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Discussion Starter #1
All, As some may be aware, I blew the head gasket on the Corniche a couple of months ago and have been working on getting it fixed. The car is now back together with he heads resurfaced and new head gaskets on.
As we were pulling the car apart, the kid that does side work for me mentioned that the one electrical fuel injector plug was disconnected. I did not think much about it as this car clearly had some shade tree work done it before but we ahead and put everything back together and reconnected everything with the exception of the air pump as I used the British tool works kit to plug up the air injection lines in the heads.

Prior to the overheating issue, the car ran great. On the initial start, the car ran terribly, like it did with a blown head gasket. I decided to unplug the WUR, cold start injector and some other electrical solenoid that had a fuel injector style plug near the fuel distributor. The car ran much better but still had a minor miss which could be a number of things that I need to diagnose.

While I unplugged everything, I suspect that what was disconnected was the WUR. I'm wondering how the car could run so well without it given its function as an enrichment device. I'll get back on it later in the week and plug the cold start injector back followed by that solenoid looking thing. I still have a slight miss and I would like to get that figured out before i dive into the WUR.
 

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WUR is not your issue. The electrical connector powers the heating element. All you are doing is keeping the fuel mixture on the rich side for a little while longer than engineered. Engine temp will heat the WUR and start leaning out the fuel mixture (pressure increase with heat)

The solenoid looking thing sounds like the frequency valve. Please take a photo of this item and post.

It might be time to invest in a smoke machine.

Lastly, electrically disconnect the oxygen sensor until you sort out your issue.
 

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Discussion Starter #3 (Edited)
WUR is not your issue. The electrical connector powers the heating element. All you are doing is keeping the fuel mixture on the rich side for a little while longer than engineered. Engine temp will heat the WUR and start leaning out the fuel mixture (pressure increase with heat)

The solenoid looking thing sounds like the frequency valve. Please take a photo of this item and post.

It might be time to invest in a smoke machine.

Lastly, electrically disconnect the oxygen sensor until you sort out your issue.
Thanks, I was thinking that if someone had disconnected the WUR and adjusted the mixture to compensate, then the WUR will seriously richen the mixture as it's feeding fuel directly the top of the fuel distributor. I'll take a picture on Thursday and when I get back up there. I have a smoke machine and a CO meter. It was definitely running super rich. i'll plug everything back one by one and see what happens. It could well be the frequency valve and if so, could do exactly what it's doing.

Thanks
 

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Discussion Starter #4
So i'm guessing that this is the frequency valve? It's the culprit. When I plug it back in, the car instantly ran badly.

28947
 

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that's a fuel pressure damper control. I have one in my 1980 SW!!
 

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Discussion Starter #6
Rob,

Thanks. When I plug it in, the car dies out. Do you have an 02 sensor on your car?

Thanks
 

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So i'm guessing that this is the frequency valve?
Yes, it is, you must have connected the wrong wire/lead to it.

My guess is that you mixed up WUR and frequency valve connectors.

With the engine running and connector disconnected, one pin should have system voltage and the ground is cycled (duty cycle) @ 50% when cold.

A dwell meter can be used to measure the duty cycle but will it will read roughly 10% error.

You can also use a noid injector test light.

Applying power and ground to this valve opens it full applying a lot of fuel pressure to the piston thus max lean.
Disconnecting the power reduces the fuel pressure to the piston but the engine will be un-responsive.
 

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Do you have an 02 sensor on your car?
The frequency valve has to have an Oxygen sensor.

His rare injected 1980 California car has it.

The output of the oxygen sensor is processed in the control module and the frequency valve is adjusted accordingly.
 

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Yes, I have a single wide band O2 pre-cat on my 1980
 

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Discussion Starter #10
Yes, it is, you must have connected the wrong wire/lead to it. My guess is that you mixed up WUR and frequency valve connectors.
No, that's impossible on this car because the WUR is on the other side of the engine. There's only one plug and It was disconnected. This car has had some bypassed work done to it in its prior life. Removing the function of the frequency valve is one of those things that happens often in the Mercedes Benz world. CIS was designed to be a fully mechanical system and the lambda setup is an afterthought. Whenever I saw Mercedes Benz that had it plumbed in, i'd throw it all out and set the car up without it.

I expect that the same thing happened here.

Yes, I have a single wide band O2 pre-cat on my 1980
Thanks, I'm surprised that it's a wide band. I almost bought a CA spec Wraith 2 last Thursday but decided that I have enough cars to deal with. It was a nice car. I can't remember seeing an 02 sensor, but if i find out , great. I'll install an AFR gauge and set the mixture up properly.
 

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I'm surprised that it's a wide band
It's not wideband... that did not exist until the mid to late 90's.
0.1 -> 1.0 Volts is what that O2 is able to output.
Focus on getting the frequency valve to operate / buzz. Leave the O2 disconnected until the frequency valve is operational.

O2 disconnected puts the system in open loop for adjustment/diagnosis.

The frequency valve will operate at 50% duty cycle and will buzz at a constant rate.

Once you get your car sorted with the freq valve operation and all vacuum leaks repaired, then focus on air/fuel mixture.

Whenever I saw Mercedes Benz that had it plumbed in, i'd throw it all out and set the car up without it.
Grey market cars were the only ones that had it plumbed in as an afterthought. Those you can throw out.
USA RR/MBZ cars all have frequency valves. It's needed in order to keep the catalyst from being damaged.
Removing the frequency valve from a fuel distributor that is OEM ported for it will NEVER RUN RIGHT.

The only way that I have been able to work around this on my now vintage race cars was to install the European specification fuel distributor that does not have the ports.
 

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Discussion Starter #12
Grey market cars were the only ones that had it plumbed in as an afterthought. Those you can throw out.
USA RR/MBZ cars all have frequency valves. It's needed in order to keep the catalyst from being damaged.
Removing the frequency valve from a fuel distributor that is OEM ported for it will NEVER RUN RIGHT.

The only way that I have been able to work around this on my now vintage race cars was to install the European specification fuel distributor that does not have the ports.
I would normally agree with everything here. However it ran GREAT prior to overheating. I've not messed with the mixture or timing etc so my goal is to get it back to where it was before it ran hot. If I do anything else, I'll be introducing new parameters which will muddy the waters.

As far is the rough running, I think it may be the plugs. I put in NGKBPR6ES in place of the Champion RN9YC that were there originally. I just put back two of the old plugs and it's running better already.
 

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Discussion Starter #13
Scratch the plugs, that's not the issue. The I'm getting spark at the wires when i put an inline tester but for some reason it seems that two of the cylinders (back two on passenger side) are not firing. Tested the compression and it appears to be good but when I put my infra red thermometer on the manifold, they are reading cooler than the other cylinders.

Only odd behavior is that the plug wires create a lot of spark when you pull them. Unlike the others which need to to have something like a screw driver put close to it. That might be a red herring and maybe the intake manifold gasket slipped. I'll bring out the smoke machine shortly.
 

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On my 93 Turbo R some of the plug leads at the back that went through a clamp had perished and petrified and the car misfired. New leads did fix it. Bugger of a job to get to the clamp bolts at back.
Just a thought
 

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Discussion Starter #15
Frequency valve will kill the car the moment i plug it in. The miss issue turned out to be injectors.
 
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