Help please! Fuel pump relay or ignition switch?

[catamount90]

Hey guys, I've got an '03 A4 B6 that was running great, but now isn't starting.

I've pretty much narrowed it down to a fuel issue, but need help at this last juncture.

• The fuel pump isn't priming the lines when you turn key to 'ON'
• The fuel pump runs when I "jump" 12V to fuse 28 (fuel pump fuse)
• The fuel pump, once running has great pressure (55 PSI / 3.7 BAR) confirmed on fuel rail
• I can't hear the fuel pump relay CLICK when key goes to 'ON'

Can anyone confirm that the fuel pump relay is the one marked 167 and is the left-most relay on the relay rail behind the fuses?

Unfortunately, I don't have another relay to throw in there for the moment unless any of you happens to know if any of the other relays under the dash will plug-and-play.

Is it possible that this is an ECU or ignition switch issue, instead of a relay issue? Any way to test the voltage coming into the relay slots to see if the "trigger voltage" is coming from the ECU?

Thanks guys!

[old guy]

There is a ton of diagnostic information in this thread: Clickty click

[catamount90]

Thanks, old guy! I'd actually read that thread in my travels. I do get 12V at the relay blades, but was hoping to see one of the "blade slots" (the control voltage slot) "kick up" for 2 seconds during the initial fuel line prime that is supposed to happen when you turn the key to 'ON'.

I didn't see any voltage spikes during 'ON' but one of the blades on the relay is very tiny and my multimeter probe wouldn't fit into it's corresponding slot on the relay panel.

It looks like I've either got a relay problem, or a problem in the ECU box. My pump charges the line great when I jump the FP fuse.

[Gmoney]

I had the same issue a few days back and Old Guy really helped me out. I found a replacement relay from Federated Auto Parts for $13.

thank you OG

[catamount90]

I had the same issue a few days back and Old Guy really helped me out. I found a replacement relay from Federated Auto Parts for $13.

thank you OG

So your problem was the relay as well? I looked up your post history and saw something about a fuel hose, but very few other details.

OG rules though!

[Gmoney]

Yeah I have had an issue with my fuel line near my fuel filter for the last 2 years. I have really only been putting a band-aid on it. i assumed without looking that was my issue. Basically my car wouldn't start and I was late to work so I had zero time to look. I ordered a new line but haven't put it on yet.

But I definitely thought I had a fuel issue. I PM"d OG since I didn't have any response's in my thread and he gave me solid advice that just backed up exactly what I thought was wrong. I didn't test the relay I just figured for $12 I would go ahead and grab one and throw it in there. I primed the pump 4-5 times and started the car up. It sputtered for a minute or so but has run solid ever since.

What you have going on sounds very much like what I encountered.

OG definitely rules.

[catamount90]

Well, it looks like I need to find a relay then! You're right, $12 is child's play when an Audi is involved. I'm slightly bummed though, I have a 1999 A4 and it doesn't share the same relay. I was hoping to borrow one for it for testing purposes. Will chime back in on this thread after I find a replacement relay... hopefully on a Sunday.

[Gmoney]

I was going to try and use my girlfriends 06 B7 A4 as well but she didn't have the same relay either. That kind of surprised me as well.

[fergmonster]

Was the pump making any noise? how about a loud noise? Many times this is just a clogged filter- then a pump failure can follow.

[catamount90]

Was the pump making any noise? how about a loud noise? Many times this is just a clogged filter- then a pump failure can follow.

Please see my first post about jumping the pump and checking the fuel pressure, and it was good.

[catamount90]

UPDATE: Today I tried another FPR. The fuel pump still wouldn't kick on with the key in 'ON' position.

At this point I can only imagine that it's either the ignition switch or ECU.

Or some kind of relay in the ECU box itself?

Really at a frustrating point right now. Any and all help is appreciated.

CN: What is your next move if your fuel pump is not 'priming' or running when the key is on/cranking and you know the pump & relay to be good?

[old guy]

If you are not getting power to the fuel pump relay with the key in the on position your ECM master control relay may not be working.

[catamount90]

Hi old guy, I actually -am- getting 12V to the relay slots. However, the "control voltage" is not firing off my relay.

Do you happen to know if a fault crank position sensor will prevent the fuel pump from priming? With my VAG, I am able to see "engine speed" increase as I crank it so I've taken this to mean that my crank sensor is working but maybe I'm assuming too much?

Do you think the ignition switch could be at fault here?

[old guy]

You confirmed 12v to the relay. Are you sure you are not getting control power to the relay? You mentioned that the slot was too small for your multimeter to check. Pick up a small plug blade from Radio Shack that will fit the control voltage slot to confirm for sure whether or not you are getting control voltage. Also use you mulitmeter to confirm a ground circuit on the ground slot for the control voltage.

[catamount90]

That's a good idea old guy, I'll try that. I can connect to the ECU via VAG so that suggests to me that it's not 100% dead. Unfortunately, the car is outside and it's winter in Vermont so my diagnostics are not very enjoyable. Brrrrrr.

[old guy]

Just to be clear, I'm referring to the ground connection slot for the fuel pump relay. Make sure you have control power going to the relay and a good ground at the slot that completes the control circuit for the relay.

Also, I'm gathering from your comment above that you may be experiencing low battery voltage from all the continuous testing. Make sure you have a solid 12.6v from the battery. If not, you need to get it fully charged before you can properly diagnose your problem. Low voltage can cause all sorts of unpredicted issues.

