Poor running - obvious symptoms - help needed

Hi, I've got myself a nice 87k mile 1983 GTi. Well cared for… lovely condition. Problem is, I have got a bit of a problem with the engine/fuel/ignition - not sure what. What has been done is: new fuel pump, accumulator, pipes, fuel filter, rotor, dizzy cap, leads and plugs. Symptons I am experiencing are:

* Good starter - runs perfect - no missing or anything from cold - for the first 5 miles - lovely runner
* Oil pressure fine, water temp fine, nothing wrong at all for 5 miles
* Then slight missing/loss of power
* Then if I get onto motorway, I gradually lose power… it may run at 70mph, but the moment I apply throttle, loses power… then I have to pull over and the thing stops eventually…
* Very odd - as once I turn off ignition, and restart - the car is absolutely fine again - for about 1 mile, and I get a repeat of the above. Switch off, immediately restart - no probs for a mile - same problem

I have run out of ideas what might be the problem. I hope someone out there in the club recognises the syptoms and can point me in the right direction. How about bad coil, low of fuel pressure, something electrical…? Other than this little gremlin the car is absolutely perfect and I can't wait to show it and use it. All help much appreciated. Many thanks  Gary

A guess - FUEL TANK AND FILLER NECK
thats what mine did and i had to fit a new tank, its not a difficult job, take a day, get the tin top filler neck and the injection tank.
To check, remove the rear seats, remove the inspection plave, remove the sender unit and shine a torch in your tank, if theres rusty deposits and crud every where then you need a new tank, and the rust will probably be bits of your filler neck falling off.

Hmmm, not sure that is the problem. If it was rust getting through to the meter unit, then it would have the problem all the time, but its fine when cold. Also, the tank is fine and the filler neck has already been replaced. All the fuel stuff was done because the car had stood for 5 years and the previous owner had all the pump work etc done because the garage said 'the petrol had solidified'- which sounds like rubbish to me - a con to get the chap to spend £400 on fuel bits.

Any other ideas? Cheers and thanks for the note

yeah true, con.  Mine was absolutely fine when cold but its was when i was driving for a bit and the rust started to swirl around, worth a check anyway, then you can tick off that its not that??

I would also say check the tank & filler neck, sounds like rust in the tank….

It could be I guess… perhaps the pick up is fine cold and been left over night… and then it picks up debris/rust when driving around… when ignition switch off, pressure falls - rust drops out… repeats… ?

I'll have a look in the tank. Filler neck looks new or almost new - so that may have rusted and caused the problem and that's why the garage changed everything from the tank to engine/metering unit. Worth a try for sure - thanks

maybe faulty pump relay?clogged up check valve in the pump?2 more to tick off the list.

We had the same issue with the 1500 carb, I did not change the tank but removed it and flushed it out and it was a rusty filler neck, it was due to the suction filter (plastic thing with small holes) accumulating rust and stopping the flow and when you turn it off and start again the bist drop off and swim about until they get sucked up again.  

You could try changing the coil that may be on it's way out and stopping once warm.  We went through ignition parts first but should have checked the fuel tank.

Let us know what the outcome is.

My '91 cabby is having similar problem. Early in the morning (cold start), it runs like a dream with no prob for 30miles, when I stop by for an hour or so and start again, the rpm fluctuate from 1300 to 600 and may stall sometimes. I had replaced the fuel pump, filter, and cleaning the fuel tank thoroughly (it's rusty inside but not quite serious). I was better for last 3K miles but now it happens again. It's time to replace the entire fuel tank, filler neck?

Without a doubt it is the "classic" rusty filler neck.
You have the precise symptoms that I had in 1993 when I bought my MK1.

What happens is that water gets to the metering head, water molecules are larger than fuel so they do not easily pass through the metering head slits and so the engine loses power and eventually stalls due to fuel starvation. You wait a bit and heat allows the water to disperse, fuel flows again until more water is dragged up to the metering head.

To compound this rusty particles and water find their way into the metering head which causes the insides of the metering head to rust !!

The only real solution is a new metering head (or one that has not experienced the rusty filler neck). Some have had success in separating the metering head and cleaning, but it is an absolute bugger to get it to seal up again !!

You may have caught it in time and get away with just cleaning the tank and fuel lines - but I doubt it from your symptoms.

Hi everyone who commented…. great news…. I got the garage to suck out rust from petrol tank (didn't fancy doing it myself for safety reasons). There was loads of rust (from the filler neck I guess…

RESULT! The car now goes like a rocket… no problems at all now.  A big thanks to everyone who advised me of this… I don't think I'd have sorted without the helpful advice… Thanks again….

Hi mate think im having similiar problems and my hunch is rust because my previous filler neck wasnt in good condition at all. Roughly how much did the garage charge to clean out the petrol tank? Cheers

Hi there…. I would recommend changing tank…. I got the garage to clean out the tank - but problem returned. I bought a new tank from GFS… £90! Fitting was about an hour of labour… That's what I'd recommend….

coil mate, defo

could this be happening to my valver? sounds similar

mine never gets goin tho!      

revs fine, then sometimes there is a dramatic loss of power

Sean1151 was that defo coil comment meant for me?