1976 911 sc (#4 cylinder not firing) (Help)

[mcdragracer]

Hi I'm brand new to this forum, the problem I'm having is #4 cylinder is not firing, I did all my basic checks and what I found is that cylinder is lacking fuel due to I swapped the lines on top of the fuel dist head at #3 and #4, now the problem is at #3 not firing, so I have come to the conclusion that the fuel feed hole from the fuel distributor doesn't have enough fuel pressure when running.

Now when I have the key on and lift up on the sensor plate #4 has a good spray pattern out of the injector (car has all new injectors), but what I seem to notice is when the engine is running I crack the banjo bolt loose at the fuel dist head and the gas doesn't seem to flow out as fast as the other one's thus coming to the conclusion I have low fuel pressure there, so my question If I rebuild the fuel distributor with a $100 kit, will that fix my problem?

The car runs great/idles fine and rev's up fine on 5 cylinders.
Engine is upgraded to 3L and everything else is stock.

[Bob Kontak]

Originally Posted by mcdragracer

so I have come to the conclusion that the fuel feed hole from the fuel distributor doesn't have enough fuel pressure when running.

Good work. What you have found seems rational.

Four is spraying a "good" pattern so why not put Seafoam in the gas tank and drive it for a tank or two vs ripping your distributor apart.

Seafoam is robust and favorably abrasive - however, not the best in all applications. Think of it as using steroids vs antibiotics.

If you get to the point four is working, change your fuel filter.

Confused as to why four sprays but does not allow the cylinder to fire. Is it weak or dead?

[boyt911sc]

Originally Posted by mcdragracer

Hi I'm brand new to this forum, the problem I'm having is #4 cylinder is not firing, I did all my basic checks and what I found is that cylinder is lacking fuel due to I swapped the lines on top of the fuel dist head at #3 and #4, now the problem is at #3 not firing, so I have come to the conclusion that the fuel feed hole from the fuel distributor doesn't have enough fuel pressure when running.

Now when I have the key on and lift up on the sensor plate #4 has a good spray pattern out of the injector (car has all new injectors), but what I seem to notice is when the engine is running I crack the banjo bolt loose at the fuel dist head and the gas doesn't seem to flow out as fast as the other one's thus coming to the conclusion I have low fuel pressure there, so my question If I rebuild the fuel distributor with a $100 kit, will that fix my problem?

The car runs great/idles fine and rev's up fine on 5 cylinders.
Engine is upgraded to 3L and everything else is stock.

MC,

Test all six (6) fuel lines of the fuel distributors with and without fuel injector installed. Look for any difference in test results. If your engine runs better with 5 cylinders, then you don't need the 6th cylinder. Keep us posted.

Tony

[Bob Kontak]

Originally Posted by boyt911sc

Test all six (6) fuel lines of the fuel distributors with and without fuel injector installed. Look for any difference in test results. If your engine runs better with 5 cylinders, then you don't need the 6th cylinder. Keep us posted.

Tony. Step away from this post and read it.

I know you are thinking three levels deeper than it appears but you are saying you don't need the sixth cylinder in a round-about way.

What are you thinking by saying this? I am curious, no argument.

I do like the test you suggest. Tall baby food jars.............

[mcdragracer]

I like Tony's answer leave it on 5 cylinders if it runs good LOL! And it does, my reference to that is that other than #4 not firing the fuel and ignition system all function normal, without a keen ear you would think it runs fine.

The history on this car is that it had been SITTING a WHILE in Idaho and was purchased by my friend and brought to CA, I was just to hook up the wiring and get it started, a complete engine over haul later, new gas tank (due to a tremendous amount of rust and very old gas), blew out all the fuel lines, new injectors, new fuel filter, removed the fuel distributor, reset sensor plate height etc its finally running, that's my nightmare, I mean story, I might try the sea foam, we use that at work, I just don't know If it's gonna do it.

If I have to go the route of going through the fuel distributor, I just wanna make sure that it would fix the problem, It doesn't look that difficult to do.

[mcdragracer]

#4 is completely dead, but when I swapped the line over to #3 hole at the fuel distributor #4 runs fine and #3 has the problem, the spray pattern on all of them look the same by the way.

It is kind of odd to me that its not firing when all the spray patterns look good.

[boyt911sc]

Originally Posted by Bob Kontak

Tony. Step away from this post and read it.

I know you are thinking three levels deeper than it appears but you are saying you don't need the sixth cylinder in a round-about way.

What are you thinking by saying this? I am curious, no argument.

I do like the test you suggest. Tall baby food jars.............

Mr. Kontak,

I am just recovering from two days of hard labor shoveling two feet snow this weekend. And adding humor when the OP mentioned that his engine was running GREAT with 5 cylinders only. The culprit could be determined by doing a flow rate test. I perform this test as part of the QC test for newly rebuilt FD.

Tony

[mcdragracer]

I was thinking of doing a flow test, but what I have determined, wouldn't a flow test show a problem with the one port in the dist head?

[T77911S]

its best to compare all 6 fuel feeds to each other.

so as tony said

compare all 6 with injectors connected then all 6 without injectors.

I sent my FD to flowtech. its not much more than the $100 kit and it is well worth it.

[mcdragracer]

That's where I'll start.

[mcdragracer]

OK, found the problem, it was the fuel distributor, the one port for #4 wasn't producing fuel pressure when running although when it was primed and I lifted up on the sensor plate it squirted just fine, due to a lack of time for me to attempt rebuilding it my friend opted to get an exchange unit which I had in 2 days, a couple of min's of adjustment and this this runs sweeet!

Thanks for all your guy's input, I will probably add a new thread on the cold start inj not working, I'm gonna look at it this weekend, I know it has no pulse as I put a noid light on it.

Thanks again!!

[Flat6pac]

To the cold start, it might behove you to check continuity between the probe in the left chain cover and your connector wire on the CS injector. Confusion between air flow sensor and CS injector plug in happens all the time without metering.

Bruce