I think I've diagnosed my WUR as faulty, with a "left field" method...?

[dino_jr]

Hello.
I think I just diagnosed my WUR as faulty, preventing my car from starting.

Electrical system/relays etc all good.
WUR has 36 ohms across its electrical terminal (the wire resistor wound around the bi-metallic strip in the WUR)
12V confirmed to be applied to the WUR when I key on.


Now, I am waiting for adaptors from eBay to allow me to connect my fuel pressure gauge to the car. The only adaptor I do have in the meantime, is one that fits the M8 thread of the fuel return line on the WUR itself.

1. This return line is sending 58psi of fuel pressure back to the fuel tank, whether the WUR electrical plug is connected OR disconnected.
2. Leaving the pressure gauge in the return line connection, acting as a “plug” (No fuel can return to the tank) the car cranked and fired up! Hurrah!

So are my checks 1 and 2 sufficient to know I now must buy a new WUR?
They are not cheap so need to be sure I don't waste money!

Thanks.

[boyt911sc]

Originally Posted by dino_jr

Hello.
I think I just diagnosed my WUR as faulty, preventing my car from starting.

Electrical system/relays etc all good.
WUR has 36 ohms across its electrical terminal (the wire resistor wound around the bi-metallic strip in the WUR)
12V confirmed to be applied to the WUR when I key on.


Now, I am waiting for adaptors from eBay to allow me to connect my fuel pressure gauge to the car. The only adaptor I do have in the meantime, is one that fits the M8 thread of the fuel return line on the WUR itself.

1. This return line is sending 58psi of fuel pressure back to the fuel tank, whether the WUR electrical plug is connected OR disconnected.
2. Leaving the pressure gauge in the return line connection, acting as a “plug” (No fuel can return to the tank) the car cranked and fired up! Hurrah!

So are my checks 1 and 2 sufficient to know I now must buy a new WUR?
They are not cheap so need to be sure I don't waste money!

Thanks.

Dino,

What MY (model year) is your car? Do you know the Bosch WUR ID number? You don't need a new WUR. All you need is perform the correct tests to evaluate the condition of your WUR. Unless you don't care spending unnecessarily, you could fix your problem/s by installing new parts after new parts until the problem/s go away if you get lucky. From reading your post, I doubt a good WUR would fix your problem. But you would need to do the correct tests to identify and isolate the culprit/s. Keep us posted.

Tony

[dino_jr]

Hi Tony... My car is a 1980 SC Targa.

In my mind, the fact that:

* Fuel is returning to the tank at a constant pressure REGARDLESS of if the WUR is "hot" or "cold"
* Plugging off the WUR return line allows the car to start.

... tells me the valve asy in the WUR is not working?

You are right I should check the other pressure around the fuel system when I have the adapters. But the sun is out here in the UK for a change and I missing the good weather!

[T77911S]

so let me get this straight:
you connected the gauge to the RETURN side of the WUR and I assume you had the valve on the gauge closed(?) and you measured 58psi?

I have never done this but with the valve closed on the return side I would think that would still be system pressure, which at 58psi is too low. that is a pressure regulator issue and/or a fuel pump issue. BUT, I would still inspect the inlet screen to the WUR while you are at it, not that this would cause this problem but it is a good check.

you need to connect to the inlet side of the WUR to determine if the WUR is bad. if the car did not start until you effectively "raised the CCP" and leaned out the mixture could mean there are other issues that are making the cold start too rich. we can address this once we know the CP's.

if the valve on the gauge is open on the return side and you have 58psi you have a restriction in the return side.

it would also help to know if your car is US or ROW.

[prschmn]

I think you'll save money in the end by getting the correct gauge setup and doing a correct
pressure test-I'm confused about how you're doing it now and not at all sure you need a WUR.

[dino_jr]

Originally Posted by T77911S

so let me get this straight:
you connected the gauge to the RETURN side of the WUR and I assume you had the valve on the gauge closed(?) and you measured 58psi?

