Fuel issue 89 mercedes

[03ozwhip]

Alright so I narrowed down my start issue to a fuel issue. I can get it to start by putting fuel into the intake. This is where I'm lost, not sure where to go from here.

Anyone have any insight? Inline 6 2.6.

[ThePenIsMightier]

I don't know anything Mercedes specific, but I'd be looking for an ancient, clogged fuel filter or a dead pump. Can you hear the pump come on, whirrr to pressurize the system, then stop when you turn the ignition on?

[ExtraSlow]

Yeah, fuel isn't getting in. TPIM has the right ideas.

[e31]

This is a common issue with the weird "distributor type" injection systems common on Mercedes of the time. Basically you will want to disconnect & back-flush the entire fuel system using Methanol. It will dislodge a bunch of muck. The more you can disassemble the better you will be able to clean.

[corsvette]

If it’s like the Bosch CIS injection system in my old Audi’s they do get gummed up. Never use gas with ethanol either. I’ve had my fuel distributor apart a few times to solve running/no start issues and it’s always been due to mucked up components. I’m on year 12 of owning the car and had it open only twice so it’s not all that unreliable. Also, make sure you have fuel pressure from the pump in the tank.

There’s a Facebook group that specializes in CIS experts. I’ve gotten plenty of great Info from them.

[ThePenIsMightier]

Oh, is this one of those Bosch CIS that I recall from late 70's VW's??! Yeah, they're sightly finicky if you get some poison fuel, but aside from that, you should be golden.

[03ozwhip]

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If it’s like the Bosch CIS injection system in my old Audi’s they do get gummed up. Never use gas with ethanol either. I’ve had my fuel distributor apart a few times to solve running/no start issues and it’s always been due to mucked up components. I’m on year 12 of owning the car and had it open only twice so it’s not all that unreliable. Also, make sure you have fuel pressure from the pump in the tank.

There’s a Facebook group that specializes in CIS experts. I’ve gotten plenty of great Info from them.

I wouldn't even know where to find gas without ethanol lol. I've never had a car like this before and I'm totally new to fixing this kind of stuff, never did it before, so any pointers would be appreciated for sure.

[Steve 90TTZ]

I previously owned a 1988 300E that had a similar issue but mine was when it was warm. The fuel pump relay cold solder joints would fail over time. It has been a while since I had mine, but I recall the relay being behind the battery. If you try tapping one of the relays, while someone is trying to start the car, it will sometimes bring it to life. I had taken apart the relay and it was quite complex and definitely ahead of its time.

I did a quick search and the following provides more detail on the relay location.

https://www.youtube.com/watch?v=kb4sf03NHj8

Great car btw.

[03ozwhip]

Edit: I'm a complete fucking tool and I shouldn't do this when im tired.

[ExtraSlow]

The female end should slide to the end doesn't it?

[03ozwhip]

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The female end should slide to the end doesn't it?

I edited my post, but yes it should.....it didn't. Because I'm a total tool.

[03ozwhip]

Alright fresh day! Lol got everything back together after a few tries because of crush washer leaks, but now, no leaks and the car is currently running.

However, the I tested the fuel pump out of the car and it was really quiet, now that it's pumping fuel, it's really loud. Is this the pump going or could it be because the fuel has been sitting foe so long, it needs a full fuel flush?

[Flexray]

I don't know much about CIS injection, but high fuel pressure can cause the pump to be loud. There should be a procedure to set the correct fuel pressures.

[03ozwhip]

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I don't know much about CIS injection, but high fuel pressure can cause the pump to be loud. There should be a procedure to set the correct fuel pressures.

I'll take a look into that too.

[ThePenIsMightier]

I would only drain a fuel tank in an extreme obvious scenario of fuel contamination. Otherwise, "dilution is the solution to pollution".
Get it low, pour an additive in and brick it full. Repeat.

[03ozwhip]

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I would only drain a fuel tank in an extreme obvious scenario of fuel contamination. Otherwise, "dilution is the solution to pollution".
Get it low, pour an additive in and brick it full. Repeat.

@ThePenIsMightier Ya thats the first thing I'm going to try tomorrow. That pump though, it's really loud, so I feel like that isn't going to be my issue, but needs to be done anyways.

[Flexray]

Starting point:

https://www.slideshare.net/guestceff...jection-manual

[03ozwhip]

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Starting point:

https://www.slideshare.net/guestceff...jection-manual

Thanks for that. I'm really not versed in doing that kind of stuff, although i might try it if i have to. I'm realizing now that it's running really rich too because I smell fuel.

[Flexray]

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Thanks for that. I'm really not versed in doing that kind of stuff, although i might try it if i have to. I'm realizing now that it's running really rich too because I smell fuel.

I treat CIS the same as carbs, I will not learn how to repair it. If I'm going to learn something, it will be in advancing technology not old stuff. But, I worked with a old guy for a few years who knew CIS inside and out and was shown many things.

These systems require old school skill to repair. They are repaired and set up using your five senses, along with the skills of old mechanical repair. Like polishing, increasing/decreasing spring pressure, removing 30 year old fasteners without damaging things, setting pressure differentials. It is hard to learn these skills from the internet, you learn them from experience. Most of the mechanics that know these systems are retired or dead. Study the manual, gain a base understanding of how the system works and gain experience.

[JfuckinC]

LS Swap it already