PROJECT VW JETTA GTI
Time to fit a replacement fuel tank and lift pump to our Jetta GTI, says Will Holman. And after that, it might even run.
All you need is a spark, an air/fuel mixture and compression. Suck, squeeze, bang, blow and bosch – a running engine. Well that’s the theory, anyway. Let’s see whether we can match it up with the practice. Our 1989 VW Jetta GTI is the later 16-valve version, so it’s well worth getting it up and running, because with 136bhp and 123lb.ft of torque it should have absolutely no problem keeping up with modern traffic. But first we need to put a fuel tank in it.
It did come with one fitted, obviously, but the steel wire that holds the float onto the petrol gauge sender unit had rusted through while the car was laid up, and the float was rattling around in the bottom of the tank. I would quite happily have flushed out the tank and fitted a new sender unit that came with the car, but the car’s previous owner had also supplied an already clean tank, and as I would have had to take the old one out to properly clean it anyway, it made sense to just fit the replacement one.
The sender unit also incorporates a lift pump that pushes fuel up to the highpressure pump under the car’s floor forward of the tank itself. One of these lift pumps also came with the car, which is very handy as they’re apparently quite tricky to come by. In fact the previous owner had located this one in Spain and had it sent to the UK, which was still, he says, cheaper than buying one here.
The sender/lift pump assembly sits in the top of the tank and can be fitted either before the tank goes onto the car, or afterwards via a large hole in the boot floor. I decided that fitting it with the tank on the workshop floor would be easier on my back than fiddling it in through the boot with the tank already in the car, but when I went to fit it, I found that the sender was too tall. With the bottom of the pickup portion already in contact with the floor of the tank, there was still so much pump poking out of the top of the tank that there was no way of getting the locking ring into place.
My immediate suspicion was that the replacement tank we’d been supplied was different from the original, with a shallower depth. So I found a steel rule and lowered it into both, only to discover they were identical. Puzzled, I studied the sender unit to see whether I could spot what was going on. The problem I had was that the old one was now broken, so I couldn’t compare the relative length of the old and new parts. But while I was studying the sender and pump assembly, I noticed a spring fitted into it, and
discovered that by pushing on either end of the unit it was possible to compress its overall length slightly. It seemed likely that the part was designed to work in at least two different depths of fuel tank, hence the sprung portion which allowed its length to vary and therefore meant it could accommodate different tank depths. The problem was that even when it was fully compressed, it still wasn’t short enough to go into ours.
I sat compressing it and allowing it to expand for several minutes – a bit like a mini Bullworker – and when I felt suitably Arnold Swarzenegger-esque, I put it down and stuck the kettle on. While sipping my coffee and still pondering the overly long sender assembly, I spotted a clip securing the hose to the top of the lift pump. It had a locating section which stuck out, and it was this catching on a part of the plastic moulding that was limiting the travel of the spring-loaded section. After twizzling it round 10 or 15 degrees with a pair of long nose pliers, I was able to compress the pump another two or three centimetres. Enough to fit it in our tank?
I fed it in and pushed down on it while fiddling the threaded locking ring into place. Bingo – one tank with a sender/ lift pump firmly fitted and locked in place. Time to fit it in the car, then. I won’t claim this would be impossible to do on your own, but it would be an absolute nightmare as you really need four arms. I borrowed two from Classics World editor Simon Goldsworthy, who held the tank in place while I tried to remember which way the three steel retaining straps went on. I can confirm that it’s not the first way I fitted two of them, so I had to employ the patented Goldsworthy Tank Jack again while I tried a different permutation.
I’m not entirely sure how many different ways you can fit three equal length steel straps to six mounting points, but we certainly tried a good number before finally hitting the winning combination and getting the tank bolted loosely in place. I then secured the filler neck into the area beneath the filler aperture, before tightening everything up and standing Simon down. It only took 20 minutes or so before he was able to lower his hands from above his head – handy, as he now needed them to help him drive to the nearest garage for a gallon of unleaded.
While he went to fetch that, I decided to check the compressions on the 1.8-litre Jetta engine. I wasn’t looking for a specific compression pressure, rather just that they were all of a similar value, and certainly within 10% of each other. When doing compression checks it’s important to have the car’s throttle fully open to allow the cylinder to fill effectively, otherwise you can get false readings. I pulled all the spark plugs out of their long mounting recesses in the top of the cylinder head and screwed the compression gauge into each cylinder in turn before giving the engine a five second burst on the starter, moving the gauge along the four cylinders as I went along.
Meatloaf said that two out of three ain’t bad – I wonder whether he’d think three out of four is OK too? I don’t. One cylinder was well down on compression, with a figure of around 50psi, compared to the other three’s 130. The car’s previous owner tells us it was running sweetly before its extended sabbatical, so we’re hoping the low reading is just down to a gummed up piston ring, which will hopefully free off once we get it running. That’s the glass half full view. The glass half empty one is that engines will often appear to run quite well even if they’ve lost a lot of compression, they just won’t pull anything like as well as they should. So we decided to try firing the thing up and see whether a sunny disposition gave enough positive energy to free off that alleged sticking piston ring, or whether in fact a pessimist is just a well-informed optimist. The jury is still out on that one because the car refused to even flicker into life. The system is set up so that the fuel pumps will only work for five
seconds when you turn the key, then stop as a safety precaution if the engine isn’t spinning. We turned the key on and off repeatedly to use those five second bursts to pump fresh petrol through the system, but nothing seemed to change. However, spraying Easystart directly into the air intake had the engine roaring into life, only to die as soon as the spray stopped.
That suggested we had a fuelling issue rather than a lack of spark or compression, so I loosened off the banjo bolt holding the fuel supply hose to the K-jet metering head under the bonnet. A little very stale fuel dribbled out (it was brown and smelled rank), but there was no sign of any fresh petrol replacing it. Ultimately we traced the culprit to the high-pressure fuel pump, so got out the credit card and went looking for a new one of those too.