Is my fuel pump dead?

[ItsCAvalos]

Hey looking for some help for my 2009 A4 Avant.

I parked my car since Friday when it was running perfectly fine. I go to start it this morning and it cranks but no start. Doesn’t even try to fire. I tried jumping the car wondering if it was a low battery but same thing, just cranked faster. Pulled codes anddddddd nothing abnormal. Same ones I’ve had (bad motor mount). I looked and swapped the fuel pump fuse located on drivers dash and still nothing. I noticed that when I unlock and open the door I can’t hear the fuel pump like I used to. Any other fuse I’m missing? Or mystery item?

On a side note, I have a 2010 S4 from the auction that doesn’t run (but I think related to airbag stuff). Am I able to scavenge any parts from that to see if it is my pump? Thanks

[Smac770]

If you don't have a DTC for the in-tank pump or pump controller, probably not that. What was the fuel pressure measuring value while cranking?

The car isn't going to prime the pump if it feels it's already primed. Come back and unlock and open door after it's sat for a few hours. The 5-pin to the pump controller is there under the seat at the pump; do you measure 12v from pin 3 to pin 4? Pin 5 is PWM signal from the ECM. Pin 1 to pin 2 is the power to the motor, to pins 1 and 5 on the 5-pin on the pump flange.

[ItsCAvalos]

I don’t have a fuel pressure measure tool so I’ll see if I can rent one tomorrow. Otherwise I’ll look more into your recommendations tomorrow


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[Smac770]

You would just query the measuring value in the ECM using the tool you say you "pulled codes" with. What tool are you using? Obviously, the preference would be VCDS.

[ItsCAvalos]

I’m using OBD11


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[ItsCAvalos]

According to OBD11, fuel pressure hovers around 1000psi when cranking


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[Smac770]

Ok, so look at fuel pressure under live data under 01-engine. That's the high pressure rail pressure. You won't have a low pressure line pressure sensor (G410) on a CAE engine.

Should be a few hundred kPa after opening the door and the pump priming, then lift up to 1000+ kPa pretty instantly. Cold start high idle might be 5000 or 6000 kPa (50 or 60 bar; 5 or 6 MPa), normal idle is around 4000 kPa (40 bar; 4 MPa).

But if you're not hearing the pump prime on opening the door after the car has sat for a long time, something would seem to be up with it. But not likely if you have no codes for such under 01-engine.

[ItsCAvalos]

I looked and nope. Highest I saw was briefly 1500 psi and that’s for a split second. Cars been cold and I’m trying to manual run the pump. During the output test I can hear the rear pump spinning


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[Smac770]

That doesn't make any sense. 1500 psi is 103 bar or 10 MPa. That would be more WOT pull fuel pressure. Maybe meant 150 psi? All the Audi specifications are in metric. It's easier to measure and discuss in metric than unnecessary imperial conversions. Be easier to log the value and then go back through the log than to expect to see much in human speed real time.

The MY10 S4 3.0T will use the same in-tank pump and pump controller under the rear seat as the MY09 A4 2.0T, but completely different HPFP on the engine itself.

Have you checked the tensioner state via the inspection port on the lower timing cover to be sure it's not fully extended? Aging 2.0T, do you know what the state of the camshaft adaptation value was? You can't get a legitimate value without the engine running and warmed up.

[ItsCAvalos]

It constantly shows 950+ psi just cranking so I’m not sure?

I need to check the tensioner but it should have like 80k or so miles since timing has been done


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[Smac770]

I wonder if the high pressure rail fuel pressure sensor has gone kaput. The orange plug sensor on the rail under the intake manifold plastic.

If you look at the value after it's sat for a while and not cranked, is it in the more expected range of 250-400 kPa?

But that value might not be overly high (is it around 50 bar?). You might need to look to other issues like spark and compression.

[ItsCAvalos]

I’ll see if I can take a video later and maybe that’ll help?


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[Smac770]

Normally I'd say just run a log. That's the useful action that's informative and easily shared.

For example, here's an image of my processed log from VCDS of a cold start of my MY09 CAEB for whatever reason I had made it.

