Fuse 34 Blown??
09-12-2007, 12:37 AM
#1
Legend Killer
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Fuse 34 Blown??
Was running the car the other night and it died.
Checked the fuses and found fuse 34 was blown. This is the fuse for the fuel pump (I think) so I put in a new fuse and tried to start the car but the new fuse was blown. So what do I check next? Could I have a bad DME relay?
Checked the fuses and found fuse 34 was blown. This is the fuse for the fuel pump (I think) so I put in a new fuse and tried to start the car but the new fuse was blown. So what do I check next? Could I have a bad DME relay?
09-12-2007, 01:15 AM
#2
Lazer Beam Shooter
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The DME relay might be a possibility, but I doubt it. Could be that your fuel pump has siezed!
Also, id check the wiring at the fuel pump to make sure it isnt disconnected somehow and grounding out against something else.
Also, id check the wiring at the fuel pump to make sure it isnt disconnected somehow and grounding out against something else.
09-12-2007, 01:19 AM
#3
Legend Killer
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I will check that
I should add that I pulled the DME relay from my 944 NA and swapped it into the 951 but the car still wouldnt run. So I put the DME relay back in the NA and now the NA doesnt run so I think whatever is going on its blowing the #34 fuse and frying my relay.
I should add that I pulled the DME relay from my 944 NA and swapped it into the 951 but the car still wouldnt run. So I put the DME relay back in the NA and now the NA doesnt run so I think whatever is going on its blowing the #34 fuse and frying my relay.
09-12-2007, 01:22 AM
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hmmmmm..........
I should also add that I just swapped out the DME chip for a new one.........but the car did run.....well it made it about 2 blocks form my house and then died
I should also add that I just swapped out the DME chip for a new one.........but the car did run.....well it made it about 2 blocks form my house and then died
09-12-2007, 02:40 AM
#6
Lazer Beam Shooter
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Something probably got hot!
Take it back out, open it up, make sure there isnt something inside of it grounding it out. I doubt this is it, but maybe the chip is damaged somehow, try swapping?
It probably ran until it blew the fuse and popped the DME relay.
Take it back out, open it up, make sure there isnt something inside of it grounding it out. I doubt this is it, but maybe the chip is damaged somehow, try swapping?
It probably ran until it blew the fuse and popped the DME relay.
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09-12-2007, 01:46 PM
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09-12-2007, 02:25 PM
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Das German Engineers, in their infinite wisdom, put das oxygen sensor heating element for on das same circuit as das fuel pump.
Thus, when (not if, when) your oxygen sensor heating element fails and shorts, you will blow the fuse and stop the fuel pump and stop the car.
Contrast that to the two Hondas that I have that have had failed heating elements in the last year. When both failed, I got a Check Engine Light. Upon DRIVING HOME and reading the code and seeing what the problem was, I happily drove around for another week or two until it was convenient to fix.
[/RANT]
The purpose of the heating element is to bring the oxygen sensor up to temperature faster than the exhaust gas would. This cuts down on your emissions while the engine is cold, because the fuel injection can run in closed loop mode faster than if it had to wait until the exhaust heats up the oxygen sensor. Since the government test include cold-start emissions, the auto makers put a heating element in the oxygen sensor to help them pass.
Assuming that this is, in fact, the problem, you can:
1. Get a new Porsche O2 sensor ($$$),
2. Get an identical O2 sensor for a Taurus (do a search) ($$), or
3. Snip the wires to the heating element (free).
09-12-2007, 02:32 PM
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[RANT]
Das German Engineers, in their infinite wisdom, put das oxygen sensor heating element for on das same circuit as das fuel pump.
Thus, when (not if, when) your oxygen sensor heating element fails and shorts, you will blow the fuse and stop the fuel pump and stop the car.
Contrast that to the two Hondas that I have that have had failed heating elements in the last year. When both failed, I got a Check Engine Light. Upon DRIVING HOME and reading the code and seeing what the problem was, I happily drove around for another week or two until it was convenient to fix.
[/RANT]
The purpose of the heating element is to bring the oxygen sensor up to temperature faster than the exhaust gas would. This cuts down on your emissions while the engine is cold, because the fuel injection can run in closed loop mode faster than if it had to wait until the exhaust heats up the oxygen sensor. Since the government test include cold-start emissions, the auto makers put a heating element in the oxygen sensor to help them pass.
