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Re: Fuel Pump, early failure detection? Posted by SWEDECAR [Email]  (#112)  [Profile/Gallery]
(more from SWEDECAR) on Mon, 25 Jun 2012 08:57:31
In Reply to: Fuel Pump, early failure detection?, bobc  [Profile/Gallery]
, Sun, 24 Jun 2012 21:31:05
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I'm not sure when to call it quit since most samples has been taken when the car came in on a hook and I scared the pump back to life banging on the tank.
This one however is a 2001 9-3 where we were chasing a no start problem which turned out to be both a failing CKP sensor (easy diagnose) and then a bad AAA battery that failed sitting overnight and then came back to life the more times you load tested it or tried to crank over the engine (very strange problem indeed).
I did run a amp ripple test of the pump to see if that could be the no start problem and it looked like this which is suspect enough but no clear cut case of being done for.
Customer thought he had had the pump replaced by the dealer over the broken catch tab recall but I said that most likely they only installed the metal brace if it needed it.
Anyway, he wanted me to replace the pump as well based on this and that I could not promise how long the pump would last.
This pump might have been replaced since it didn't have the metal bracket but also didn't have any broken catch tabs so it is hard to say.
What I thought was odd though was when I cut it open to look at the copper commutator and found all plates being blackish in color and the two brushes in good condition.
Scratching on the commutator surface revealed that they were in fact of some carbon composite instead of copper so it looks like that Walbro and maybe others too have starting to use new materials in the commutator.
I could not really find any evidence why the ripple looked like it did but one theory might be if the commutator plane is not flat enough (like a warped brake rotor) maybe it can fling the brushes away enough to create that rippled?
Anywho, one interesting outcome of this was when the customer called me a week later letting me know that the car run much better and that slight stumble at idle he had had for awhile was gone, a stumble that was still present after I replaced the CKP sensor a few weeks earlier.
So maybe this pump just didn't have enough oomph to keep up at all times.
Anders
, Sun, 24 Jun 2012 21:31:05, Mon, 25 Jun 2012 08:57:31 <-- Viewing This Message, Mon, 25 Jun 2012 07:17:29
, Mon, 25 Jun 2012 16:41:25, Mon, 25 Jun 2012 07:01:44, Sun, 24 Jun 2012 22:22:07
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