I wanted to test the fuel pump by pulling a supply line and seeing if there's any pressure on start up.
I was wondering if the top tube on the fuel rail was the supply line.
Sorry. Can't off the top of my head remember top or bottom. I want to say top though. Look at the rail, whichever has the separated hard line coming out of the fuel pressure regulator is the return
well I've ran vag com a couple times and it hasn't found anything
and I haven't checked for spark because...
sometimes the car starts. After a failed attempt to start I will leave the key in ON position, after some time the CEL will light (I can hear the throttle adjusting and I possibly hear the fuel pump prime) and I can crank it and the engine will fire up. When it finally turns over the CEL turns off and the car will sometimes run for 15 seconds and kill itself or it will run perfectly.
coil, plugs and wires have about 7k on em.
I figured to check fuel supply. Is this a bad assumption?
If I pull the supply line from the rail and attempt to start the car I should get a nice stream of fuel shooting out of the line, correct?
If no fuel is present, can I assume the pump is shot?
Though I haven't table top tested a relay with a 12V supply I can feel it "click" when I turn the key to start.
I don't smell gas at all when cranking away on the engine either.
What is consistent though is
failed attempted start > CEL light > throttle body high pitched tone > successful start
though sometimes throwing the CEL light doesn't happen.....
As for your problem, I would start by replacing the ignition switch. Buy it from germanautoparts.com and look in the mk3 faq/diy thread for two ways to do it.
usually ign switch cause weird problem. common issue is vehicle will have power but no crank issue. but im saying that that might be possible issue as well but... do no fuel comes out on any lines? did u jump the fuel pump or see if u had 12v going to it? it primes when key is on "ON" position for 3 to 5 sec and then while u crank. because of nature of how relay works it might have carbon build up so in sever case and it does happen contacts gets bad internally also pull it out and look at prong to see if you have heat damage on any prong if it does replace it! Dont for get to use VW Bible
visually inspected 167 relay in slot 12 - looks good but I understand about carbon buildup
Im going to take a voltmeter to the pump later today.
When should the pump have 12v going to it? does the key need to be in ON or START position?
I've ran across different info on pump priming - I've read it only primes when cranking and I've also read that it primes with key in ON position....
On a mk3 the pump should prime when the key is turned to on. Remove the relay and put a jumper wire between the two big pins I believe it's 86 and 87 to get constant power to the pump with the key on. I forget the hot wire color on the pump harness but I know ground is brown and the purple with black stripe is fuel level signal.
For $13 the switch gives you great piece of mind. The last one I did took me less than 25 minutes. I use the method where you remove the whole steering column and that's the 5th one I've done. That thing controls so many things and does very odd things when it starts to go bad...
Thanks for your input on this.
I replaced the switch and I'm still getting the same start up difficulty.
I wanted to clarify the relay jump- do I take a small gauge wire and jump from 86 to 87 and turn the key to ON and expect to hear the pump running in the back of the car?
I'm going to post another thread about "no start - CEL - Throttle adjustment noise" to see if someone has run across this before.
Thanks again and any other input would be appreciated
I sorta have the same problem turn key no prime from fuel pump hooked battery up to fuel pump started right up. now my fuel pump doesnt work picking up a new one thursday. checked to see if i was getting a signal to pump and its getting signal, steady 10 volts or so when i turn the key. any thoughts? heres a link to my thread
Thanks for the direction on this pump test. I'll have to check it out when I get home.
couple quick questions though....
If I pull that top line and send it into a bottle a properly working pump will feed fuel while cranking the car correct?
Also, that colored board you attached (thank you for that) - is that located above the relays?
If everything is working properly then yes it will pump fuel into the bottle. The pic that i posted is the back of the fuse box. If you look at each slot it has a letter and inside of the slot have numbers which are for the pins. so you want to put a wire into m2 and use the y slot for you power source.
Thanks for all the help.
I've just gotten back in town and want to try this jump but wanted to find out one more bit of info. Sorry for my late response.
Should I perform the M2 to Y jump with the fuel supply line removed from the rail and then attempt to start? I'm assuming yes because of possible flooding potential.
Also, I did remove the top line from the rail and can confirm that while turning the key to START and cranking the engine no fuel is discharging from the line.
I've didn't wait for the ECU light to turn on and then attempt the start with the line off. I do know the car will start when the light does come on though.
Can this be a potential ECU problem? Should something be reset or is there a vag com test I can perform? Again, this seems so odd because once the car fires up it normally runs perfectly and only sometimes will start and run for 15 seconds and suddenly shut down.
It's definitely a delayed priming issue.
The line will supply fuel after some time of having the key in the ON position. Until the CEL lights up there is no priming with the key in ON.
Another variable that might have some effect is the extreme heat - it seems that the last couple of days, which have been 20 degrees cooler than the 90+ days we have had for the last month, the time of the CEL illuminating has happened much quicker. During the heat I waited for a minute or two for CEL, whereas the last couple of cooler days the CEL lights up in seconds.
any other ideas?
Appreciate the help.
car is not a swap.
only motor tune is a c2 chip and a high flow air intake.
Another random note-
Whilst accelerating around 80mph last night the car choked up twice in quick succession and each choke lasted a half second. wasn't a good feeling. CEL lit up in synch with the choke.