Assuming that this is, in fact, the problem, you can:
1. Get a new Porsche O2 sensor ($$$),
2. Get an identical O2 sensor for a Taurus (do a search) ($$), or
3. Snip the wires to the heating element (free).
Das German Engineers, in their infinite wisdom, put das oxygen sensor heating element for on das same circuit as das fuel pump.
Thus, when (not if, when) your oxygen sensor heating element fails and shorts, you will blow the fuse and stop the fuel pump and stop the car.
Contrast that to the two Hondas that I have that have had failed heating elements in the last year. When both failed, I got a Check Engine Light. Upon DRIVING HOME and reading the code and seeing what the problem was, I happily drove around for another week or two until it was convenient to fix.
[/RANT]
The purpose of the heating element is to bring the oxygen sensor up to temperature faster than the exhaust gas would. This cuts down on your emissions while the engine is cold, because the fuel injection can run in closed loop mode faster than if it had to wait until the exhaust heats up the oxygen sensor. Since the government test include cold-start emissions, the auto makers put a heating element in the oxygen sensor to help them pass.
Assuming that this is, in fact, the problem, you can:
1. Get a new Porsche O2 sensor ($$$),
2. Get an identical O2 sensor for a Taurus (do a search) ($$), or
3. Snip the wires to the heating element (free).
Could this short in the O2 sensor have fried my relay?
So once the O2 sensor heating element shorts does it stay shorted or will it only short again when it heats up? I put in a new fuse and it was immediately blown again when I tried to turn on the car so that would have to mean that the O2 sensor stays shorted or I have some other problem??
09-12-2007, 02:37 PM
#11
Hey Man
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Good info. I never knew that. Are you saying that 'if' the heating circuit fails it always shorts or can the element just fail 'open' and not cause further damage?
09-12-2007, 02:59 PM
#12
Three Wheelin'
Wow. Its really that simple! I had this exact issue last fall at Putnam Park. Kept blowing the fuse for the fuel pump. Thought is was seized but pulled it out and tested it and it ran fine. Hooked it back up and blew the fuse again. Beab951 helped me pull the fuse panel and we started checking for shorts, sure enough one of the branches of that circuit had a short in it. I forget which one at the moment. We cut the wire and I drove it home. The next weekend I rewired it and blew the fuse some more. Again, cut the damn thing. I've been running without that branch of the circuit since then without issue. If the issue is the O2 sensor I'll replace it and wire that one wire back up.
09-12-2007, 03:15 PM
#13
Legend Killer
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Wow. Its really that simple! I had this exact issue last fall at Putnam Park. Kept blowing the fuse for the fuel pump. Thought is was seized but pulled it out and tested it and it ran fine. Hooked it back up and blew the fuse again. Beab951 helped me pull the fuse panel and we started checking for shorts, sure enough one of the branches of that circuit had a short in it. I forget which one at the moment. We cut the wire and I drove it home. The next weekend I rewired it and blew the fuse some more. Again, cut the damn thing. I've been running without that branch of the circuit since then without issue. If the issue is the O2 sensor I'll replace it and wire that one wire back up.
Did your DME relay also get toasted? I need to test mine but I think it was fried and I think I fried my NA relay too............
09-12-2007, 03:27 PM
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Thanks for the explanation. On option #3 do you mean just cut all the wires or is there 1 wire I can cut that will eliminate the heating element but still allow the O2 sensor to do its thing?
Could this short in the O2 sensor have fried my relay?
So once the O2 sensor heating element shorts does it stay shorted or will it only short again when it heats up? I put in a new fuse and it was immediately blown again when I tried to turn on the car so that would have to mean that the O2 sensor stays shorted or I have some other problem??
Could this short in the O2 sensor have fried my relay?
So once the O2 sensor heating element shorts does it stay shorted or will it only short again when it heats up? I put in a new fuse and it was immediately blown again when I tried to turn on the car so that would have to mean that the O2 sensor stays shorted or I have some other problem??
But, first things first: disconnect the O2 sensor (by unplugging the connector) and see if fuse 34 stops blowing. I'm not sure whether the fried relay could be related. Although my O2 sensor and DME relay were both bad when I got my car. Perhaps not a coincidence.
09-12-2007, 03:29 PM
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I used the word 'when' because it seems like they have a MTBF of about 6 years. Often enough that das engineers should designed a better failure mode than car immediately loses power.