'73 280 won't stay running - Page 2 - Mercedes-Benz Forum

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post #11 of 18 (permalink) Old 04-13-2009, 10:13 PM
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Your car is a 1973 so no computers, they weren't invented then. (Ok, that's a joke). Looks like that area could use a good cleaning. Always start with the basics, spark, gas, air.

Near Manassas Va. '65 220S, 2006 Ford Crown Victoria Police Interceptor, '99 Volvo V70, '72 350SL 4 speed

Not part of the in-crowd since 1952. It's BRAKES not breaks. You break a bone, use brakes to stop your car. /rant

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post #12 of 18 (permalink) Old 04-14-2009, 01:19 AM
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Have you checked you've got fuel pressure? if it runs when you poor some fuel into the carb but not otherwise i'd be checking the fuel system, the smoking ballast resistor might be an issue, but possibly not your main one.





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Originally Posted by wbain View Post
Your car is a 1973 so no computers, they weren't invented then. (Ok, that's a joke). Looks like that area could use a good cleaning. Always start with the basics, spark, gas, air.

Mines got an ECU in it, its a '75 though.

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post #13 of 18 (permalink) Old 04-14-2009, 05:18 PM
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Wbain is correct, start with the basics. You said it idled for a short time when the carbs. were primed. You never said if this is the dual overhead cam 6 with a single 4 bbl. carb. (on the driver's side), or the single overhead cam 6 with two 2 bbl. carbs (on the passenger side). Since it sounds like you've already replaced all the fuel lines, the fuel pump (both are on the driver's sides) may be bad, or a bad fuel filter, if installed. The pumps are rebuildable and also available rebuilt for a fairly reasonable cost. You can check for fuel by disconnecting the fuel line at the carb(s) (if the two 2 bbl. do just one) and direct the line into a small can or bottle. (As I recall this is easier with the 4 bbl. <rubber hose> than with the two 2 bbl. <metal lines> setup.) Have someone crank the engine for a short time and see if fuel starts flowing into the container. It should pulse with a fairly good squirt on each pulse. IMPORTANT: Although there should be no ignition source near the carb(s) on either engine, you should still exercise extreme caution not to spill any fuel. If you're getting fuel (you should get about 1/2-3/4 cup in about 15 seconds) I would start looking at the carb(s). The fuel, if any, in the container should smell "fresh" and not smell like varnish. The carb(s) could possibly have bad varnishy fuel, water, corrosion, or float issues, just to ID a few potential problems. No matter which carb(s) you have, the tops can be removed easily while still on the vehicle and inspected for proper integrity. If you get to this point, let us know BEFORE you begin this action. Hope this helps.

If the vehicle has been sitting for a long time, you very well may eventually have to check the carbs. I think you said you drained the tank. What was the fuel like in it?

Last edited by mbbuff; 04-14-2009 at 05:27 PM.
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post #14 of 18 (permalink) Old 04-14-2009, 09:59 PM Thread Starter
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The engine in my vehicle is a single cam with two 2 barrel carbs. The gas in the tank was horrible and the reason I had to remove it was because the pick up line was full or varnish. I would like to check out the carbs before I dig into anything electrical. If someone could walk me through this process a bit I would appreciate it greatly! I may as well make sure that this is not the issue, or is the issue, before I go crazy with everything else.
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post #15 of 18 (permalink) Old 04-15-2009, 12:23 AM
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Look in the 'Online Resources' post at the top of the forum and then the second post down. Lots of good Zenith info there.

Clean out all the gas gum, the fuel pump, the return line and the carbs. Get the tank cleaned too.

