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This can't be right...

2K views 13 replies 5 participants last post by  jackjtr 
#1 ·
Someone had messed with my Warm Up Regulator before I bought the car. The adjustment "dowel" or "pin" had been hammered in really far.

After replacing chain guides and checking ignition timing, I went to start it, and it wouldn't idle under 750rpm. It would start to cough and stall. Before replacing the guides, it wouldn't run under 1000rpm.

I decided to bring the WUR back to its stock position, so I took the bottom off and hammered the pin back to where it sat before someone messed with it.

I reinstalled it in the car, and now it seems to be running very rich, to the point where it won't even start. I pulled a plug and it was damp with gasoline.

From my understanding, hitting the pin in creates a lower control pressure, resulting in a richer mixture, and vice-versa. So, why would my car seemingly become richer after adjusting back to the "normal" position? It just doesn't make sense to me.

Do I just need to get myself a set of CIS gauges and set everything correctly, or is there something else I should check?

Thanks for reading this already well-covered topic.
 
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#2 ·
I think the only way to check if your WUR is working properly is to measure the fuel control pressure. See the other thread going on. Make sure the vacuum lines are tight.

The control pressure should be around 1,5 bar on cold engine and around 3,5 on hot engine.
 
#4 ·
Right, but hitting the dowel in on the WUR would cause a richer mixture, correct?

I'm going to be swapping in a known working unmolested WUR from my 380 this morning to narrow it down to the regulator itself and not another issue in the fuel system.


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#5 · (Edited)
There are other portions to the fuel system that control how the engine runs. Without a test gauge (even a cheap harbor freight one) you don't know where you are on any of the pressures, system, control, residual and so swapping parts to maybe get it to run a bit better is a shot in the dark maybe fix proposition. The WUR swap may indeed have it run a bit better, but you still do not know if it is running correctly. Chasing your tail in other words. You may in fact only luck into curing a symptom of what the actual problem is.

Once you have your pressures tested, issues fixed that are pinpointed with the pressure test and everything set to spec operational pressure wise, then you can be concerned with actually getting the CO adjusted to have it spot on.

To answer your question, knocking in the pin will reduce control pressure. This lower pressure acting on the Primary Pressure Regulator will cause the engine to be richer if all running correctly.

 
#6 ·
So I swapped WURs with my 380, and still a no start.

I had messed with the mixture adjustment screw. Not more that about 2 full turns though. Would this be enough to cause a no start? I adjusted it counter clockwise. Would a too lean mixture cause a no-start and a smell of fuel at the exhaust?

The mixture screw has an effect on all mechanical positions of the sensor plate, not just idle, correct?

I've been desperately trying to get my hands on some gauges locally, but shops either got rid of them a long time ago or start yelling at me when I inquire about renting them.


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#7 ·

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#13 ·
Why do you want it to idle below 750?

If you check the online service manual ( https://www.startekinfo.com/StarTek/outside/11883/PROGRAM/79450sl.html ) specs and the proper way to diagnose and adjust the engine is listed.

According to the idle speed adjustment section the correct idle for your car should be 700 - 750 minimum

https://www.startekinfo.com/StarTek/outside/11883/PROGRAM/Engine/107/M117_45/073-100.pdf

I'm glad you ordered the fuel pressure test gauges. Once you get them you can truly test, adjust and fix those items actually needed. I would, at this point, stop swapping, guess adjusting things and basically leave the car alone until you can hook your gauges up and go from there. You stand the chance of getting the car so screwed up by just guess adjusting things, that it will take a lot of work and maybe more money to fix than just doing the job right in the first place.

Here is some reading for you too.
http://www.benzworld.org/forums/r-c...3-first-time-attempt-check-cis-pressures.html

If you do a search on the site you will find a number of posts about getting everything set right. Some include links to Bosch fuel injection manual pdf copies as well. Sorry, don't have the links handy as it looks like I just downloaded the books while I had the chance.

When you get your gauges post what you get for pressure readings. System, control (with/without vacuum), residual (valve open/valve closed)
 
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