K-Jet Experts - please help (latest update Pg 6!!)

I didn't mean buy one, there's no one more tight fisted than me when it comes to cars.

cedar said

I didn't mean buy one, there's no one more tight fisted than me when it comes to cars.

  I'm pretty close!

Things just went from bad to worse. Managed to get hose made up to be able to use my original fuel pressure testing kit correctly, then when assembling it I've sheared the adaptor from metering head to WUR. These are of course obsolete so I'm on the hunt for a replacement bit. At least I was able to get the sheared bit out pretty easily.

Damn!
What does it look like? I may have one…
I bought a spare metering head years ago, no idea what's on it, or where it is for that matter but I could check.

J

Circled in yellow J. It's a double threaded adaptor. 

I'll hunt through my stuff tonight and see what I've got.

Found a brand new one - https://www.rosepassion.com/en/diagrams-porsche-924-1981-eu-924-2-0-coupe-manual-gearbox-5-speed/engine-and-fuel-feed-36/injection-line-injector-valve-1667/063133558-p5648-screw-socket-063133541-5648
not cheap mind!

Stupid money alright. I've ordered a used one from Crazyquiffs for the bargain price of £18.50!!!!

 

Needs must I guess!
Found loads of similar things in 'proper' sizes - the VW sizing is just too specific to them.
I'll take care with mine if I ever have to remove it!

I've managed to cobble together the fittings and done cold pressure test. The results are strange:

System pressure is 7 bar
Cold control pressure is 3 bar
Residual pressure is rock solid

Help!! Does this mean a restriction in the return line to the tank?

At last, some progress. Found the return hose onto the fuel tank to be kinked, obviously restricting return flow. Temporarily moved it clear and repeated test & now I've got a healthy 4.9 bar system pressure.

Now I'm just waiting for that metering head connector to reinstate the system as it was and try to fire it up again. Still not certain this is the only fault, but will soon find out.

Possibly a daft question, but can you not fire it up with the test harness in place? It's giving you a flow between metering head and wur..

You're right J. I've just ran out of time today though.

Just sneaked 10 mins in the garage there, no joy. Still turning but not firing. However the cold control pressure seems very high at 3 bar so I think I'm gonna adjust it down using the Allen scew under the brass dome.

I almost feel like I need to start this thread again, as I'm running out of options now.  The most recent info gathered is:-

Now that I've got the fuel return line sorted, I've repeated the testing of pressures with the fuel pump relay linked out:
System pressure = 4.9 bar
Cold control pressure = almost zero (hard to read scale so low, but around 0.2-0.4 bar)
With the pressure gauge valve left open, when I switch off the fuel pump, the pressure goes from 0.2bar to reading around 3bar. I presume this is residual system pressure taking over? The pressure remains solid for at least 10 mins after shutting down the pump, so assume the pump NRV and accumulator are working.

I have tested the CSV during cranking over, and I'm getting no fuel flow at all. I am getting voltage to the connector during cranking so the thermo time switch appears to be operating correctly.

I have pulled all the injectors, and with them directed into jars, while cranking the engine, again no flow at all.  With the fuel pump relay linked to allow the pump to run, I've loosened the lower half of the air box, and by lifting the air flap manually from inside the airbox I am getting really good flow from all 4 injectors, with a nicely coned spray pattern.

I'm getting 22.6ohms resistance across the WUR terminals which appears to be as expected.

It seems as though when cranking the engine, the air flap is not lifting enough to get the injectors to flow. This car has a stage 2 head now fitted, with 2.2 Audi throttle body and matching WUR. I'm reluctant to go making loads of adjustments with no logic, but could it be that I need to adjust the mixture screw to allow the air flap to lift more for the given start conditions and actually release the fuel to the injectors? Or could I have a massive vacuum leak somewhere preventing the air flap from lifting sufficiently (I've had a look around and everything is secure and no splits, so think this is unlikely to prevent starting completely).

I though about engine timing, but until I actually get fuel to the injectors during cranking over, I don't think I can progress.

Can some of the forum k-jet gurus please guide me though my next steps.

This reminds of when I rebuilt my engine many, many years ago, exactly the same symptoms. Mechanic friend said did I make sure I had good compression, and therefore suction for the flap? So I took the plugs out and put a small amount of oil in each cylinder to help ensure good compression. Plugs back in and it fired straight up and ran from that point on. Now I'm no expert, but it made sense to me at the time…

I would double check the valve timing and if that is okay try the suggestion in the previous post, put a little oil in each bore or get hold of a compression tester.
If your Audi WUR has full throttle enrichment you will get a lower control pressure if the vacuum pipe is not connected but I'm not sure how low.

Thanks again for the advice.

So, I've checked all the timing marks from engine crank pulley, cam sprocket, piston 1 at TDC with cam lobes level and pointing upwards, the flywheel mark is visible in the inspection port and the distributor is pointing bang on the mark.

I did as suggested and put a little oil into each plug hole, then boxed it all up and it did actually fire for a few seconds but would not rev and just spluttered like mad until eventually dying. It did fire a couple of times after this by putting foot to the floor on throttle pedal, but again it wouldn't rev and just died. Then it just went back to turning over and not starting.

My father-in-law watched the pressure gauge (I'm still rigged up with the k-jet pressure test kit) and as soon as it started cranking the pressure dropped to zero, is this right?

I've tried adjusting the mixture screw to see if it helped to start it but made no difference.

My next plan is to recharge the battery fully and get a compression test done across all 4 cylinders. Is there any coincidence that I'm having a couple of minor electrical issues that could be linked to starting? My VDO gauges are going full scale when I turn on ignition and my front indicators aren't working at all (either using the stalk or the hazard switch).  I'd imagine something major would prevent the starter from even turning the engine.

So you've confirmed you have spark. So it's not that.
Can you pull one injector, put it in a jar, and try and start it to confirm if it's delivering fuel on cranking? That may be a daft idea but for a brief test it might be okay. Other wiser folk may say don't!
Even if the timing was off a bit it should still start.
Is there a vacuum pipe you can pull and put your finger over to see if you are getting vacuum? Possibly the one the goes into the big rubber section just before the throttle. Pull the pipe that comes in the bottom of that?
Appreciate these are random ideas but they might help rule something out.
My first engine rebuild I had the cam timing way out. Used the dot on the outside of the cam pulley instead of the inside. Luckily it was a standard cam so non interference. Yes, I know, but I was young and stupid. That fired briefly but wouldn't run at all!

Which WUR are you using? The original or the one with vac? Seems odd that the control pressure is so low.
Did you check out the retrovw vud on you tube I linked in an earlier post?