fuel pump woes! maybe?

[avants2turbo]

car wasnt starting, changed the two crank sensors and the old girl fired up, drove it about 15 miles, then 15 miles back that evening, parked up and went out to her the next day and no start again!

the car is currently running a full RS2+ setup around the 400bhp mark on a beleived to be origional ABY fuel pump (17 years old) i have been seeing some hessitance as the car comes onto boost but then eventually clears

so ive now done some tests

first test was the blink test to pull codes and that revealed nothing but the usual 2111 which is obviously because the car was not running

i then replaced battery to give car best chance of starting

second test was to remove cam cover/coils etc and plugs, then i cranked it over and all plugs are sparking in sequence, good strong spark

third test was to remove the cover on the fuel pump relay and attemp to start the car, the relay snaps on cranking and stays closed until i stop cranking


so i may be wrong, but i assume as the car is sparking in sequece and the fuel pump relay is energising the crank sensors and cam pos sensor are all functioning correctly but there is no fuel supply, so its gota be the pump?

anything else i can check? or is the pump condemmed?

any way of checking the pump? in the car or out the car?

[DJones]

car wasnt starting, changed the two crank sensors and the old girl fired up, drove it about 15 miles, then 15 miles back that evening, parked up and went out to her the next day and no start again!

the car is currently running a full RS2+ setup around the 400bhp mark on a beleived to be origional ABY fuel pump (17 years old) i have been seeing some hessitance as the car comes onto boost but then eventually clears

so ive now done some tests

first test was the blink test to pull codes and that revealed nothing but the usual 2111 which is obviously because the car was not running

i then replaced battery to give car best chance of starting

second test was to remove cam cover/coils etc and plugs, then i cranked it over and all plugs are sparking in sequence, good strong spark

third test was to remove the cover on the fuel pump relay and attemp to start the car, the relay snaps on cranking and stays closed until i stop cranking


so i may be wrong, but i assume as the car is sparking in sequece and the fuel pump relay is energising the crank sensors and cam pos sensor are all functioning correctly but there is no fuel supply, so its gota be the pump?

anything else i can check? or is the pump condemmed?

any way of checking the pump? in the car or out the car?

Un bolt the fuel return pipe to the tank, disconnect the POS's so it wont fire and crank it over for 15 second with the return pipe in a measuring jug. Times the result by four and it wants to be about 2.5 litres.

The true test is to apply circa 1bar of boost to the fuel pressure regulator but the above will confirm if you have fuel supply issues or not.

Hope it helps.

Darren.

[avants2turbo]

which is the return pipe? presumably its one of the braided pipes to the rhs of the inlet manifold?

[DJones]

Trace it from the bottom of the fuel regulator at the rear of the fuel rail the front is the feed.

[BrianSmith_S2]

Be careful when you do this, i tried this when i had starting issues a few months ago. Cant remember which line caused the problem but one line stopped pumping when i turned off the ignition.... on the other it kept pumping after i removed the key from ignition... was quite scary cos i got covered in fuel as i tried to reconnect the fitting nearly went up in fire with the S2 and ended up having to pull the fuel relay to stop the flow of petrol.

[avants2turbo]

Be careful when you do this, i tried this when i had starting issues a few months ago. Cant remember which line caused the problem but one line stopped pumping when i turned off the ignition.... on the other it kept pumping after i removed the key from ignition... was quite scary cos i got covered in fuel as i tried to reconnect the fitting nearly went up in fire with the S2 and ended up having to pull the fuel relay to stop the flow of petrol.

wow!!

thats mental! ive got a massive fire extiguisher in the boot, think ill keep it to hand!

[UrS4boy]

Fuel Pump Testing and Replacement Info

Good job of making sure the issue was not the cam position sensor. By establishing that there was spark and the FP relay was energized during cranking, you have proven to yourself (and us) that the cam sensor is working and that the ECU is firing the fuel pump relay. Unfortunately, the FP must be dead. You could have somebody listen for the fuel pump during cranking or you could just jump the fuel pump by powering it directly through its fuse, as explained here (for a C4 AAN but the idea will be the same for your car):

http://www.elektro.com/~audi/fuelpump/index2.html

Fuel Pump Replacement procedure for a C4 AAN FP (similar but different):

http://www.elektro.com/~audi/fuelpump/

General 20vt FP info:

http://forums.quattroworld.com/s4s6/msgs/22623.phtml

Be careful and good luck.

