN? I'm in the "if it ain't broke" camp, so I probably wouldn't have changed it unless it appeared brittle or was weeping.

When I did the delete it was a 4 hour job to do the EGR portion, start to finish. The exhaust portion and tune was tackled the next day, another four hours start to finish. Wouldn't call either job long or tedious, just involved. But everyone's calculus is different.

 

[qluvr]

Didn't know about the plastic coolant valve, do you have a PN? I'm in the "if it ain't broke" camp, so I probably wouldn't have changed it unless it appeared brittle or was weeping.
When I did the delete it was a 4 hour job to do the EGR portion, start to finish. The exhaust portion and tune was tackled the next day, another four hours start to finish. Wouldn't call either job long or tedious, just involved. But everyone's calculus is different.

your scope of work isn't so terrible/long. Replacing a '13 or later HPFP is indeed much harder/longer, as the turbo has to come loose or out, which means removing frozen turbo-manifold bolts (super difficult unless you drop the engine).
The plastic coolant valve's shaft is a known leaker at high mileage and it's inexpensive and quite easy to replace while you are in the 'V'. Mine was leaking out the shaft seal. don't have the part # handy, but easy to spot on ETKA just to driver side of the HPFP and oil cooler ('13 on).