Ungo Alarm, fuel-cutoff valves, and warm-up regulators

Hi, all-

Over the last couple of weeks I've been preparing my car for a fun drive from Virginia to Michigan's Woodward Dream Cruise. As part of its sprucing up, I replaced the radio with a new unit from Alpine, and in the process uncovered a bird's nest of wires attached to what I've learned is part of an Ungo alarm system. Did all of the 400i's from 1983 come with this system? A number of its wires had been disconnected by the previous owner leaving the system completely nonfunctional, and so I removed it from the vehicle while adding the new stereo wiring.

This is where my simple radio install may have become a more complex fuel problem. On each engine bank, the alarm was connected to an electric valve that runs inline one of the fuel lines between the warm-up regulator and the fuel distributor. I'm not certain whether it's on the regulator inlet or outlet fuel line, although it’s on the line that connects to the side of the fuel distrubutor rather than the top, and I think that's the inlet. I don't see these valves in the workshop manual, and so I presume they were installed when the alarm was installed as fuel cut-off valves, although their placement in the fuel circuit has me puzzled.

The problem arises when I remove them from the fuel circuit. The car will run momentarily, sputter and then stall. It cannot be restarted until the valves are put back into the fuel circuit (disconnected electrically), with 10 to 20 seconds of cranking.

At this point I should mention that while I've had some experience on Volvos and VW's with similar forms of the Bosch fuel injection setup, I've never owned one with a warm-up regulator, and so my knowledge is short on this topic. If I've understood the workshop manual correctly, the regulator reduces its outlet pressure to the fuel distributor to enrich the mixture, and increases pressure to lean out the mixture. So I imagine that with the warm-up regulator removed from the circuit (i.e. the alarm fuel cut-off valve activated, or fuel line capped at distributor), the car should run rich, perhaps so rich that it wouldn’t run at all. On the other hand, with the alarm cut-off valves removed, the regulators should be receiving full fuel pressure, and delivering a pressure to the distributor determined by engine temperature and vacuum (lower pressure for richer mixture when cold or under throttle, higher pressure for leaner mixture when warm and under light throttle).

As I discovered this problem last night, I haven’t had a chance to check fuel pressures or vacuum lines. But before I start, I wanted to confirm what these valves are, and if any of you have them too. Also, is it common for the warm-up regulators to fail, and do they normally fail open-circuit (high-pressure) or closed-circuit (low pressure)?

Thanks in advance for any advice.

Bret

 

Hi, Steve-

Thanks for your reply... this make a lot of sense. I was envisioning the fuel flow in reverse, but your description clears up the function for me.

It also brought to my attention that the fuel cut-offs are on a line that was not in the original fuel circuit. I'll attach a couple of photos to illustrate.

To accommodate the fuel cutoff, a fuel line was added between the input of the WUR (my new acronym for the day!), and the fuel return on the distributor. Although I haven't tested them, I'm guessing that the valve is closed when de-energized, effectively removing the new fuel circuit and allowing the control pressure to be managed by the WUR. When the alarm was activated, the valve likely opens, bypassing the WUR and bringing the control pressure low. By removing the valves, I did the same thing.

What I think I'll do this evening is remove the additional fuel line along with the valve and see where this leaves me, and before that I'll go through the entire system and make sure that all of the vacuum lines are in order. I suspect you're right that I may need to tweak the system once it is all back to stock. Now where did I hide those pressure gauges?

Thanks again,

Bret
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Hi Steve-

You may be right. I removed 2 boxes in the process of taking out the alarm system, and perhaps one of them was a sort of ECU. Given that so much of these boxes were disconnected prior to my removing them, it was impossible for me to tell whether the second box may have served another purpose. Looking more closely at the valves, they do appear to be something more than simple flow valves.

The good news is that with the valves and added fuel lines removed, my car starts right up and seems to be running a bit more smoothly at idle. I'll be checking the pressures tomorrow to confirm there's no residual issues.

Thanks for all of your help on this one!

Bret