Mercedes-Benz Forum banner

1 - 19 of 19 Posts

·
Registered
1984 380SL
Joined
·
36 Posts
Discussion Starter #1
My car is having some trouble starting - and it's getting worse. Pretty sure it's the warm up regulator.

I took a look at it, and it seems like there is a rubber connector for, like, a vacuum line or something, but it isn't connected. Here's a picture:

2649935


Is something supposed to go in there? The curved one.
 

·
Registered
1985 380 SL
Joined
·
144 Posts
There is nothing to be connected here, it is a just vent line. These versions dont have the entire housing under vacuum.
 

·
Registered
1984 380SL
Joined
·
36 Posts
Discussion Starter #4
Gotcha! So I just ordered a replacement - is this a simple swap that I can do myself?

It looks like it’s in an easy position on the engine and is just a few connections.

Any details I might need to know?
 

·
Outstanding Contributor , Bob's Your Uncle!
-----'83 280 SL----- 5 speed....The PIG
Joined
·
29,626 Posts
An 84 380SL WUR venting to atmosphere?
I'm no expert....but it should be venting back into the crankcase vent or something else with passive vacuum.

And that electrical harness on the WUR needs looking at. No 12V to the WUR and you'll experience some problems.
 

·
Registered
Joined
·
112 Posts
if the heater is still good I have taken them apart and cleaned them. The WUR is basically a controlled leak to the return side of the fuel system. A lot of times they become clogged and don’t allow fuel to pass when cold. I also drill and tap the pivot pin and install a bolt and washer. Then with a fuel gage hooked up I dial in the pressure based on the ambi temperature and pressure on the graph. Then alter slightly to get no flat spots on throttle snap.
 

·
Registered
1989 W124 260E
Joined
·
2,025 Posts
After that would put things right,, i saw a picture of a wur with no nylon pipe going to inlet manifold i just thought it was missing .So with the pipe it takes in ambient air pressure .So how will poster know which one he has on his engine?
 

·
Registered
1984 380SL
Joined
·
36 Posts
Discussion Starter #13
So I think I'll do the replacement today - is there anything I need to worry about? Is there pressure in the fuel lines that needs to be released? Will fuel return to the lines easily after the swap?

Seems like it mounts on pretty simple, the vacuum line is simple, the atmosphere rubber is simple - just want to make sure the fuel lines are simple as well.

I'll put down a shop towel around WUR as I replace to catch any gas that comes out, but is that all I need to worry about?
 

·
Registered
1984 380SL
Joined
·
36 Posts
Discussion Starter #16 (Edited)
Well, as with most of my repair attempts - went out there with my hex wrench - pushed and pushed and pulled and the bolt wouldn't budge (I even used a long socket as a sleeve for extra leverage and grip) - then the wrench strips and I'm done for the day. How do you folks get these bolts to budge!?
 

·
Registered
1984 380SL
Joined
·
36 Posts
Discussion Starter #17
Ok, so I swapped the WURs - easy after I got the mounting bolts off. The replacement WUR still required me to pump the gas to start the car - and then hold the gas to keep the car running. And the car was producing a pretty bad smell from the exhaust.

Put the old WUR back on, behavior is the same.

The smell is new. The car stalls at idle even after a bit of warming up - that's new. Did I screw something up here? Or do I just have two bad regulators?
 

·
Premium Member
1983 380 SL
Joined
·
3,187 Posts
The WUR is a "dumb" device that works from a 12 volt source heating a bi-metal that alters the output "control pressure" getting to the top chamber of the FD (Fuel Distributor).
The system pressure lives in the bottom chamber of the fuel distributor. The control pressure lives in the top chamber of the fuel distributor and is controlled by the WUR. The fuel metering plunger lives between the two pressures in its own silo like chamber.

When you first start the engine the WUR provides low fuel pressure to the top chamber (top of the fuel metering plunger) which allows the fuel metering plunger to ride higher in it's chamber thus allowing more of the fuel metering slots to be exposed which results in a mixture enrichment. As the WUR bi-metal heats from the 12 volts supplied to the WUR it slowly raises the "control pressure" (pressure in the top chamber) which forces the fuel metering plunger lower in it's chamber thus exposing less of the fuel metering slots which in turn makes the mixture leaner.

If you suspect the WUR then your first step should have been to check the control pressure. If the WUR is doing its job, then on initial start from cold, the control pressure should be around 20 psi. As the WUR heats (not the engine but the bi-metal in the WUR) it increases the control pressure to somewhere in the area of 50 psi (maybe even 60psi). If those are the results you get when checking the control pressure (checked at the top of the FD) then the WUR is doing it's job and need not be replaced.

The WUR is not to be confused with the cold start valve which is actually just a 9th injector that pours raw gas into the intake when the engine coolant temperature is below a certain value.

Before you start changing more parts, check the system pressure and the control pressure. If you need advice on how to do that just ask... there are many here who will show you how. If both the system pressure and the control pressure check out then it's time to look elsewhere for your problem. There are many things that can cause your symptoms, so we need to take each one in it's turn.
 

·
Outstanding Contributor , Bob's Your Uncle!
-----'83 280 SL----- 5 speed....The PIG
Joined
·
29,626 Posts
And that electrical harness on the WUR needs looking at. No 12V to the WUR and you'll experience some problems.
Post #5
 
1 - 19 of 19 Posts
Top