911SC ('83) fuel pump problem?

[lox]

Hello all!

This morning I ran out of gas on my way to the next gas station. I refueled the car (911SC '83) with approx. 4 gallons - after a refreshing walk.
Now I was hopeful that the car would start, but that was not case. The engine was cranking but it did not start. I tried it several times but no success, so I decided to wait up to 2hours before I tried it again but that did not help either. The fuel pump on the car has been replaced just recently as the old one was worn out.
Any hints on what the problem might be or how test/fix it?
Thanks everyone
Lox

[vash]

did you try to bleed the system? get the ignition on, and then lift the air sensor bar in the airbox. 10 secs of this and i can hear my injectors scream (or squeal)

[lox]

No, I have not tried this yet, as I was not sure what to do. I assume I have to open up the air box and somewhere underneath the filter I will find the air sensor bar? Now, if I lift it for 10 sec. what does that do? What does the screaming noise indicate? Should the car start after that? I'm sorry about the basic questions.
Thanks again

[Bill Douglas]

Yup, lift the air cleaner out and stick your hand in. You will find a metal thing, and lift it for 3 seconds to start off with. Then try unfixed's 10 seconds. Unfixed is probably right, but try 3 seconds first

[lox]

Ok, I just tried it and I can hear the two noises, one sounds like a high pitched screaming noise, which stops when I turn off the ignition and the other noise is more of a lower pitched "brrrrrrr" sound when I lift this metal thing. I tried it for 10+ seconds re-assambled the air box and tried to start the car, but unfortunately the car did not start.
Should I try it longer than 10 sec. ? Could the fuel pump be damaged because it was running dry?

Thank you all

[cantdrv55]

I think the high pitched sound is coming from your CDI. The low pitch may or may not be coming from your pump. Any way you can have someone hold up the bar for you while you crouch down by the doors to listen to the fuel pump? Some guys say the fuel pump is loud but mine's the strong, silent type. Could be the filter also. Was that replaced at the same time?

[red911]

Have you turned on the ignition and gone to the front of the car to listen for the sound of the pump? I had a problem similar to this where I thought I ran out of gas but it was actually the fuel pump relay. That is the red one in the fuse panel. I swapped it with the A/C relay and that got me back home until I could get the replacement relay.

[juanbenae]

i like the filter idea. if you ran it out the last bit of fuel may have been tainted.

[lox]

Hello Everyone!

Thank you all for your valuable responses. I did learn quite a bit about my car, which I did not know before. At the end of the day I replaced the fuel pump and the car is running again. I hope that no other parts did get damaged?! I guess time will tell.

Thanks again,
Lox

[RoninLB]

Originally posted by lox
I replaced the fuel pump and the car is running again.

Hey Lox.. how many miles on the old pump ?

[lox]

The first pump lasted approx. 115000, the second approx. 3000 and the third hopfully longer. ;-)

Cheers,
Lox

[Groesbeck Hurricane]

Lox,

How do you know the second pump is bad? I'd try and find a way to test it.

[lox]

Groesbeck Hurricane,

would it be fair to assume that since I replaced the fuel pump and the car is running again that the fuel pump had been fried? If I would have known a simple way of testing the fuel pump before I replaced it I would have done it, for now I'm happy the car is running, and I will make sure that I will never again run out of fuel! ;-)

I also talked to a Porsche mechanic and he told me that the fuel pump is the most likely part that will brake if one runs out of gas, as the fuel pump needs fuel to be cooled and is not very forgiving if there is no fuel.

Cheers,
Lox

[Groesbeck Hurricane]

Lox,

I'm not sure how to test it without trying to run it. I forgot that the pump is cooled by the fuel, I was just hoping the second one was still good or at least worth keeping around, just in case. I'd probably re-install to see if it works now, but that would be overkill. Happy motoring!

[Dr. injection]

Yes i can assure you 100% that your 2nd pump is shot, the pump electric motor is not designed to run in dry mode because its 100pct free of air cooling, all normal electric motors requires cooling either from liquid, gas or air. In my bible (150 pages about CIS) its clearly stated that under no circumstances must the pump be allowed to run in "dry" mode as the fuel is meant to cool and lubricate the motor armature / coal friction sticks/ "dry bearings". If its allowed to run dry it takes only a few minutes to fry it, if your a electric motor expert you can rebuild it with new coal sticks but if you dont know anything about that return it to your local bosch dealer and tell them its defect and they return it to germany for remanufacture. For that reason the fuel filter is located on the pressure side of the pump and not logically on the suction side cleaning particles from the gasoline.

[RoninLB]

Originally posted by Dr. injection
. For that reason the fuel filter is located on the pressure side of the pump and not logically on the suction side cleaning particles from the gasoline.

good explain.
and may I add that the tank lower plug screen should be considered 100k mile maintence . it's more subject to screen weakness than dirt.. all imo

[klatinn]

Hmmm?

If you run out of gas, the engine stops. The CIS plate falls to its lower stop. This interrupts the current to the pump through the pump relay and consequently the pump can't run dry.
Am I missing something?

[Jim Sims]

Only if the air flow switch is hooked up will the pump stop running in the event of fuel exhaustion and engine stall.

"coal friction sticks"!? graphite brushes and bearings?

[Dr. injection]

Yes thats what i mean, sorry im from norway didnt know the words for those off hand. Saying the fuel pump is ok after he just replaced it and the system is working now, thats like saying "hey try starting the car with the battery disconnected.. never know". A small CIS engine can run pretty long at idle even with pump surging with little fuel to work with, if the graphite bushes is exposed and its getting pretty warm then it can run dry. And yes even the early CIS systems turns the pump off if the engine stalls. I had my engine (bmw m20b25) flooded with gas and it ran for a few minutes with the pump relay out of the socket.

[Jim Sims]

Welcome to the board Dr. injection. I have good friends in Norway near Oslo. Cheers, Jim