WUR Problem?

[Brian Fuller]

1978 SC. Car was purchase 3 years ago. I was able to drive it home but remembered it did not perform well. Had a cold start problem but drove it 15 miles home. Pulled the engine, cleaned everything. Put back together and now tried to start 3 year ago to the date.

Cold start problem remains an issue. Car starts but if you press the gas pedal, the engine bogs and pops. After 5 minutes the engine runs better and you can rev with some popping noise in the engine. Driving the car you feel the engine surging when cruising at 30mpg and does not perform well with popping noise (I don’t think it’s backfiring in the exhaust - sounds more like in the intake area) I did test for vacuum leaks. Pressurized the system and sprayed soapy water everywhere, manifold, injectors, exhaust manifold etc. No indication of a leak. Car has pop off valve.

AAR Test
Half open at 80 deg. With power to the AAR, it closed after about 5 minutes.

CIS Pressure test

1. Installed the pressure gauge between WUR and FD with shut-off valve on the WUR side (edit: originally misspoke and said valve was on FD side)
2. Jumped FP relay terminals #87A & #30.
3. Turn the ignition switch @ ON and start the FP.
4. With the valve closed (FP running) system fuel pressure was 4.8 bar
5. Opened the valve control fuel pressure to engage WUR; pressure would not drop below 4.5 bar. After 4 min. no change in fuel pressure. Turned off FP and after 10 min. pressure slowly dropped to 1.5 bar
6. Triple checked my test equipment and connectors for anything that might constrict the flow of gas blowing 60 psi through hose connectors. Air flowed freely. Also checked gauge accuracy using compressor air (60 psi from my compressor connected to fuel test equipment) and the test equipment gauge read 60 psi
7. Retested twice more, same results; fuel pressure at 4.8 bar would not change much when I opened the valve to the WUR. Same results as above.

Deduced I have some constriction in the lines somewhere.

Constriction Test

1. Connect the CIS pressure gauge between the WUR and FD
2. Disconnected the main return fuel line fitting behind intake runner #3.
3. Connected a temporary plastic hose for the return line from FD to a one liter bottle to collect the recycled fuel during the test.
3. Turned on FP and the bottle filled in less than 10 sec. Fuel pressure almost reached 4.8 bar
4. I tested return main fuel line to fuel tank by blowing air through line, I could easily push remaining gas in line through the tunnel fuel line and then could hear bubbling noise in fuel tank. (as part of restoration fuel tank was pulled and cleaned and new tunnel fuel lines were installed.

I now believe the constriction is at the WUR. Can a WUR get clogged internally?

WUR Bypass Test

WUR screen looks clean. WUR # 0438140045
Test of continuity OHM 27.7
11.5 volts to electrical connector when FP is on.

1. I left the fuel pressure line attached to the FD.
2. I have a lot of fuel line parts so I was able to bypass the WUR and connected other pressure test line to the WUR banjo. Thus the WUR is eliminated from the system completely.
3. Turned on the FP and the gas flowed easily through the system. The Fuel pressure gauge did not move. There does not appear to be an issue with constriction in fuel lines
I believe now believe the constriction may be in the WUR.


Thinking I’m going to send Tony a PM and get his thoughts. I’m not familiar with all that can go wrong with a WUR but it’s my belief that this one has a problem.

[pete3799]

CSI pressure testing- shut off valve goes on the WUR side.

[Brian Fuller]

Pete, I misspoke. I had the valve on the side of the WUR. Regardless, when the valve is open, wouldn't the pressure drop? Then, over a four minute test time, the WUR would start to raise the pressure to spec? But mine pressure is not changing. Remaining at around 4.5 or 65 psi.

[ossiblue]

Originally Posted by Brian Fuller

Constriction Test

1. Connect the CIS pressure gauge between the WUR and FD
Disconnected the main return fuel line fitting behind intake runner #3.
2. Residual fuel will flow out when you break this connection and be ready to have a piece of rag or a container ready.
Connected a temporary plastic hose for the return line from FD to a one liter bottle to collect the recycled fuel during the test.
3. Turned on FP and the bottle filled in less than 10 sec. Fuel pressure almost reached 4.8 bar
4. I tested return main fuel line to fuel tank by blowing air through line, I could easily push remaining gas in line through the tunnel fuel line and then could hear bubbling noise in fuel tank. (as part of restoration fuel tank was pulled and cleaned and new tunnel fuel lines were installed.

I now believe the constriction is at the WUR. Can a WUR get clogged internally?

Can you clarify something in your constriction test?

I believe, on your car, the return line from the WUR runs up to the rear of the FD where it connects with the fuel pressure relief valve. From there, both the FD excess fuel and WUR excess fuel share the same line back to the tank.

Your test description sounds like you disconnected this common return line without isolating the return line from the WUR. Because you got a rapid fill of your container from this return line and the fuel pressure did not change, only means the fuel was coming from the FD relief valve. Unless you isolate the return line that comes directly from the WUR and test to see if that line is blocked, you cannot tell if the lack of fuel flow from the WUR is from the line or the WUR itself.

