docmirror

While you're picking up your 'noid light from Autozone, grab a can of carb cleaner. Take off the air cleaner cover, and remove the air cleaner. Have someone crank the engine while you spritz a bit of carb cleaner into the intake(don't worry, you won't blow up).

If it fires, you have an injector fault. Diagnose from the actual injector wires backward using the noid light. Note that the injectors have 12V on them continuously and the injector pulse is toward ground, so if you check one side to chassis ground and it's on solid, try the other wire on the injector to ground, or use the noid light from one injector wire to the adjacent wire in the harness.

If it doesn't fire, or backfires out the intake, you have a spark/timing fault.

Report results.

WallyP

Nowadays, not all carb cleaner is flammable...

risaac928

This is going to be good....too bad you guys cant post some pics to follow....or post some You Tube Videos on what you are doing. This would be nice so that others can put some eyes on what you are doing.

G8RB8

Hit it with a little ether or propane. If it fires the problem is fuel delivery. If not it's spark or compression. Don't try to keep it running with ether!

Sorry
Didn't see Doc's post above, but +1 on Wally's too.

SeanR

Get the noid light, then you can skip the flammable liquids.

If you have a noid light and a spark plug, you can rule out two entire systems on the car. If both of those go bang, then you have a fuel delivery problem.

Ricardo Vega II

Cool guys! I truly appreciate all the pointers and help. Ill give it a shot maybe Friday and tell you guys what come of it. You guys are the best and enjoying my new membership on Rennlist and how great of a group you 928 lovers are.
Ricardo Vega II
1987 928 S4 Black

Dean_Fuller

OP says his dash does NOTHING when the key is engaged.

If injectors shouldn't the dash have lights????

Could this be a bad ignition switch? Or an issue with the alarm system.

Ricardo Vega II

Cool guys! I truly appreciate all the pointers and help. Ill give it a shot maybe Friday and tell you guys what come of it. You guys are the best and enjoying my new membership on Rennlist and how great of a group you 928 lovers are.
Ricardo Vega II
1987 928 S4 Black

NoVector

Playing along as I'm still screwing with my no start:

Spark at the plugs rules out the alarm, ign switch, and RPM sensor, right? Meaning, the EZx is happy with what it's seeing.

Wet plug (and gas vapor/smell out the tail pipe) indicate fuel pump and injectors are working, right? I.e., fuel made it into the cylinder.

Ricardo Vega II

Sean or any other person that knows, if I was to purchase that Bosch injector noid is there only one model of this? Or is there different versions of a Bosche injector noid? I was just wanting to maybe order one to try out that side of the troubleshooting on my broken down car.
Thanks.

Ricardo Vega
1987 Porsche 928 S4
Black

G8RB8

Spam damners

docmirror

There are a bunch of kinds. Any test light of 12 Volts will work. Here is a page that will help you make your own if you like to save money.

http://www.noidlight.com/making-your-own-noid-light/

Or purchase your set.

http://www.autozone.com/autozone/acc...ntifier=948078

Ricardo Vega II

Hey guys, just wanted to say that I swapped out the XII and XXV relays and that didn't work. I then took out a spark plug n see some gasoline n smell it on the tip of the plug. At this point I don't have an injector noid light so that's the next step.
Anything else that I might be missing out on on trying out?
Ricardo Vega II
Broken Black Porsche 928 S4

Ricardo Vega II

Oooopppppssss! Hold on guys! I only tested the horn relay that is good for the LH relay, I didn't swap out the EZK nor the fuel pump relays. I skipped those other two. So let me give that a shot.
Thanks
Ricardo Vega II

dr bob

Ricardo--

I see that you started a follow-up thread to this one. Do yourself, us, and future readers, the favor of keeping all of this info and suggestions in one thread.

----

There are three things needed for an engine to run: Compression, fuel, and spark at the right time.

-- Compression requires cams and valves working at the right time, so the belt comes in to question. Out here in the real world, cam belt failures are quite a bit less common than failures of fuel system or ignition components. It's worthwhile checking cam timing so you can rule out belt issues, easy enough by popping a couple covers and verifying a few markers. Realistically, the belt problems show up a lot less frequently than other problems. So verify, but don't expect to find a problem.

-- Spark requires a few things, like a good crank position signal, plus all the components good all the way through the plugs. You can do a bit of sleuthing by testing one plug one each igniton (distributor/coil) to see if you have spark. There are spark testers that are not any better than putting an old plug in a spark plug lead, ground the plug against engine metal. watch for a fat blue spark when the engine is cranked with the key. No spark means no run.

-- Fuel issues get more interesting. The fuel system requires that the EZK (spark) controller is good since it feeds the fuel injection controller to let it know the enngine is actually running. It also requires that the fuel pump runs, (fuel pump relay and the pump itself), and that it supplies current to the injectors at the correct pulse width. The fuel pump relay and the LH relay must be good. You get a gross check of this function using the 'noid light, checking the signals sent to each injector.

The S4 uses a "junior timer" connector for each injector. The system supplies constatnt battery/relay voltage to one pin of each injector, while the other pin is selectively drawn close to ground potential when fuel flow is required. With the 'noid light connected, you should see flashes on the light as you crank the engine on the starter motor. No flashing means no fuel flowing during cranking.