Not fuel pump- is it the relay?

[biketsai]

B6 A4 1.8T- the car just would not start one day. It cranks just fine but it does not fire up. I have heard some odd noises in the rear coming from the pump or filter in the past few years so I assumed it finally went out.

Replaced the pump and filter but it did not start up. In my B5, I know when I turn the key into "ON", I can hear the pump whine but I do not hear that in the B6. Can you hear it in the B6? After installation, I went to remove the fuel supply line off of the top of the fuel pump canister and a little gas that was pressurized squirted out- Im not sure if this indicates anything.

So maybe it is the relay? Are these things known to go out after 145k miles?

[Luxus Panzer]

http://www.audizine.com/forum/showth...-Bad-Fuel-pump

[biketsai]

http://www.audizine.com/forum/showth...-Bad-Fuel-pump

Thanks. I saw that, but only one guy alluded to it being his relay and the OP got his to work after he did his fuel pump.

[Luxus Panzer]

Thanks. I saw that, but only one guy alluded to it being his relay and the OP got his to work after he did his fuel pump.

So did you do the test in the thread to rule out your fuel pump??

[biketsai]

So did you do the test in the thread to rule out your fuel pump??

Will give it a shot later this week. Unfortunately the car is about 30 mins from me so I am hoping to prepare all possibilities before I head out there.

[biketsai]

Should I be able to hear the fuel pump "humm" on a B6?

[Let it snow]

Should I be able to hear the fuel pump "humm" on a B6?

Yes. Turn the key but do not start it. It will prime for a second or two and you should hear it.

[Luxus Panzer]

Yes. Turn the key but do not start it. It will prime for a second or two and you should hear it.

Agreed, however, in my experience it will not prime every time you turn the key forward like older Audi models (B4). It will prime the first time for sure...bit I think if a specific pressure is present it will not re prime.

I just replaced my fuel pump at Xmas.

[walky_talky20]

^Correct. First time for sure, after that it's hit or miss. It's not pressure dependent (there is no fuel pressure sensor), but I think it's temperature dependent (or something). You can always have somebody put their ear to the trunk floor/FP access panel and then tap the starter for a second.

Make sure you have spark and injector pulse.

[ECS Tuning-Audi]

Coolant temp sensor. I had this issue last winter.

Jason

[biketsai]

Coolant temp sensor. I had this issue last winter.

Jason

What led you to that conclusion? Lower sensor or the one behind the head?

[ECS Tuning-Audi]

What led you to that conclusion? Lower sensor or the one behind the head?

Behind the head.

There's a few threads if you search that say change the coolant temp sensor if you have starting issues and your fuel delivery is good. Coolant temp sensor controls the enrichment for starting. So when you have a bad sensor the ECU doesn't know how to adjust fueling for starts.

Before I changed the sensor I tried a new relay which didn't work. I knew my fuel pump was working because I would hear it prime when I keyed the ignition on. And my fuel filter was only a couple weeks old.

As soon as I put a new coolant temp sensor in (Genuine sensors are recommended) haven't had the issue since.

I believe there even was an ECU code for the coolant sensor too confirming it needed to be replaced.

Jason

[Luxus Panzer]

My bad pump primed. It even moved SOME fuel when I held the starter on....Just not enough fuel to keep engine running.

[walky_talky20]

^This can happen.

Ideally, you would want to verify the line pressure is not meeting spec (ie: with a fuel pressure gauge), before you buy an expensive pump and begin the task of replacing it. If you are familiar with how it's supposed to sound, you can sometimes identify a faulty pump by how terrible it sounds while in operation.

[biketsai]

^This can happen.

Ideally, you would want to verify the line pressure is not meeting spec (ie: with a fuel pressure gauge), before you buy an expensive pump and begin the task of replacing it. If you are familiar with how it's supposed to sound, you can sometimes identify a faulty pump by how terrible it sounds while in operation.

I replaced the pump and filter already (figured it was time anyways at 140k). I did not hear any sound like I am used to hearing.
So I wonder if you will hear the sound run if you have a bad CTS? I am thinking there is still something up with the electrical side of getting this thing on. Bought a $8 relay so it might be worth a shot.

[Charles.waite]

What about the crank sensor? That's a very common "cranks but no start" culprit, especially at that age and mileage. Often doesn't throw a code or a cel too. It just up and dies randomly.

[biketsai]

What about the crank sensor? That's a very common "cranks but no start" culprit, especially at that age and mileage. Often doesn't throw a code or a cel too. It just up and dies randomly.

Ordered one of those too. I'm hoping to throw that in and a fuel pump relay.

[biketsai]

Had pressure at the fuel rail, put in a new relay and that didnt work.

Changed the crankshaft position sensor and that was it! Had a little trouble starting it at first, I must have flooded it. With some advice from another member, I kept going trying to crank it for long periods of times and then it finally started. CEL blinked for about 10 seconds to get the fuel out and then the light went off.