jpitman2

I think you misunderstand the working of the WUR. When you open throttle the airflow moves the air plate, which pushes a piston in the FD up, and exposes more holes to feed fuel to the injectors. The pressure at the WUR acts against the FD piston to REDUCE the amount of fuel to the injectors. When cold the WUR back pressure is low which allows a rich mixture to flow. As the engine heats up the WUR pressure goes UP, reducing the travel of the piston, and leans the mixture out. Most of the heat comes from the engine block into the WUR body, but the 12V heats the bimetallic strip also.
Fuel pressure is related to flow and restrictions, and ability of pump to produce flow. You should check flow by disconnecting the return line at the RHS cam cover, and connecting a hose from the engine side pipe to a container; run the pump for 30 seconds, and you should get a flow of ~ 1350cc. Keep an extinguisher handy, take care!
Your symptom of low power indicates either a low flow of fuel, or a HIGH control pressure. Mine did this exactly when control got up to 55psi against a system pressure of 75psi. With hot control of 45psi the car is excellent at any speed, and starts well at any temperature.I have heard of FG being rebuilt badly and incorrect fuel feed to WUR.
jp 83 Euro S AT 57k

GerritD

thanks for you clarification , it is much clearer to me know.
So based on your explanation it comes down to either flow issue, either bad WUR.
This narrows down my problem.
I will check and keep you informed.

GerritD

Here some interesting results :
- fuel flow from pump (measured at inlet
tube on engine ) = 1550cc / 30 secs
- fuel flow from FD just before inlet WUR =
240 cc / 60 secs

So it seems that all flows are within specs

kr
Gerrit

jpitman2

Testing fuel flow specs are to measure flow at the RETURN connection AFTER coming out of FD, not at inlet. The figure looks good, but would prefer to see the return figure, as there may be a problem in the FD. I dont know where flow before WUR is specified - where did that come from. This flow to WUR is only used to control action of airplate and delivery to injectors, its not used by the engine AFAIK.
jp 83 Euro S AT 57k getting a new belt as we speak!

GerritD

According to a Kjet specialist that I know ,
the flow delivered to inlet WUR so that WUR
can properly work, it should be
between 160 and 240cc / 60 secs.
So in my case I am . This probably means
that my WUR is the culprit.
But to make sure that my FD is not the culprit
I will measure the return flow also.

what flow specifications for the return flow?
how and where should I measure?

jpitman2

See my previous - return line over RHS cam cover, 1350cc in 30 secs.
jp 83 Euro S AT 57k

GerritD

Are you sure I should have almost the exact flow in and out? Since FD and WUR will
surely lower flow as they are in the flow path.
I am measuring 475cc / 30 secs at the return
line over the engine.

jpitman2

Your flow IN test is misleading because the pump is not working against a pressure regulator. The flow OUT test shows how much fuel is flowing AFTER the pump produces the required pressure. Since the 475cc is ~ 30% of the spec, there is your problem - lack of power. Somewhere on the engine is a pipe with a blockage...
jp 83 Euro S AT 57k

GerritD

This what I found in the Ben Watson Workshop Manual :




So in my case where control pressure cold is normal (1.2bar) but doesn't rise to warm control pressure (3.6bar)
the Control Pressure Regulator is defective.
I suppose that with Control Pressure Regulator, they mean WUR ?

jpitman2

Yes, control pressure regulator is WUR. Look at the diagram of the insides of the WUR - there is a steel shim diaphragm moved by a pin on a spring, controlled by the bimetallic spring. If a piece of dirt gets between the shim and its seat that could cause fuel to flow all the time and prevent the back pressure from rising. If the shim or its seat get damaged (corrosion?) it would cause the same problem. I think you need to open up the WUR!
jp 83 Euro S AT 57k

GerritD

Since the WUR has been overhauled 3 months ago by a Kjet specialist , I will send it back for inspection as there is still warranty on the part.
Strange that new parts fail in such matter...and it suddenly occurred, not gradually.

GerritD

I have a question regarding my WUR not functioning correctly before I would do any intervention on it as it is sealed. :
- bimetallic heater strip inside the WUR is used to raise control pressure from cold faster before engine is actually warmed up and warm control pressure is reached.
Since the resistance of my WUR is 24Ohm and I have 12V on the electrical plug of the WUR, I may assume that my bimetallic heater strip is OK ?
- Since my control pressure does not rise (it stays on 1,2 bar (17 PSI)), will it be usefull to tap the regulator body more inwards in order to raise the warm control pressure (so more pressure on the spring that is pushing against the diafragma ) ?
- I have a bolt on the WUR to adjust cold pressure (by lowering the pin to which the bimetallic strip is connected) but in my case my cold pressure is not problem, correct ?
- I suppose there are no fuel leaks in the diafragma as this would be quite visible and would short circuit my heater strip when fuel would pour on it , not ?
- are there any other tests I can do with the WUR out of the car ?

jpitman2

If 24 ohms is correct resistance for heater, thats OK.
I would not adjust anything until you get the warm control rising as it should. If its faulty as fixed by somebody else, dont mess with any settings. If the problem is caused by a fault in the repair, good for you. If its caused by foreign matter (dirt, grit) getting in due to dirty fuel, they may charge you for a fix.
Important - tell them what the symptom/problem is, DONT try to tell them what you think the cause is ! Its their job to find out, and ask if they have tested it before you take it back.
jp 83 Euro S AT 57k

GerritD

The only thing what I can do is clean the WUR by rincing the inlet/outlet via proper fuel or carburator cleaner. Just to rule out a clogged WUR.
I just find it strange that my problem suddenly occurred...if dirt would be my problem, I would have noticed a more and more bad running engine ..Last time my engine ran well, it was during a very hot summer day (38°C / 100°F ),
perhaps heat caused something to snap ?

jpitman2

If some dirt is trapped under the shim, rinsing it wont help - the spring pressure on the shim will hold the dirt in place. Try it, but I doubt it will help. IMHO I think it needs to be opened up.
jp 83 Euro S AT 57k