Help with No-Start

[walt]

I dropped the engine to replace the fuel injector sleeves and o-rings and at the same time replaced the fuel filter, spark plugs and a few other small items. Now the engine tries to start for 1/2 second and quickly dies out.

When removing the engine I gave the multi-pin connector at the rear fuse panel a nasty pull but could not detect any damage. I also started blowing the 5A fuse #18 for the interior lights and OX sensor when I crank the engine. The sensor connector near the fuel filter is banged up fairly good probably from changing the filter. The car does not have an OX sensor.

[walt]

Pic of connector

[Bob Kontak]

Originally Posted by walt

Now the engine tries to start for 1/2 second and quickly dies out.

This is just a starting point. Has nothing to do with the O2/Lambda system. Pull air cleaner cover and filter. Turn key to on but not start. Lift the air sensor arm upwards. You should hear noise indicating fuel pump has engaged and pressure is being applied inside your fuel system. If no noise we can go from there.

Lambda system. Car should start and idle poorly if Lambda/interior fuse is blown. If O2 connector is disconnected it will run fine and probably idle smoother than if connected.

There is a connector on the back rail between the shocks. It's a 12 pin, not the bigger 14 pin you may have stressed. There are circuits in that cluster that give power to the frequency valve and probably control a few other Lamda box related controls (say, an off idle switch or WOT switch) that change how the frequency valve controls fuel.

That said, if something is mechanically compromised (squished/broken) in that connector it may allow a short to occur when switched power is applied blowing the fuse. Just take a peek at that connector and see if it look like it has integrity. It's hard to get a good look. Maybe a mirror/flashlight.

You may want to pull off the cube relay on the Lambda box and start the car to see if the fuse does not blow. If it does blow issue is more than likely upstream of the Lambda box.

[Bob Kontak]

Originally Posted by walt

Pic of connector

Use it as is. It's ugly but functional.

[walt]

The fuel pump is not coming on when the sensor plate is lifted but the 12 pin connector looks fine. Where is the Lambda box, under the passenger seat?

[TibetanT]

Yes! Under the passenger seat is where the Lambda box lives, or rather should be.

[Bob Kontak]

Originally Posted by walt

The fuel pump is not coming on when the sensor plate is lifted but the 12 pin connector looks fine. Where is the Lambda box, under the passenger seat?

OK - You found a big problem. Lambda circuit is secondary to fuel pump. You may have more headaches with the Lambda but you are not starting without fuel pressure.

These are the thing I know off the top of my head.

Check/wiggle fuel pump fuse. Spin it to bust corrosion. Squeeze the contacts a wee bit together. Scrape contacts if full of the white stuff you see on battery terminals. Some say use a number 2 pencil in a drill, eraser side out, to clean off the crud.

Wiggle the red (fuel pump) relay in the front fuse box. Closest to the driver. Take it out put it back in. Spread the pins a micro bit with a single edged razor blade to make wider. Just make a better connection.

Run the lift test.

Change out a red one for a black one.

Run the lift test.

OK - that's the easy stuff.

Behind the air sensor there is a connection. Just below the black rubber bellows but definitely behind. That connection must have the correct wire to it and it must be fastened properly. Your fuel pump will not run unless that connection is tied into to the front red relay. First step, is there a wire connected?

[TibetanT]

Did you remember to hook up the ground strap?

[Bob Kontak]

Originally Posted by TibetanT

Yes! Under the passenger seat is where the Lambda box lives, or rather should be.

The cube relay is on/near the front driver's side corner.

[boyt911sc]

Originally Posted by walt

The fuel pump is not coming on when the sensor plate is lifted but the 12 pin connector looks fine. Where is the Lambda box, under the passenger seat?

Walt,

Spend a few minutes reading DKLever48's thread about FP relay tests. Everything you need to know how to test and evaluate the 5 terminals will give you a head start in troubleshooting your current problem. I strongly recommend using a 12-volt test light. If you have any question, just ask. Keep us posted.

Tony

[Bob Kontak]

Originally Posted by boyt911sc

Spend a few minutes reading DKLever48's thread about FP relay tests.

http://forums.pelicanparts.com/porsche-911-technical-forum/673014-fuel-pump-relay.html

You will get it.