If I misunderstood your post or your testing, I apologize. My main question to you is, have you tested the line from the WUR, in isolation, for blockage?

Edit: after rereading your WUR bypass test, it sounds like you did find fuel flowed freely through the WUR return line, but your description of the connections was confusing to me. If you made connections directly from the FD port to the WUR return line, and fuel flowed freely, then that does leave only the WUR as a point of blockage.

[gazzerr]

You have verified that it's getting supplied voltage. If so then yes your WUR is bad.

I'd say either the heater coil is bad or the internal plunger connected to it is bad. I don't know if 27 Ohms for a cold 045 WUR is within spec.

[Brian Fuller]

Ossiblue, thank you for your comments. This helps me to clarify~

I did purchase all new lines, tunnel pressure line and and tunnel return line, new filter in tank, and all new lines that make up connections to the filter/accumulator/ and WUR, etc. Everything new.

"I believe, on your car, the return line from the WUR runs up to the rear of the FD where it connects with the fuel pressure relief valve. From there, both the FD excess fuel and WUR excess fuel share the same line back to the tank."

Yes, that's correct see illustration below:

"Your test description sounds like you disconnected this common return line without isolating the return line from the WUR."

Yes, in my first test I did this. I was trying to see if there might be a clog in the return line at the tank. But then reconnected everything and moved on to a second test which I called the "WUR Bypass test"

I had concluded that the constriction might be in my WUR. What I was trying to do is bypass the WUR to see if fuel would flow freely through all the lines. I connected "B" see illustration below to "B" above and "A" to FD with the fuel test gauge in between and valve open.

(copied this image from other post)

What I am discovering is when I am doing the standard Fuel pressure test my pressure is way, way too high. What I have tried to do is isolate where the constriction is and it would seem that fuel is not getting through the WUR... my pressure goes high and stays high 4.8bar.

When I bypassed the WUR, the fuel flows freely and there does not seem to be any constriction in any of the lines.

BTW, I did disconnect both fuel lines from the WUR and blow compressed air (60psi) on the WUR fuel intake side, very little air would pass through. But I don't know if this is proof that the WUR is clogged. Which begs the question, do WURs get clogged? As I mentioned the screen looked clean so it would have to be an internal clog.

All the Best,

Brian

[ossiblue]

Originally Posted by Brian Fuller

Ossiblue, thank you for your comments. This helps me to clarify~

I did purchase all new lines, tunnel pressure line and and tunnel return line, new filter in tank, and all new lines that make up connections to the filter/accumulator/ and WUR, etc. Everything new.

"I believe, on your car, the return line from the WUR runs up to the rear of the FD where it connects with the fuel pressure relief valve. From there, both the FD excess fuel and WUR excess fuel share the same line back to the tank."

Yes, that's correct see illustration below:

"Your test description sounds like you disconnected this common return line without isolating the return line from the WUR."

Yes, in my first test I did this. I was trying to see if there might be a clog in the return line at the tank. But then reconnected everything and moved on to a second test which I called the "WUR Bypass test"

I had concluded that the constriction might be in my WUR. What I was trying to do is bypass the WUR to see if fuel would flow freely through all the lines. I connected "B" see illustration below to "B" above and "A" to FD with the fuel test gauge in between and valve open.

(copied this image from other post)

What I am discovering is when I am doing the standard Fuel pressure test my pressure is way, way too high. What I have tried to do is isolate where the constriction is and it would seem that fuel is not getting through the WUR... my pressure goes high and stays high 4.8bar.

When I bypassed the WUR, the fuel flows freely and there does not seem to be any constriction in any of the lines.

BTW, I did disconnect both fuel lines from the WUR and blow compressed air (60psi) on the WUR fuel intake side, very little air would pass through. But I don't know if this is proof that the WUR is clogged. Which begs the question, do WURs get clogged? As I mentioned the screen looked clean so it would have to be an internal clog.

All the Best,

Brian

Thanks for the clarification Brian. You'll see I edited my post as you were typing and now I see that all lines appear to be clear. The problem seems to be with the WUR, as you've found.

You can disassemble the WUR easily. Once the bimetallic arm is removed, you can open the bottom of the diaphragm housing and remove the two metal diaphragms. You'll now be able to see the inside of the entry and exit ports. The port bores are very small, but you should be able to see light through them and blow air, with your mouth, through them (though it will be difficult.) It should be clean on the inside of the housing, and the diaphragms should be clean as well. There is an O-ring that seals the bottom of the housing that should be checked before reassembly. This is the only area that could account for the blockage. Since your control pressure never changes from your system pressure, the only possibility, other than a blockage, is the pin that pushes up on the diaphragms is not adjusted correctly, but that is a bit remote if no one has been messing with the WUR.

Regarding the post about the functioning of the heating element, at this point the issue is moot. The heating element only causes the pressure to rise from cold control pressure and yours does not drop below system pressure. Still, it's good to check the functioning of the heating element. You can do that easily, especially if you disassemble the WUR for the blockage. Apply 12v to one pin of the element plug and ground the other. Can you feel heat emanating from the heating element? Even if you don't disassemble the WUR, after about 4 minutes you should be able to feel the heat through the body of the WUR if the element is doing it's job.