Good luck!

[catamount90]

Just to be clear, I'm referring to the ground connection slot for the fuel pump relay. Make sure you have control power going to the relay

I definitely have a ground connection at the relay, but I can't tell how "good" it is. My continuity tested didn't go off when I grounded it on the frame but it did read a pretty low resistance (185).

and a good ground at the slot that completes the control circuit for the relay.

I took your advice and found a slot of metal to stick into the control circuit. When completing the circuit between the control on the relay slot and the ground slot while flipping the key to ON I saw no continuity or change in resistance. In other words, I don't think the ECU is sending the control ground through.

My battery is good to go, I've been keeping it on a float charger.

I wish there was a way to tell, through VAG, if the "control" to the fuel pump was being sent.

[old guy]

OK. Try one more thing. Use your metal insert and check for control voltage with your multi-meter to a known ground instead of through the relay ground slot and see if you get a control voltage reading when you turn the key to the on position or when cranking the car.

[catamount90]

OK. Try one more thing. Use your metal insert and check for control voltage with your multi-meter to a known ground instead of through the relay ground slot and see if you get a control voltage reading when you turn the key to the on position or when cranking the car.

Same thing... nothing when I ground the control voltage to a known ground (instead of the ground on the relay harness) while turning the key.

The ECU is definitely not passing me a ground.

[old guy]

Same thing... nothing when I ground the control voltage to a known ground (instead of the ground on the relay harness) while turning the key.

The ECU is definitely not passing me a ground.

Damn!! Hate to say it but at the moment I am stumped. Sounds like the ECM just isn't trying to activate the fuel pump. I will take a look at the wiring diagrams and see if I can come up with anything.

Sorry!

By the way, have you replaced fuse #28?

[catamount90]

Well I surely appreciate your time old guy. Your knowledge is invaluable to so many of us.

I've checked fuse 28 many times. Even jumped it to make sure the pump works. The pump works :/

I guess my next step is replacing the ECM. Ugh. It was running great until this happened.

And just to be clear, a faulty ignition switch would probably not be the cause of this, right? I mean, the car does crank. What about a crank sensor... can a bad one tell the ECM to kill the fuel pump signal?

[old guy]

Well I surely appreciate your time old guy. Your knowledge is invaluable to so many of us.

I've checked fuse 28 many times. Even jumped it to make sure the pump works. The pump works :/

I guess my next step is replacing the ECM. Ugh. It was running great until this happened.

And just to be clear, a faulty ignition switch would probably not be the cause of this, right? I mean, the car does crank. What about a crank sensor... can a bad one tell the ECM to kill the fuel pump signal?

I don't think it would be the crank sensor since you indicated that you could see the motor speed while cranking through VCDS. If it wasn't functioning I don't know where else the ECM could get that signal. I am looking at the wiring logic right now to see if the ignition switch could be a cause of the problem. If nothing else, the switch is a hell of a lot cheaper than a ECM and might be worth a shot before spending the big $$.

[old guy]

OK...From what I can gather from the wiring diagrams the ignition switch provides continuity to the relay while cranking and once the car starts the ECM provides the control circuit. what I haven't figured out yet is why your pump doesn't prime when you initially turn the key to the on position. Unfortunately that appears to be initiated by the ECM when you first activate the starter switch. It is beginning to look to me like the ECM isn't doing what it is supposed to do. Since you are able to jump the relay and get the pump to work you could go ahead and do that to get the car running and see if you can find a shop with some more advanced diagnostic equipment.

Sorry!

[catamount90]

Well, I just tried that. Jumped the pump to prime it and then cranked it. Wouldn't catch. Didn't even feel like it wanted to run.

GRRR. It's looking more and more like the ECM, but I can't even free the wiper arm and I'm afraid I'm going to crack the windshield if I pry on it at all.

old guy, thanks for your support this evening. It was much appreciated.

[old guy]

If you jump the relay the pump should continuously as long as the ECM master control relay is powered up. The wiper arm can be a real bitch to remove. Just spray it with a little PB Blaster or Liquid Wrench and keep wiggling it back and forth. It should eventually come loose. You can also try loosening the nut about ¼" and pull up on the arm while tapping down on the nut. Watch out for the windshield!

[old guy]

I thought about this a little more last night. If you have 12v power to the relay block with the key in the on position you should be able to jump the power across the relay and force the pump to run. If the motor still doesn't start you may have a different issue altogether. Have you checked all of your engine management fuses? Have you confirmed that the injectors and plugs are firing?

[catamount90]

I thought about this a little more last night. If you have 12v power to the relay block with the key in the on position you should be able to jump the power across the relay and force the pump to run. If the motor still doesn't start you may have a different issue altogether. Have you checked all of your engine management fuses? Have you confirmed that the injectors and plugs are firing?

That's funny old guy, as I was laying in bed this morning I thought the same thing... why don't I try running a jumper across the relay itself and try cranking? I'll do this today.

I have confirmed that the plugs are firing... but as far as the injectors **** I'm not sure how to check those. I guess I should probably check the timing as well, although it ran -until- I parked it.

[tzippria]

So what happened?!

I joined this forum with a similar problem and have had no luck tracing down the issue. Did you have to buy a new ECM?

[catamount90]

Hey guys, sorry that I never updated this thread. I got the car to fire up again after running a throttle body adaptation with VAG. I guess the throttle body was all out of wack. At least, that's my story and I'm sticking to it.