Compression test questions

patcal · Post by **patcal** » 15 Oct 2021, 12:11

Want to do a compression test tomorrow. Need to know which fuse or relay to remove so as to disable the fuel pump & ignition. This is on my 2004 S60 2.5T. Thanks.

TisMe · Post by **TisMe** » 15 Oct 2021, 13:59

My fuel pump relay in my XC70 was in the panel to the left of the steering wheel. Read the diagram on the rear of the panel, your fuses could be configured different from my car.

If it's not there it's gonna be under your hood, you'll find it with swiftness. I doubt a fuel pump relay will be buried in the trunk.

patcal · Post by **patcal** » 15 Oct 2021, 14:13

TisMe wrote: 15 Oct 2021, 13:59 My fuel pump relay in my XC70 was in the panel to the left of the steering wheel. Read the diagram on the rear of the panel, your fuses could be configured different from my car.

If it's not there it's gonna be under your hood, you'll find it with swiftness. I doubt a fuel pump relay will be buried in the trunk.

Thanks

TisMe · Post by **TisMe** » 15 Oct 2021, 14:52

patcal wrote: 15 Oct 2021, 14:13
TisMe wrote: 15 Oct 2021, 13:59 My fuel pump relay in my XC70 was in the panel to the left of the steering wheel. Read the diagram on the rear of the panel, your fuses could be configured different from my car.

If it's not there it's gonna be under your hood, you'll find it with swiftness. I doubt a fuel pump relay will be buried in the trunk.
Thanks

No worries!

Just checked my car, it's fuse 33, a 15A. Again your mileage may vary, different model and all that.

Post by **RickHaleParker** » 15 Oct 2021, 16:33

patcal wrote: 15 Oct 2021, 12:11 Want to do a compression test tomorrow. Need to know which fuse or relay to remove so as to disable the fuel pump & ignition. This is on my 2004 S60 2.5T. Thanks.

No need to pull fuses and relays.

Even with the fuel pump cut off, the injectors will still spray fuel until the fuel pressure is pumped down. You can reach down and disconnect the fuel injectors. That will cut off the fuel delivery immediately.

Removing the ignition coils and the spark plugs to do the compression test will shut down the ignition.

patcal · Post by **patcal** » 18 Oct 2021, 10:48

Well I finally got that compression test done. I only did a dry test. The numbers were:

#1=155
#2=135
#3=160
#4=135
#5=125.

Number 5 seems a bit low. Plugs looked OK but they were NGK & I had the Volvo plugs on hand. Any thoughts on those numbers? Thanks.

ignatz · Post by **ignatz** » 18 Oct 2021, 15:02

There's a 24.56% difference between 160 and 125. If those readings were correctly taken, that indicates something wrong.
How does the car run?

patcal · Post by **patcal** » 18 Oct 2021, 15:17

ignatz wrote: 18 Oct 2021, 15:02 There's a 24.56% difference between 160 and 125. If those readings were correctly taken, that indicates something wrong.
How does the car run?

Car runs great, great gas mileage but its using oil. Since my last oil change, 1700 miles ago, I have had to add 2 quarts to keep it toped off. No leaks & no smoke. Not sure what is going on.

TisMe · Post by **TisMe** » 18 Oct 2021, 15:30

This could be a silly inference, but perhaps you just haven't found the leak yet? Seems like a fair amount of oil to "burn" when your engine is puttering with gusto.

Also, have you run an OBD scanner just for fun? Probably won't help diagnosing your oil consumption but could maybe throw a code with subtle inference to your compression variation.

patcal · Post by **patcal** » 18 Oct 2021, 15:35

TisMe wrote: 18 Oct 2021, 15:30 This could be a silly inference, but perhaps you just haven't found the leak yet? Seems like a fair amount of oil to "burn" when your engine is puttering with gusto.

Also, have you run an OBD scanner just for fun? Probably won't help diagnosing your oil consumption but could maybe throw a code regarding your compression variation.

It really does run well. True on the oil leak. Nothing dripping or staining where I park. I hooked up VIDA & there where no codes. I haven't used the compression tester in about 10 years. I have heard of them sometimes being inaccurate. Maybe I will buy another one redo the test dry & wet this time.