I've just bought a 1990 Mk2 Gti 8v and all was well untill yesterday morning when it wouldn't start... [:^(] It's sparking OK but the plugs are totally dry and a bit white after turning it over for quite a while. Fuel pump sounds as if it's coming on as it should but no fuel seems to be getting to the plugs - I'd expect them to be soaked after trying to start for a while? I've searched similar threads and going on that I am picking up a new 'blue temp sensor' tonight which should aid the cold start injector? The car won't start with that sensor removed or the terminals bridged. I would've thought there would still be some fuel from the 4 injectors getting to the plugs even without the cold start injector, so I'm doubtful that this sensor will help. Is there anything I can check between the injectors and the pump? Would it be worth changing the fuel pump relay? Fuse is fine. I doubt this has anything to do with it but the previous night to it not starting I put about 3/4 of a tank of BP ultimate petrol in it - I don't know what the previous owner used. Thanks in advance for any help!
Hi Si - bought another one then?! How many are in the fleet at the minute? Sounds like the lift pump in the tank might have failed. Get under the car, pull the wiring plug off the main pump. Switch the ignition on and you should hear a faint hum from the lift pump running. If not, it's time to take it out and check it. Don't know the history of the car, but check it's getting power to the lift pump. You need to unscrew the black disc in the front of the boot floor, and you'll see the top of the tank under there. The big plastic nut on the tank usually needs a hammer and a socket bar / tyre lever to get it moving, and you'll see the wire in there. The main pump tends to get noisy if the lift pump isn't running, as it's running dry. How does it sound? If there's no fuel, it ain't the blue temp sensor, although it's always handy to have a spare one with a digi car. Digifant cars don't have a cold start injector as such - the ECU just opens the regular injectors for a bit longer when it's cold. You can always bridge the fuel pump relay out by taking out the relay, and using a couple of male spade connectors or thick wire ends in the slots where the big blades of the relay go. That should mean your fuel pumps are permanently on when the ignition is on. Not a long term solution, but ok to try if you're diagnosing problems. That'll tell you if the relay is the problem. I think it's probably the lift pump though.
in addition to the above its worth popping the ecu and 5 pin plug near ecu off and cleaning the pins up. could be ecu isnt earthing the injectors due to corrosion. the fuel rail gets power whenever the fuel pump is on so try checking the red wire to the fuel rail gets 12v when the pump is powered up. may need to test from red wire to ground somewhere, as the ecu will send a pulsed signal across the pins which you probably wont be able to pick up with your average multimeter
Hi Mike, thanks for the quick reply! I had a brief and regrettable affair with a clio 172 but it didn't take long for me to get Mk2 cravings again... I'll have a check of the lift pump tonight as long as the weather holds out. It doesn't sound noisy or dry but I haven't really known the car long enough to notice any difference. Is this the right part - 183VG0320 FUEL PUMP-IN TANK G2 1.8 8v F.Inj 8/83 >10/91 ? That's taken from the GSF website and not a bad price. I'm guessing VW would want considerably more! I'll let you know how I get on and post some pics and more info up soon. Cheers Simon
Ok, so I've changed the lift pump and still no joy. Everything sounds like it's working ok, lift pump is definitely pumping out enough fuel but nothing is coming out of the feed from the main pump. Could it be that the main pump is blocked or dead but still sounds ok? I don't mind getting a new one but at 100 I want to be sure that's going to sort it! ECU plugs all seem fine. I also bridged the fuel pump relay as Mike suggested but didn't make a difference. Any suggestions would be great, thanks!
I doubt it's the pump - more likely to be a dead wire in the injector harness. If the pump was running and the injectors opening it would at least give you SOME fuel, not leave you with totally dry plugs?
Thanks for the reply. There's no fuel coming out of the main pump to the injectors and the pipe from the pump to the injectors is clear. If the injectors are open or closed it wouldn't make a difference would it - there's still no fuel?
Ah, I should read the thread first! I thought you had it all connected up. So both pumps running, but no fuel? The only things that could really cause that are a blocked lift pump filter (which you've changed), blocked line from lift pump to main pump, or dead main pump - but I've never seen a main pump so dead it wouldn't at least pump something? Have you taken it off and run it in a bucket of petrol or anything, to see if there is any action going on? I suppose the impeller could have spun on the motor shaft or something, but I've never seen that happen!
Fitted a new main pump and it's all sorted! Thanks for all the help guys. Great info and quick replies as always
P.S. I ran the old pump submerged in petrol as suggested and it wouldn't pump anything at all so I'm guessing it had seized or something. There's a first for everything!
Glad you got it sorted, Si. If it hums it's still moving I think, but I guess it could be blocked or damaged inside. Worth pulling it apart for a look? I have a dud pump too. It would be interesting to see if dead pumps can be cannibalised to make a live one. So is this one your daily driver, or have you bought it as a fixer-upper?
I'll have it apart tonight and see if I can work it out... I've bought it as a daily driver so I'm hoping that's a one off problem and it'll be ok now! I'm starting a new job in Banbury next week so I will be needing the car for the daily commute. It may be a bit of a risk over the winter but it's just had a full service - plugs, leads, dizzy cap etc etc so I'm hoping she should be ok with the cold mornings! If the weather decides to clear up any time soon then I'll get some pics and info up in the Members Gallery - she's a beauty! Cheers.
With two new fuel pumps it should be pretty hard to kill it. Anything else is normally fixed by changing the blue temp sender, which you already bought
Right, I've had the old pump apart and couldn't seem to find any obvious blockage or seizure. Put it back together and tested it in the same way again and the shaft from the motor to the propellor doesn't move. It was all free moving when I spun it by hand. I had to peel back one end of the metal casing to get it all apart so even if I did get it working again it would need repairing or a replacement case. I'm sure if you were really keen then it could be done...
