the euro 250 lives! Drives great...WON'T IDLE! (and other Solex stuff)

[blankenship]

so, my w123 gasser (euro 250 that recently got a 2nd lease on life) won't idle for anything.

it's so strange...she drives well, and the throttle is responsive. sometimes it's taken a squirt of starter fluid to get her going, but once warm she starts right up (though she immediately develops a high/low fluctuation and will die quickly). strange, when stone cold she seems to operate better, but only for a block or two. afterwords, she'll die at every stop sign/light and when parked, unless you put your foot on the gas and rev/coax her.

i've checked all the vacuum lines, and they hold pressure.
i've checked around the base of the Solex carb for leaks by spraying WD40, and haven't been able to affect and change.
the accelerator pump seems to be working/spraying fine, and she's got new plugs and wires.

one thing i've noticed is that the secondaries (the flaps over the larger barrels (?)) seem never to open, and appear to stick a bit. the vacuum dashpot keeps them pulled closed no matter how high the car's revved. when the car is shut off and i push on the secondaries, they do not operate smoothly, but, rather have a couple 'snags' and seem to stick at a few spots...if you open them all the way, they'll most likely seize and stay there. could this be my problem area, or would it only cause poor performance at very high throttle?

thoughts on all this would really be appreciated.

[Mike D]

Sigh, the "Solex Blues". If I only had a nickle....

The Solex is a wonderfully overengineered replica of the Rochester Quadrajet. In peak operating condition it was one of the finest fuel distributing devices ever made.

Now, let's look at reality, it's a piece of 31 year old cast pot metal, brass bushings, neoprene pieces and steel shafts. It has probably been, undertightened, overtightened, adjusted, mis-adjusted, retightened, re-re-adjusted, neglected, filled with crud, been heated and cooled 6 gadzillion times, re-re-readjusted and tightened some more.

First step is to disconnect the fuel pump feed line. Drop a length of fuel hose into a half gallon of lacquer thinner (not mineral spirits or paint remover), connect the hose to the fuel pump, start the car and let it suck up the lacquer thinner. Shut the car off using the dome light switch (private joke folks!) and let the thinner soak in the carb for 20 minutes. Reconnect the fuel line, start the car and see if you've gained anything. Drive it for a bit and check for improvement. Repeat only ONCE.

Post your results and we can go from there. Go ahead and give me a call tomorrow Lee. I'll be home all day repairing storm damage to my work shop and I could use the relief.

[t walgamuth]

Originally Posted by blankenship

so, my w123 gasser (1982 euro 250 that recently got a 2nd lease on life) won't idle for anything.

it's so strange...she drives well, and the throttle is responsive. sometimes it's taken a squirt of starter fluid to get her going, but once warm she starts right up (though she immediately develops a high/low fluctuation and will die quickly). strange, when stone cold she seems to operate better, but only for a block or two. afterwords, she'll die at every stop sign/light and when parked, unless you put your foot on the gas and rev/coax her.

i've checked all the vacuum lines, and they hold pressure.
i've checked around the base of the Solex carb for leaks by spraying WD40, and haven't been able to affect and change.
the accelerator pump seems to be working/spraying fine, and she's got new plugs and wires.

one thing i've noticed is that the secondaries (the flaps over the larger barrels (?)) seem never to open, and appear to stick a bit. the vacuum dashpot keeps them pulled closed no matter how high the car's revved. when the car is shut off and i push on the secondaries, they do not operate smoothly, but, rather have a couple 'snags' and seem to stick at a few spots...if you open them all the way, they'll most likely seize and stay there. could this be my problem area, or would it only cause poor performance at very high throttle?

thoughts on all this would really be appreciated.

I would have not thought that using wd40 is the way to go on testing for vac leaks. I would use ether.

It sounds/acts like a vac leak to me. Did you put a vac guage on it? That will tell you a lot in a hurry if you have one. If you don't have one you owe it to yourself to buy one if you are thinking you will continue to operate the car with the carbs.

I had similar carbs on my old BMW bavaria and swapped them out for one Q jet. There used to be a q jet clone that Edelbrock made which might be worth considering, and there are weber conversion kits available from JAM. Folks here have tried both in the last year or so and there is at least one thread on the general subject.

Good luck.

Tom W

[Rick76]

Make sure that the idle shutoff solenoids are receiving power. There are two mounted low on the carb pointing forward. Could just be a fuse problem.
As far as your secondaries, they will only open under high load where the vacuum is low. Sticking secondaries are quite often signs of over-torquing which warps the carb. You may be lucking and it might however just be gummed up. Not likely causing your idle problem.

[MunichTaxi]

If so, you can try plugging it (and the line from carb). Let us know if it improves.

Also, you probably have a TDC transmitter near the timing pointer on the the Crank wheel. How does the wire look?

[blankenship]

performed various checks per those suggestions, and still no go.

*plugging the retard port - no effect

*TDC transmitter wire looks pretty darned good

*confirmed power to idle solenoids (via black wire...no power to orangish one...i imagine it's on some kind of time/temperature switch?)

*had previously tested vac lines w/ my mightyvac...all hold pressure.

i didn't actually try the lacquer thinner thing yet....the only posts i can find in regard to that are by a user named Barry123400, and there's not much feedback per his technique, so i'm a little skittish.

also, because problem is DEFINITELY temperature related. started her up this morning (w/ starter fluid) and she idled GREAT for several minutes, before eventually starting the high/low rev and dying. after that, she continually stumbled, and would hardly stay running long enough for me to make it from the driver's seat to the accelerator linkage. running through those various tests wouldn't change her.

thoughts?

