WeiRD...AGAIN, or something...SOLVED!!!

[Ulf]

I know that the WRD and related issues has been covered ad nauseam in several topics here - I've searched through most of them, but so far haven't been able to interpret them all enough to give me a clear picture about why my car stalls (or rather dies completely) when reaching running temperature (about 80C/175F). Car has new points, plugs, condenser, leads and coil, so I'm pretty sure it's not electrical. It's been running great for the past couple of weeks right up until this weekend.
After the car stalled, my brother and I took the thermostat above the WRD (the early type) apart, cleaned it with water, WD40 and compressed air before testing it by immersing it in hot water. The pin was about 5 mm out to begin with and moved about the same amount further out after getting warm. This didn't help much as after re-assembly the - now cold again - car started just fine and idled really sweet right up to the point where it got warm again and stalled...

Long story short, my questions are:

Could this be vacuum-related?
Can the WRD somehow be bypassed? It's a summer only car anyway
Is it possible that the CSW is at play and can this too be bypassed or perhaps given a switch to turn it off manually?

Br

Ulf (who's just about to give up on Pagoda ownership altogether) 

[Benz Dr.]

You have an idle mixture problem. Once your engine is warm there isn't enough fuel to keep your engine running. Check fuel pressure and volume plus fuel return into to tank.  If all of that checks  out you can turn the knob on the back of your IP several clicks until you start getting a normal idle speed. A split linkage test will tell you if you're rich or lean.

[Ulf]

Thanks Dan, but it cuts out when warm regardless of whether it's idling or running at 60 mph

[Bonnyboy]

It really sounds like a fuel issue but if the fuel flow volume check doesn't work I would go back to electrical.     

I would suggest taking it to someone with a scope to look at the electrical side of things when cold and when hot.  I drove a 1938 Diamond T for the museum for events and parades for 20+ years and for 3 of those years once it got real hot it would act up and die.   Turned out to be a faulty condenser that when cold, spec'd out ok but when hot would die.  (Mechanics for City replaced the fuel tank, the fuel pump, fule lines and inline filter and did some carb work and it still died)

The museum finally let me work on it after I threatened to stop driving the thing and once on the engine analyser we could see the condenser acting up and then the truck would die.     I also had a BMW with a broken lead from distributor and when it got warm the broken wire inside would arc and the car would run erratically.  brand new out of the package lead.    Don't they say 80% of fuel related problems are electrical and vice versa.....?

Good luck.

 

[Iconic]

Thanks Dan, but it cuts out when warm regardless of whether it's idling or running at 60 mph

Ulf,
Do yourself a favor and listen to Dan.
You haven't given a ton of details but this sounds like what I experienced.
Measure the pressure and flow (or just the flow as I did) at the connection where the return goes back to the tank. If it is not up to spec, then that is the problem and there is a clog in your fuel system. Most probably in the return line. If the fuel flow is restricted, then the injection pump heats up and "vapor locks" (whatever that is  ). The constant flow of lots of fuel through the whole system keeps the pump cool. The engine consumes only a small fraction of what is being pumped in a circle. I found this clog in 2009 and I have been a happy camper ever since.

[Benz Dr.]

One more thing you should check:
 Remove the return fuel line in the engine bay and get a long air wand and hook it up to the return fuel line. Wrap a cloth around the end of the fuel line so fuel won't be able to blow back into your face. Remove your fuel cap from the fuel tank.
Give the line a small shot of air. If everything is open you should be able to hear air bubbling up through the fuel in the tank. If it isn't open there's a good chance that the air pressure will blow the hose right off the end of your line. This is where you will thank me for telling you to wrap a cloth around it.

Obstruction could be in the line under the car or in the return line that's inside the fuel tank. Until you have ALL of this stuff working right you will spin your wheels, and not Pagoda wheels.  

[Ulf]

Thanks Dan, Boonyboy and Iconic, will give the fuel return line a blow during the weekend and see what happens - the trouble is that I'm not mechanically inclined whatsoever and there are no competent Pagoda-mechanics around over here anymore (they are enjoying their retirement, playing golf etc.) and the last guy who dealt with my car left it outside in the rain for the 2,5 months that it apparently took to replace the points, condenser and air filter on the I.P. :-(

So all your advice is greatly appreciated as I've only had one day of trouble-free driving for the past year...

