924Board.org

Nobbi · Joined: 24 Aug 2006 Posts: 1397 Location: Germany

Hello,

i am dealing with an engine problem.
My engine is running only on 3 cyl. instead of 4.The 2nd one is cutting out.
I have a good ignition timing and spark on all 4 plugs.Also the gas is coming good through the lines.The engine fires and starts like normal but only on 3 .......
When i pull the sparkplug 3 are lightly coloured black and the one from cyl.2 is wet from gas.

Help will be appreciated.

Nobby

morghen · Joined: 21 Jan 2005 Posts: 9102 Location: Romania

change the plugs first. or you could also swap the spark plug from No.2 with No.3 for example..to see what happens.
_________________
Supercharger and EFI kits
https://www.the924.com

924RACR · Posted: Sun Mar 25, 2007 11:16 pm Post subject:

It also wouldn't hurt to pull that injector and chcek the spray pattern - it's possible it's peeing fuel instead of spraying a proper mist.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

Nobbi · Joined: 24 Aug 2006 Posts: 1397 Location: Germany

Hey,

i changed the plugs and ckecked the spray pattern.Looks ok.
But still not running.A couple of weeks ago the garage adjusted my valves,could this have some kind of affect ?

Nobbi

Paul · Posted: Sun Mar 25, 2007 11:51 pm Post subject:

I'd do a compression check next.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

Nobbi · Joined: 24 Aug 2006 Posts: 1397 Location: Germany

Hey,

did a compression check, it is about 7 bar on the 2 nd cyl.
couldnt check the other ones .But it looks like the compression isnt to bad.It should run atleast with the others.
What are youre rates on an ok-running car?

Have- to -drive-Z3-Nobbi

morghen · Joined: 21 Jan 2005 Posts: 9102 Location: Romania

dude i have over 11 bar on all cyls. 7bar is bad.

sorry i think you have a bad cyl

_________________
Supercharger and EFI kits
https://www.the924.com

moone924 · Joined: 05 Feb 2003 Posts: 869 Location: Douglas Wyoming

put in a jumper in instead of the fuel pump relay and pull the injectors. Make sure none of them are spraying. They should only spray when the sensor plate is moved. I had a similar problem once when there was a small tare in the diaphragm in the fuel distributor on my NA 924. The small tare let enough gas through to flood out one of the cylinders.
--
_________________
Ryan Moone

Always shopping for a nice s2 931 to baby.
New philosophy : one car project at a time.

moone924 · Joined: 05 Feb 2003 Posts: 869 Location: Douglas Wyoming

that's about 100 psi.... which is low by euro standards, my old early engined USA 924 NA only had 90psi across the board.
_________________
Ryan Moone

Always shopping for a nice s2 931 to baby.
New philosophy : one car project at a time.

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

90psi? Wow! A 7.5:1 931 will push over 110psi.

7 bar is really low for your engine. Check the other cylinders.
_________________
1980 931S
15psi boost, MS-II, EDIS, 951 IC, custom intake, Ford 5.0L throttle body, Forge BOV, WB o2, G31 w/LSD, 964 wheels, 968 rear sway, Bilsteins, 200# Welt. springs. A laptop, and a partridge in a pear tree.
1991 964 C4 Cabriolet

Smoothie · Posted: Tue Mar 27, 2007 2:08 pm Post subject:

Suprisingly, Porsche's tech specs actually show 6.0 bar as the wear lower limit - and for all 924NA-931 engines regardless of CR.

There's some stuff here on doing dry, then wet (with oil) compression tests - http://www.924board.org/viewtopic.php?t=18382&start=7

Sometimes you can have a sticky piston ring that affects compression, and a top-cylinder cleaning with a detergent like MMO (Marvel Mystery Oil) may loosen it up. Actually, the wet part of the compression test might even free it up. These procedures will produce clouds of smoke though, so don't do it in a garage - or even outdoors near homes that have windows opened.

Top cylinder cleaning can also remove carbon deposits - more detail on that here - http://www.924board.org/viewtopic.php?t=18019
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

Nobbi · Joined: 24 Aug 2006 Posts: 1397 Location: Germany

Thank you folks !!

I learned a lot more and do check it again.
Let you know when on the road again!

Nobbi

fiat22turbo · Joined: 18 Jan 2006 Posts: 4040 Location: Portland, OR

Hmm, at least you have compression on all four cylinders! Mine has no compression on number 1 (I'm dreading pulling the head for fear of finding a holed piston or worse)