Spark, fuel and compression?

Kelly Bell · Kelly Bell's Garage

Well, my 911 reto project was running, after 9 years of sitting, but suddently a few days ago, it just quit. New Fuel Injectors, new fuel pump, new fuel lines, and tank, I have spark at the plugs. I can smell gas when I crank it. I'm stumped.

Any ideas?

Por_sha911 · Por_sha911's Garage

Timing?

Kelly Bell · Kelly Bell's Garage

Well, I fooled around with that. there are just a few degrees you can change the ignition timing on my 911, as the bolt holding the distributor down has a check on it, so it cant be moved too much.

I was thinking the points (it has CDS), but if I have spark at the plugs, it seems the points cant be so bad. I did change the distrubutor cap and the rotor..............

Jeff Higgins · 09-18-2005, 06:34 PM

Sometimes plugs will fire when pulled from the head, but not under compression. Even if they were brand new when you got it running after its 9 year hiatus, any tuning issues that caused them to foul might have ruined them. Did they look fouled when you checked spark?

2.7RACER · 09-18-2005, 06:57 PM

Let's see, we have compression, we have spark, and we have fuel. Should run right, if they all happen when when they are supposed to.
If the spark timing is off significantly it won't go bang. What else could be happening?
My personal experience shows that flooded cylinders don't fire. Once with my CIS and once with carbs.
I would pull out one or two injectors still connected to the fuel line. Put the injectors into a large glass jar. Turn on the ignition, but do not crank the motor. If the injectors are spraying you have found your problem. Either the mixture screw is set too rich allowing immediate fuel flow or the air flow sensor plate is stuck in the up position.
If you have made some adjustments to the mixture recently, that would be my first choice. If you haven't touched that little almost hidden screw then check the air flow sensor plate for freedom of movement.

Kelly Bell · Kelly Bell's Garage

When I pull the plugs out, they are soaking wet and smell like gas, also they turn black, even tho they are new.

felix_browne · 09-19-2005, 02:33 AM

if it was me i would suspect flooding or fouled plugs or both as one can lead to the next. before pulling the injectors i'd clean the plugs (if they need it) and remove the fuse that deals with the fuel pump. - sorry i don't know which one without looking and my service manuel is at home - but with that fuse removed crank the engine for a few secconds, wait for a few secconds and repeat a few times. if it starts to stumble or even start for a seccond or two then you know it is flooding out and at least then you have a good idea that the issue is with the fuel system.

bug man nrg · 03:07 AM

do a quick check on the injector feed .pull of the air filter and put LITTLE gas in the tb and try to start it .
If it starts and keeps running you have a air lock .
If it starts and cuts out after a few seconds check your fuel pump.
The pump might come on but is not moving fuel .
Pull off the fuel line and see if fuel is comming out when you try to start it
if your fuel side is good then pull the plugs and see if they are wet
if plugs are wet put new one's or burn of the old one's

Jeff Higgins · 09-19-2005, 05:39 AM

Quote:

Originally posted by Kelly Bell
When I pull the plugs out, they are soaking wet and smell like gas, also they turn black, even tho they are new.

There ya go; find out why it is doing that. Even brand new plugs won't live long in that environment. Figure out where your over-rich condition is coming from and fix that, then put another new set of plugs in.

Did it foul plugs even when it ran? The reason I ask is that if you continue to crank an engine that won't fire, it will make the plugs all wet and smelling like gas. The black soot only accumulates when it's running. So it sounds like they first foul (black soot) when it's running, possibly to the point of not running any more; they then foul more from cranking (gas smell and all wet).

Try this: let it sit over night with all of the plugs out so the cylinders dry out. Put some brand new plugs in and see if it fires then. If it does, drive it immediately to a shop with an exhaust gas analyzer and see how the mixture is doing. If you can get that far it should tell you a lot about what is going on.

Kelly Bell · Kelly Bell's Garage

Thanks, guys, I'm gonna work on it with these ideas. I'll be back!

Por_sha911 · Por_sha911's Garage

Definately dry things out and get fresh plugs in there. Double check your wires on the cap to be sure you have them in the right order and in the right places. Also. make sure all your plug wires are snapped on tight to the plugs (you will hear a distinct click) and snug on the distributor cap. I am assuming you haven't taken the distributor out (if so, you might have put it back 180 degrees out).

Kelly Bell · Kelly Bell's Garage

OK, I pulled out an injector, and placed it in a clean jar and swiyched on the ignition and gas came out all rigt - lots of it. A half inch within 30 seconds. So, do I back off the mixture until it stops spraying gas? I know the injectors are good, I just changed them all...........

Kelly Bell · Kelly Bell's Garage

bump. Anyone know why my injectors are doing this?

patkeefe · 09-24-2005, 05:39 PM

Check your plug wires. This happened to me a while back; it was the one time in ten that it was not a fuel delivery problem. You will get spark, but the spark is pretty lame. Check the resistance in the wires, and the coil wire.

Kelly Bell · Kelly Bell's Garage

Do you know what the resistance should be?

patkeefe · 09-25-2005, 03:44 AM

3 k ohms. Do a search on plug wires and early_s_man if it's electrical in nature.
Pat

patkeefe · 09-25-2005, 04:16 AM

3 k ohms. Do a search on plug wires and early_s_man if it's electrical in nature.
Pat

2.7RACER · 06:20 PM

Kelly,
When you put your injector in the jar and got fuel flow you got the answer to your dilemma. The fuel IS NOT supposed to flow with the motor off.
Either the air sensing arm and plate are not dropping down to the correct idle position or the mixture screw is set too rich.
First check the sensing arm for freedom of movement. If the plate is rubbing and dragging, move it so it doesn't.
If the above arm and plate move freely, take your 3mm allen wrench and turn the mixture screw as described in previous posts counter clockwise (left=leaner) about 1/4th turn. Recheck injector fuel flow. Turn the mixture screw just enough to stop the fuel flow when the motor is off and the fuel pump is on.
This will stop the flooding of your motor.
I experienced the same thing a few years ago with my '76 2.7 CIS.
Flooded motors don't start.

Kelly Bell · Kelly Bell's Garage

Hi Doug. Wel, I have checked the sensor arm and it seems to move freely. I have backed off the mixture screw 3 full turns, in 1/2 turn increments. I still get fuel flow with the key turned on. I foole with it all day. When I adjust that screw, it doesn't seem to affect anything.

2.7RACER · 08:33 PM

Kelly,
Sorry for not getting back to you right away. I found a couple drawings from another post (not mine).

Notice how the mixture screw interacts with the arm which raises and lowers the control plunger. You can see if the sensor plate cannot drop down the control plunger is held up causing fuel flow.
You need to verify the sensor plate is not caught against the smallest diameter of the air inlet, which would cause fuel flow with the motor off.
It may be necessary to readjust the sensor plate so it is centered in the air inlet and free to move up and down.
If you still can't get the fuel flow off by lowering the control arm, then there may be something going on inside your fuel distributor. I can't help you if that's where this goes. At that point it may be necessary to replace the fuel distributor.
Bottom line the fuel is not supposed to flow until the sensor plate is sucked up a little by starting the motor. Good luck.