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Northy

911SC bucking at 1500 revs

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I fetched the box from the garage and the code seems to check out on www.protect.bosch.com - so it appears to be a real one (although there seems to be no record of that site in Google, which is a little suspicious...) 

Not sure if I’m pleased or not! At least that would have explained the low pressures!

 

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43 minutes ago, Northy said:

I fetched the box from the garage and the code seems to check out on www.protect.bosch.com - so it appears to be a real one (although there seems to be no record of that site in Google, which is a little suspicious...) 

Not sure if I’m pleased or not! At least that would have explained the low pressures!

 

Do you not think that a copy would have the correct QR code on the box. ? Looking at the video, I think an examination of the pump itself is the best way to tell if it’s indeed fake? 

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Posted (edited)
5 minutes ago, GrahamTompkins said:

Do you not think that a copy would have the correct QR code on the box. ? Looking at the video, I think an examination of the pump itself is the best way to tell if it’s indeed fake? 

Maybe yes, and I will check it out. But I entered the code quite a few times and instead of succes it was valid it started saying it is a valid code but it’s been entered a lot of times. So I think they’ve guarded against the same code being used on every box. 

But yes, I will check the pump out further. I might even put the other one on just for belt and braces. 

Edit : it’s a unique 18 digit code with the address. Not just a QR code. 

Edited by Northy

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Posted (edited)

Just leaving this here for anyone else looking for replacement CIS fuel pressure regulator shims - these guys had some made up for the De Lorean and they fit all CIS K-Jet vehicles (apparently): https://www.deloreango.com/uk/fuel-pressure-regulator-shims.html  They also do a hot start o-ring kit that has the rubber o-rings for the primary pressure regulator: https://www.deloreango.com/uk/hot-start-o-ring-kit.html  

Maybe @Type911 should get some in stock from them...might be a useful addition to your shop 🙂

Edited by Northy

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Nice work Lewis. I used shims from there top adjust system pressure on the 924 👍.

I know its thinking ahead, but my cold control pressure was almost zero (too rich during warm up I think - still struggle to get my head around this!). I adjusted it following instructions from Luke I think. It was straightforward to do and it fixed my cold start idle hunting issue a treat and also a stumble that I used to get when warm at around 1800 rpm in a high gear. It was straightforward if and when you need to do that.

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On 5/12/2019 at 7:14 PM, Northy said:

Thanks for the feedback Luke.

Ive been using the Bentley manual and Jim’s CIS primer as reference: http://cis911primer.com/pages/test_pressures.html

Lots of different opinions on engine on or off. I did both for good measure 🤷🏻‍♂️

I’ve not had any time to investigate further than about 15 mins just now. My first port of call is to understand why the system pressure is low. Cold and warm control pressures don’t really matter at this stage. Since the main system pressure is low. So just now I quickly pulled the fuel pressure regulator valve out of the delivery head to check it wasn’t gummed up. I also wanted to see if the fuel pump is still making different sounds when it’s left on for a while (now that I’ve opened up the red relay terminals a bit). 

Pressure regulator valve seemed fine and only had one shim in it (I’m not 100% on what standard is but the new replacement comes with quite a few - add to increase pressure - it’s got a 928 part number: 928 110 920 01).  I just gave it a blast of carb cleaner and have put it back in for now. 

After that I ran the pump with the isolator valve closed, WUR plug disconnected (not that it will impact system pressure). It struggled to make 3 bar system pressure. Balls.  

Two odd things I noticed.

1) the gauge has a bleed valve - I thought maybe I’ll bleed it through till fuel flows freely, just to make sure it’s not an airlock interfering with the readings. Fuel does come out but it’s more like a slow trickle than a flow. Seems weird. I would have though 3bar of fuel would fly out. Maybe the gauge is gash and I should compare to another gauge?

2) holding the main inlet fuel line to the accumulator, you can feel the fuel rushing through it. If you do the same with the line going from the accumulator to the fuel filter, you can feel the flow is not as fast.  Whereas the line coming out of the bottom, which I think is a return, clearly has a lot of flow. Maybe it’s all just heading back to the tank before it’s getting to the fuel filter and on to the delivery head?

The pump is definitely still changing pitch from time to time. Like it speeds up for a bit then slows down again. Perhaps ranging between 2 seconds and 10 seconds when it does change pitch (it’s always changing to go up in pitch - like it’s going quicker).

So more strange things to consider... 

When I get some more time I’ll get the under tray off again and inspect the fuel pump fittings, check the lines aren’t leaking or twisted and check the voltage (hopefully capturing it during one of these weird pitch changes). I’ve bought a new standard pump too, as a back up. 

