1998 S70 non-turbo air pump replacement and decreased mpg

kscomp0 · Post by **kscomp0** » 11 Feb 2007, 19:44

This is a 1998 S70 non-turbo with approximately 115,000 that was made for the U.S. market.

I had the local dealership read the codes in response to a check engine light and was informed that the air pump was malfunctioning and should be replaced; I was quoted a cost of $700. Thankfully, I ran across this site and read the repair thread (https://www.matthewsvolvosite.com/chat/p ... php?t=8537) that was based on the information at:
http://volvospeed.com/Repair/airpump1.php

Volvospeed recommended that: "When undertaking the repair, install a new SAS valve with gasket, Air Pump and relay.", but the OP in the thread on this site said that: "I took all the advice:
replace SAS
replace solenoid
replace pump output hose"

Is it necessary or also recommended to replace the solenoid, and is this the solenoid valve marked by 13 on the parts list at http://www.fcpgroton.com/csv70/csv70airpump.htm
Would a faulty solenoid have come up as another error code?

Also, page 1 of the volvospeed article states that "When any of these codes are set, fuel trim is disabled." My wife noticed a decrease in the gas mileage. I don't have exact numbers on the gas mileage, but the decrease was significant enough to be noticed and the tire pressure was normal.

Could the faulty air pump be causing the decreased gas mileage due to the fuel trim being disabled?

I believe that the fcpgroton diagram contains the parts that I need (right?), but does anyone know of another online supplier for these parts that might be cheaper and that people have used?

Thank you for any advice.

greasefingerss · Post by **greasefingerss** » 11 Feb 2007, 20:39

It would not be logical to me that a bad air pump would disable the fuel trim. The air is introduced after the combustion process and I believe that it is only used in Open Loop Mode (a cold engine; before it reaches operating temperature). Most vehicles do use the oxygen sensor until Closed Loop mode! Nothing makes sense here so if I understand it correctly the air pump is used only for the first 10 to 20 minutes (depending on the ambient temperature or the time it takes for the coolant to reach 186 F (Open Loop Mode). Maybe someone with more experience could explain it.

With engines that I have worked on, a sudden drop in fuel mileage is due to misfiring (engine in need of an electrical tune-up) or a drifting/bad O2 sensor.

Please realize that I am new to Volvo

Post by **pfeener** » 11 Feb 2007, 21:38

The air pump CEL will disable the fuel trim, but I've never noticed any drop in gas mileage when I had this CEL. Also the air pump will run in both open and closed loop conditions. It runs for a couple of minutes when the car is started cold, but will also run in other situations when the car is fully warmed up.The O2 sensor is typically good for about 100K miles. If yours is over that I would look to the front O2 sensor first to resolve your drop in gas mileage.

Parts from FCP are about as cheap as anywhere. I recommend you stick with genuine Volvo parts.

greasefingerss · Post by **greasefingerss** » 12 Feb 2007, 05:09

pfeener wrote:The air pump CEL will disable the fuel trim. Also the air pump will run in both open and closed loop conditions. It runs for a couple of minutes when the car is started cold, but will also run in other situations when the car is fully warmed up.

Well that does it then

kscomp0 · Post by **kscomp0** » 12 Feb 2007, 06:11

Thank you for the replies!

Will a faulty O2 sensor initiate an error code?

turbotim2 · Post by **turbotim2** » 12 Feb 2007, 06:28

What was the code you got (or the dealer got)? I would not replace all of the components at once. You can test the air pump, it will either run or not. If it does run then look at your relay, and so on. And yes, a faulty O2 sensor will send a code. That code is very important in your diagnosis.

kscomp0 · Post by **kscomp0** » 12 Feb 2007, 08:29

I called to check on the codes, but they did not record them. At the time, they recommended an air pump and check valve (and an ABS module because that light was also on), so I would think that there wasn't an error code for the O2 sensor.

I should have a good estimate of the mpg later this week.

To test the air pump: Pull it out and hook it up to a battery to see if it runs? Any safety warnings?

io · Post by io » 12 Feb 2007, 10:06

To test the air pump you don't even have to take it out of the car. The relay for the pump is located under the hood in a kidney shaped box in front of the fuse box (I think there are three tabs used to release the cover from this box). Under the cover is a diagram explaining what each of the relays is for. Remove the relay for the air pump. You'll notice that this relay has four connectors on the bottom of it - two large spade connectors and two small ones.

To test the pump, short (connect together) the two large spade connecters in the kidney shaped box with a piece of gauge 14 or thicker wire. The key does not have to be on. If you hear the pump running when you short the connectors it is OK.

You can test the relay itself by swapping it with the "Main" relay that is beside it. After you swap them, if the car will start the relay is OK.

Hope this helps,
Nick

kscomp0 · Post by **kscomp0** » 12 Feb 2007, 11:41

Thanks Nick--that is a huge help. I really appreciate you taking the time to reply.

greasefingerss · Post by **greasefingerss** » 12 Feb 2007, 17:07

My air pump goes on as soon as the ignition key is placed in position II (not starting the engine) and with a cold engine.