fritz k.

A problem with the check valve on the front pump would probably occur permanently, the system pressure would be too low than.

If she stalls and starts poorly this indicates an uncontrolled AFR change. That can be on the fuel side but I would rule out false air first and the turbos have a lot of possibilities for false air. That's why you can check it in a reasonable way only with a smoke machine, which is available e.g. from Autool from around 100 bucks.

Fritz

911 2

i have a smoke machine, what am i checking foe, vacum leaks, if so what is the procedure

fritz k.

A good place to introduce the smoke is the thin hose connection for the wastegate on the left side of the intercooler. Remove the hose and blow the smoke into the intercooler.
Also, open the throttle to allow the smoke to enter the intake manifold.

Then search the entire engine compartment and the turbo area for smoke with a suitable lamp.

911 2

I have rebuilt the wur and checked the fuel pressures before starting and my control cold pressure is still lower than what is should be according to the manual, the remaining pressures are still the same well may have increased by a psi form before the build

System pressure 92psi was 91 psi before rebuild

Cold control pressure 22psi, goes to 25 psi when pump switched off, this is at 12.7c when infra red thermometer pointed at the WUR, manual states, at this temp, the cold control pressure should be 36psi, so 14psi down.
Before the rebuild, cold control pressure was 34 psi at 27.5c, should have been around 47psi, roughly 13psi down

So the control pressure is down

Control pressure with the heater activated in the WUR is 58psi, same as before the rebuild, manual states it should be 65psi, so still 7 psi down

Control pressure drop within 10mins was to 29psi and, manual min drop is to 23psi
Control pressure drop after 20 mins was to 25psi and manual min drop is to 20psi
I think this has improved and held the pressures until I released the pressure via the relief valve on the gauge

Any idea please what is causing the control pressures, cold and warm, to be lower than what the manual states and the effects this will have on the running of the car, how can i increase the control pressure so it is in spec

wicks

When I was rebuilding my FD I had to sort out the fuel pressure regulator on it, which had quite an effect on pressures, just a little thought but you're probably past that. You have the Bosch K-jet manual yes? Remember something about the amount of voltage hitting the WUR needs to be high enough for it to work right.

911 2

Thanks, I did not realise the voltage had to be 14v, problem is even a new battery will not produce 14v unless the engine is running, the fuel pressure tests are all done without the engine running
Even if I get 14v, the cold control pressure is still 13psi down
Is the FPR separate to the WUR, if so where is it located
I have already replaced the fuel accumulator
It seems even after rebuilding the WUR iI am still getting the exact same results, the control pressures are lower as the WUR was at 12.5c a opposed to 27.5 c before the rebuild
Would the WUR need adjusting internally after a rebuild, if so I assume it has to be opened again, there is an adjustment screw underneath but not sure what that adjusts

911 2

From the further research I have done, it seems, when rebuilding a WUR, it will still need adjusting to get the control pressures to spec
I assume there are only two ways to adjust it

1. open up the WUR and turn the allen head screw but this is trial and error and opening and closing the WUR a few times, cant be good for the gaskets
2. Knock or pull out the pin located on top of the WUR, if im going to do this I may as well tap the pin and put in a bolt for adjustment, as if you knock it in to much then the WUR has to be opened up again and the pin knocked back out, I can then adjust it whilst on the car and fuel pressure gauge attached

Thoughts please

fritz k.

Sorry, but you read too little and write too much. Again: The lower membrane is only responsible for full-load enrichment and works from 0.3 bar boost pressure. The Allen grub screw in the membrane only changes the full load enrichment.

A useful way of adjusting the pressure is to adjust the upper spring pre load by using thin washers. Result:

911 2

From what I read and the the companies I contacted who build the wurs, none of them suggested using washers, all advised adjustment of control pressure via movement of the pin, modification of the pin with a bolt just makes it easier to set the pressures accurately.
If the washers worked for you that is good and maybe another way to adjust the pressures but I dont really want to have to open the wur regulator again as all the seals are new

peterpullin

you do not know what you are doing, i fear!

we all started at this point - we asked, wrote, readed and finally understood.

your problem is NOT the wur. you had to start wit the basics: shim the pressure regulator in the fd until values are in spec.

if there is minor corrections left you can do them in the wur.

but before adjusting wur find out WHY your specs are out. may be your fd leaks internal. that is why you have to check injectors for similar flow.

or, better give your car to a specialist that dies not kill your engine. you are on the best way to do so!

fritz k.

Of course, the rest of the peripherals should also be in propper order. Here is an example of the injectors after about 75,000 km.

Three old injectors on the right, three new injectors on the left.

wicks

Also side note pertaining to fuel flow, recommend every fuel head be rebuilt at this stage (30 years old), the membrane in there has really lost its flex, though the o-rings were still in pretty good shape (high quality rubber mfg). Membrane was pretty solidified but hadn't developed a hole/tear yet. But definitely wasn't doing it's job well.

Nyx

FYI.

When testing CIS pressures you must use a calibrated gauge. The reference values are close together so a dial which is out will give false recordings.

a local instrumentation lab can do this for less than $100.00

I was using the SIR Tools Bosch CIS gauge set and it was way out. (10%)

911 2

Fritz are you running a 1 bar boost spring or standard boost as your warm control pressure is exactly at factory spec for standard boost,
I have now rebuilt and set my warm control pressure to 4.3bar, this is in spec ( 4.5bar +/- 0.20bar) on boost the car will run a little richer,

On 0.5 bar of positive pressure, from the mityvac, my fuel pressure drops to 1.44bar, this is in spec of the manual, which allows a drop of 1.3 bar +/- 0.20bar

Nyx you have a good point, gauges can vary, I will be installing a wide band AFR Uego gauge and will tweek afr with this once on the road.

Adjusting the warm control pressure is a real pain, as the WUR has to be opened up and dismantled each time

fritz k.

I use this to regulate the boost pressure. But I'm not sure if I understand the question correctly, because the spring in the wastegate does not affect the setting of the WUR.

What have you done to come to specs with control pressure?

Fritz