K-jet fuel pump(s) / no start troubleshooting

Hello from Down Under.

I'm trying to bring a stored 1990 16v Corrado K-jet back to life. It hasn't run for several years and pretty much everything rubber in the fuel tank turned to chewing gum in over that period.

I've replaced the external fuel pump and the short lines around it, and also the seals and in-tank fuel pump. (Clutch slave and master replaced as well which might give you an idea of the state it was in). The car is tidy and quite clean mechanically, mileage wise it has around 100k miles on the clock.

The car has a fresh battery and cranks healthily, but the best that I've managed to get out of it was a single stutter, not really even a cough.

When the ignition key is turned I hear a pregnant pause and then a thump coming from the region of the underside fuel pump. I'm not convinced that the lift pump is even working but I can't figure out how to troubleshoot it from an electrical stand point or test its output.

Any suggestions on where to go from here would be gratefully received.

Cheers

Craig

 

Thanks John,

I'll give that a go and report back.

 

It’s taken a fair while to find enough time to get back to working on the old girl. I tried swapping the relays today. Still just a brief thump from the main pump under the car and nothing from the in-tank pump.

The fuses all look ok but I’m stuck now on the fuel pump power circuit logic. Should the lifter pump in the tank work continuously when the the 18 relay is in socket 12?

I don’t have a specific current flow diagram for the 1990 KR Corrado, am relying on a mish mash of mk2 16v and Passat wiring diagrams to get a sense of what I’m looking at so I am fumbling around in the dark a little. How is the lifter pump energised? Is it in parallel with the under car pump?

 

I've finally managed to get time to lift the car and check the wiring. I pulled the pressure pump plug (full of dust under the rubber boot) and the earth terminal was corroded. I've replaced the terminals and still get the same thump from the pressure pump.

Fresh battery.
5-6 Ohms resistance between the brown wire and the chassis at both the lifter pump and pressure pump terminals.
12.59V at both power wires when relay 18 is installed and ign on.
The relay is ticking on and then off as it should.

I have yet to apply 12v directly to the pumps, that is my next step.

I am starting to suspect an earth problem. Where should I check from here? Battery-chassis strap? Any others?

 

If you have 12+volts at the wiring by the pumps, then your earthling is fine. I had to replace all of the pumps for my golf kjet to work.
Does sound like your pumps knackered. Good luck

 

I hope not - but I’m not discounting it. That said, what are the chances that 2 new fuel pumps are both shot?

 

Well shouldn't be..... but 12v at the connector shows voltage.!!
Take them out and try them on a bench maybe

 

6 ohm's between earth and chassis is far to much.

Saying that if you check it with pumps powered on you will get a skewed reading. If you test brown to chassis voltage (millivolt) with pumps powered then that is a more meaningful reading.

Really you need to test power and ground at the pump connector when pumps connected, if that is 12.6v then your pumps aren't working..

 

You could do a load test with a 60w headlight bulb, if it lights that the wiring is more than likely ok.

 

It turns out Cressa was right - my new pump was seized, so whilst I waited for another new pump to arrive I took the opportunity to re-galv the metal parts and fittings around the fuel pump housing. It's all back together, and the fuel pump housing looks like new. The car runs, but runs like rubbish. It does have Schrick 268/276 cams, and previously had a lumpy, hunting idle, but right now cold idle requires some throttle to stop stalling, and the car hesitates, stumbles and doesn't accelerate. The idle screw has no impact on idle speed.

The fuel accumulator is leaking out of the rear screw, so a replacement is next. Could a leaking accumulator have an impact on control pressure and idle?

It has a new ISV and I've checked all the vacuum hoses and plug connections. Any advice on checking the idle control unit?

Where to next? Temp sensors? Control pressure?

 

In conjunction with pumps and fittings has the fuel filter been replaced ?

I would check ISV and confirm it’s getting voltage and is operational, would also be worth getting your hands on a genuine blue temp. sensor in case that’s after going for a burton.

 

You are getting there Definitely replace the regulator if it is leaking but by all means test the actual fuel pressures.
I am yet to do mine but will be soon when I finally sort a pressure gauge kit.
As above with the checks but may also be worth checking the air plate is sitting correctly. I'm no expert with this part but adjusting it will need the co setting up

 

The fuel accumulator is leaking out of the rear screw, so a replacement is next. Could a leaking accumulator have an impact on control pressure and idle?

It has a new ISV and I've checked all the vacuum hoses and plug connections. Any advice on checking the idle control unit?

Where to next? Temp sensors? Control pressure?[/QUOTE]
Sounds like the accumulator is leaking to a point where you don't have enough system pressure hence the bad running,mine still idles fine even with the accumulator leaking but most likely wouldn't take any throttle.
Cheers.

 

I’ll get onto the accumulator asap, likewise the filter and isv voltage whilst waiting for parts. Pressure checks after that once it’s all back in one piece.

I’m not sure that I have a blue sensor on the block/head. I seem to have 3 single pin black sensors around the coolant pipe by the distributor and another at the back. Under them is the thermotime switch.

There are a couple of sensors by the oil cooler and one on the radiator.

Where does the ‘blue’ sensor live on a mk2 valver?

 

Correct the blue sensor is for dijifant 8v so ignore that,the rest you mentioned are correct for your motor,cheers.

 

Well fcuk me sideways, I thought the blue temp sensor was common across the Mk2’s