[boyt911sc]

Brian,

Try to clean the micro mesh inside the WUR and re-test. If you are unsuccessful in cleaning the screen filter, send the WUR to me and I will do the cleaning for you and measure the control pressure.

Tony

[Brian Fuller]

Update: Tony, I sent you an email. I'm packing up the WUR to send to you for testing.

BTW, just for fun I ran one more test. Again, system pressure is 4.8 bar or 70psi (note: in my previous post I said 60psi which was wrong; 4.8bar is closer to 70psi not 60psi as I posted earlier, which is WAY to high!)

Just for giggle, I left the test equipment on, bypassed the WUR with the test equipment (FD connected via gauge and test lines and connected to the banjo fitting) Turned on the fuel pump and adjusted the valve on the test line to bring down the pressure to from 4.9 to 3.2bar. I started the car. VAROOOOOM! Car engine sounded like it just drove off the factory line! Pretty sure now this WUR has been contributing to the poor engine performance.

Of course, once I get the WUR fixed, you know I'll find something else wrong!

All the Best,
Brian

[boyt911sc]

Originally Posted by Brian Fuller

Update: Tony, I sent you an email. I'm packing up the WUR to send to you for testing.

BTW, just for fun I ran one more test. Again, system pressure is 4.8 bar or 70psi (note: in my previous post I said 60psi which was wrong; 4.8bar is closer to 70psi not 60psi as I posted earlier, which is WAY to high!)

Just for giggle, I left the test equipment on, bypassed the WUR with the test equipment (FD connected via gauge and test lines and connected to the banjo fitting) Turned on the fuel pump and adjusted the valve on the test line to bring down the pressure to from 4.9 to 3.2bar. I started the car. VAROOOOOM! Car engine sounded like it just drove off the factory line! Pretty sure now this WUR has been contributing to the poor engine performance.

Of course, once I get the WUR fixed, you know I'll find something else wrong!

All the Best,
Brian

Brian,

As you have experienced, you could run your engine without a WUR. Having a gauge and a valve installed in lieu of a WUR would do the work for running the engine. Driving the car is quite different. Please let me know when to expect the WUR so I could plan ahead and get it tested.

Tony

[Brian Fuller]

Just pulled the WUR and packed for shipping. Will go out Tuesday.

[CENTER]

[boyt911sc]

Brian,

If I remember correctly, you have a different fuel distributor on your engine for MY '78 (?). While I have your attention, could you post the number of the FD and the AFM (air flow meter)? Thanks.

Tony

[Brian Fuller]

Tony,
Posted AFM and FD with pics below:

AFM



FD

[Brian Fuller]

Tony, looks like I will not be shipping the WUR to you after all.

Good News! I figured I could not ship out my WUR until Tuesday since Monday is a holiday. Figured I had the afternoon to learn something about how I could at least clean it and look for blockage. I found Steven Hauer’s 12 page PDF on how to disassemble, inspect and clean the BOSCH WUR.

Just as suspected, there was a blockage. However, the debris was behind the intake screen in the port. I could hardly get 100 psi to pass through the port. I tried lots of carb cleaner but nothing would dislodge the blockage.

Finally, I got a small stainless steel wire about the size of a needle and treaded from the inside of the WUR through the port toward the screen. A few more blasts of air and carb cleaned and it opened up! I’m just disappointed I didn’t find whatever it was on the cloth I laid on my bench. BTW, the inside of the WUR looked like it was new. Very clean.

Reinstalled the WUR, put the pressure test equipment back on and got the following readings.


System pressure 4.9 bar
Opened the valve to the WUR

One minute: 2.3 bar
Two minutes: 2.6 bar
Three minutes: 2.8 bar
Four minutes: 2.9 bar

It's getting late so I have not yet tested with the engine running to record the pressure with the vacuum line attached. I'll get to that sooner or latter.

Turned off Fuel Pump to record Pressures after five and ten minutes:

5 minutes: 1.5 bar
10 minutes: .80 bar

Start Your Engines
Pulled the test equipment off and reattached fuel lines. And started the engine. Vaaaaroooom! The engine started with no problem. No more bucking or surging. No more popping.

Really pleased at this point. I will have to recheck the timing since I tried to do it when the engine was running on 4.9 or 70 psi!

All the Best,
Brian

[gazzerr]

Awesome!

[rwest]

Successful trouble shooting- what an awesome feeling, congratulations!

[Ngrich99]

It's a wonderful WURld, when you figure it out and it runs right! I went through the same thing with a car that sat for eight years. Lots of reading and going through the components logically and now a great running car. Congrats!

[boyt911sc]

Originally Posted by boyt911sc

Brian,

Try to clean the micro mesh inside the WUR and re-test. If you are unsuccessful in cleaning the screen filter, send the WUR to me and I will do the cleaning for you and measure the control pressure.

Tony

Brian,

It feels great when you are able to successfully fix things yourself. Good job!

Tony