Br

Ulf

[Iconic]

Ulf,
Please be very careful when handling fuel.

[Ulf]

I will, promise :-)

[Ulf]

Have taken the day off tomorrow to fiddle with it and try Dans advice, but I'm not sure which is the return fuel line, can someone pls point it out in one of the attached photos?

Br

Ulf

[Bonnyboy]

Be careful starting there -  I had poor flow - stalling car etc. and replaced the fuel pump - took the car out and same damn thing - checked where you are and had proper fuel flow and started to really think about what else it could be - then based on advice from Benz Dr. I started back at the fuel tank and worked backwards.   I found a kink just under the edge of the firewall and lo and behold I fixed that and the stalling went away. 

If you start where you are looking you could still miss something.   Start at the fuel tank and go backwards - that way you can follow the line. 

[Ulf]

Small update, now the car won't start at all  and so far I've only been able to confirm that there is good flow from the tank to the pump and there is power to the ignition coil/distributor/plugs. The CSV in the intake manifold squirts happily almost filling the air filter canister with fuel after repeated unsuccessful cranking of the engine. But as the car can't move I haven't been able to access a compressor to check the return line, but this wouldn't account for its inability to start anyway. So I'll give up for now as this is beyond my few skills and will instead continue my hunt for a competent mechanic - and naturally pass all of your great advice on to him

Thanks a lot for your input

Ulf

[ja17]

Sounds like you may have fouled the spark plugs. Try a fresh set. If you have fuel, spark on time and compression, the car will start.

[Tyler S]

If you are getting so much fuel that it is flowing into the air filter canister then you have a problem. Check that the CSV is not mechanically stuck open. Repeated starting attempts should not yeild more and more fuel. The thermo time switch could be defective or wired wrong. Remove the small 7mm screw on the cold start valve housing. Turn the key to run position to activate the fuel pump but do not attempt to start. There should be NO fuel coming out of that opening.

[Benz Dr.]

That's one of the things with having a problem, it often involves having other problems.

 During restoration, or simply working on your car, it's always best to start with the end in mind. If you want a number 1 car, then you have to do everything to a number 1 level right from the beginning to end up in the right place. Changing gears half way through the job won't work out well for anyone. What does this have to do with this problem? Not much, but if your goal is to have a running driving car,  it's best to break it down into basic 101 type jobs. Fuel, compression, spark and then break those jobs down into smaller jobs. Far too easy to over think a problem. Often times when I finally discover the source of a given problem it usually turns out to be something simple and stupid. So simple in fact, that I overlooked it.   

[Kevkeller]

Often times when I finally discover the source of a given problem it usually turns out to be something simple and stupid. So simple in fact, that I overlooked it.   

Isn’t that the truth!  When I first started working on things I was very methodical. As I got more experience I started overlooking the easy things thinking it wasn’t it or I’d just overthink it. Then as you said things so simple weren’t even looked at.  So much wasted time.

[Ulf]

Update again - have found a guy who has restored a couple of Pagodas before and dealt with them quite a lot. When I told him about the symptoms, he suggested that I should let him fit the 123 electronic ignition. He seems pretty sure this will cure EVERYTHING - I'm not so sure...
His rationale is that the current ignition set-up simply can't provide enough of a spark once the engine gets hot, but wouldn't it need LESS of a spark to run when hot as opposed to cold??? His quote for the parts and work seems fair enough (the equivalent of USD 1000 - labor rates are quite high here in over-taxed Scandinavia...), but still a bit steep considering that I already had everything changed last year - condenser, leads, points, the red ignition coil from Bosch + ballast resistor. His quote also includes a new ignition coil from Bosch, but is this a different one than one normally fitted?

I'm a bit lost here so I would really appreciate your input before proceeding with this :-)

Thanks again

Ulf

[Paul & Dolly]

Hi Ulf,

Sorry you have these problems.

Personally I cannot see the 123 as a " cure all", and there are plenty of cars (including mine) that run fine on the original set up.

I think that you do have a problem (when you get the car running again ) with the return fuelsystem to the tank.If this is not operating correctly, then the "flower pot" in the tank does not fill, and after a few minutes of running under power ,you effectively starve the engine of fuel, as the fuel is supplied to the primary pump via the flower pot.