[avants2turbo]

FKing fuel pump!!! i really hate this car!!

right, removed the fuel pump, hooked it up to a battery with 14.5 volts, and it span like a goodun, so thought ok, lets see if it actually works, so dunked it in a pint glass full of water, put the pump in and it emptied it in like 2 seconds!!

right, back to the car!

unplugged the connector at the fuel pump (4 pin) and ignition on got my little helper to close the contacts on the fuel pump relay, bang, 12.5v (so the pumps getting power?) plugged it back into the top of the pump, got my little helper to do the same again, couldnt hear the pump, so then got 'LH' to crank the car over, still no noise!

right, next step, unplugged the injector plug and got the multimeter on it,
ignition off - 0v
ignition on - 12.5v+
cranking the engine over - drops from 12.5+ to about 10-10.5v (all constant, no pulsing)

right, next step, fuel pump all back in the tank all connected back up-
split the fuel line (the one that comes directly off the bottom of the rail below the fpr) put both ends in jars, the solid line was dripping/trickling and i then turned over the engine and the braided line nothing of any note came out, and the solid line just kept trickling???

did the same with the other line and nothing of any note came from either, even when cranking!?


WTF!!!!

soooooo.. the pump worked out of the car, there is power to the pump connector when the relay is activated either by hand or by cranking the engine over, you cant hear the pump when its in the tank, theres power to the injectors (shouldnt they be pulsing though not steady current?) and there doesnt appear to be any fuel pressure at either fuel lines?!

right, so, i installed another pump from the avant in my workshop, did all the same again and same...

anyone got any ideas this is driving me mental!

[mcandmar]

Fuel pump in a bucket sounds fun, must try that

Injectors will receive constant power, they are grounded when fired so you should see continuity on the negative side when cranking.

You really need to confirm if the injectors are firing, you should be able to feel/hear the injectors firing when cranking over, old trick of holding a screwdriver against the injector and your ear should help.

Your pump test result is odd though, with the fuel line disconnected and the pump running it should have had a steady stream of fuel coming out. A clogged filter or pinched fuel line is a possibility.

[DJones]

FKing fuel pump!!! i really hate this car!!

right, removed the fuel pump, hooked it up to a battery with 14.5 volts, and it span like a goodun, so thought ok, lets see if it actually works, so dunked it in a pint glass full of water, put the pump in and it emptied it in like 2 seconds!!

right, back to the car!

unplugged the connector at the fuel pump (4 pin) and ignition on got my little helper to close the contacts on the fuel pump relay, bang, 12.5v (so the pumps getting power?) plugged it back into the top of the pump, got my little helper to do the same again, couldnt hear the pump, so then got 'LH' to crank the car over, still no noise!

right, next step, unplugged the injector plug and got the multimeter on it,
ignition off - 0v
ignition on - 12.5v+
cranking the engine over - drops from 12.5+ to about 10-10.5v (all constant, no pulsing)

right, next step, fuel pump all back in the tank all connected back up-
split the fuel line (the one that comes directly off the bottom of the rail below the fpr) put both ends in jars, the solid line was dripping/trickling and i then turned over the engine and the braided line nothing of any note came out, and the solid line just kept trickling???

did the same with the other line and nothing of any note came from either, even when cranking!?


WTF!!!!

soooooo.. the pump worked out of the car, there is power to the pump connector when the relay is activated either by hand or by cranking the engine over, you cant hear the pump when its in the tank, theres power to the injectors (shouldnt they be pulsing though not steady current?) and there doesnt appear to be any fuel pressure at either fuel lines?!

right, so, i installed another pump from the avant in my workshop, did all the same again and same...

anyone got any ideas this is driving me mental!

The injectors are switched by an earth output signal from the ecu, so yes power should always be constant when the ignition is switched on at the injectors.

The fuel relay is also triggered by an earth output signal once the engine has done one revolution.

Take all the wires off the fuel pump and hard wire it with a temporary 12v supply, the pump should run continuously then start the engine.

It would be much easier with the car in front of me..... but you are closing down on what ever it is. Everything is switched by earth from the ecu so i would check the fuel pin on the ecu is sending out an earth signal, cant remember which pin. Will have a look..... or listen to the fuel relay and make sure you hear it click when cranking..

I would leave the injectors alone for now cuz if you dont have fuel coming out of the return pipe on the bottom of the FPR then no fuel is getting to the engine so no point looking at the injectors..

[avants2turbo]

so a constant voltage at the injectors when cranking is right (all i did, dont know if it was right, was set the multimeter to volts and one probe on each terminal and cranked it over)

[newsh]

Just a thought, you haven't got a dodgy alarm / immobiliser install have you?

[avants2turbo]

Just a thought, you haven't got a dodgy alarm / immobiliser install have you?

does a bear sh*t in the woods!!!!!

[Gazjen]

I was just about to suggest an alarm or immob you might have 12.5v at the fuel pump but have you tested it with the fuel pump supposedly running to see if the pump is dragging down the voltage?

If it is you could run your own supply to the pump to see if that gets it to start

I've seen a few looms where they intercept the feed to the fuel pump and then it goes through the alarm via a relay