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280se - new to me, warm stalling!

Started by SteveDuNord, 04 May 2022, 10:57 AM

Type17

My car had a dead fuel accumulator when I bought it, but everything else (mixture, fuel pressures, WUR, etc) was fine.

The symptoms were:
Cold start (overnight, or after about 1 hour) - fires up quickly, no problem
Hot restart (within 1-4 minutes of shutoff) - still no problem
Warm restart (within 5-60 minutes of shutoff) - fires instantly for half a second, but then stalls. Then it takes about 8-12 seconds of cranking to catch, but everything runs fine after that.

If the symptoms aren't exactly like that, the accumulator may be ok, and it's something else, or the accumulator may be faulty, but there are also other issues.
'76 350SE in Silver-Green

SteveDuNord

About to embark upon the fuel pressure test and guess what? Immediate stumbling block!  ::)

My WUR has two steel fuel lines running into it, one of which is fouling the other. I can't remove the one I need to attach the fuel pressure kit to.



I'm hoping once I've removed the smaller fitting, it well let me bend the fuel line enough to fit the tester line.

Swear I'm cursed.

Also, it doesn't look like a banjo fitting to me, so do I just screw straight into it, or use a banjo fitting as supplied with the kit? I suppose screw straight into it. I'll probably explode.

'77 280se

daantjie

Quote from: SteveDuNord on 20 July 2022, 06:04 AMAbout to embark upon the fuel pressure test and guess what? Immediate stumbling block!  ::)

My WUR has two steel fuel lines running into it, one of which is fouling the other. I can't remove the one I need to attach the fuel pressure kit to.



I'm hoping once I've removed the smaller fitting, it well let me bend the fuel line enough to fit the tester line.

Swear I'm cursed.

Also, it doesn't look like a banjo fitting to me, so do I just screw straight into it, or use a banjo fitting as supplied with the kit? I suppose screw straight into it. I'll probably explode.



Soak in PB Blaster overnight.  Go slow and use counter hold.  It's normal for them to be tight after all these years, usually rust bonded.
Daniel
1977 450 SEL 6.9 - Astralsilber

SteveDuNord

#78
Quote from: daantjie on 20 July 2022, 06:40 AMSoak in PB Blaster overnight.  Go slow and use counter hold.  It's normal for them to be tight after all these years, usually rust bonded.

You misunderstand: they're not corroded, they're hard steel fuel lines that don't want to budge - especially the one I need to move in order to attach the pressure gauge fitting.

I had to bend it, and now it won't go back into shape. I can only get one hand in there. The WUR will remain disconnected until I find a solution. I don't understand the thinking behind this design, it's like they never expected anybody to mess with it.  ???

The testing kit I bought doesn't come with the correct fitting, I realise that banjo bolts are good for 99% of kjets but not this one.

Instead I have what looks like a 11/12mm threaded fitting, the same kind fitted to the fuel distributor and injectors.

I swear this car with be the death of me.  ;D

Oh hold on, the seller of the test kit said read the instructions. Apparently I also need to remove the threaded part of the WUR fitting in order to fit the supplied banjo bolt.

Always read the instructions.
'77 280se

rumb

You will need to use a T fitting. You could also fit it to the other end of the line.
'68 250S
'77 6.9 Euro
'91 300SE,
'98 SL500
'14 CLS550,
'16 AMG GTS

SteveDuNord

A lot of photos for such little progress but just in case it helps someone in the future:

These are the offending fittings, the larger of which needs to be removed:



I rounded off the larger nut trying to get purchase with the spanner - the smaller one gets in the way, so both need to come off.
Here's the wee one, which came out easily enough.



There's precious little room down there, and you'd have to remove the oil filter etc in order to get at it from beneath the car. Which would be a mess.

So with the wee nut removed you can get the spanner on the big nut, but of course it would not budge:



Sprayed on plenty of wd40 (of course I only have a giant can that barely fit down there  ;D  )

and I'll take Daantjie's advice and leave it overnight. I think a gorilla must have screwed this one on!

