Under hood pump runs after motor turned off on 94 PA

[Tuffguy610]

Hey all,
My co-worker has a 94 Park Ave that he just picked up. Its got 80k miles on it, runs pretty good. We found a pump under the hood right behind the airbox (L27 car) that runs for about five minutes after the car is shut off and the key removed. It looks as if its some sort of vacuum emissions device or something. What is it? Can anybody clarify what it is and what its purpose is?? Thanks for your help.

[willwren]

That's the compressor for the ELC (electronic level control), the air portion of the rear gas struts, designed to keep the rear of the car at the proper height in spite of heavy loads. Its' also a calculated part of the roll equation in suspension and handling.

I suspect the rear struts are leaking air, even if the gas portion is good. Start looking for leaks. It's not uncommon for it to run with the car off (normal), but not for 5 minutes at a time.

[J Wikoff]

It would probably hit some pressure cutoff and the rear end would be sky high if it was, but check to see if the sensor arm on the right rear suspension hasn't been knocked off, too.

[sonoma_zr2]

On the 94, the elc is hot at all times. If the air system was leaking, it would be coming on periodically and draining the battery. On the 97, the systems level sensor has a solid state relay that kicks off the system after 5 mins of runtime, but is not hot when the car is off. If the 94 uses the same level sensor, then maybe it works off of the same principle.

[willwren]

The system changed between 94 and 95 in how it works. 95 is not hot at all times, but 94 is. The overload/runtime circuit is the same between them though. The only difference being whether it runs of always on or ACC power.

[TDS-94SSEi]

Ha, I have to say that the first time I encountered this on my 94 Bonne, I was concerned. Was working on something in the driveway and the car was parked nearby. All of a sudden I heard the compressor kick on and that caught me by surprise. Yes, my OE struts were leaking at the time. And if we left the car sit undriven for a few days, the battery would usually be dead when we went to start it afterwards.

Replaced the OE struts and haven't experienced it since. found back then that, if I pulled the compressor fuse, that the rear end of the car really wanted to sag down, measured almost 1-1/2" lower than where the leveling system wanted to keep it.