Won’t start, cylinders flooding

[FirstDotLast]

Hey all,

I recently did a bunch of engine out work on my 1986 930 and after putting everything back in, it turns over and cranks but won’t run.

When the engine was out, the majority of the fuel system was overhauled, fuel tank was drained, all the fuel lines, fuel pump, fuel filter, etc were replaced and were tested before the engine went back in the car for leaks and pressure. Fuel pumps work great. Also some vacuum leaks that were present have been fixed.

Now when starting the car, the car cranks but won’t start and the cylinders flood. Gasoline starts dripping out of the exhaust joints.

If it’s flooded, and I remove the fuel pump relays, then start, the car runs for a second off of the residual fuel then cuts out of course.

Here’s what I checked so far:
- timing is correct and at Z1 mark the distributor rotor is pointing at the notch
- removed air box and the mixture plate moves up and down smoothly, no sticking that I can tell
- plugged the cold start injector line and same condition, too much fuel
- pulled all spark plugs and they are all at least a little bit wet which tells me it’s before the injectors? Unlikely all 6 injectors are bad

Could this be the mixture being way off? That seems unlikely as it shouldn’t have changed but I did fix all the vacuum leaks. Could it be bad plugs? Also seems somewhat unlikely. Any other ideas of where to look? Why is it getting so much fuel/not combusting it? Thanks!

[mark houghton]

Well of you've seen my recent thread about injectors squirting, at least mine isn't as bad as yours. Those injectors cannot squirt fuel unless the air plate metering arm is deflected so far as to open the fuel delivery ports in the fuel distributor without engine vacuum pulling the arm down against the control pressure established at the WUR. Two possibilities come to mind: Either someone adjusted the mixture screw down way too much (in which case you'll hear the injectors squeal with ignition on but car not running...provided you pull the metering arm plug to the safety switch to force the pumps to run), or your WUR cold control pressure is way out of whack, i.e., too low, so when you crank the engine and the metering arm deflects...it's deflecting too much and dumping in too much fuel. The amount of fuel you're describing is a boat load. Best guess is something wrong with the WUR. Do you or your wrench man have the gauge setup to check system and control pressures?
Of course the other place to look is ignition, which might be more probable. How is your spark coming off the coil?
EDIT: One more thought might be the fuel return line to the tank. That's an integral part of how the WUR controls pressures. People on here need to chime in with more knowledge than me.

[Alan L]

+1 above.
Best place to start would be the WUR pressure, and confirm you do have spark.
Alan

[Bucketlist]

You need to hook up a set of cis gauges and check fuel control pressures. Post what you find so someone can help. Did you have your fuel distributor apart? Is your system pressure regulator all there? Let us know what you find.
Also read:
https://forums.pelicanparts.com/911-930-turbo-super-charging-forum/547032-sticky-common-answers-why-my-car-doesnt-start.html
Good luck!

[FirstDotLast]

I did go through the sticky and debugged as many things on the list as I could so far. Got a bit busy with the Easter holiday today but will hookup the gauges this week and check the fuel pressures.

Forgot to mention I checked the ignition also and every spark plug individually is firing just fine. Also, as I mentioned, once I unplug the fuel pumps, the car runs for a second and sounds great while it burns off the gas that was in to the system.

Really leaning towards a fuel/mixture problem. I’m not sure if there’s a more proper procedure to bleed the fuel head but I have about 7 gallons of gas in the car and ran the system for a full 5 minutes straight with the metering sensor unplugged. While I was doing that I briefly pressed the metering plate down and heard fuel flood the cylinders via the injectors. Everything individually seems to be working properly, hopefully the fuel pressures give me more insight.

[FirstDotLast]

Originally Posted by mark houghton

or your WUR cold control pressure is way out of whack, i.e., too low, so when you crank the engine and the metering arm deflects...it's deflecting too much and dumping in too much fuel.

Also, just to check my understanding...right now, when the car is cranked, I watch the the metering plate and it barely moves at all. My understanding is that in that case, the FD is opening very little or not at all yet somehow fuel is getting in to the cylinders. Maybe it's possible the pressure is too high thus causing the arm to not deflect enough and so there's not enough fuel to ignite in the cylinders? This seems unlikely though given that there's enough fuel that it drops out of the exhaust. Is there another place the fuel can be coming from? I've tried with the cold start valve plugged and same condition.

[mark houghton]

Originally Posted by FirstDotLast

My understanding is that in that case, the FD is opening very little or not at all yet somehow fuel is getting in to the cylinders. Maybe it's possible the pressure is too high thus causing the arm to not deflect enough and so there's not enough fuel to ignite in the cylinders? This seems unlikely

Seeing as how you've got fuel drooling out of the exhaust, it's not a lack of fuel :-)
Just cranking the engine doesn't create enough air flow as it would with the engine running, so don't expect the metering arm to deflect a whole lot. When cranking it needs to move just enough to trip the safety switch and power up the pumps, just a small amount...a millimeter if even that but I've never watched mine while cranking or running. Once running, if your control pressure is way too low, the arm may deflect way too much. Let's see what your control pressures look like and go from there.

