280SE starting problem

[OzBenzHead]

G'day, folks.  

Wondering if any of you might like to hazard a diagnosis by distance ...

My 116 280SE (December '79) has realised it's summer and has decided to revive its summer bad habit of last year. I thought it had self-repaired, but it was just hibernating.

I drive Boris then turn him off. Five or 20 minutes later, he refuses to start. No amount of cranking gets a kick out of him. The only solution is to wait - between 30 minutes and an hour - after which he'll be his usual, obliging self.

Fuel pump runs - can hear it, and have disconnected a hose to find fuel gushing enthusiastically.

When cranking him with no result, there is a strong smell of fuel (like flooding, if he were a carby-fed job).

I suspect a dodgy cold-start device.

In attempts to find or fix, I've removed air cleaner, removed electrical connections from the fuel-and-air department, removed vacuum tubes, "encouraged" things with an "American screwdriver" , wiggled and rattled all the linkages ... Nothing. Nada. Null. Zero. Zilch. Zip.

On one such occasion last summer, I sat in the car for about half an hour - having given up and taking a patience-regenerating nap - when I thought I heard an underbonnet click - rather like you'd expect a releasing (or engaging)  solenoid to sound.
I turned the key and, hey presto - he started.

There is never a warning. There is no rough running. There is no cure but time (and cooling).

Pick your brains?   :?

[Denis]

Well I agree with your hunch.

Start the car and then disconnect the cold start injector. See if the problem still happens with a warm engine. A car with a warm engine should start nicely w/o the injector.

There is a thermo time switch in the cylinder block taht connects to the cold start injector. It prevents the injector from starting when the engine to prevent flooding.

Bonne chance

Denis (very cold day here but a good espresso always helps))

[Denis]

Styria, you may be right but with K-jet I usually had problems with the internal check valve not maintaining pressure in the feed line.

Maybe the 1979 is something different than what i've seen.

Denis

[OzBenzHead]

Something I forgot to mention earlier:

The first time Boris refused to start today, I decided to try a roll start - as I was on a gentle slope.

Rolled away, and at about 20 km/h pulled the handle into "L" - away he went, no problem. No spluttering, no farting ...

When this started happening last year, I had the pump, and pressure to the engine bay, checked. All were okay. That's as far as I got with the testing before winter set in and the problem went into hibernation.

[OzBenzHead]

Something I've just now found in the manual (a US-market one, so not sure if everything in the fuel department is relevant to my UK-market, Oz-compliant car) ...

In the circuit diagrams (and some "how to check for leaks" illustrations) there appears to be, in close relationship to the cold-start valve, a device called a thermal time-out switch.  There are no photos of it, so I've no idea what to look for under the bonnet. The cold-start valve is just what and where I thought it was, but this other doover could be any shape, any where.

Any clues?

[Denis]

Hi OzBenzHead

Locate your fuel distributor. It will have lines going to each cylinder injector. There will then be another one, it goes to teh cold start injector.

The device has a fuel ine and an electrical connector on it. That connector goes to the thermal switch.

regards

Denis (mild snow today)

[OzBenzHead]

Denis:

Had I read your earlier post properly, I'd have seen your answer to my later question!

So that's what the short electrical line is between the cold-start valve and the injection unit.

I shall play around with those and see what happens.

Think it's going to be one of those weeks where I stand on my head a lot, burn my fingers, and use a lot of 'French'; Boris has developed a vacuum leak in the central locking circuit, so it's out with the vacuum gauge ...

Last night I was informed I had no number plate lights; checked them and the plug was disconnected. Don't know how long it's been like that, because the left rear lamp unit has to be removed to access the socket, and the plug was outside of it. The car has been through two annual roadworthy inspections since I last had the tail lamp units out.

Here's hoping those three things are my quota for the month!

[Denis]

I can supply some real nice french !!?%%?*??^^&&& words, just to prove to styria that I am not really a gentlemen. I usually use such terminology on my Audi 80 I never should have bought (one hell of an over-rated car IMHO)...may be German but that's like German canned wurst in pig fat.    

Bonne chance

Denis

[Denis]

Hey styria, let it be known that french wine is utterly the BEST, like scotch from Scotland is the best whiskey. Just for fun, let it be known that some thieves have a special profession in France : they steal 38-ton trucks loaded with prime CHAMPAGNE ! They head straight to hiding places in Belgium : beaucoup money in those trucks.

My car background : I was taught auto mechanics by a scotsman who worked at De Havilland aircraft in 1938-39 : I own a set of calipers he gave me - genuine British tool of the era - he said that the only good practices are aero practices - torque to spec, clean threads, look for discoloration in steel, always use lockwire (? on cars ?). So I had about 33 years of wrenching from light bulb replacement ;-) to changing a gear in a WWII US Army Jeep, rebuilt several VW beetle engines and modified (illegally) a Volvo B21ET to more than 200 hp without going bankrupt or leaving physical evidence. Worked on "garbage" autos and consequently reflected on the meaning of auto mechanics.

I concluded that the best cars are older German ones(or Swedish ones) and the more expensive (initially), the better. They deserve to survive as they exude a certain quality mentality that is quickly disappearing in this pressed-toaster-metal-disposable-in-3-years car world. Had some experience on Citroen DS21, Audi 80 and Golf 2. I also worked for Renault in training courses (I'm a technical writer by trade)

I owned "classic" Volvos and Mercedes (W114,W123,W116,W109), and would not touch any other Mercedes model than a W126. Will probably dump the Audi 80 in the spring and put my efforts in the great W116. My favorite Mercedes is the 220SE convertible of 1961, designed by Paul Bracq with whom I am acquainted.  