I have never done this but with the valve closed on the return side I would think that would still be system pressure, which at 58psi is too low. that is a pressure regulator issue and/or a fuel pump issue. BUT, I would still inspect the inlet screen to the WUR while you are at it, not that this would cause this problem but it is a good check.

you need to connect to the inlet side of the WUR to determine if the WUR is bad. if the car did not start until you effectively "raised the CCP" and leaned out the mixture could mean there are other issues that are making the cold start too rich. we can address this once we know the CP's.

if the valve on the gauge is open on the return side and you have 58psi you have a restriction in the return side.

it would also help to know if your car is US or ROW.

Hi.

Car is a UK spec car, so ROW ?

You are correct, I removed the return line from the WUR and put the pressure gauge in its place as per the picture (#5), so fuel cannot return to the tank.



I suspect the 58 psi value may be low due to low battery volts at the pump (car hasn't run for 3 months) and also the M8 threaded fitting of the WUR return line is a 3/16" bore, restricting the fuel somewhat to the gauge... Typical system pressure is 65+ psi right? My car is "close" to OK I think.

Indeed I plan to measure the pressure into the WUR when the correct M12 & M14 adapters come in the post. I just figure for now, as I said, the car starts and runs with the return outlet of the WUR "Blocked" hence fuel pressure must be OK in general?

I remember there is/was an idiots guide to Fuel system diagnosis on this forum somewhere, can someone link to a decent thread? Thanks.

[prschmn]

The size of the hole doesn't matter since you're deadending the line anyway.
System pressure is too low though.

[Steve F]

Here you go


CIS Troubleshooting for Dummies

[T77911S]

mark is correct.

if it started with a hi CCP which is what you created by "plugging" the return line you have a too rich issue. could be several things and I may miss some.
low system pressure can make it richer
mixture waaaay off
plunger stuck. you could have broken it free after starting.
bad injector(s)
not likely but something to consider, issue with CSV system- on too much or too long

I would not conclude anything until all pressures are checked and if system pressure is too low that is fixed.
I put my battery charger on 10amp and put it on the batt when running pumps for extended periods.

[fanaudical]

Hi, Dino - As others have said, wait for the correct adapters to show up and do the pressure test as prescribed. There's lots of experienced help here, so report back with results.

[dino_jr]

Well, I just got home and my adapters have arrived!
So I remove the feed from the FD to the WUR to discover the thread is M10... guess which adaptor I did NOT order
The FD end is M10 too



Can someone tell me the pitch of this thread? M10x 1.0 ?
Or is there another point to measure system pressures? I have M8, M12, M14, and M16 fittings

[timmy2]

Separate the fitting on the line. Take the nut with the line off the fitting in your photo. Put the double male fitting back into the WUR, connect to the top of the fitting where the line was removed.

[dino_jr]

Ok... is there an M12 thread under there then?
For now it absolutely will not loosen, I've soaked it in WD40 and will try in the morning. Thanks

[boyt911sc]

Originally Posted by dino_jr

Well, I just got home and my adapters have arrived!
So I remove the feed from the FD to the WUR to discover the thread is M10... guess which adaptor I did NOT order
The FD end is M10 too



Can someone tell me the pitch of this thread? M10x 1.0 ?
Or is there another point to measure system pressures? I have M8, M12, M14, and M16 fittings

Dino,

The WUR has the following thread/pitch size:

Inlet : 10-mm x 1.0
Outlet: 8-mm x 1.0

Injector : 12-mm x 1.5

You would need a 12-mm x 1.5 (male/male) adaptor for your pressure gauge. Do you know how to use and install the CIS pressure gauge? You seem to be totally lost doing the test.

The inlet for the WUR has an adaptor (10-mm x 1.0 and 12-mm x 1.5). Install the pressure gauge with 12-mm x 1.5 fittings between the WUR and FD. Place the shut-off valve closer to the WUR. Keep us posted.

Tony

[SalParadise]

Originally Posted by dino_jr

Dino, what the heck size wrench are you using on those adapters and fuel line nuts? Looks like you're rounding off everything. Better get yourself some real metric wrenches with those new adapters.