As regards your non starting issue, I agree with Dr Benz, maybe  go back to basics,
I hope yopu can find some local help.
Is there no one close in a Mercedes Benz Club, or even older car club ?

Good Luck

Paul

[Benz Dr.]

OK, start here. Remove the large fuel hose from your tank that's going to the fuel pump. Put a clamp on the hose while you undo your gear clamp at the pump and then let it drain for a while. If fuel comes out at full head that will tell you that the main screen and hole in the flower pot isn't plugged. You don't need to drain the entire tank and really only need enough to drain the contents of the flower pot. Your tank should be less than half full during this test.
If this test works out then go to the test I described earlier in this thread. If you can hear air bubbling up through the fuel in your tank odds are your return line isn't plugged. Having fuel flow up to your engine is critical but so is the fuel flow back to the tank. It's my belief that too many owners only look at flow to the engine and don't think about the return to the tank which is, in my opinion, a fatal error.

On a slightly different note. Once your spark plugs get wet or fouled you might as well get new ones. If you can get your engine to start you might be able to drive it long enough to get the plugs to clean but that doesn't always work. 

[Ulf]

Thanks Dan and Paul, I have established that there is fuel coming to the pump (a lot actually), but still need to do the bubble-test via the return pipe when I can get my hands on my dads compressor (hopefully this weekend). New plugs are on their way too, but there seems to be consensus that the 123-conversion is more of a nice-to-have rather than a need-to-have :-)

Br

Ulf

[Pawel66]

Ulf, 123 is just modern, more reliable distributor that holds the ignition timing better and can be adjusted easier. Some models also offer immobilizer. It eliminates mechanical system of ignition advance, points and condenser.
If your original system works ok, 123 is certainly not a must.

[mbzse]

.../...If your original system works ok, 123 is certainly not a must

I would say, main advantage is no maintenance or adjustment needed after the initial setting of the 123 system is done. You can run your car say 10-15 yrs ahead without touching the ignition system.
No modification of the engine or car; you can easily re-fit original distributor unit if you choose to.

To refurbish a "traditional" Bosch distributor requires re-bushing the main axle, clean the centrifugal mechanism and replacing points condenser as well as other work. Not a low cost endeavour.
Another matter, the points you can buy today are much lower quality than the parts supplied 40-50 yrs ago. They wear out in say 3-4000km so you need to monitor them frequently

[Ulf]

Hejsan my Swedish friend, you're absolutely right - my new mechanic/best friend has discovered that there is almost no spark despite new coil, points, condenser, leads etc. and that the work performed in the autumn of last year was mediocre at best. So now we're going electronic, he has already ordered the parts. He is going through the fuel system as well (based on the advice mentioned above), but so far hasn't found anything wrong here, so hopefully the new ignition system will cure this as well - fingers crossed as the weather is great :-)

[mbzse]

.../... So now we're going electronic, he has already ordered the parts../...

To each his own, of course. I have no affiliation with the 123 manufacturing company...

As always, use search function here in Forum to read up on 123 ignition tips if you want to learn more about the system.
When fitting a 123; use only copper ignition wires. Plugs, well I use NGK in my cars.

  It is wise to install a grounding wire in the M4 hole in the distributor body of the 123, run this wire to the engine head. Also exchange the ignition coil, these degrade with time and high tension in 123 system may well be too much for a 40+ years old coil... No ballast resistor needed (bypass it).

Hardly anyone in our M-B club here has an old Bosch regular type distributor in their hobby car these days.
As for different looks, I paint my 123 black and if you are a stickler for authenticity you can fit an inert condenser and vacuum actuator pot on it!
/Hans

[Tyler S]

Ulf, reading through your posts, I do not see if the ballast resistor has been checked/replaced. You mentioned weak spark with new coil etc. Resistance of the ballast resistor needs to be matched with its appropriate coil. Also, a faulty ballast resistor can exhibit the symptoms you have. As the resistor gets hot, the resistance can increase to the point that you loose current to the coil. These can be deceiving to check as the circuit must be under load to properly diagnose. A volt meter is not good enough. An Amp clamp around the positive lead to the coil will show any issues the resistor may have.