'83 911sc start problem

GVW · GVW's Garage

I am having trouble getting my 1983 911sc to start up. I drove it about a month ago and it ran fine and put it away with no problems (the fuel was really low when I did put it back in to the garage). It's been about a month now and I am trying to start it and it just spins over. So, I added about 5 gallons, hoping that just the fuel was low, still won't start. I checked and I am getting a good spark, now my next idea is to see if I am getting fuel (maybe I sucked up some dirt from the botton of the tank, since it was so low when I drove it last. My question is where is a good place to start to see if I am getting fuel. I was hoping some of the experts on the board could help me out and give me some ideas on this or some other ideas in areas to look.

Thanks, Glen.

Superman · 10-28-2002, 03:37 PM

Remove the air cleaner cover. Put the key in the ignition and turn to "ON." Reach into the air box and push up on the air flow sensor plate. You should hear two things. 1. The fuel pump running, under the gas tank and 2. The whine of the injectors that are spraying.

If you are getting a nice, fat blue spark, and the pump and injectors are working, then your cold start system has trouble (cold start valve, thermotime switch).

GVW · GVW's Garage

Superman,
I did what you mentioned and I hear the whine of the injectors, which is fairly loud, but I am not hearing the fuel pump. I am doing this in my garage, so I am getting a echo maybe from the injectors. Is the fuel pump loud enough to hear over the injectors? Or do I need to get another person to raise up on the air sensor plate and go up to listen to see if the fuel pump is running?

Thanks, Glen

john walker's workshop · 10-28-2002, 04:50 PM

if you feel some resistance when the arm is raised, and you hear the injectors whirring, then the pump is running. now check for spark by removing the coil wire from the center of the dist cap and having your helper activate the starter while you see if a spark jumps 1/4" from the wire end to something metal, like the edge of the fan housing. got spark and fuel, you know it has air, so it should start

GVW · GVW's Garage

I am getting spark, I hear the injectors whirring noise when I raise the air flow sensor plate, I don't hear anything from the fuel pump,

Quote:

if you feel some resistance when the arm is raised, and you hear the injectors whirring, then the pump is running

So could the problem be the cold start valve? When I spin it over, there is no sign of it wanting to start. If it was the cold start valve that is bad, wouldn't it atleast act like it wants to start somewhat? I sprayed a little started fluid and it would act like it is getting a little fuel and begin to start, but when just die then. Any other suggestions?

Thanks to all who have me out so far.
Glen.

john walker's workshop · 10-28-2002, 07:28 PM

maybe it's the frequency valve that's buzzing when you lift the arm, and not the injectors spraying. you need to do a visual check for spray. pull out one injector and then raise the arm, with the key on. they pull right out with minor effort. just an o ring holding it in. check the fuel pump fuse. 6th fuse from the windshield going forward. the fuel pump relay is the one closest to the windshield. it may be red. swap with one of the other relays to test. the pump is in front, under the car, behind the gas tank, under the metal plate. you can touch it with your finger as someone cranks the key to see if it vibrates.

Speedy1 · Speedy1's Garage

I'd bet it is the fuel pump relay, use to have a similar problem. Do this turn key forward to run position, open the trunk remove the fuse cover and listen for the wineing buzz of the fuel pump. It's under the car but it sounds like its under the back side of the spare tire. The relay that controls the pump will be to your right if you are leaning over the drivers side fender it may be red, pull it out and put it back in a few times maby its just a bad connection. Mine was and It would just die,anytime. Good luck !

GVW · GVW's Garage

I checked the fuel pump relay by pulling it out and putting it back in a few times, with the key in the on position (no change). I replaced it with another relay to test as well (didn't make a difference) and I also checked the fuel pump fuse and it looked ok. I can not remember how loud the fuel pump should be, but it should be a recognizable sound I would think, (it is a fairly loud hum from another vehicle I have) but I am not hearing anything from this area. (all I hear when I turn the key to the on position is the ignition buzzer, which is loud) and I also went underneath the car and had someone turn the key to the on position and did not feel anything when touching the fuel pump. I haven't checked for a visual fuel spray, by pulling an injector yet. Since I am not hearing the fuel pump, I am assuming I woudn't get a spray from an injector, right? or I am wrong with that?

Thanks for all of the help so far.

Glen.

Superman · 09:27 AM

If the fuel pump is not running, you will get no spray whatsoever. Turning the key on will not necessarily run the FP. With the key on, and the air flow sensor plate raised, your FP should operate. The '83 SC has metal fuel lines that you need to disconnect in order to remove the injector. Do not bend those metal lines.

Like others, I am suspicious that your FP is not running.

I have another suggestion, but it will not make your car start. Put they key in an open the door. Reach into the trunk, behind the brake MC, toward the dash area...toward the fuel level gauge. When your finger touches the door buzzer relay, you will know it because it will be vibrating. Pull on this relay until it comes out of the car. Place it in a box labeled "Porsche parts I will never need again."

Speedy1 · Speedy1's Garage

OK. One more time under the car and this time bring a test light a 12 volt neg. ground type, or a volt meter, and ground one side. Turn the key to the run postiton and probe the wires to see if you can get voltage there when the key is turned to the run position and the air flow sensor plate is wedged open a bit. (be careful it can be sensitive use a piece of cardboard to wedge it open.) If you get voltage I'd be shopping for a fuel pump if you don't know the status of the pump it might be a good idea to replace it anyways. Good luck!