If the pump all checks out I think it’s on to the accumulator and fuel delivery head. Maybe I should order the delivery relief valve, so I’ve got a stock of new shims. If that doesn’t work. I think get it off and have it rebuilt.  There is no point moving on to other parts until the fuel supply and system pressure is right. 

Interested in your thoughts guys, all advice welcome 👍

Actually i didnt think your system pressure was low. Lowish yes, but the spec if 4.5 to 5.2 and the 4.5 you had is technically in spec!!! But even so, I would adjust it at the pressure regulator valve on the side of the FD, the o-rings can go and need replacing, but just for an adjustment, you simply change one of the copper washers for another one until its in the middle of 4.5 to 5.2 (i.e 4.85).

The extra ones in the kit as you thought are just to get different pressures, only one copper shim. 

The gauge....yes you need to bleed it, you turn it upside down and squeeze the bleed thing if you have it, it will bleed out. You should do it once or twice. it should bleed to out a bit (a trickle is normal), and then jump straight back to where it was on the gauge. Make sure your CIS tester is connected correctly, valve on the LEFT, so when you turn the valve closed it can only show the system pressure, and when the valve is open it shows you the control pressure. I would rebleed for system or control, then when control is done and cold, plug the WUR in and just watch the gauge rise to what ever the hot control should be. 

Can you post your graphs for me, do both, the bentley and the porsche factory manual, you can download the factory manual from the link above....

The warm system pressure is a bit of a red herring. While it is weird....the fuel pressures are done with the engine off! so technically the warm for system is never measured, in fact i dont think i have ever measured it. Certainly you could be on to something, but as its not part of a normal diagnosis procedure (it is not in any of the manuals to do it this way), then ignore it and treat it for now as a red herring. 

The accumulator you can test, I cant remember but the procedure is in the book. I think (from memory) you disconnect the bottom pipe and basically see if any fuel comes out, and more than that I cant remember. 

Heres what you should do :

1) Forget about the Hot System pressure for now, do your tests with the engine off, and fuel pump hot wired, cold engine. Use the right shim to set your pressure to whatever the book says for your FD (post the picture), probally between 4.5 and 5.2, in that case go 4.85. Once that is set, test the rest pressure over 10, 20 and 30 minutes. Compare to specification. This is the cold system pressure, or just system pressure, and all we care about. Maybe we will end up full circle back to this for this mysterious hot system pressure.....but for now I would move on, as the books certainly dont do it this way. 

2) Now Test your cold control and warm, again post the graphs and the results. One of the manuals you have to apply vacuum for it to work as per the graph hence why i said check both graphs, post a picture. Once you have the warm steady, suck on the vac connection for the WUR and watch i it change the warm control pressure. If it does not.....figure out why...Basically the engine vacuum changes in response to the throttle plate, which changes the fuel pressure at the WUR, when finished test the rest pressure over 10,20 and 30 minutes, compare to specification.

Start with those tests, and post the results, with the information from the workshop manual, if all looks okay then move on....if not then fix this and try the car before the next steps.....

Luke

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Had a system pressure control valve sieze in a 924 metering head before. Corroded in the sleeve. The shims are also stupid money from Porsche. System pressure is system pressure there's no hot or cold as it's dictated by the pump,  control valve and the return to the tank . There is only vacuum at idle when the plate is closed on turbos there is a separate enrichment hose which boost enriches the mixture . Drops the control pressure off on full boost . 

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Posted (edited)
On ‎5‎/‎15‎/‎2019 at 8:39 PM, PorscheApostle said:

Had a system pressure control valve sieze in a 924 metering head before. Corroded in the sleeve. The shims are also stupid money from Porsche. System pressure is system pressure there's no hot or cold as it's dictated by the pump,  control valve and the return to the tank . There is only vacuum at idle when the plate is closed on turbos there is a separate enrichment hose which boost enriches the mixture . Drops the control pressure off on full boost . 

The vacuum also controls the control fuel pressure between IDLE and WOT and back again, exactly the same as a throttle position control regular did mechanically on the  early 73 to 76/77 911 CIS, its all in the books....The main point is the HOT Control Pressure which is governed by the WUR must change with XXXX vacuum applied, between say 3.0 bar and X.X bar (for 76/77) and on, according to specification , if it does the check when running, that you are seeing the same vacuum….if your are not check for vacuum leaks, IF the WUR is not responding to VAC changes, then take it apart, and rebuild it. If it's all tickety boo, move on to the next point, as there are a loads more things to look at!!. 