'77 280se

rumb

#81
You could remove the WUR from the car to get the stubborn one off. A 6 point socket would be a better grip than a spanner.
'68 250S
'77 6.9 Euro
'91 300SE,
'98 SL500
'14 CLS550,
'16 AMG GTS

daantjie

Quote from: rumb on 20 July 2022, 12:41 PMYou could remove the WUR from the car to get the stubborn one off.

Indeed this is a good tip then you can safely heat the offending coupling with a propane flame then let it cool and it should break loose.
Daniel
1977 450 SEL 6.9 - Astralsilber

SteveDuNord

Quote from: rumb on 20 July 2022, 12:41 PMYou could remove the WUR from the car to get the stubborn one off. A 6 point socket would be a better grip than a spanner.

That might be my next step, the only problem being access to one of the mounting nuts which is tight. Why'd they have to bolt it to the side of the engine?  ;D
'77 280se

SteveDuNord

WUR off!



And cleaned up a bit



Bathed in wd40 - oops! Checked the disconnected hoses and found no oil in them, so definitely not blowback.



Might as well test while it's off. I believe this reading is correct.



Plenty of contact cleaner to get rid of the oil:



Managed to break the larger fitting with a spanner and hammer: look at this gunk in the filter screen:



And finally I can attach the banjo fitting. Same done with the top of Fuel distributor. Testing can commence!



Car wouldn't start so I jumped the fuel pump.

Control pressure:
With pump running 4.3 bar.
Pump stopped 3.1 bar.

System Pressure:
er, virtually the same readings. 4.4 with pump running, so slightly higher.

Am I doing something wrong? I made sure to shut off the valve for System Pressure.

Checked the gauge and it hadn't dropped much 30/45 mins later. So not likely accumulator related. But maybe.

Will repeat later and see if I can't test with engine running.








'77 280se

SteveDuNord

Ok so this time I turned the mixture screw a 1/4 turn to the right and voila, engine started.

Valve open 4.4 bar (i.e almost 5 bar, just to be clear).
Valve shut 5 (just over)

Connected WUR electric connector. Valve open.
Ran engine for a little while:
Just under 5
Rose to just over 5.

Engine off
3 bar
+ 10 mins 2.4 1/2
+ 20 mins 2.4

Not much of a drop. So a physical check of the accumulator will be needed.

One thing to note - the disconnected hard line to the WUR is dribbling a tiny amount of fuel. Nobody mentioned anything about that!  :o I suppose it could be residual fuel?
'77 280se

Jan S

I'm not sure I understand your readings.

When the car is cold and the valve is open (control pressure) you should be measuring in the area of 1 bar, maybe 2 bar if your ambient temperature is high e.g. 30 deg C. When the car is warm it should be in the area of 3 bar plus/minus. This all depends on the spec of your WUR.

What is the last 3 digits on your WUR? The number is 0 438 140 XYZ ... what is XYZ?

System pressure (valve closed) should be 5-6 bar.
1975-mod W116 450 SE with 6.9 engine

SteveDuNord

Quote from: Jan S on 21 July 2022, 12:16 PMI'm not sure I understand your readings.

When the car is cold and the valve is open (control pressure) you should be measuring in the area of 1 bar, maybe 2 bar if your ambient temperature is high e.g. 30 deg C. When the car is warm it should be in the area of 3 bar plus/minus. This all depends on the spec of your WUR.

What is the last 3 digits on your WUR? The number is 0 438 140 XYZ ... what is XYZ?

System pressure (valve closed) should be 5-6 bar.

I'll be able to tell you tomorrow when I whip it back off. I didn't realise the gauze filter is actually several layers of gauze, so I'll be taking them out for a good clean.

My control pressure is way high, 4.4 bar. From what I've read, it's likely to be WUR related.

I also need to run the return flow test again because last time it was low. I think a fuel filter change would be wise.

The system pressure is fine by the looks of things (around 5). So that's something.
'77 280se

raueda1

Quote from: SteveDuNord on 21 July 2022, 03:16 PM
Quote from: Jan S on 21 July 2022, 12:16 PMI'm not sure I understand your readings.

