MK5 Golf GTI
All Things Mk5 => Mk5 General Area => Topic started by: Tuffy on February 07, 2018, 07:22:52 pm
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Hi guys. Hope someone can help me. Car was ticking over nicely on the drive on Sunday then suddenly cut out
Have traced it to no power to the fuel pump in the tank. Guessing probably fuel pump relay...which please correct me is located in the fuse box in the engine bay.?. Do any of the relays under the dash control the fuel pump? can someone just confirm relay number please?
Also any other ideas as to why power wouldn’t get to fuel pump...other than a broken wire?
Btw...have scanned and no codes present
Thanks in advance
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Did you check the 15 amp fuse behind the side panel, adjacent to the steering wheel? Think it's F27, but check your manual because internet information is sketchy at best.
Where did you test for 12V? Before or after the pump controller?
There are 2 fuel pump relays, both are under the steering wheel behind the cubby drawer area. 1 is for the tank pump and the other is for the mechanical pump. I believe they are the white ones taped to the fuse board, numbered 449, but as I say, have a look at the manual (Page 96 iirc) to confirm.
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Thanks pudding checked before a after the controller..... replaced relay 167 in the fuse box in the engine bay..... and swapped the two 449 relays round in the compartment under the cubby hole. I have my doubts if it’s either of them as the one that controls the fuel pump I believe also controls the interior light and there’s no issues there....
The 15 amp fuse appears to be fine too...
any other suggestion mate??
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167 is normally the fuel pump relay number, but VW make changes frequently, hence why referring to the manual is a good idea. I got the 449 info on the net ages ago when I had similar issues, but in my case, it was an failing pump so didn't need to bother with any relays in the end.
So no power to the controller? There must either be a break in a wire somewhere, or the fuel pump relay is not being commanded on......in which case we need to look at the ECU trigger wire.
Have you got VAG-COM?
Did you try bridging the fuel pump relay with a couple of spade connectors and a wire? That bypasses the ECU and the relay and confirms power to the pump, and if still no power, it's a broken wire somewhere.
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167 is normally the fuel pump relay number, but VW make changes frequently, hence why referring to the manual is a good idea. I got the 449 info on the net ages ago when I had similar issues, but in my case, it was an failing pump so didn't need to bother with any relays in the end.
So no power to the controller? There must either be a break in a wire somewhere, or the fuel pump relay is not being commanded on......in which case we need to look at the ECU trigger wire.
Have you got VAG-COM?
Did you try bridging the fuel pump relay with a couple of spade connectors and a wire? That bypasses the ECU and the relay and confirms power to the pump, and if still no power, it's a broken wire somewhere.
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At this point mate it goes above my head to be honest and I have to let my auto electrician take over😄
No vag just a generic snap on sonus which showed no codes.
Regarding testing the pump... he took a feed straight from the battery via a testing probe to the pump and it powered up.
That’s where my knowledge starts a stops
I’m just trying to get some ideas as he’s stupidly busy and can only call in when his passing
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OK :happy2: I'm sure he will do some continuity tests and other bits and pieces. At least the pump itself is working!
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Appears to be mate. Just hope it’s not a fault in the ecu itself 😬
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The ECU fault codes the pump relay normally, so the next test will be to see if the ECU is energising it. Check for a voltage on pin 86 of relay 167 whilst cranking. If there's a signal there, it's gotta be a break in a wire from the relay back. That's a long wire, so will be fun tracing that!
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Thanks for that mate. Will update when we trace the problem 👍🏽
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Bit of an update. Nothing worse than searching for a solution to a problem ... then after four pages it hasn’t been updated with the solution.
It’s all pointing to a intermittent fault with the fuel pump control module that lives on top of the fuel pump under back seat. (Small black box) it’s not sending the correct signal to the fuel pump.
Anyone else had this issue??
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It's not an unknown problem and I think VW have revised the part, search on you tube for humble mechanic fuel pump module which explains about the way they fail.
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Was going to say the code for a relay isn't because there isn't a relay...it is for the controller just mentioned. I had the code once and went off searching every fuse diagram for every MK5 build period just to find there wasn't a match to my actual fuse and relay layout.
Anyways, I found there is no relay and the problem was with the controller. I replaced it and added a Torqbyte PM3.
But yours seems to be sorted now. Yes, it has been revised a number of times...mostly due to overheating and causing engines to quit running momentarily. Her they're showing the revision has reached "H"; 1K0-906-093-H...replacing D, E, F, and G. I have the "G" because the "H" doesn't work with the PM3.
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Thanks for that....haven’t ordered one as yet.. how much are they from TPS?.
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Ok guys.... the sarga continues... replaced the control module and still not starting... we have all the relevant power coming in before the control module and coming out.
If we power the pump via a probe direct from the battery it will prime.... connect the plug back into the top of the pump again turn the ignition it doesn’t 🤔😡.
