Faulty fuel pump causing car to run off battery?

Factual Questions
1

I’m pretty sure we’re getting BS’d by the mechanic at the shop we’ve taken our old 1995 Buick Park Avenue to, and I’m looking for some knowledge on this issue so I can either understand it or call BS on it when I talk to the owner about it tomorrow.

Almost 2 weeks ago I stopped for $10 worth of gas and couldn’t get car to crank after pumping. I got a jump off, talked to guy helping me for a few minutes and went to drive home with fingers crossed. I immediately noticed the battery light was on but thought it just needed to be charged by alternator after dying. The car wouldn’t accelerate and would seem to try to choke out when the accelerator was pressed. After about a mile it completely gave up and I had to pull it off the side of the road. The battery had completely drained and it would only ‘clickclickclickclick’ when I tried to crank it.
I had it towed to a shop around the corner that fixed my car the last time with a different problem. As I suspected, they called me and said it was an alternator problem and replaced it with a ‘life time warrantied’ part. A few days later when headed to work, the battery light *again *was on, and the car would start to ‘choke out’ if the RPMs went above 1K. If left around 1K it went a fair speed, and needing to get to work (2nd week at new job after being without work for a year +) I rode it as far as I could until it just kept losing speed like the first time and I had to pull off and call the shop again. They came out, jumped it to get it onto the tow truck (died again while they were turning their truck around into position) and took it back to the shop. When I asked them what problem they found with it, I was specifically told they found NO problem with it but replaced a bad battery cable to see if that helped. When I picked it up the 2nd time the mechanic just kept going on about how the battery was fine, see they tested it and no problems with the battery, see the test sheets?? etc etc etc. I told them I KNOW the battery is good, that it shouldn’t be the problem because it had just been replaced only a month or so ago with a new one. My concern was with the alternator.
The car again drove for a few days until yesterday we left to go get groceries. Again the battery light came on and it wanted to chug and choke out when the accelerator was pressed. This time instead of driving it until it died, since we were near the house still we simply pulled it off the road and called the shop. The person answering the phone, upon hearing it was having the same issue for a third time, stated “AGAIN?? That’s the 2nd alternator that car has had! The mechanic needs to get them from a different source because where they are getting them from obviously has a bad batch!” Mind you, when specifically asked, I was only told they had found no problem the 2nd time but had replaced a ‘bad battery cable’.
When we called after a few hours to get a status update first we’re told that they were ‘just going to crank it up and drive it in’. The mechanic claims that THIS time, it’s ‘not their fault’ and that it seems to be a ‘pilot’ problem…that the battery is fine and it’s just not cranking. We tried to inform him that, yes, it cranked and the battery seems fine because we just didn’t run it into the dead zone like the first two times. Now, even though the symptoms are the same as the first 2 times it died, this guy is trying to claim that it is a different problem and is now blaming the fuel pump which of course means more money. I’m not a mechanic in the least but I don’t understand how a fuel pump issue could be causing my car to run off the battery until dead.
So, again, basically I’m feeling really screwed over by this guy at this point and I’m supposed to speak with the owner about the issue tomorrow so he can “explain” how a faulty fuel pump can be causing my car to run off the battery and die. I’m hoping for a little outside knowledge on this so I can either understand or call bs on them.
And advice or input is appreciated. Thanks.

2

Could be a wiring harness or computer problem.
Looks like this car has a (needlessly complicated) charging system - the voltage regulator gets a signal from the computer telling it to “turn on.”
From Here.
So, the alternator may be fine.
First thing I would do is to check if the alternator is, you know, actually charging the battery.
Put a meter on the battery, and see if the voltage rises towards 14v with the engine running. If it doesn’t, your battery is not being charged.

And, I don’t see how the fuel pump could be involved…

3

Well i certainly am not following everything here but will comment on what i do know.
I call BS on the fuel pump being suspect here (from what is reviled).
I would not eliminate the battery yet, No tester that i know of can prove a battery good without a time period. They do do a good job of confirming a battery as bad.
Your alternator is no good at charging a low battery. You will see included with all new and rebuilt alternators to make sure your battery is good and fully charged before starting. An alternator is a battery maintainer.
When your car is not starting and giving you the click-click-click, turn on your headlamps and watch them when you are trying to start and getting the clicking(solenoid chatter), and if your headlamps stay bright you have a battery cable issue or ground issue.
ETA; If the headlamps dim when trying could also be a cable issue but more likly a low/BAD battery.
I feel for you Brother! best wishes getting this resolved.

4

Paging Rick or Greasy Jack to GQ!

5

Don’t know about the Buick wiring and computer system, but I had “kinda” similar issues with my Jeep Grand Cherokee. Sometimes the alternator charging, sometimes not. Alternator and battery both tested out just fine. Turns out it was the main computer module, which wasn’t sending the appropriate signal to the alternator to turn it’s charging ability on.

