Newbie 250C carbs question

[Mike D]

Simple enough to test. Wire a horn/test light/buzzer to the start terminal. Run a ground to the device. Turn key to "Start" position. Added device should activate. Work back from there to the NSS.

That is MBTex.

Yeah, those verplunkt screws are a pain. I use an offset screwdriver to access the one screw. Keep a magnet handy. You WILL need it to find the screw which you will drop two or three times.



You do have the instrument binnacle out, don't you?

Are the two "low" cylinders adjacent?

[richmike114]

Ok that makes sense. I will work on troubleshooting more as it gets warmer. 21 deg in NE PA today.

Those screws are a pain!

Yes the instruments binnacle is out.

[richmike114]

And no they were not adjacent. Just dry. A little oil and they pumped up. And they stayed that way.

[meltedpanda]

just a thought but can you check for power at starter? or at least continuity from starter switch. Could be a bad solenoid. BTW beautiful car

[richmike114]

Thanks for the compliments. I appreciate that.
Well. I found it.
In between the NSS and the starter there is a complete break in the wire harness! Right under the Power steering reservoir on the drivers side the wires run up the front clip and are attached to the body by a factor clip. This occurs right before they meet with another harness. They are completely cut through!
Either they wore out that way or they were eaten by mice I guess. Not clean but real jagged.
Someone had messed with the NSS before and broke it. Bought a new one and Now that’s fixed. Guess I didn’t need a new ignition switch though but that would explain why I had no power at the NSS.
Also the cars reverse bulbs were both removed. Wonder if whomever worked in it before was trying to trouble shoot it and the NSS. Maybe the same hack who broke the old NSS?
Anyways I could not feel my fingers enough to wire it back. Too cold. Should be warmer this week.
Can’t wait to get this running. Want to get it into the garage and on a lift so i can properly go through it.
Plan on putting back the rebuilt carbs, coating the fuel tank, changing the fuel pump- been sitting since 1995- checking the valve clearances, detailing the valve cover and air cleaner, changing the fluids etc.
thanks for all the advice thus far!

[cth350]

it could have been two hacks. One breaking the switch and the other trying to bypass it.
The missing lightbulbs could be explained by a short in the wiring leaving them on all the time, so that missed opportunity would have been after one or the other faults.
-CTH

[meltedpanda]

detective work for sure, but that is half the "fun"
when you have some time , check out my journeys

http://www.peachparts.com/shopforum/vintage-mercedes-forum/134622-1971-220-a.html
http://www.peachparts.com/shopforum/vintage-mercedes-forum/376816-dolly-finally-my-finny-journey-continues.html

may find some tips in there , keep us posted !

[vwnate1]

Welcome Newbie ~.

Your car looks great and sounds like it'll be terrific once you get it sorted out .

[richmike114]

Ok got it cranking!
Adjusted the valves. Changed the oil with Dinosaur 10-40 and high dose of ZDDP and a new filter.
New VC gasket
New Fuel pump- not cheap, filter and lines. Bypassed the 25 year old fuel in the tank. Ran it Roadkill style.
Put the carbs bask in that I rebuilt.
Took quite a few cranks but the filter filled up and she fired for the first time in 25 years!
You should have seen what blew out the tail pipe! Acorns, stuffing, twigs. Lol.

That’s the good

The bad is it won’t idle. Not sure if the accelerator pumps are working either.
Also have a leak at the fuel return valve on the front carb. Pretty good leak. I pulled the return valve and I didn’t rebuilt it because no parts came in my $120 full rebuild kit from out host. That’s per carb! Damn expensive and I used almost none of the kit.

So I thought I had a bad vacuum leak which is why it won’t idle. I plugged the power brake and the other 3/8 inch bung on the intake manifold. Didn’t seem to help.

Ran out of fuel so I’ll try again another day.
First I’ll look for that fuel return valve. Then I’ll work on the idle

[dobrodan]

If your dwell and timing are dialed in you probably don't have the throttle plates adjusted correctly. Did you set them on the bench per spec? If so they should be pretty close. Do you have a Unisyn or other carb synch tool? That's the only way to get them right. Keep messing with it and you will get it.
Your fuel return valve is probably leaking because of a bad diaphragm. There is only one
place I have found them, here:
https://classiccarbs.co.uk/product/zenith-inat-carburettor-fuel-return-needle-valve

If the diaphragm looks good it can still leak at the rivet.

[vwnate1]

Don't forget to chek those tiny brass idle jets ~ if it's about to stall out unscrew one 1/4 turn, if the engine suddenly tries to run again that's the problem : the idle circuit .

You're almost there ! .

[richmike114]

Ok so here is where I am now.
I fixed the fuel return valve with some rubber gasket maker and sealer.
First Car won’t idle. Feels like a huge vacuum leak. I blocked off the 2 big culprits, the lead to the power brake booster and the one on the intake that goes to the air cleaner.

Is there another one that I could be missing?

Second The rear carb seems to be doing the Lions’s share of the work. The rear accelerator pump is squirting. The rear exhaust manifolds are hot
The front manifold is not.
I adjusted the fronts accelerator pump and put on a new rubber diaphragm. Still no squirt.
I checked the floats and they are in spec
Car won’t start unless I squirt some fuel in the bores.
Car needs quite a bit of throttle to keep it running. Won’t idle. I went through about 2 gallons in 8 minutes. My fuel source is just a gas can as I didn’t want to use the tank bc the car sat for 24 years.
The front exhaust manifolds are warm to hot. The back are HOT.

Any ideas fellas?

[vwnate1]

I'd look at failed intake to cylinder head gaskets next....

[Sugar Bear]

Agree with vwnate1, look for an intake manifold leak at the gaskets. Can the carbs be switched front to rear for test purposes?

Good catch on the temp difference on the manifolds. Going back to things flying out of the exhaust, I'm wondering if one of the exhaust pipes and/or manifolds is blocked.

Good luck!!!

[richmike114]

Never thought of an intake manifold leak. I’ll look for that next.
And ya know what? I was running it and there is still crap blowing out of the exhaust! I wonder if there isn’t something stuck in there. Hmmmm. Ok. Thanks for the encouragement all of you. Maybe a combo of both
I prob could switch the carbs too. They are difficult to get off however.
I’ll report back