Although the pump primes when powered directly from the battery could it still be faulty?
Could the control module be picking up a problem with the pump and preventing it from running
Running out of options now other than trying a new pump..... just odd that it primes when powered by a direct feed
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It's looking like a pump is the next step really. The direct 12V feed from the power probe would run it flat out, whereas the controller varies the current according to ECU demand. Perhaps the pump is just old (worn commutator) and unresponsive to the controller?
Only other thing it could be is a dodgy pin in the controller-to-pump plug?
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Thanks mate
Yes it’s the only thing we can think to try.... I’ll order one from TPS on Monday... connect it without sinking into the tank ... if it doesn’t purge I guess I could return it??
Are they around the £120 mark from TPS?
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Probably not wise running a fuel pump motor dry, they don't like it! Do it for a few seconds only. The thing with returning VW parts though is they insist on seeing the fault themselves, so you'd have to take the car to the dealer with the new pump not working so they can diagnose it before refunding you. Annoying.
Yeah around that. I bought one 2 years ago and I'm sure it was £130ish with the VAT. I was getting fuel surging issues on fast corners when the tank was 1/4 full or lower. Turns out VW made some modifications to the pump to stop that, and also an overheating issue on long journeys, so you will get the latest and greatest pump.
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Thanks again mate.
To be honest there’s not much else it could be now. Just making us doubt ourself a bit when it purged with a direct 12v feed
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The direct 12V feed from the power probe would run it flat out, whereas the controller varies the current according to ECU demand.
This is possible for a worn out pump. The max feed from the controller to the lpfp is 16 amps. I doubt 16 amps is supplied when the prime command is sent from the ECU to reach target line pressure in the low side. 16 amps is likely only supplied when the lpfp duty cycle is at 92%(its max) and has a draw from the high pressure side. Anyway, hope the new lpfp works finally.
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Sorry...so are you saying the pump could well be goosed although it powers fine with a direct feed 🤔🤔??
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Yep. I suspect it is worn out / lazy and needs a full current kick to bring it to life. As above, the PWM controller does not give the pump full current unless commanded so by the ECU. I think a new pump will sort you out :happy2:
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Right, the controller is a PWModulator...so, feed power from it varies in order to maintain fuel's low pressure within its line. The car's battery will supply 300 to 1000 amps(range for most car batteries)...so way more amps than what the pump normally receives when it was directly connected to the battery. I have a Torqbyte PM3 between my controller and lpfp and it takes the signal from the controller and increases the amps up to 36 amps for the upgraded lpfp.
So, Pudding is correct in that even a badly worn pump, if not completely shot, will run given more amps.
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Ok guys. Another update. What with the bad weather and my mercanic being flat out busy we still haven’t solved the starting issue
Have now established that fuel is getting through to the hpfp, the reason the pump wasn’t purging was pressure had built up enough in the hpfp, when pressure was released it purged fine and the fuel came through.... but still turns over and doesn’t fire🤔🤔🤔
. Have removed the hpfp, spring pushes freely and no damage to follower.... will screw a gauge to it and see what psi it’s pushing on crank over. Would it be fair to say that it should be pushing around 1700 psi ?
The only code that’s flagging up now....which wasn’t there before is for the throttle body.... could that cause a non start
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You're looking for around 50 bar at idle mate. I'm not sure many cheap fuel pressure gauges can even cope with that, let alone the 110bar in boost! Will have to be logged with VCDS.
The mechanical pumps are known to fail, so don't be too surprised if it's busted. Around £250 from the dealer for a new one. Aftermarket ones like Loba are better quality than OEM and set you up nicely for tuning :happy2:
I would also confirm the ECU is commanding the HPFP. During cranking, the engine relies on the LPFP to start the engine (should see 7 bar after turning the ignition on) and as soon as it fires, the ECU tells the HPFP to kick in. I would confirm that signal is present, which is the sensor on top of the HPFP.
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Cheers pudding.
Are you saying if it’s not giving the command it could be an ECU fault?? Because I assume if it was a goosed sensor on top of the hpfp it would log as a hard fault
Also it’s not actually firing, so would the ECU be talking to the sensor on top of the hpfp until it actually fired ??
Could the throttle body fault cause a non start??
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Yeah it would log it as a fault. I doubt the ECU is faulty but it's just a process of a elimination thing. Sometimes old school diagnosis is required because ECUs don't fault code everything.
If the HPFP was dead I would expect coughing and spluttering at least, but if it's just not firing at all, it could be other things. Crank sensor, ignition faults etc. Have you confirmed you're getting a spark?
Throttle body would defo be fault coded, but with VCDS you can run an adaptation on the throttle in 'Basic settings'. Channel 06 if I remember. You will hear the throttle moving and VCDS will say "ADPT. OK" if all is well there.