Warm up regulator 1979 320i

[BMC New York]

Anyone know how to test this to see if it is working correctly?

[Cjp2003]

Cis fuel pressure tester. What's wrong with your car?

[BMC New York]

Very hard to start but once it's running it runs great even tho the idle seems a little high

[Tom D]

hard cold start or warm?

[maternhuo]

it runs great even tho the idle seems a little high

[BMC New York]

Cold start, once warmed up it is good

[Cjp2003]

Yeah it's possibly a
dirty screen in the WUR.

[Tom D]

^ most likely.

it's the WUR's job to enrichen the fuel mixture needed for cold running and it does so by bleeding off some of the gas pressure of the operating system. except for the intake screen getting dirty there's not much to go wrong with them, but if the screen is dirty and gas does not flow it will not like starting from cold.

remove the WUR and soak the screen with some carb cleaner.

[BMC New York]

Tom, I am getting fuel from the return like on the cold start injector. I have not tested the injector, do they work in conjunction? I am new to this fuel injection stuff

[Tom D]

there is a 5th injector that gives a quick squirt of fuel at start up but doesn't have enough duration to warm up an engine, that task falls on the WUR.

the fuel pump supplies more then enough fuel to run the system and so the excess to dumped back into the tank. the WUR takes the already pressurized gas that's in the fuel distributor and bleeds off some of the pressure, that gas is also dumped back into the tank.

there are three different fuel circuits, system, control and the cold start injector.

the system runs the car and operates at about 75psi.
the control runs the cold/warm up and runs at about 60psi plus. it does so by bleeding off the pressure of the system. as the engine warms the port in the WUR gets smaller and smaller and the pressure goes up and up until the port actually closes and the system pressure takes over.

[pommeree]

Control pressure specifications.
The graph depicts control pressure as it relates to engine temp.

[BMC New York]

Well I guess I will try and find this screen for the WUR and let you guys know how I make out, I have been tempted to just put an I take and carb on it

[BMC New York]

Seems to be the cold start injector was bad so after I change that I will let everyone know if I still have a problem and see where to go from there thanks again for the help

[Tom D]

BM, start with the WUR, that's where your problem is.

[BMC New York]

Ok, had the cold start injector cleaned and check it is NOT getting any signal( power ) to open when the key is on or when cranking it. I got 7.2 volts on the power terminal and nothing from either terminal that goes to the WUR. Ok I am stumped once again.

[BMC New York]

Ok change the cold start injector after having it cleaned and checked. Getting 7.2 volts at the time switch but nothing from the WUR at all, ok I am stumped once again

[Tom D]

power, or lack of it to the WUR is not the problem.

the WUR is mounted directly to the engine block and therefore is heated and cooled by the block itself. here's how it works

engine block/WUR are cold and the pressure bleed off valve inside the WUR is open. as I explained above, by bleeding off some of the fuel's operating pressure the injectors will run rich for warm up operation. as the engine, block and WUR warm up the WUR's valve is slowly closed and the fuel's operating pressure is raise back up to 75psi. that's it, simple as that. so what's happening most likely in your case is the screen in the WUR is clogged and not allowing the pressure to pass through and by doing so lower the system pressure, you must remove the lines and soak the screen with carb cleaner.

okay now for the electrical. the power going to the WUR is a timed thermo switch. it works by laminating two thin metal strips back to back made from different alloys. when you heat the bi-metal strip it will expand, but because not all metals expand at the same rate the strip will bend to one side. this strip will push on the valve as it bends and close the WUR's valve.

so now put it all together. the engine is cold and the WUR's valve is open. you start the car and immediately the system' pressure is dropped, the fuel runs rich, the bi-metal strip recieves power and starts to heat up eventually closing the WUR's valve before the WUR itself actually fully warms, this was done for emission reasons.

[pommeree]

Another important point:
The cold start injector is controlled by the thermal/time switch on the coolant neck.
That system is completely independent from the WUR.

The WUR also receives power to the bimetallic strip per Tom's description so that control pressure is increased at a prescribed rate rather than rely on the atmospheric conditions along side the block.

HTH.

[BMC New York]

If the screen is clog and this problem is still there is there any where that rebuilds the WUR or is it a do it your self thing?

[Tom D]

there is an outline in the FAQ/DIY section above.

- - - Updated - - -

one more thing. the screen doesn't get clogged by crap in the gasoline so don't be looking for a black and dirty mess, but rather from the gas turning to varnish which is invisible to the eye.

just because it looks clean doesn't mean it's passing fuel.

[BMC New York]

I can't find the FAQ/DIY. Section on the app, what a day

[BMC New York]

Lol never mind blonde moment

[BMC New York]

Is there any voltage reading off the connector that plugs in to the WUR? Mine is nothing, just wondering

[David320i]

there is an outline in the FAQ/DIY section above.

- - - Updated - - -

one more thing. the screen doesn't get clogged by crap in the gasoline so don't be looking for a black and dirty mess, but rather from the gas turning to varnish which is invisible to the eye.

just because it looks clean doesn't mean it's passing fuel.

Old thread alert. My '79 320i is experiencing the same cold start symptoms. In addition to the difficult starting, once the engine eventually runs I have to apply enough throttle (around 2K rpm), to keep the engine running. Also, there is a large cloud of white smoke coming out of the exhaust and goes away once the engine is warmed up a bit. I have tested the cold start and that seems to be fine. Thanks Tom D for the diagnosis. I just put the car in storage for the winter, so it will be Spring before I have a chance to remove and clean the WUR. I appreciate the info.

[BC535is]

Having first hand experience back in the day with an e21 and the notoriously finicky WUR, it needed to be tested with an inline pressure guage setup (custom made) and adjusted to obtain a good cold start mixture. It is a quasi adjustment that is more trial and error. Maybe a new WUR is an option. All things considered the associated temp sensors are also suspect and easier to deal with.
Good car with a few quirks. The e10 was such a simple and easy car to maintain - but that seems to be the way we look back on prior BMW series, isn't it?

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