In conclusion, I would rate myself as a very competent amateur mechanic.

OK styria, OzBenzHead and I will now stop our excessive forum hogging ;-)

Denis from Paris

[OzBenzHead]

Well, folks, here's where I'm up to with the (non)starting:

No further misbehaviour for a few days (weather was coolish); then, yesterday, when it was stinking hot, again no problem.

However, last evening, when Boris was stone cold, he refused to start. This time there wasn't even the usual smell of excess fuel (the norm whenever he's refused to start before). Also, this was the first time the problem has occurred when engine - and ambient temperature - were cool.

I disconnected, in turn, the electrical connections from (1) cold-start valve; (2) safety switch; (3) thermo-time switch - all to no avail.

Left him stand overnight and, with those connections still broken, tried to start him this morning. Nothing.

Reconnected all the leads - no start; then found a little vacuum canister near the firewall on the injection side of the engine; it had a vacuum hose going in one side and, in the other, a fuel line back to the fuel distributor. A second fuel line was attached to the side of the unit; it snaked away out of sight.

I disconnected the vacuum line, turned the key, and - hey presto! - Boris started first crack. There was (or perhaps I imagined it?) a slight roughness - not quite a cough, more like a catch in the throat (not usual for Boris) - when I revved the engine by pulling on the accelerator linkage. I reconnected the vacuum line and all returned to its usual, smooth self. Next two attempts to start - straight afterwards - went well.

Three hours later, I've just started him again - first crack, no problems. Vacuum device is still connected.

What is this vacuum device, and what - if anything - might it be contributing to the problem? Here's a photo of it:

.

[OzBenzHead]

Okay - I've found the picture in the manual, and it's the pressure damper.

However, nowhere in the ensuing pages of the manual does it get a mention, so I'm none the wiser how it works or how/why it can malfunction.

[Denis]

Hi Ozbenzhead

In a running engine, the fuel distributor pressure to the injectors is controlled by the flap position and the so-called warm-up regulator.

The fuel distributor if fed a lot of fuel, excess is sent back to the fuel tank. When the fuel distributor pressure is momentarily too high, the "pressure regulator" or pressure control valve that you located allows the extra fuel to return to the petrol tank. That is the purpose of the valve. Normally that device just needs a calibrated spring to shut the valve until the fuel distributor pressure exceeds a value. I have no idea why you have a vacuum connection there. My guess is an anti-pollution requirement. You need to know more about your car's emissions control design (oz version).

As an aside,the cold start injector is just that, a "choke substitute" when starting. It gets its power from the starter (cranking) with an override (shut inector) from the time switch if the engine is hot (to prevent flooding). At this point, I would look elsewhere for your problem as I initially thought you did not have this device operating at all.

Just a recap on the injection : when you turn the key, the fuel pump pressurizes the system (i.e the fuel distributor gets pressure) so that it will be able to feed the system. A few things can happen to prevent this pressure from feeding all injectors at startup : 1 - the warm up regulator is stuck/defective 2- your "pressure regulator" lets all the pressure BACK to the fuel tank :-(
3- a stuck/defective check ball somewhere in the fuel pump (that is the usual position in generic K-jet).

At this point, I would wonder WHY that vacuum line seems to be holding the valve open (causing loss of pressure in fuel distributor) as pulling it like you did takes all vaccuum away and closes the "pressure regulator" - ensuring no fuel return to tank - so the fuel distributor then pressurized ! starts right up ? sure as everything is ok.

Sorry for the size of the post but I think you are getting near the solution. best of luck.

Denis
Paris in the snow

[OzBenzHead]

Denis:

Boris is a British-market model, privately brought to Oz when five years old.  He has an Oz compliance plate, but that probably means very little, as for a very long time anything "British" was more-or-less okay, unmodified, for Oz standards.

Whilst the manual makes references to the "pressure regulator" - and has illustrations of same - it calls this device a "pressure damper", and in the illustration it is not the same device at all. When the text refers to the "pressure regulator", it refers to a device with electrical components/connections - not vacuum.

As for warm-up regulators, the only warm-up regulators pictured in my manual (issued in the US, but purportedly covering all models)  are the North American type, of which no such example exists on Boris.

About the only anti-pollution device required on Oz cars of that era (to the best of my knowledge, anyhow) was positive cranckcase ventilation, whereby a breather tube takes blow-by fumes from the rocker cover and the cranckcase and feeds them back into the carby/injection breather.

Boris obviously has those PCV devices, but that's about all that I can find.

Anyhow, thanks for your ongoing feedback. I'm sure that by a process of trial, error, and elimination, I shall arrive at the cause and (hopefully) its solution.

[Denis]

Unfortunately, I am going by memory on this as my 350SE has D-jet. K-jet is a very reliable system : general flow is controlled by the flap in the fuel distributor while the actual pressure is done by the  "pressure regulator" - aka warm up regumator in US documentation. It might be THE defective part here instead of the "pressure damper". But usually a bad pressure regulator makes for a poorly running engine somehow.

The "pressure damper" is quite accurately just some kind of volume limiter.

Good luck

Denis

[OzBenzHead]

Well, folks, after testing the entire fuel system, it turns out that the problem is in my distributor.

It jams open in any old advance/retard position. It's not the vacuum side - that was tested and works okay, up to and including the diaphragm - so it's something mechanical in the dizzy.

Shall shop around for a rebuilt/exchange job before I spend large $$ on a brand-new one.

It's good to at least have pinned down the problem area to a specific device at last.

BTW: That device I showed in the pic was not connected to any vacuum supply but, rather, was an atmospheric-pressure regulated fuel damper for the return-to-tank system. Nothing wrong there.