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1971 250CE (W114)
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Discussion Starter #1
Hi

I have a W114 1971 250CE that's giving me trouble on starting - the battery is new, it's turning over okay but doesn't sound even close to starting.

I think it's a problem with petrol getting to the engine. The fuel pump appears to be running (i.e. with someone else turning the engine, I can get underneath at the back and feel the fuel pump "whirring"). The translucent tubing going in/out of the pump has fuel in it as does the tubing going in/out of the fuel filter. I disconnected a tube at the end of the supply manifold to the injectors but I'm not getting any petrol coming through (when I disconnected initially, a small volume spilled out) when turning it over - I presume I should be getting petrol flowing here?

If so, I'm guessing that it's either a blocked fuel filter or that the pump isn't actually pumping even though it sounds/feels like it is? Any recommendations appreciated

Thanks in advance
 

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Can you post a picture of your engine bay? I am wondering what type of fuel injection you have. Most (or all?) US w114 were dual zenith carbs, not injected. I can’t recall why type of injection the injected ones have.
 

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68 250S, 91 300se, 98 SL500, 450SEL 6.9, 14 CLS550 Past MB's; 300SD, 300E, 300TE, 190E, ML420
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Sounds like you need a new pump - and filter.

Fonzi, CE = Coupe Einspritz
 

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1999 E320
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Fuel,and spark Makes things work. Did you confirm spark? Fuel volume may not be sufficient so check both filters I. Lime if it has one and screen in tank then look to fuel volume. Is fuel pump original or is it aftermarket. I don’t recall the 72 having an electric fuel pump
 

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1971 250CE (W114)
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Discussion Starter #8
Fuel,and spark Makes things work. Did you confirm spark? Fuel volume may not be sufficient so check both filters I. Lime if it has one and screen in tank then look to fuel volume. Is fuel pump original or is it aftermarket. I don’t recall the 72 having an electric fuel pump
There's spark at the distributor cap anyway. I decided to check fuel first - should I be getting petrol coming out where I removed that tubing? If so, I'll disconnect the tubing before the filter and secondly after the fuel pump to see what I'm getting at both points.
 

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Now that we understand what system you have, yes, d-jet pumps are in the back by the tank. Unless the plumbing has been altered, you should have a line from the filter to the engine bay, and one from the fuel pressure regulator back to the tank. I can’t really see which line you disconnected, but if it’s the return line, it might make sense that the pressure regulator isn’t sending fuel back to the tank (if the pump isn’t making enough pressure, or filter is clogged).

If you can assure you’ve disconnected the supply/pressure side of the fuel line, that would help.

Regulator circled. Injectors are on the pressure side of the regulator.


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1971 250CE (W114)
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Discussion Starter #10
Now that we understand what system you have, yes, d-jet pumps are in the back by the tank. Unless the plumbing has been altered, you should have a line from the filter to the engine bay, and one from the fuel pressure regulator back to the tank. I can’t really see which line you disconnected, but if it’s the return line, it might make sense that the pressure regulator isn’t sending fuel back to the tank (if the pump isn’t making enough pressure, or filter is clogged).

If you can assure you’ve disconnected the supply/pressure side of the fuel line, that would help.

Regulator circled. Injectors are on the pressure side of the regulator.


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Hi

Apologies for the delay in replying, I was away for the weekend.

Thanks for the explanation above, the line I've disconnected is not on the supply side of the regulator, it's on the return side.

I'll disconnect a line on the supply side and see what's happening.

Thanks again
 

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1971 250CE (W114)
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Discussion Starter #11
Hi

I disconnected a line on the supply side of that regulator but got no flow. I then disconnected a line on the pump side of the fuel filter and got flow as per the attached video.

Link

Does that flow look sufficient? Is the lag in flow because the line isn't primed (because I've broken it)?

Next step replace the fuel filter?

Thanks
 

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1967 250 SL, 1965 300SE lang
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Your link requires a microsoft login.
 

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1971 250CE (W114)
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Discussion Starter #13
Apologies, about the link, I think I've fixed the problem in the links below.

I removed the tubing before the fuel pump and there's flow there so I was going to buy a filter. Before I did, I decided to check again at the inlet manifold to the injectors and it turns out that I am getting flow there o_O

Here's the flow at the inlet manifold:

Inlet manifold

As you can hear in the video, the engine doesn't sound close to starting. I tried priming the pump several times (i.e. turning the key to engage the fuel pump but not the ignition) and then attempting to start the engine. When I do this, the engine begins to start but then cuts out almost immediately as if it's losing fuel pressure (?).

I also took a video of the fuel pump and the inlet / outlet to it, is the air bubble here anything to be concerned about?

Fuel tank

On a side question, I was also inspecting the rust on the car - see videos below. It's much worse than I thought, in particular on the driver side. Is this salvagable? Or terminal?

Rear

Passenger side

Driver side

Thanks in advance
 

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I was just working on getting a d-jet running, and putting 12 V on the injectors (with a spare part plug from an air intake sensor) caused some to click, and others to not. I had to replace 7 of 8 on the car I was working on. Fortunately I found 7 clickers in my spare parts bin. I found a lot that didn’t click too. My car runs after putting injectors that click when 12v is applied.

My cold start valve clicked, so I didn’t switch that.


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That white hose on the fuel tank looks very dangerous. You should replace that right away. I dont think there should be air bubbles there at all.

the drivers side rust looks pretty bad. anything can be fixed but do you have welding equipment? Paying someone to fix that would be expensive. the passenger side doesnt look all that good either. Are the floor pans rusted also? look under drivers carpet. How about a photo of outside of car? Take an awl and poke the rust to see if it breaks thru.
 

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I’m going to guess the air in the inlet line to the pump signifies an empty tank, or more likely a swirl pot that is not filling quickly enough with the gas from the tank because the tank is gummed up from old bad fuel and maybe rust. (That’s a scenario I’m working with in my driveway here too.)

Try running your pump off a container of fuel instead of the car’s tank. Take note that the regulator will send fuel back to the car’s tank unless you have the return-to-tank going to your container of fuel also.


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1971 250CE (W114)
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Discussion Starter #17
I’m going to guess the air in the inlet line to the pump signifies an empty tank, or more likely a swirl pot that is not filling quickly enough with the gas from the tank because the tank is gummed up from old bad fuel and maybe rust. (That’s a scenario I’m working with in my driveway here too.)

Try running your pump off a container of fuel instead of the car’s tank. Take note that the regulator will send fuel back to the car’s tank unless you have the return-to-tank going to your container of fuel also.


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Okay, will try that (y)
 

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1971 250CE (W114)
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Discussion Starter #18
That white hose on the fuel tank looks very dangerous. You should replace that right away. I dont think there should be air bubbles there at all.

the drivers side rust looks pretty bad. anything can be fixed but do you have welding equipment? Paying someone to fix that would be expensive. the passenger side doesnt look all that good either. Are the floor pans rusted also? look under drivers carpet. How about a photo of outside of car? Take an awl and poke the rust to see if it breaks thru.
When you say "dangerous", in what way? That it could pop off or what?

Yeah, the rust is pretty bad although the bit I've shown you around the driver's door is the worst of it. The driver's side sill is in bad enough shape, you could see me poking my finger into it in the video. The floor pans aren't bad.

Here's a few pics of the outside of the car
 

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