Near Manassas Va. '65 220S, 2006 Ford Crown Victoria Police Interceptor, '99 Volvo V70, '72 350SL 4 speed

Not part of the in-crowd since 1952. It's BRAKES not breaks. You break a bone, use brakes to stop your car. /rant

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http://www.bgsoflex.com/megasquirt.html
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post #16 of 18 (permalink) Old 04-16-2009, 06:57 PM
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My '74 280C has two ballast resisters. This seems strange, but the wiring diagram I have shows this is correct. When I bought the car it was not running and previous owner had screwed up the ingition wiring. Get a wiring diagram and carefully trace and check each wire and component for electrical conductivity.

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'73 280
'74 280C
'81 240D
'88 300TE

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1973 280 W114 (Driver - 140,000 miles)
1974 280C W114 (Now running - driven off and on this summer)
1968 200D (Engine rebuild planned)
1964 200 (gasser parts car) & 1966 200D (complete car - Got to run. Now to see if clutch can be repaired.)
1980 300D W123 (Parts car - engine runs, but trashed)
1981 240D W123 4 speed ( In sad shape when bought - many parts from '80 300D has back on the road. Needs work, but shows promise.)
1988 300TE W124 (Does not run. 180,000)
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post #17 of 18 (permalink) Old 04-17-2009, 04:22 PM
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You may want to check this website and pick up some manuals if you plan to really get into this.
Classic Technical Literature

The carbs. on your vehicle should be Zenith progressive 2 bbl. with vacuum controlled secondaries. First, remove the fuel line before you start removing the top screws. It's been at least 10 years since I've worked on one of these, but as I recall there are about 8-10 slot head screws around the perimeter of the top. There are also air bleed metering screws (brass with small holes in the slots), and maybe one or two others, which you don't want to mess with, at least not at this time. These are all located toward the center of the carbs. You'll also have to remove the center stud, if installed, that secures the air cleaner. I think those had long screws though that screwed into the top center of the carb. The top should be loose now. Note: You may have to lightly pry up on the top, as it may be stuck. Use caution not to pry too hard and distort the top, and do not pry on a gasket surface. It should pop loose fairly easily. If it doesn't come loose by now, there were some carbs. that had one more screw down inside one of the venturis. There is also the choke linkage that must be disconnected. If there is linkage to the accelerator pump (I think it was just a cam type arrangement) you'll have to unfasten it too. Remember how everything is hooked up, paying attention to screw lengths (I think they're all the same though), linkage retainers, etc. It may help to lay everything out on a paper towel (in clock fashion) arranged the way you took it apart. That way you can put it back together in exact reverse order.

Once the lid is off it should be readily apparent if there is corrosion, varnished fuel or other problems. It should be very clean inside though. If it is bad, as I suspect, you may have to remove the carbs. I hope this is not the case, as it is a pain. Do you have access to compressed air, if needed later? Let us know how this goes.

Last edited by mbbuff; 04-17-2009 at 04:31 PM.
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post #18 of 18 (permalink) Old 05-20-2009, 08:59 AM
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My first Mercedes was a 73 280 with the twin cam 6 & 4 barrel carb. I never had the same issues you describe but for what its worth, here's my history during the years I owned the car: It was beautiful inside & out when bought in 1986, but ran & drove poorly due to a burned valve & broken rear shock, so it was cheap. I overhauled the head & fixed the shock. After 3 trouble free yrs, at 100K it had some trans issues when the clutches began to disintegrate, clogging the filter. I was quoted $1700-$2400 to repair but I pulled the trans & had it rebuilt for only $500 at a shop the dealers used. Aside from brakes, battery & tires, the only issues were a sticking float on the carb I fixed by a clean/rebuild & once it would crank but not start when that wire from the coil to the starter came loose at the starter(this took me a while to diagnose). We sold the 280 after 10 years, when it again had some shifting issues that careful adjustments by a shop in Seattle cured & I was told it would eventually need another rebuild. Good luck with your project, these were great sedans. (edit) I just remembered mine had a vacuum pump like those on diesels, it needed some rebuilds over the years, not sure if your model had this feature) Don

Last edited by ollo; 05-20-2009 at 09:04 AM.
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