I’m betting the fuel pump issues are a result of low voltage. The fuel pump isn’t getting a full 12v+ so it’s acting funky.

6

First the basics. What engine is in this car? Is it the 3800 Series II V-6?

Is the Service Engine light lit? If so, have you had anyone read the codes?

7

A number of cars have the alternator computer controlled. This is not unusual.
I am not a GM expert, but I know from being in the industry rebuilt alternators can be great or they can be junk. As in dead out of the box OR dead in a week.
GM cars also tend to eat fuel pumps.
So the question becomes, can the fuel pump cause the alternator not to charge. As I said I am not a GM expert, but this does not pass the smell test to me. I can’t for the life of me think of a failure mode for the fuel pump that would knock out the charging system.
Now if Gary T or Greasy Jack comes along and has information to the contrary, I have no problem admitting I’m wrong.
Based on the link from beowulff if the car was in my shop, here is what I would do: [ol]
[li]I would spend some serious time looking at the wire and connectors between the alternator and the PCM This could be an issue with a bad or corroded terminal. [/li][li]I would then wiggle the harness with the engine running to see if there is maybe a wiring issue inside the harness (It happens)[/li][li]If the harness and the connectors look ok then I would run the car monitoring the system voltage until the alternator stopped charging. (I’m going to guess the failure is temperature related, based on what has been written) [/li][li] I would then check for voltage on the wire from the PCM to the alternator. If the wire shows voltage the alternator is toast (again)[/li]If the voltage is missing, the PCM is failing.
[/ol]
Please when you speak to the shop, ask them exactly why and how the fuel pump is causing the electrical system to fail. Then post it it here. This I have to hear.

8

I just checked with a GM expert. He agrees with me.

9

I wonder if it could be the ignition control module. My 1991 Park Avenue would run fine until the module got too hot and then it would clunk out. It would crank but never fire. As soon as the module cooled off, it would fire right back up again.

Easy way to check for that is put cold water on it after the stall. If it starts after the cool-down, that’s a pretty sure sign.

10

I am with Rick on this one. Here goes my rant about some “mechanics”.

I had the same problem with my wife’s '95 Park Avenue. Two shops could not find and fix the problem. She got told all kinds of BS about the issue over the course of two weeks. I had to fix it myself. So after working 12 hour days at work I got to work on her rig for four more hours. Lucky me!

It turned out to be the wiring in the harness close to the alternator. I hooked up a voltmeter to the battery. I then started the car, and watched it while I jiggled the wires around the alternator. I could cause the alternator to fail by pushing and pulling on this harness. I unwrapped the harness and checked the wires as I went. Several wires were burned in half. I replaced these wires with new ones. After checking to be sure I had fixed the problem, I re-wrapped the wires. What a mess!

All totaled it took me eight hours over two days to have my wife’s car back on the road again. I sometimes think that all the younger “mechanics” are complete idiots! Most of them seem to have very limited troubleshooting skills. Some are crooks, but I think that most of them just do not have a clue as to how these systems work.

11

Especially if you’ve been driving around with a bad alternator and a nearly dead battery. Odds are good that there are damaged plates and the battery is shot.

12

If the alternator is not charging, there’s a fault in the alternator, PCM (main computer), or the relevant wiring. The fuel pump does not enter the picture.

If I were to reach for a possible (though not particularly plausible) relationship with the fuel pump, it would be the fuel pump relay (not the pump itself) having a short that overloads the fuel pump relay driver in the PCM that somehow affects the charging control circuit in the PCM. Possible, perhaps, but I wouldn’t want to try to defend this notion without some very specific test results that support it.

"The mechanic claims that THIS time, it’s ‘not their fault’ and that it seems to be a ‘pilot’ problem…"
The term “pilot problem” is not one I’ve run across in my 40 year career. The best sense I can make of it is he means the alternator control signal from the PCM isn’t working properly.

"…the battery is fine and it’s just not cranking."
This doesn’t make sense either. If the battery is indeed fine and it won’t crank, that indicates a starting circuit problem (battery cables, ignition switch, starter relay, neutral safety switch, starter), which has nothing to do with the charging circuit and won’t turn on its warning light.

That they put a second alternator in but told you otherwise is quite disconcerting. I don’t know why anyone would be tempted to lie about that. It undermines the trust that you should be able to have in their integrity.

I could see there being defective replacement alternators, a PCM going out, a wiring problem, or some combination of these. I can’t see a faulty fuel pump causing the symptoms described, and I too would love to hear the explanation for that.

It sounds to me like there’s a lack of sufficient mechanical competence and a lack of adequate communication skills on the shop’s part. And that’s stating it nicely.

I agree that at this point the battery might be suspect. It may be wise to replace it regardless of what else is found.

Good luck, and please keep us posted.