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New problem: Car died, started and ran briefly, now dead

 
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bureau13  



Joined: 07 Sep 2017
Posts: 81
Location: South Florida

PostPosted: Sun Apr 08, 2018 11:40 am    Post subject: New problem: Car died, started and ran briefly, now dead Reply with quote

So basically, I was almost home, when I pulled up to a stop sign and the car died, dash warning lights on etc. I thought maybe I somehow just stalled it. Started it back up again, drove a little further, then it started sputtering and died again. Started it up again, very sputtery but got a little momentum and coasted most of the way home, pushed it up to the curb and parked it. Won't start at all now (it cranks, just won't catch). During the time when it was running rough, it gave a couple pretty loud backfires.

Any thoughts? I'm wondering if I have a fuel issue...one of the pumps maybe?
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1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
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1987 RX-7 Turbo II (Sold)
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bureau13  



Joined: 07 Sep 2017
Posts: 81
Location: South Florida

PostPosted: Sun Apr 08, 2018 1:50 pm    Post subject: Reply with quote

Quick question about fuel pump behavior in this car: If I put the key in and turn it on (but not all the way to crank it) I hear the fuel pump (or something) hum briefly...maybe a second...and then stop. Is that correct? Under normal circumstances should it do that? Or should it keep running?
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-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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bureau13  



Joined: 07 Sep 2017
Posts: 81
Location: South Florida

PostPosted: Mon Apr 09, 2018 1:21 am    Post subject: Reply with quote

I jumpered the relay (that relay box is NOT positioned for convenient access!) and both pumps appear to be running. In fact, it then started, and I moved it to my driveway.

At which time I noticed something else. Well, I noticed it before, but I'm dumb and it didn't occur to me. My fuel light was on, but the gauge was reading a quarter tank. I had been assuming the light was just coming on too early, because the gauge generally seems to function properly. Is there some sort of sensor that shuts off the fuel pump if it detects a low fuel situation? Not sure what the point of that would be, but given that it won't start with the relay (although the fuel pump stops and starts with key, which seems to be correct) but will with the jumper tells me that's the problem, or it's the relay somehow...like it briefly will connect and then can't hold it?

I'm going to order another relay just in case.
_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1559
Location: MI

PostPosted: Mon Apr 09, 2018 1:53 am    Post subject: Reply with quote

Overboost switch possibly... The brown wire I think going to the pressure switch on your intake just before your TB, ground that wire to the chassis, test that pressure switch for good ground on its contact..

I think that is the most likely, could also be that relays fault, or the tack signal to the relay..

Buzzing.. You sure you are talking about the pumps or the frequency valve? under the hood?
IIRC the freq valve will die along with the fuel pump when fuel pump power gets killed by the overboost switch, and tack signal, or relay fault, or bad grounds..
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Fifty50Plus  



Joined: 28 Feb 2008
Posts: 1008
Location: Washington DC area

PostPosted: Mon Apr 09, 2018 5:47 am    Post subject: Reply with quote

Before you go crazy chasing fuel pump cut off wiring, throw a few gallons into the tank. I'd trust the tank empty light just slightly more than the fuel gauge.
Sometimes the simple solution is the answer.
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gerben1986  



Joined: 13 Mar 2008
Posts: 218
Location: The Netherlands

PostPosted: Mon Apr 09, 2018 6:17 am    Post subject: Reply with quote

Also check the ignition coil, I also have had the experience that the car died because the ignition coil was getting too hot, could restart and drive another 10 meters. But then the car quited and a couple of hours later it started again...
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bureau13  



Joined: 07 Sep 2017
Posts: 81
Location: South Florida

PostPosted: Mon Apr 09, 2018 10:41 am    Post subject: Reply with quote

Fifty50Plus wins the prize! I knew it wasn't the overboost switch, since that is already disconnected and the wire grounded. The buzzing to which I referred was from the back, the fuel pumps. I jumpered the relay and felt both the external pump and the tank near the bottom, both were vibrating a bit like the pump was working.

The gauge fooled me because I've seen it show almost empty, after the light had been on for a while, but I guess it's not that precise. And I'm still not really sure why jumpering the relay allowed it to start and run...but I added fuel and put the relay back in, and it seemed to run fine. I guess I'll have to keep an eye on it, but it seems I just need to trust that when the light tells me to get gas, I should do that.

Fifty50Plus wrote:
Before you go crazy chasing fuel pump cut off wiring, throw a few gallons into the tank. I'd trust the tank empty light just slightly more than the fuel gauge.
Sometimes the simple solution is the answer.

_________________
-----------------------------------------
1982 931
1986.5 Silver 928S
2007 Hummer H3 (Daily Driver)

Past lives (I miss them all):
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)
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View user's profile Send private message
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