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911virgin
 
Join Date: Nov 2008
Location: Richmond VA
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Fuel pump fuse 1983 911SC cab

Ok, so I am out last weekend for a nice cruise with the top down in my 1983 911SC I was on my way home and the car is running great. Get on the highway I go about 7 miles and I lose fuel intake. I get no reaction when depressing the gas pedal. I pull over pop it out of gear and the engine quits and won't restart. This at night on a lightly traveled highway. I get it towed home and now I start to figure out what is wrong. It is evident that it is a fuel problem. I check the fuses in the engine compartment and all is good. I check the fuses up front and find the fuel pump fuse is blown. I replace the fuse and the car starts right up. I have the front hood up and notice in my moment of joy that the fuse I just put in is smoking. I check the amperage to make sure I put the right fuse in. Put a new one and same thing happens. Can anyone tell me why all of a sudden I am literally burrning the fuel pump fuse? Thanks.
Old 06-26-2010, 03:02 PM
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You might have a pump going bad or dirty connections

fuel pump fuse keeps blowing 79 911

Bad Fuel Pump Melted the Fuel Pump Fuse Wire

Blowing the fuel pump fuse

Fuel pump fuse........
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82 911 SC Targa-Rosewood
04 Jetta TDI
05 Jetta GLI

Last edited by GothingNC; 06-26-2010 at 03:19 PM..
Old 06-26-2010, 03:13 PM
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911virgin
 
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Thanks that is what I was afraid of. Doesn't look to be all that difficult to replace but I am going to check all of the connections. Thanks for the link to that other thread. The funny thing is the car was running great and then in the blink of an eye it quits. My first thought was if the pump was going bad I would have noticed the engine skipping or sporadic starvation of fuel but then again maybe not. Again thanks for the advice. It is greatly appreciated.
Old 06-26-2010, 03:20 PM
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Electrical troubleshooting.........

Quote:
Originally Posted by 911VAvirgin View Post
Ok, so I am out last weekend for a nice cruise with the top down in my 1983 911SC I was on my way home and the car is running great. Get on the highway I go about 7 miles and I lose fuel intake. I get no reaction when depressing the gas pedal. I pull over pop it out of gear and the engine quits and won't restart. This at night on a lightly traveled highway. I get it towed home and now I start to figure out what is wrong. It is evident that it is a fuel problem. I check the fuses in the engine compartment and all is good. I check the fuses up front and find the fuel pump fuse is blown. I replace the fuse and the car starts right up. I have the front hood up and notice in my moment of joy that the fuse I just put in is smoking. I check the amperage to make sure I put the right fuse in. Put a new one and same thing happens. Can anyone tell me why all of a sudden I am literally burrning the fuel pump fuse? Thanks.
911VAvirgin,

For the SC's, FUSE #16 is used by the following items: FP, FPR, WUR, AAR, TTV (optional), etc. It could be anyone of the following that is causing your problem or a 'short' somewhere in the circuit (current track #106). So isolating these components from the circuit will identify the culprit/s.

I would bet my money that either the FP or FPR (fuel pump relay) could be causing this problem. But most likely the FP. This is how I would start investigating this anomaly. Disconnect the (+) connector for the FP (and tape it) and perform a FP test by jumpering terminals #87a & 30 (FP Relay) with ignition switch @ ON position. Observe very closely fuse #16.

If fuse #16 (25 amp) passed the test, do another trial. This time connect the (+) line for the FP and repeat the above test. Measure the current draw of the FP during the test. Observe the fuse because it would probably be smoking again!!!!! Keep us posted.

Tony

Last edited by boyt911sc; 06-26-2010 at 03:42 PM..
Old 06-26-2010, 03:39 PM
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You were Lucky that the only damage was a blown fuse.

Here is the carnage when the PO had a blade fuse bypass installed and too much resistance caused a slight fire.

I ended up replacing both relays and sockets and the 10-piece fuse holder 3 years ago

Wire to the right was the blade fude holder.

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82 911 SC Targa-Rosewood
04 Jetta TDI
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Old 06-26-2010, 03:41 PM
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911virgin
 
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Ok, I replaced the relay and I am still burning the fuse. i am also getting a strong odor of gasoline. I guess my next step is to replace the fuel pump? Any other suggestions or is this the route I should be taking? Thanks for your input.
Old 06-30-2010, 04:15 PM
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Troubleshooting........

Quote:
Originally Posted by 911VAvirgin View Post
Ok, I replaced the relay and I am still burning the fuse. i am also getting a strong odor of gasoline. I guess my next step is to replace the fuel pump? Any other suggestions or is this the route I should be taking? Thanks for your input.
911Virgin,

Replace the fuel pump if you have verified and confirmed it is defective after a test. Most likely it is the culprit but you don't want to buy a new FP and found out later that the fuses are still burning. Something is very wrong with the wiring circuit that causes this problem.
Some example of problematic fuel pumps I encountered this spring. The top one was burning fuses like yours. While the two (2) at the bottom of the picture had fuel leaks but still delivering sufficient fuel pressure. These were not desirable for installation. Good luck.