[Alan L]

When you say you'plugged' the CSV, what do you mean?
Alan

[FirstDotLast]

Originally Posted by Alan L

When you say you'plugged' the CSV, what do you mean?
Alan

I put a regular bolt of the correct size in the line so no fuel could flow to the CSV to eliminate that as a cause

[Alan L]

Where did you do that? At the fuel head? Did you substitute the banjo bolt?
All you needed was to pull a wire - on the TTS or starter solenoid.
Alan

[FirstDotLast]

Originally Posted by Alan L

Where did you do that? At the fuel head? Did you substitute the banjo bolt?
All you needed was to pull a wire - on the TTS or starter solenoid.
Alan

Yes at the fuel head to ensure no fuel went to the injector. That being said, it’s around 70-80 degrees F here so I’m not sure the cold start valve matters at those temps.

[Alan L]

Except if it is malfunctioning and firing every start - like mine was - and flooding the engine. Fuel in the exhaust.
Alan

[FirstDotLast]

Originally Posted by Alan L

Except if it is malfunctioning and firing every start - like mine was - and flooding the engine. Fuel in the exhaust.
Alan

Ah right that’s fair. If I cut off the fuel to the valve and I’m still getting flooded, it must not have come from there I suppose (or that’s one of the potential issues eliminated as a source)

[Alan L]

Yes, you seem to have eliminated the CSV.
So that takes us back to WUR pressures.
When you pull the plug at the back of the airplate (key on) you get pumps whining - are you hearing the injectors as well, or just pumps?
Alan

[FirstDotLast]

Originally Posted by Alan L

Yes, you seem to have eliminated the CSV.
So that takes us back to WUR pressures.
When you pull the plug at the back of the airplate (key on) you get pumps whining - are you hearing the injectors as well, or just pumps?
Alan

Just the pumps and fuel rushing through the return and then when I push down on the plate, I hear the injectors start squealing

[Alan L]

Right, so we need WUR pressures.
Alan

[FirstDotLast]

Busy work week, finally made it in to the garage. Here's some fuel pressures I was able to get:

WUR part #: 0438140-153
Temp: approx. 24 deg C (75 deg F)
Cold pressure: 32 psi -> 2.2 bar
Cold System pressure: 97 psi -> 6.68 bar
Warm pressure: 54 psi -> 3.7 bar
Warm System pressure: 98 psi -> 6.75 bar

The other thing is that I ran the pumps for about 10 minutes to get the warm pressure, I think when I first turned the key I heard the injectors squeal for just a half second or so.

Then, after getting the pressures, I wanted to see if anything got in to the cylinders so I started pulling the spark plugs. All the plugs were at least a bit wet but when I pulled cylinders 1 and 5 fuel came pouring out...a lot... like the cylinders had to be full. Thank god I didn't try to start it first as the engine would absolutely have been locked.

So it seems like these pressures are pretty much fine but does it seem like fuel is getting pumped to the injectors even when the car isn't running? I shouldn't be getting fuel to the cylinders when running the pumps, it should go through the return line to the tank right? The piston in the FD is definitely not stuck, it moves up and down smoothly and at the bottom is in contact with the mixture plate arm.

Not really sure where to go next other than trying to adjust the mixture screw

[FirstDotLast]

Ok a bit of progress, I turned the mixture screw out 2 full turns and the car idled but it idled like garbage. Lumpy, blowing tons of smoke everywhere. The AFR was bouncing a bit between 10.5 and 11.2 which seems like it's still way too rich. If I keep turning the screw out, car starts to die.

Guess it was a really bad mixture problem after fixing vacuum leaks but now need to get it to idle properly.

[mark houghton]

Holy crap, you had cylinders 1 and 5 filled to the top with fuel? No bueno amigo. Who knows how much is sitting in the other cylinders. It may be wise at this point to drain and refresh your oil, pull all the plugs and let that gas evaporate. Maybe stuff an air hose down through the plug holes to speed that up. Unless I'm missing something in your description, can't think of running it with all that gas in the cylinders and likely maybe fouled plugs. Mixture adjustment won't tell you anything until all that gas is gone.

I'm scratching my head here. Your pressures are fine, all acceptable ranges. If you've been following my recent posts, take a close look at the position/height of the metering plate. If it's too low...as mine is for whatever reason...then you will squirt gas through the injectors as soon as you turn on the key. You left your pumps running for 10 minutes just to warm up the WUR for your pressure tests and dumped pints of fuel into the cylinders. That was my concern the other day when I checked my pressures, so instead I connected external power to the WUR to heat it up (3 minutes is enough) for the warm CP before just briefly running the pumps up to pressure.

So you got it running with 2 lean turns (that's a lot btw) on the mix screw, but still way too rich. Surprised your idle didn't improve with adjusting it even leaner. I'm not being much help, just brain dumping at this point. Something way out of whack, we're all missing something here.

[FirstDotLast]

Yea something is definitely out of wack. When I pulled all the plugs and hand cranked the motor it flushed the fuel out of the cylinders and I let them dry out. I have fresh oil and brand new spark plugs to put in once I get it at least somewhat idling.

My mixture plate doesn't look off, it sits properly in the bottom of the cone.

Even more strange -- I backed the mixture screw all the way counter clockwise as far as it would go trying to lean it out and same conditions, AFR at ~11. So now I sort of have no idea where I am on the mixture screw except all the way lean and still getting way too much fuel. Is it possible there's an issue with the fuel head that would show as correct pressures but push fuel to the injectors? Or am I getting in to bad injector territory.

It's really showing symptoms of the fuel head pushing too much fuel in to the intake despite all the pressures looking correct and the piston definitely not being stuck. If I remove the fuel head, what should I look for?