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

Nice. Thanks for the link. Very comprehensive.

 

Fast forward a couple of weeks, one new fuel accumulator (the xx-040 version in the Corrado, happily it was cheaper than the 16v Golf version), and not one but two new high pressure fuel pumps...Managed to get the ISV working - cleaned the plugs on the sensors, ISV, throttle switch, but ultimately the ISV controller plugs also needed cleaning. Leaving a car parked for a few years really isn't a great idea!

System pressure is now rock steady at 5.05 bar, control pressure looks pretty high, 3.3-3.7 bar. The injectors were all slowly dribbling fuel at a similar rate so I checked the airflow meter plate and it was gummed up in the idle position. It feels like the piston in the metering unit is jammed so it looks like it's time to disassemble it. I may as well do the WUR mod at the same time.

Any tips on rebuilding the metering head? Do you always need a rebuild kit?

 

Thanks - another small step towards getting to know K-jet better. Is there a go to source or are the rebuild kits much of a muchness?

 

Hi mate good to see you are moving on,I didn't replace my accumulator and ended up repairing the leak and all back to normal.
Thoughts are your injectors are @ fault here,they are super simple but if dirty or have had water thru them you have a further issues that cleaning won't sort,
same applies to the fuel distributor ,your injectors should hold full system as designed but get your metering flap freed up first and see .
Yes my metering head was very dirty due to the blowby from the old KR engine and same with the ICV valve and throttle body,made a real differance.
Good luck.

 

A few days ago I stripped the metering head, threw almost all the bits in the ultrasonic cleaner and rebuilt it with new seals and filter screens etc. the control piston was solidly gummed up and not moving.

The cold control pressure was way too high so I have proceeded to go down the same track with the WUR. It looked pretty tidy from the outside but internally was quite mucky. The metering pin in particular was buried in thick sticky residue where it met the spring hat.
The inlet line had a decent amount of rust particles in the filter screen so it has all been disassembled and put in the ultrasonic bath a few times. Hopefully I’ll get it back together on Friday and see it runs.

Am reading up on how the various pressure settings are setup within the WUR but I haven’t moved the fuel capsule or bimetallic strip mounting pin as yet. Hopefully I won’t have to.


It is all quite satisfying so far. Let’s hope it runs!

 

My last quip was a little premature. Injectors ultrasonically cleaned, new seals, fuel metering head and WUR all rebuilt, now back installed and ready to start setting fuel pressures...only the (new) pump won't go again. I haven't been under the car with a multi-meter to diagnose, that can wait for tomorrow, but at this stage the battery voltage is good, the ignition switch appears to be ok in so far as when I turn the key to "ON' the fuel pump relay clicks. I've also put the #18 relay in, same thing. The ISV buzzes. All sounds right.

All that I have done is remove and refit the fuel system in the engine bay, the car has been on the trickle charger in the meantime.

I'm starting to think there is some sort of electrical gremlin but I can't for the life of me work out where to start next. There was a simple immobiliser fitted to the car when it was new but that is long gone. Possibly the wiring repair job is behind this. Current flow diagrams for bedtime reading this evening unless there is something else that I'm missing.

 

The plot thickens. There is battery voltage at the plug, yet once again the pump is dead.the underdash wiring looks ok This is a head scratcher. That is 2 blown pumps and the car hasn’t even been driven.

There is enough life in the battery to crank the motor ok, voltage is 13.2V. I’ve started another thread over in the electrical section just in case.

 

Update: After much head scratching it turns out that my 'fix' for the rotten in-tank pump connections was wonky. The tubing that I used appears to have been too flexible, so when the lifter tank ran it twisted on the end of the pipe and mostly closed off the fuel flow to the pressure pump. Result: Overheating and failure.

At the suggestion of an engine builder friend I've replaced it with the rigid and convoluted tubing from inside some AN6 and AN12 braided teflon fuel pipe. It took a little persuasion with a heat gun but is now in place and all seems to work. I used the lifter tank pump to drain the old fuel and replace it with fresh 98 Octane.

The system pressure now appears to be 5.4bar (engine off) with the new pump in and the metering head uncalibrated. One of the injectors is dribbling so 4 new ones are on the way from Spareto.com in Europe. There aren't too many parts in the system that haven't been replaced now - just the pipes and the tank!

I really envy you guys in the UK - waiting several weeks for parts to make their way down under really stretches both the budget and the project length out.

So next step is on to setting up the WUR and the injector balance once the injectors arrive (hopefully) next week.

I've watched a bunch of youtube how-tos and read instructions that talk about adjusting the cold and warm pressures by knocking on either the fuel cell, the brass plug at the rear of the regulator and the pin that holds the bi-metallic spring in place and to be honest I'm getting all turned around.

Is it possible to check the cold control pressure with the engine off? I'm getting 2.6 bar cold with the pump running but the engine off which seems high but I'm not sure where to adjust it.

 

At this stage my metering head and WUR rebuilds seem to have worked. I purchased 4 measuring cylinders (fairly cheap and way more accurate than the plastic bottle method shown in most YouTube howtos), and spent a bit of time calibrating the 4 new injectors. After half a dozen runs I had them all within 1 ml of each other. A bit of patience helps here, in the end I got down to 1/8th of a turn increments to get them right. The factory manual specs call for a tolerance of +/- 8ml when 80mls of fuel has been delivered at full airflow plate lift but I couldn't find a time frame for the 80mls to be delivered. (ie 80mls in 2 mins or similar).

The earlier Porsche K-Jet workshop manual calls for 120mls in 2 mins, I got to about 95 mls in 2 mins but I'm shooting in the dark without a wideband O2 sensor or a rolling road to check the mixture.

Anyway, it fired up and the Corrado (aka the Orange Roughy) ran for the first time in years. Albeit with a huge flat spot on acceleration and ropy idle. Warm control pressure is now set to 3.4 bar which may or may not be right given the system pressure is at the high end of the spec at 5.4 bar.

Next step ignition timing. My old timing light has vanished so off to the parts store for a reminder that I'm getting older - "hi, do you sell timing lights?"..."um, what's a timing light?...Do you have a picture of that?...What do you use that for?....I think I may have seen one once" (Subtext: Dinosaur).

Fast forward a few frustrating hours and the ignition timing was set to the factory 6 degrees and it now revs sweetly. Such a satisfying sound! Thanks for all your help to getting to this point.

I've been dealing with one last hurdle today - one rear brake was seized. My newly installed N.O.S. mk 4 rear callipers have turned out to have badly corroded pistons so I've rebuilt the original ones and now need brake hoses to suit which is a minor issue.

 

Great news. I think the 80ml is in 40 secs as I have just been doing mine. I will check in the Bentley manual later for you
Well done in saving a Corrado

 

Cheers, I'd appreciate it. Now that you mention it, it's been a long weekend. My 95 mls at full lift was in 40 secs. I got the 2 mins thing mixed up from the idle test. For what it is worth, I've just had a look at the the old Porsche K-Jet workshop manual. It quotes 120-130mls/cylinder/min at full lift; 40-45mls/cylinder/min at part lift and 6-6.8 mls/cylinder/min at idle.

Hopefully that corresponds with the Bentley.

 

Found it. 80ml in 40 secs

 

Brilliant. Thanks!