Edited by Strictly

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Posted (edited)

New pressure gauge arrived from Pelican. Also changed the o-rings on the pressure relief valve in the fuel distributor and added a shim (from De Lorean pack above). Plumbed the guage in and rock steady 5 bar system pressure 👌

These are my pressure readings. My car is an 83 SC with no oxygen sensor so there is no graph for my model in the Bentley manual. However, my age with the same WUR part number is listed on the CIS primer (81-83 / 089 WUR) http://cis911primer.com/pages/test_pressures.html

System pressure : 5 bar

Control pressures engine off, my figure followed by what it should be in [ ]

- Cold control pressure : 0.8 bar [circa 1.5 bar at 15 degrees - based on nearest graph that starts at same pressure/temp as primer website]

- Warm (engine off but WUR connected for about 15 minutes): 2.7 bar [ 3 bar]

Suck on vac: 3.5 bar [ 3.6 bar engine running ]

Residual pressure leaks down: valve closed

0 mins 3.2 bar

10 mins 1.9 bar

20 mins 1.6 bar

[ all well within spec ]

Opened the valve at 20 minutes and pressure didn’t change (suggesting pressure regulator is fine too).

So, the good news is the system pressure is perfect now and it’s mainly my cold control pressure that is about 0.7 bar low.  The warm is circa 0.3 bar low.

I might try tapping the pin down a bit and see what it does. @Lesworth did you use a small hammer or c-clamp method to do the one you did?  Presume WUR off the vehicle to do it? 

System

34D16BF7-4E16-45A3-8E6E-420E31930798.thumb.jpeg.f6d1da8483c6f7abb2cb01e569af35d1.jpeg

Cold pressure (engine off, vac off, wur not plugged in)

0AEAFF8C-8CCC-4F9D-B409-6FF51BAD29C6.thumb.jpeg.fb2dd3a6abd33b57fa018ffc6e44e0d3.jpeg

Warm pressure (engine off, vac off, wur plugged in for 15 mins)

04E5E0DA-F502-4D6A-9C96-A80CB546DA7F.thumb.jpeg.a946ebbe9fe1005aa299b189351f382d.jpeg

Pages from

Bentley Manual - my car and WUR not actually listed. Nearest is probably 1979 one? Since the later ones have oxygen sensors and mine doesn’t. 

4D1F6FD2-3B3E-4D59-84FA-7CB98D11556D.thumb.jpeg.e7abeb49187a3a4d5441bf24049f35cf.jpeg

9B5222C7-AB9D-4948-9E94-FF333F8E4474.thumb.jpeg.6f7d5cba9d74ce3c4cef69482cc51e3d.jpeg

Edited by Northy

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Edit - before I try to adjust the WUR I’m going to repeat the tests with the engine running as per Bentley book. Just to see if vacuum from running engine brings it into spec. 

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Fascinating stuff Lewis. Part of the reason I got rid all together. Might be time to remind you of this comment............

;)

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48 minutes ago, Phill said:

Fascinating stuff Lewis. Part of the reason I got rid all together. Might be time to remind you of this comment............

;)

Don’t! This has 100% been on my mind. Having spent a grand on CDI+ and another 600/700 on other bits I’m pretty conscious I’m halfway to the ITB party. I think if the fuel distributor and WUR need replacing I might have to more seriously reconsider it. 

I would eventually like to go EFI though. I’m estimating that’s £5k once you’re mapped. 

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Cost me £2500 all done.

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Ok a few things.

CIS/EFI

First of all stick with the CIS, sure we would al love EFI, but CIS works just fine,...when its working, and plenty tunable

WUR

I have thought about building an adjustable WUR, perhaps one day, but for now you can just adjust your WUR then next time build and adjustable one

WUR PART NUMBER

Take a picture of your part number. Note the one in picture has two part numbers a 145 and a 045, the correct number for this one is the 045. Its just an example take your rubber hose off clean and take a picture, then we can be sure of the graph!!!

====

More comments in a sec

 

 

 

Wur21473017307.jpg

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Ok , so above first. Don't touch the pin yet, it depends on which one you have, taping it down on most will make it richer, that's lower pressure, that is the opposite of what you want. I will explain how to do cold and hot....

So good news on the system pressure, I think next step is wait for the last three numbers of the wur...to be sure we are talking 100% about the same pressures. I'll check back in a few days. 

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Just to add while your waiting, for checking the WUR control pressures, you need 

  1. Pressure Gauge
  2. Vacuum Gauge
  3. Temperature Gauge

You need all 3 to fix your position on the graph....as per one of my early posts on the topic, you can download the factory workshop manual, I use both, not just the Bentley. 

running with the idea you have a 089 wur fitted just for to explain...show your part number pic as above posts....