Tony
Old 06-30-2010, 05:00 PM
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Quote:
Originally Posted by 911VAvirgin View Post
Ok, I replaced the relay and I am still burning the fuse. i am also getting a strong odor of gasoline. I guess my next step is to replace the fuel pump? Any other suggestions or is this the route I should be taking? Thanks for your input.
Replace or bypass the fuse holder and you'll be fine.

The FP surge current is HUGE in relation to the ruse rating so even a few milliohms of fuse holder resistance can have dramatic effects. Over time, and HEAT, the fuse holder looses its "springiness" and does not clamp the fuse tightly enough.
Old 06-30-2010, 06:46 PM
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Quote:
Originally Posted by 911VAvirgin View Post
Ok, I replaced the relay and I am still burning the fuse. i am also getting a strong odor of gasoline. I guess my next step is to replace the fuel pump? Any other suggestions or is this the route I should be taking? Thanks for your input.
Listen to what Tony says.

Test the FP and get Amp readings.

If the pump fails the test, installing a new one is not difficult except I recommend to drain the tank.
Do a search on how to replace the pump and the short hose from tank to pump; lots of info here.

When a fuse blows, there is a reason and to by-pass the fuse is NOT smart.

Smell gas?

Must investigate!
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1995 seafoam-green 993 C2, LSD, Sport seats.
Abstract Darwin Ipso Facto: "Life is evolutionary random and has no meaning as evidenced by 7 Billion paranoid talking monkeys with super-inflated egos and matching vanity worshipping illusionary Gods and Saviors ".
Old 07-01-2010, 06:40 AM
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911virgin
 
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Ok I will test first for sure. I just started reading up on replacing the fuel pump and you are right not too difficult. No question about draining the fuel tank. Thanks guys for all of the help. I will let you know how it goes.
Old 07-01-2010, 06:41 PM
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911virgin
 
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oh I forgot to mention that the new relay I put in was hot to the touch as well as the fuse burning off. Does that mean anything to anybody?
Old 07-01-2010, 06:45 PM
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Quote:
Originally Posted by Gunter View Post
Listen to what Tony says.

Test the FP and get Amp readings.

If the pump fails the test, installing a new one is not difficult except I recommend to drain the tank.
Do a search on how to replace the pump and the short hose from tank to pump; lots of info here.

When a fuse blows, there is a reason and to by-pass the fuse is NOT smart.

Smell gas?

Must investigate!
Sorry, I guess I should have been a bit more explicit...

bypass the fuse HOLDER with a separate fuse and holder.
Old 07-01-2010, 07:09 PM
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oh I forgot to mention that the new relay I put in was hot to the touch as well as the fuse burning off. Does that mean anything to anybody?
Most relays will be WARM to the touch after being energized for a long period.

Not HOT and not really uncomfortarbly warm, just noticeably WARM.
Old 07-01-2010, 07:12 PM
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Quote:
Originally Posted by 911VAvirgin View Post
oh I forgot to mention that the new relay I put in was hot to the touch as well as the fuse burning off. Does that mean anything to anybody?
Yes, test the pump and see how many Amps it draws.

Clean contacts help.

I would first remove the skid plate to get at the pump, then I would open both wire-contacts, clean the ends and posts, re-connect and then test the Amperage.

If the Amps are within specs, the other components on the same fuse may be at fault.

Relay should be warm but not hot.
I assume that you have the RED relay?

Check the relay socket to be sure that it didn't melt.
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1980 Carrerarized SC with SS 3.2, LSD & Extras. SOLD!
1995 seafoam-green 993 C2, LSD, Sport seats.
Abstract Darwin Ipso Facto: "Life is evolutionary random and has no meaning as evidenced by 7 Billion paranoid talking monkeys with super-inflated egos and matching vanity worshipping illusionary Gods and Saviors ".

Last edited by Gunter; 07-02-2010 at 06:43 AM..
Old 07-02-2010, 06:40 AM
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911virgin
 
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The relay is warm to the touch after less than 30 seconds
Old 07-02-2010, 06:28 PM
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Question

Virgin: Are you waiting for a miracle?

How many Amps does the pump draw?

Let us know what you find and what else you're doing to solve this problem.
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1980 Carrerarized SC with SS 3.2, LSD & Extras. SOLD!
1995 seafoam-green 993 C2, LSD, Sport seats.
Abstract Darwin Ipso Facto: "Life is evolutionary random and has no meaning as evidenced by 7 Billion paranoid talking monkeys with super-inflated egos and matching vanity worshipping illusionary Gods and Saviors ".

Last edited by Gunter; 07-04-2010 at 04:40 AM..
Old 07-03-2010, 07:00 AM
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Check this just to be safe

I just replaced my gas tank and fuel pump because it was doing the same thing, melting fuses. I would remove the fuel level sender and see if you tank is crudded uo, one reason the pumps pull to much load. I would also carefully look at the condition of the fuel hoses going from the pump to the plastic tubes running trough the tunnel to the engine. Maybe it was new fuel presure or moving it around while replacing the pump but mine sarted to leak, Better to be carefull and safe and check these lines they are pretty old at this point.
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