[dino_jr]

Not guilty, previous owner clearly tried chewing on the nut or something!
Just found that male-male connector on another website, there is indeed an M12 thread on the other side it seems... I'll continue tomorrow, thanks for the help everybody

[RarlyL8]

Here is a picture of the fuel pressure gage installed. Standard CIS fuel gage kits contain all the adapters you need. (This pic is of a 930 but works same for 911).
If you are seeing system pressure at the WUR it is likely that the gage flow is shut off at the WUR and not going through it. Low pressure may simply mean you need to charge the battery while doing your test (always a good idea). Also verify your fuel pump is getting 12V minimum while running. Return pressure to the tank is system pressure. Return volume can give you a clue if WUR is occluded.




This simplistic instruction may help you set your test gage up and use it properly.

[dino_jr]

That diagram is fantastic Rarly, just what I needed thanks.

OK so I measured some more stuff...


1) With the gauge attached to the FD only, I see 67psi. I believe this is my "System" pressure.


2) With the gauge attached on a T-Piece between the FD and WUR, I see 15psi
with the WUR electrical plug connected OR disconnected. I believe these are my "Hot" & "Cold" pressures, the same number!

This suggests to me the WUR is indeed sending the majority of the fuel back to the fuel tank, all of the time. Hence the injectors are starved of fuel, and car doesn't run. FYI the WUR wiring sees +12V when keys are on, and the WUR resistance is 36 ohms.

So, WUR is indeed the culprit? Stuck valve and/or busted bi-metallic strip?

[ossiblue]

Originally Posted by dino_jr

That diagram is fantastic Rarly, just what I needed thanks.

OK so I measured some more stuff...


1) With the gauge attached to the FD only, I see 67psi. I believe this is my "System" pressure.


2) With the gauge attached on a T-Piece between the FD and WUR, I see 15psi
with the WUR electrical plug connected OR disconnected. I believe these are my "Hot" & "Cold" pressures, the same number!

This suggests to me the WUR is indeed sending the majority of the fuel back to the fuel tank, all of the time. Hence the injectors are starved of fuel, and car doesn't run. FYI the WUR wiring sees +12V when keys are on, and the WUR resistance is 36 ohms.

So, WUR is indeed the culprit? Stuck valve and/or busted bi-metallic strip?

Comments on the Bold in your post.

The pressure readings do not correlate, as you think, to the amount of fuel to the injectors, and the way they do correlate is bit counter intuitive. Pressure is not volume. In a CIS system, pressure readings at the WUR inversely reflect the volume of fuel to the injectors--the higher the pressure, the less fuel is injected. Conversely, the lower the pressure, the more fuel is injected. As said, it is counter intuitive unless you understand the workings of the system (something I won't explain here due to time, but is easily found out.)

With this in mind, your reading of 15 psi is very low for a warm WUR, but may be in spec. for a cold WUR, depending on the ambient temperature and the particular WUR. Given that the reading doesn't change with current to the WUR, suspicion is it is a cold reading and unless the engine is run to the point that heat from the engine warms the WUR, you will not know your warm pressure.

Bottom line is, the CIS diagnosis is more complex that your currently understand, but you can easily get familiar and be able to diagnose yourself with a little input and feedback.

[boyt911sc]

Originally Posted by RarlyL8

Here is a picture of the fuel pressure gage installed. Standard CIS fuel gage kits contain all the adapters you need. (This pic is of a 930 but works same for 911).
If you are seeing system pressure at the WUR it is likely that the gage flow is shut off at the WUR and not going through it. Low pressure may simply mean you need to charge the battery while doing your test (always a good idea). Also verify your fuel pump is getting 12V minimum while running. Return pressure to the tank is system pressure. Return volume can give you a clue if WUR is occluded.

[/img]

Brian,

I hate to disagree with your post (highlighted above in bold letters). Since this is a Technical Forum, I feel many would be mislead by your statements. You are a Bosch authorized rebuilder as you mentioned before and people would believe whatever you say regardless if it is true or not. As an avid CIS troubleshooter and no formal training from Bosch Technical School I should never question the 'experts'. But I have a moral responsibility to the community to differentiate a myth from fact.

The 'Return line pressure is not and will never be the System Pressure. And the return volume is not a good indicator for WUR to be occluded. BTW, I learned something today from your post. Never knew what 'occlude' meant until I looked at the dictionary. Definition: (1). To cause to become closed; obstruct. (2). To prevent the passage of. And other definitions.

At this point, I would consider you statement/s as a typo unless you want to discuss this subject with facts and data.

Tony