 

 

Capture2.JPG

Capture.JPG

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As you can see you have to triangulate your pressure based on vaccum and temperature....

Bentley, the lazy f**kers just tell you to have the engine running.....which is great....if you don't have a vacuum leak, and your engine running vacuum at idle corresponds to.....450 to 550mBar....

So basically you need more equipment!! Multimeters often come with a temperature probe, and a vac gauge is cheap enough, you can probally get both of what you need for under 50 on ebay, and you will use both to repair your SC!! I don't often use the vaccum gauge, except for CIS, but the multimeter for sure!!

 

 

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Posted (edited)

There is one benefit….as before you DONT need the engine running, you can do all of this on a stone cold engine, which is a lot safer and less noxious. Once you sort the WUR you can move on to the injectors and the FD, but for now...its the WUR for breakfast lunch and dinner

====

So to summarise, ill log back in a few days. In the meantime

A)take a pic of your WUR part number

B) download the FACTORY manual (fuel section), If you scroll back you will find my link,

3) buy a vac gauge (or if you have to have the engine running, but this does not really help your diagnosis...if you have a vac leak....as your WUR you set up will then not actually be right!

4) get a temp gauge or multimeter with a temp probe,

and then...lets look at those pressures. If they are out, I will tell you how to adjust them. To have the WUR rebuilt is about £250+VAT so considering your saving cash and getting "free" tools in the process instead of shelling out, all while learning, all is good

p.S I started just like you, and now know a lot more. Far from an expert, for sure, but the WUR I do know, I have had 3 or 4 apart and set for warm and cold

 

 

 

Edited by Strictly

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:blink: good luck Lewis, I'm subscribed. You'll be able to set up business if you get your head around all this and sort it!

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I had a similar bucking problem, rebuilt and calibrated Air Flow Meter - and all now good!

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Posted (edited)

@Strictly thanks for the advice Luke. 

The WUR has part number: 043814089 - which corresponds with the details on the CIS primer website 

4506C906-4C29-43DC-9229-66EF9A120188.thumb.jpeg.6cc90ca16e9822ad4ed2fc41095859d5.jpeg

See below, the mesh filter/screen on the inlet side looks pretty good and clean to me. So the low pressure probably isn’t a blockage. The car is used pretty much weekly, so it’s never stood for very long in my ownership (nearly 20 years). 

8DF27DB0-C707-473D-8F00-3C777EB84F2C.thumb.jpeg.8044af7d1a6dd81f08326400ec175c0b.jpeg

Next step has got to be open it up and push the pin back up. I’ve got a new main seal coming Thursday/Friday. I’ve left the nuts soaking in penetrating fluid and will have a crack at them tomorrow and see what we’ve got.  The resistance across the electrical connector was 36 ohms (I think - it was either 26 or 36 - I’ll check again tomorrow).

One bummer was shearing the WUR mounting bolt. Luckily I can get two nuts on it, so I’ll soak it loads and gently try to wind it out over the coming days. Maybe with some carefully localised heat from my butane soldering iron (if I dare!). 

24ADCCC1-5154-48A4-BDCC-876AE09E62B7.thumb.jpeg.47659d33b3207f95d10a11bb89c08339.jpeg

So the question is drill a hole in the WUR and make it adjustable (as per pelican guide above) or just tap the pin up and then slowly tap it back down when it’s back on the car to set the pressure. 

Thoughts from the collective? 

Edited by Northy

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Lewis, when going to remove the stud try a couple of sharp taps to the top of the stud with as big a hammer as you can get in there.  This often shocks seized studs loose.

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2 minutes ago, Ian Comerford said:

Lewis, when going to remove the stud try a couple of sharp taps to the top of the stud with as big a hammer as you can get in there.  This often shocks seized studs loose.

👍 will do. 

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16 hours ago, Ian Comerford said:

Lewis, when going to remove the stud try a couple of sharp taps to the top of the stud with as big a hammer as you can get in there.  This often shocks seized studs loose.

Hurrah! armed with this, liberal penetrating oil and patience (not one of my normal virtues) I got it out unbroken 👍

Here are some questions; perhaps @Strictly will know the answers:

1) My WUR has 2 vacuum lines, I assume it's the one on the side that connects to the thermo switch that I apply vacuum too? 

2) Temperatures - I bought a laser thermometer, is the temp in that chart the outside temp or the temp of the WUR body? a good 3-5 degrees difference in the two today. 

Will carry on once the kids in are in bed later!

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