Radio cuts out when I step on the gas?

[targa871]

Hello, Just in the last few days. I have a very weird problem, most every time I step on the gas, my radio looses all power, then when I take my foot off the gas & slow down the radio comes back on.
I have checked the normal stuff, wires, fuses, connections all look ok. One thing I have noticed is the fuel pump is on the way out, it's very noisy. Could this cause enough draw when accelerating to kill the radio? I have not noticed anything else that is affected. Any help would be great. Thanks.
BTW...1987 911 targa.

[berettafan]

Sounds like a gift from the Porsche Gods to me.

But seriously, could be a fire waiting to happen. If fuel pump is drawing too much power and is not fused.....

Gonna take a WAG and say you have clogging in either tank/lines/pump/all of the above.

[targa871]

The engine runs fine, no stumbling or anything. Just a noisy fuel pump & the radio cuts out under acceleration. Would electrical interference cause the radio to cut out?
Any help? ideas?

[dshepp806]

So, the only electrical component affected is the radio? No dimming of lights, etc. when radio goes out?

What type of noise is the pump making? How are sure it's the pump?

Doyle

[targa871]

yes. the only affected component is the radio. the fuel pump buzzes & vibrates & makes a high pitched wine. I confirmed it was the pump, by going under the car while it was running & was touching & listening to components. I ended up taking off the pan that protects the pump & the steering rack. The lines run over the steering rack. It looks right but it is very tight. Very weired problem.

[1980 911 sc]

its called the sound barrier...

[porschenut]

I suggest you forget the radio until you've replaced the fuel pump. It shouldn't be noisy and you don't want to be left stranded suddenly while on the road.

However, do this: turn the radio on with the car parked. Reach up under the dash behind the radio and start wiggling some wires to see if the radio cuts out. It sounds to me like there's a loose connection at the back of the radio that is shifting slightly forward and back when under accel or decel.

[david914]

Originally Posted by porschenut

I suggest you forget the radio until you've replaced the fuel pump. It shouldn't be noisy and you don't want to be left stranded suddenly while on the road.

However, do this: turn the radio on with the car parked. Reach up under the dash behind the radio and start wiggling some wires to see if the radio cuts out. It sounds to me like there's a loose connection at the back of the radio that is shifting slightly forward and back when under accel or decel.

Good suggestion. You might also try mashing the accelerator pedal all the way (engine off) and see if the radio cuts out. It's possible that some radio wiring may have found its way down near the pedal and/or linkage and is being opened or shorted by movement of the pedal.

[Mark McClure]

Maybe you are accelerating too fast and scaring the radio.......happens with my wife......again a blessing from the Porsche gods.

[dshepp806]

I agree: connection related, somehow.


Doyle

[targa871]

Update: I changed the fuel pump, it's quite now. Checked the lines for pinches/restrictions...good. rechecked the radio connections. I had the antenna shielding wire connected to ground with the main ground. I removed it, & the problem went away for a few days.
I'm sure that was just coincidence. I have noticed that the seat belt warning light comes on when the problem happens.. I have checked all the related car grounds, they are good. I have checked the connection at the warning lights, good. I have checked everything at the 3 relays behind the fuel gauge...good. I am at a complete loss. Is there anything I'm missing. I have also done the wiggle test on related wiring harnesses. Note: the car does not need to be rolling for the problem to happen. Help?

[Zeke]

It seems to me that most wiring issues that I have read over the years have more to do with grounding than anything else. There are several ground bunches and all need to be cleaned every once in a decade. A slight movement can interrupt the ground.

Also, wires break at the connector even though the insulation looks perfect. Again, slight movement breaks the continuity. Tough to find.

I would say that since there are so many wires right near the pedals, that the movement you will find is something to do with your foot or the carpet. So, try to drive the car with your foot slid down on the pedal and see what happens. Don't move the carpet.

[86 911 Targa]

Originally Posted by targa871

Update: I changed the fuel pump, it's quite now. Checked the lines for pinches/restrictions...good. rechecked the radio connections. I had the antenna shielding wire connected to ground with the main ground. I removed it, & the problem went away for a few days.
I'm sure that was just coincidence. I have noticed that the seat belt warning light comes on when the problem happens.. I have checked all the related car grounds, they are good. I have checked the connection at the warning lights, good. I have checked everything at the 3 relays behind the fuel gauge...good. I am at a complete loss. Is there anything I'm missing. I have also done the wiggle test on related wiring harnesses. Note: the car does not need to be rolling for the problem to happen. Help?

Andrew,

It's not clear to me if you are losing audio, or power to the radio.

However, intermittent electrical failures can be very hard to resolve.

So, is it audio, or power?

And, do you have a multimeter?

Gerry

[targa871]

It seems to loss ignition power. It does not loss its memory, so battery power is fine.
Yes I have a multi-meter. Thank You all for the help.

[dshepp806]

The OP states in the original post that he's "loosing radio power"....not just "audio".

Doyle

[dshepp806]

Sure smells like ground issue to me....and just one...

Doyle

[86 911 Targa]

Originally Posted by dshepp806

The OP states in the original post that he's "loosing radio power"....not just "audio".

Doyle

O.K., I missed that.

[kiwiokie]

I have the same problem on my SC. Perhaps it is designed to cut power to the radio while the seat belt buzzer is doing its thing so the radio does not drown out the sound of the all important buzzer?

[targa871]

I started to probe the radio wires while the problem was happening, what I found was, 17-19volts while the engine was higher than idle.
I changed the voltage regulator, checked the charging voltage, perfect now at 14.4 volts & went for a drive. The radio stays on, no seat belt light & the fuel pump is nice and quite again. WOW, That was a hard one. Thanks for all your help.
Cheers.

[dshepp806]

Finally,..a quantitative bit of info.....................(voltage).

Keep an eye on her,..as that DME doesn't like spiky, high voltage situations.

Wonder why that seat belt light came on?

Good fix!!!!!!!!!!!!!!!!!!!!

Best,

Doyle