[Hit Man X]

Ah, the ol' Solex. My 280S does the same, won't idle but is fine at part throttle and WOT.

I'm not wasting any more effort with mine, I've decided to go to that Holley 4360 replacement. For sub-$300, you too can enjoy your car again.

[stevebfl]

First this is not the carbs used on a US Bavaria. Those were two barrel Zeniths similar to what might be on a US 250/8 or 280SE.

This carb is a Solex 4A1 similar but not the same as the ones used on the M110 280.

The secondaries are vacuum operated and as such you will never see them open unless you have a dyno. The secondaries make or break this carb but won't have anything to do with idle unless they do not fully close.

To make this thing run on idle one must shut the throttles till the idle circuit is involved. Look down the front barrels (carefully, it might back fire in your face), can you see fuel being emitted by the venturi. This is the main metering system and no fuel should be emitted at idle. If it is then you have too much air passing the throttle... close it. If closing it causes the car to die then you are probably getting no fuel through the idle passages. One can blow down through the idle air correction jets and sometimes clear an obstruction but first one must be sure those idle solenoids are working. You verified power, with the car off can you hear the solenoid click when the cable is touched to it with key on engine off.

The major difference with this carb and the US oneis that there is a large screw between the solenoids that is an idle air screw. I have very little experience with that screw but it should be open enough to get enough air into the carb to run without the throttles being open.

Another few hundred pages of advice and you might make it all work. The tops warp as stated causing air leaks into the idle airbleed passages, a new gasket or a double one in that area sometimes will rig it. The secondary airflap spring tention is critical to the transition to secondaries but as I said not important to idle.

[blankenship]

thanks for the input, steve. did those checks but still no go.

-verified the solenoids by disconnecting them and then turning on the key. when i connect power to each one, i hear a distinct 'click.'

-there's no fuel coming out of the venturi at idle....only when you blip the throttle and the accelerator pump actuates.

-i saw a hole between the solenoids where i imagine the idle/air screw you refer to is located on equipped models. i can't see inside the deep hole, but put a thin flat-head screwdriver in there (on each of my 250's), and can't seem to feel any screw...maybe they didn't come equipped with that adjustment.

-i've always thought it best to check for leaks with WD-40 or the like...not ether. it seems that sometimes you man get a misdiagnosis (or explode) by spraying ether everwhere with the engine running...and i've imagined before that the ether vapors get sucked into the intake and improve idle...thereby faking you out. thoughts?

-this is DEFINITELY time/temperature related...so strange...she idles high and evenly when first started, for 2-5 minutes. then she stumbles to a halt, and won't idle thereafter. any other ideas would be GREATLY appreciated!

[pj67coll]

What about a fuel supply problem rather than a carb problem?
Tank pressure, fuel pump, fuel line etc?

- Peter.

[blankenship]

gosh, man...maybe.
is there any fuel supply scenario anyone can think of that would have those sorts of symptoms?

i replaced all the lines that were questionable, and i don't smell any fuel spillage. i drained all the 3-year-old gas out of her, and refilled with new, but didn't replace the filter or pump. i'd always though the pump was an 'all or nothing' deal.
anyway, like i said, she seems to accelerate well and everything at driving speed, but won't idle once warm, and you've gotta use starting fluid to get her going.

thoughts?

[ctaylor738]

You should pull the top plate off the carb and take a look in the bowl. I suspect you will find a ton of sediment blocking the jets. Take it apart, soak everthing in carb cleaner, rinse, and blow out with air.

You haven't said if you have the mechanical fuel pump. If you do, it may not be delivering enough fuel at cranking to replace the fuel that's evaporated while it sits. You can test it by unhooking the line at the carb, putting into a jar and watching for a "good spurt" while cranking. I would replace the filter on priniciple.

No idle when warm sounds like blocked idle jets, as Steve B pointed out. Another good reason to clean the carb.

Is the choke place closing completely? Do you get a squirt from the accelerator pump when cold? If so, the car should at least fire.

Have you checked the choke pull down? Unhook the dashpot and apply vacuum with a Mityvac. The choke should open 2-3mm.

[250 Coupe]

Every thing that ctaylor738 said plus my '76 280C would not idle if I tightened the air cleaner hold down too much as it would warp the carb and cause a vacuum leak.

If you get a chance to sniff the tailpipe as it's idling, or at least trying to and it smells sharp and makes your eyes burn, it's running way too lean.

If you get a chance to cover most of the air horn when it is warmed up and it begins to idle better, you are running lean.

My '76 450SEL tends to idle funny and run-on more if it's low on fuel, which has nothing to do with your problem but shows that low fuel level problems do exist.

Michael

[250 Coupe]

Just a random thought here.

Is there a fuel return line off the carb back to the tank? Could it be that at idle the pump output is low enough that the idle jets are uncovered but at speed, the pump output overcomes what is lost back to tank?

Michael

[300SDog]

Thats a interesting thought about fuel return valve stickin and return line not flowing properly. Probly ye wanna start by blowin out the return line with compressed air. Somebody i think it was "nachi" our southeast asia expert here published a thread on bypassing the troublesome solex return valve located on top of float bowls. Search "solex" topic posts authored by *nachi* even coupla yrs ago here on the Vintage Forum.

high/low rev and dying

Among techs this is called "hunting" when engine rpm struggles to smooth out. Its fuel flow related. Reckon with return flow blocked/disfunctional its like floodin itself.

And what did the old plugs look like when ye replaced em? Ther's yer best gasoline tech diagnostic tool - color/condition of spark plugs. Black'n dry = rich; Brown = correct; White, scorched tips = lean.