82 911sc wont start

vdub117 · 07-19-2011, 05:01 AM

So a little back story on my problem here...about a year ago one of my rubber intake runner seals blew out. I did a partial drop removed the cis and replaced all the rubber seals. When I put it back together is where I screwed everything up. I accidentally switched the two two pronged plugs, which I now know go to the aar and wur, and I fried some wiring. Motor came out, car ended up sitting for a while and I just recently got around to fixing it. So I rewired everything that had been damaged, and put the motor back in, and crossed my fingers. Suprise suprise it didnt start.

So I have tested spark and that doesnt seem to be the issue. Turned the ignition to on and pushed up on the flap, and I hear nothing from the fuel pump. Only thing I can figure is that its something to do with the fuel pump wiring but I want to be sure before I go tearing into the unknown.

Are there any tests I can do to pinpoint my problem? Any help is greatly appreciated.

I attached a couple pictures, the po did something with the fuel pump relay to complicate things for me

Thanks in advance, Graham

vdub117 · 07-19-2011, 06:06 AM

I took a couple videos of it cranking over if these help at all

YouTube - Broadcast Yourself.

YouTube - Broadcast Yourself.

boyt911sc · boyt911sc's Garage

Test the FP by jumpering terminals #87a & #30 (FP relay socket) with the ignition @ ON position. What fuel pressures (control & system) do you get? Is the FV (frequency valve) also running? Connect an inductive timing light and check for ignition. If you have good ignition, sufficient fuel pressure, and insignificant vacuum leak, your engine should have no problem getting to START in conjunction with high engine cranking provided by the starter/battery. Keep us posted.

Tony

vdub117 · 07-21-2011, 07:16 AM

Thanks for the advice I jumpered the terminals on the fp relay and got the fp to run by doing so. However, after taking out an injector and letting it collect in a glass im still not getting fuel to the motor. Poking around a little more I found a plug on the passenger side with nothing ran top it. What color wire runs to this plug?

vdub117 · 07-21-2011, 07:23 AM

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by vdub117

Thanks for the advice I jumpered the terminals on the fp relay and got the fp to run by doing so. However, after taking out an injector and letting it collect in a glass im still not getting fuel to the motor. Poking around a little more I found a plug on the passenger side with nothing ran top it. What color wire runs to this plug?

vdub117,

A running FP will not deliver fuel to the injector/s until the FD plunger goes up. Remove the air filter & cover to get access to the AFS (air flow sensor/plate). With the ignition @ ON position (not start), lift up the air flow sensor/plate..........fuel should start coming out from the injector/s. Don't lift the air plate too long (1 - 2 seconds max) to prevent too much fuel in the intake manifolds.

Have you checked/inspected if the FV (frequency valve) was vibrating when the FP was running? If the FV was not running when the FP was ON, you have problem with power from either relay or fuse #18. Keep us posted.

Tony

vdub117 · 07-22-2011, 02:21 PM

Is the fv under the passenger seat or is that just the computer for the fv?

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by vdub117

Is the fv under the passenger seat or is that just the computer for the fv?

The frequency valve relay is located under the passenger seat beside the ECU (lambda). The FV is located at the rear side of the engine near the CSV (cold start valve). I suggest that you get some reference manual/s and do some readings to know more about your car.

First thing you should do is investigate if your engine has an operating lambda unit and OXS. The previous owner might have removed it. Test the FP. While the FP is running, touch or feel if the FV is vibrating or not. Keep us posted.

Tony

boyt911sc · boyt911sc's Garage

Get a set of fuel injection gauge kit and learn how to use it. This is a mandatory tool for fuel injection troubleshooting job. Without knowing your fuel pressures, you are just wasting your time and effort trying to locate the problem/s. You may get lucky at one point, but you cannot rely on luck all the time.

How long have you been trying to find the problem for your no-start trouble? A week? Without running your engine, you should be able to determine the following:
Fuel pressures (control, system, and residual)
Air leak or vacuum leak
Ignition (spark during cranking)

For all you know, you might have a big air leak some where preventing the engine from making a complete combustion. Keep us posted.

Tony