6mil928

In the year and a half that I've owned my 928 I've changed the fuel filter on it twice. I'm getting a surging again and think it may need to be changed again. If I'm lucky I've put on 4-5k miles since owning the car. How often do you guys change or through performance feel that your fuel filter requires changing?

SeanR

Jason, have you had the tank out of it for a cleaning? The filters don't need to be changed often. I'd look elsewhere for the issue.

6mil928

You might be right Sean. I was considering that as well. Just getting a feel for what the norm is

dr bob

I just broke 90k on my S4, and figger I'm at about half of normal fuel filter life. I do have a couple on the shelf just in case though.

A sage 928 advisor, whose name I won't mention cuz I don't want Jim Bailey to be embarassed, once opined that he had never seen a fuel filter replacement cure a no-start problem. I'll speculate that Jim sold a lot of fuel filters anyway.

Based on that and the tiny amount of experience I've had, I'll postulate that a fuel filter won't cause siurging in a car at idle. Ever. At full oad only. If it runs OK at full load yet surges anywhere short of that maximum fuel demand, the problem is not the fuel filter. Confirm this with a rail-mounted pressure gauge or with exhaust CO feedback from the sensor. Change the sensor becuase it's cheap and easy to rule it out completely. If you have a tank full of rocks, it makse sense, Of course if you have a tank full of rocks and sand, you should probably remove the rocks and sand from the tank anyway. Think hot soapy water and a shop vac after draining the tank of fuel completely. Rinse, repeat...

Mako 928

I changed mine when I first bought the car 6 years ago as part of a "base line" tune up.
I again just changed it last month when I replaced the fuel pump.
So for me it is time to change it when.....
1. New purchase of a car.
2. change the fuel pump.

zoltan944

Dr. Bob sounds right, there is so much fuel being sent up front that is returning that under low load conditions it would unlikely be the fuel filter.
Having said that, I would agree with Greg, as those are the only 2 times I could ever think I would change it. Undocumented history of a 10-20yo car not having it done and along with the fuel pump

Cheburator

Look at your maintainance schedule in the warranty/service book. The one which came with my German LHD 1990GT says that Fuel Fulter should be changed every 40,000km or 25,000 miles

Vlocity

I change my fuel filter every other year and that is probably WAY to often. What I would do if nothing else seems to be the fix would be to check the strainer in the tank, as I know that the plastic ones can collapse then replace the fuel pump. You also have to consider that the fuel pump is being run by a small wire that is now 20 plus years old.

For my SC car, I had a friend build be a new strainer built around the original end. A large spring was welded to it and then covered in brass mesh to act as the strainer. I ran a 12 AN line to the new Bosch 044 race pump. For the electric I put a designated relay in the battery box and used a 10 gauge wire for both power and ground and lengthened the existing pump positive wire as the "trigger" for the relay.

This may be overkill on a NA car, but putting in a fresh pump and a designated relay at the back of the car would be a smart thing to do if you have to go in there.

Good luck.

Can you verify that you have a good MAF by switching with some one?

Ken

6mil928

I don't have a maf on my 81 I have an AFM.

Vlocity

Doh, Should have looked at the model year.

Fuel pump and a designated relay if all else fails. Is the pump original?

Ken

6mil928

Far as I know. I have not changed it. Car is running fairly strong. I just have this surging that bugs me. Seems like I changed the fuel filter last time and it cured it. I've done so much work on the car all the repairs are starting to run together in my mind

jackson101

Sounds like the injection control is trying to compensate for something,...02 readings. Does this car have a frequency valve that constantly adjust the fuel pressure according to 02 sensor readings ( Lambda sensor feedback,etc )? Also, when you own and maintane multiple vehicles, get yourself some maint. software to keep track of repairs, cost, part #'s, contacts and details...etc. A free version I use is called " cars " , it's free and fairly comprehensive. Down load it right from the net.

Vlocity

Mike,

I know how that is...I think to myself crap, I just changed that and go back and find a receipt and it was 6 or 7 years ago. I've been wrenching on mine for 15 years now.

Let us know what you decide to do.

Ken

James Bailey

As mentioned they seldom cause a running issue and IF they do it is at high load high RPM. In the US now that all the underground gas station tanks are fiberglass and ground waterleaks etc are closely checked contaminated fuel is pretty much a thing of the past. Does it hurt to change it more often ? probably not unless you tweek the metal hardline trying to get it off And apparently I did not SELL enough fuel filters nor did I sell trans filter service kits to someone who was hoping that it was all their Roger box needed to start shifting right again !

6mil928

Good advice on the software I'll check it out. I changed the O2 sensor after I bought the car. I pulled it when I dropped the exhaust recently and it looked good. Could be going bad I guess. I was also wondering if my air fuel mixture might be off. I believe it can be adjusted on the throttle body. Someone a while back was talking about back firing on deceleration due to the mixture being too lean. Mine does back firing when I let off the gas most of the time.