Fuel Pump Early failure detection experiment; results - Saab 9-5 Bulletin Board - Saabnet.com
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Fuel pumps are vexxing little things, they fail seemingly without warning. I hate that.
Encouraged by Anders posts I thought it might be worth trying to monitor the pump and see if a failure pattern could be detected. So about 7 years ago with ~82k on the car, I began recording the amp draw signature; Credit goes to Anders for this idea.
Here's how I did it with ~$150 worth of equipment sourced from ebay: http://www.saabnet.com/tsn/members/gallery.html?memberID=473&do=show&id=10773
At that time (dec-2007, 82k) the signature looked good:
~5 years later (jun-2012, 134k), with no symptoms whatsoever, I saw the first change in the signature:
(see my post here for more details http://www.saabnet.com/tsn/bb/9-5/index.html?bID=241528)
At the time I was not decided if I should replace the FP, or wait. I decided to "run to failure" to see just what would happen, how good a predictor this was, and how long I had until the pump failed completely.
At about 145k I started to notice symptoms of a weak or failing pump:
- occasional hard starting in the mornings
- frequent hard starts when fuel level was low.
- stumbling on hard acceleration
In my quest to push this until failure, none of this deterred me from using the car. In fact, last night I returned from a 400 mi trip. (granted, not a wise choice to take a car with multiple symptoms of a failing fuel pump on a 400 mi trip ... but it worked out)
Complete failure came this morning my driveway at ~154k. (btw it may or may not be significant that my driveway is common failure location for Saab fuel pumps!)
This is a very small sample, and there are likely other failure modes of a fuel pump. But here is my take:
1 - monitor the fuel pump amp draw twice a year or every 10k. Erratic signature is the first, and a very early, sign of failure
2 - be aware of seemingly benign user symptoms. These symptoms, combined with the mileage/age of the fuel pump, are significant and indicate that you should replace the fuel pump at your earliest convenience:
- hard starts in the morning
- stumbling on hard acceleration
these symptoms are often dismissed, especially since they are infrequent or intermittent.
Another approach is to replace the fuel pump every 120k miles. this is reasonable too considering that the cost to replace the insert is <$100 and I've heard that the entire assembly can be had for ~$250 now.
me, I'll continue to monitor and replace when the signature (or symptoms) suggest that the end is near.
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(#473) 
[Profile/Gallery]
(more from bobc) on Mon, 29 Sep 2014 11:37:11
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, Tue, 30 Sep 2014 18:36:05