When the car is cold and the valve is open (control pressure) you should be measuring in the area of 1 bar, maybe 2 bar if your ambient temperature is high e.g. 30 deg C. When the car is warm it should be in the area of 3 bar plus/minus. This all depends on the spec of your WUR.

What is the last 3 digits on your WUR? The number is 0 438 140 XYZ ... what is XYZ?

System pressure (valve closed) should be 5-6 bar.

I'll be able to tell you tomorrow when I whip it back off. I didn't realise the gauze filter is actually several layers of gauze, so I'll be taking them out for a good clean.

My control pressure is way high, 4.4 bar. From what I've read, it's likely to be WUR related.

I also need to run the return flow test again because last time it was low. I think a fuel filter change would be wise.

The system pressure is fine by the looks of things (around 5). So that's something.
Hey Steve, I'm late to this thread but anything related to K-tronic gets my interest.  Quick question - are you moving through the troubleshooting sequence covered in the K-jet troubleshooting manual?  It's in the manuals section. I ask cause there seems to be a bit of jumping around.  Here's a suggestion:  Start at the beginning of the manual and go in sequence.  For example, if your fuel pump volume and return line aren't perefect nothing else will be either.  Don't ask me how I know this.  But I do and I keep relearning it.   ???   Cheers,
-Dave
Now:  1976 6.9 Euro, 2015 GL550
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

SteveDuNord

Quote from: raueda1 on 26 July 2022, 09:59 PM
Quote from: SteveDuNord on 21 July 2022, 03:16 PM
Quote from: Jan S on 21 July 2022, 12:16 PMI'm not sure I understand your readings.

When the car is cold and the valve is open (control pressure) you should be measuring in the area of 1 bar, maybe 2 bar if your ambient temperature is high e.g. 30 deg C. When the car is warm it should be in the area of 3 bar plus/minus. This all depends on the spec of your WUR.

What is the last 3 digits on your WUR? The number is 0 438 140 XYZ ... what is XYZ?

System pressure (valve closed) should be 5-6 bar.

I'll be able to tell you tomorrow when I whip it back off. I didn't realise the gauze filter is actually several layers of gauze, so I'll be taking them out for a good clean.

My control pressure is way high, 4.4 bar. From what I've read, it's likely to be WUR related.

I also need to run the return flow test again because last time it was low. I think a fuel filter change would be wise.

The system pressure is fine by the looks of things (around 5). So that's something.
Hey Steve, I'm late to this thread but anything related to K-tronic gets my interest.  Quick question - are you moving through the troubleshooting sequence covered in the K-jet troubleshooting manual?  It's in the manuals section. I ask cause there seems to be a bit of jumping around.  Here's a suggestion:  Start at the beginning of the manual and go in sequence.  For example, if your fuel pump volume and return line aren't perefect nothing else will be either.  Don't ask me how I know this.  But I do and I keep relearning it.   ???   Cheers,

I have been following kjet guides but the service manual guide is great, so thanks for the heads up. Starts with inspecting the throttle linkage which is something I'm interested in addressing.

Jumping around? Guilty!

My fuel filter arrived but I'm thinking of handing this over to a mechanic because I'm reluctant to jack this big boy up. They can also fit my new shocks and change the brake fluid.

In the meantime I had the WUR back off for a strip down. I attempted to remove the gauze screens for inspection but they wouldn't budge. In the end I jabbed a hole in the screen (actually stacked gauze screens). Some people just remove them, so am not overly concerned.

Also attempted to inspect FD fuel inlet filter, but found mine is more of an integral metal bud rather than replaceable filter. The part is called a divider rather than filter. I bought a new one as it's pretty cheap and the connection was leaking after refitting.

https://www.amazon.co.uk/gp/product/B0068MSDLW/ref=ox_sc_act_title_1?smid=A1MI0LOLD9ZMHB&psc=1

Performed another flow test with a fully charged battery, ended up with just over half a litre in 1min. Which is nowhere near enough.

I'll get the garage to do another flow test after changing the filter and see if a new pump is required. The tank was flushed just a couple of years back, so fingers crossed.
'77 280se