850 Air Pump – Check Engine Light

CAR: 1997 850 GLT Wagon - 75000 miles

PROBLEM:

Air pump sounded like a fork stuck in garbage disposal at every cold
start, is now not running at all. Check engine light is on.

QUESTIONS:

1. Is there any way to permanently disconnect or disable air pump
without triggering check engine codes or other engine or ECU problems?
I live in warm climate (Los Angeles) so air pump does very little good
and repair is $$$.

2. Is it true that "fuel trim" is disabled when check engine light is
on? What happens if you keep driving like this?

 

No. You would have to reprogram the ECU. The air pump reduces
emissions during cold starts, and even in your climate your first start
of the day will classify as a cold start.

Whether fuel trim is disabled when the light is on depends on what fault
turns the light on. In this case, fuel trim is not disabled. However
with the light on for this fault, you would not know when you had
another fault.

If you fix it, make sure that you change the valve that closes off the
air pump from the exhaust. This sticks open, and moisture from the
exhaust collects in the air pump which is what kills it.

--
Mike F.
Thornhill (near Toronto), Ont.

NOTE: new address!!
Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

I was told by a dealer that if I just ignored the air pump problem
that it would lead after some time to failure of the O2 sensors,
and that failed O2 sensors would eventually ruin the catalytic
converter. You probably don't want to go there.

 

Mike -

I thought the moisture comes from the poor design of the air pump
mounting location in the wheel well area. So you're saying it's the
valve sticking that causes the pump to fill with water and rust out? I
think the whole air-pump system is a lot of expensive, difficult to
access parts for very little benefit in return. So, below are the best
prices I could find for the air pump job. The valve alone is an $86
item. At the risk of sounding cheap, is there any way to tell if the
valve is okay without replacing it? Thanks.

Prices from www.fcpgroton.com

New Air Pump 1996-1997 (Pierburg) $265.00
Air Pump Check Valve (Anti Backfire Valve) Genuine Volvo $86.00
Gasket for Air Pump Check Valve Genuine Volvo $2.10
Clamp For Air pump check valve 1 req Genuine Volvo $1.75
Clamp for Air pump check valve 2 req Genuine Volvo $1.35
Air Pump Relay 1994-1997 Genuine Volvo $39.95

Total (US)$397.55

 

I thought the air pump just blew air into the exhaust gases to help
the cat warm up faster (a bit like blowing onto the embers of a fire).
If the air pump tube is blocked up, then how would this lead to the
failure of the O2 sensors?

 

The valve opens with vacuum. With no vacuum applied it should be closed
tight. If you take the larger hose off the valve, then no exhaust
should come out. If you then apply vacuum to the smaller hose, then
exhaust should come out. However, I doubt that your valve is good,
since the airpump is bad.

--
Mike F.
Thornhill (near Toronto), Ont.

NOTE: new address!!
Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

The "air pump" is actually a vacuum pump. A turbo has pressure on the
intake, not vacuum. That is why you have a vacuum pump. It provides vacuum
for the heater/AC and cruise controls. Call a junkyard. Should get one for
less than $50.