[walt]

Everything checked fine except terminal 85 maintained ground when the air flow sensor plate was lifted. The DKlever post went off on another direction and I am uncertain what to check for next. Fuel pump runs when jumping #30 and 87a. Thanks for the help so far - making progress.

[timmy2]

Did you disconnect the cold start injector connector and air metering plate connector while you were in there?
You may have them swapped. (Many have done this)
Cold start injector should have yellow and red/black wires. Air flow switch should have brown and brown/red wires.

Or, you may have pinched and grounded the brown/red wire from the air flow switch somehow.
Disconnect it from the back of the air flow switch and see if the engine starts.
If that doesn't work, disconnect the red/brown wire from the white T connector just below the CDI box(with a red wire)
Keeping the red wires connected and try to start.
Could be a ground in the wiring for the safety switch, or could be the safety switch itself.

[theiceman]

Originally Posted by timmy2

Did you disconnect the cold start injector connector and air metering plate connector while you were in there?
You may have them swapped. (Many have done this)
Cold start injector should have yellow and red/black wires. Air flow switch should have brown and brown/red wires.

Or, you may have pinched and grounded the brown/red wire from the air flow switch somehow.
Disconnect it from the back of the air flow switch and see if the engine starts.
If that doesn't work, disconnect the red/brown wire from the white T connector just below the CDI box(with a red wire)
Keeping the red wires connected and try to start.
Could be a ground in the wiring for the safety switch, or could be the safety switch itself.

this .. I bet you hooked up the safety switch and the CSV wrong ( mixed them up ). was nice of Porsche to make them both blue.. the pump isn't starting because the safety is tripped.

fun part is getting in there to troubleshoot.

[walt]

The wires are sheathed and I can't tell what color wires go where but, I have a black plug going to the air flow plate and I have a blue plug at the CSV. Sound right? I really didn't pay much attention to it at reassembly thinking Porsche would have made all the plugs different to avoid this.

[theiceman]

if you have an 82 should you not you have one to the back of your air meter also ?

[boyt911sc]

Originally Posted by walt

The wires are sheathed and I can't tell what color wires go where but, I have a black plug going to the air flow plate and I have a blue plug at the CSV. Sound right? I really didn't pay much attention to it at reassembly thinking Porsche would have made all the plugs different to avoid this.

Walt,

The electrical plug has a rubber cover protecting the wires. Remove the rubber protector and inspect the wire color. It's good to have the colored plugs but don't rely on it 100%. It might have been replaced or fixed before, who knows. If you have not labeled the plugs when you removed them earlier, it would be prudent to use some common sense and inspect the wires.

I had a hard time troubleshooting the fuel pump with a newly rebuilt engine wire harness. The engine harness had all the right colored plugs and with the correct labels. But one misplaced wire for the AFS (air flow sensor) in a new wire harness was the culprit. Not only you need the right colored wires but the actual connection is critical. Connect the brown wire at the wrong side, and it won't start.

Test the continuity of the terminal #85 (FP relay socket) and if it does not open or break the circuit after lifting the AFS (air flow sensor) plate, you have located the problem. Keep us posted.

Tony

[boyt911sc]

Originally Posted by theiceman

if you have an 82 should you not you have one to the back of your air meter also ?

Theiceman,

Could you clarify a little bit more what should not be there? Thanks.

Tony

[timmy2]

Originally it would have been Blue to CSV, Green to Air Flow switch, Black to AAR, Grey to WUR.

For the CSV think blue is cold, for the Air flow safety switch think Green is go.
Black is always the AAR (Unless changed) so no memory tricks...

Check the wires for colors under the rubber cover at the plastic housing, Pry it off and pull it back.

[walt]

These are the wire colors in place:
CSV = (2) yellow and (1) Red with black stripe
Air Meter = (2) Black with Red stripe
AAV = (2) Brown and (2) Reddish with yellow stripe

The CSV looks right but could the AAV and air meter be crossed?

With the Air Flow sensor and AAV plugs disconnected I still have a ground connection at #85.