CAEB cold start log sample.jpg

I assume I pressed the start button around 6.1 seconds and the engine started the process around 6.3 seconds. I assume I got ignition probably around 6.8 seconds.

We see the fuel pressure had been primed up to low 400s kPa. If I have a set up where I measure the overnight cold pressure without the door priming, it would be closer to 300 kPa. But we see it takes no time for the fuel pressure to come up to operating spec. We see the fuel pump specified value, the PWM duty cycle to the in-tank pump controller, go to normal range immediately. This is a cold start, so it's going to take the idle up to 1200 for a bit to warm the cat. But we see in this instance, the fuel pressure specified remains at the normal idle value of 4000 kPa. The burst up to 5000 kPa is not sustained, so it must not have been a cold, cold start. Otherwise, I'd see it sustain 5000 kPa for a while.

But that yours is bursting well outside the expected range, it's like the engine lacks control of the pump output pressure. But if you have no codes, ....

[ItsCAvalos]

Hmm I can’t quite figure out how to data log using OBD11 and the iPhone. However, after sitting for 24 hours the car still read 950 psi of fuel pressure. After trying to crank several times it reads 1057 psi.


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[ItsCAvalos]

I checked plugs and coils. Coils looked fine but plugs definitely have seen better days. I swapped them out with a used set I had laying around and same thing. Changed coils too and nothing.

I took a video too but I don’t know how to upload it

[Smac770]

If it's still reading 950 psi after hours of not being attempted to be started, I'd have to guess there's an issue with the pressure sensor. And if it is an issue with the pressure sensor and it's reporting way more pressure than actual, the ECM is going to cut the fuel delivery volume by the HPFP as much as possible, resulting in little to no actual fuel in the rail. This might also be why you're not getting any fuel pump priming; the ECM thinks the high pressure rail pressure is already well above priming threshold.

It's not likely a wiring issue since the value is not pegged to "max or min" and you say you don't have any error code for the sensor.

[ItsCAvalos]

Well I’m disappointed to say the new pressure sensor didn’t fix it. Interestingly enough, when I went to start it, the old sensor read somewhere around 96psi and almost fired up but didn’t. Swapped it out and the sensor still measured 900ish psi when cranking but still didn’t fire up. While unplugged I got the trouble code for open circuit for the sensor so that part works.

I also tried unplugging the sensor on top of the HPFP and heard it cavitation. Tomorrow, once my battery charges up I think I’ll crack the fuel lines like Naptown Tuner has in his video.


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[ItsCAvalos]

So more diagnoses. I cracked open both high and low pressure lines and fuel came out so that’s good I guess. Funny enough I discovered that if I unplug my fuel injectors the car gets closer and closer to starting but doesn’t. Is there a module for those or something? No fault codes still but open circuit when I unplug them.

Also on a side note I broke the retainer clip for the fuel injection so if anyone knows the part number or something for it let me know please


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[Smac770]

The fuel injectors are wired directly to the ECM, via an 8-pin plug hanging off the back end of the intake manifold.

Not sure what you mean by retainer clip.

The plug on top of the HPFP is not a sensor; it's a solenoid that the ECM pulses at a specific point relative to the engine timing to control the injection volume. That's why if the chain is aged and the exhaust cam is not quite where it should be in the timing, the ECM's pulses will not align with the pumping by the exhaust cam and incorrect fuel volume is injected into the high pressure rail.

[ItsCAvalos]

These are the best pictures I could get. New iPhone likes to switch camera and not focus.

IMG_7234.jpgIMG_7229.jpg

[Smac770]

1, that's the original style tensioner.
2, I can't really make out the notches, but it looks pretty extended.

I would say it's time for a timing chain job, and to replace the tensioner as well (the tensioner does not get replaced normally, only if you still have the original time bomb design, which you do).

youtu.be/3Dd5Gnvq40g?t=705
So he's counting four teeth, the VW doc says 7 or more and chain has to go.

[B44]

buddy did you check your in tank fuel pump? Second if you keep the key plugged in on mode and wait should throw some code.

[ItsCAvalos]

I think I counted 8. I thought it would throw a code before then instead of instantly not starting.

Yes I checked and cycled the pump with OBD11. There is fuel pressure at both high and low pressure lines.


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