Steve J.

My Euro '78 CIS 5spd was federalized by Wallace Labs (cost - $6,700) when the second owner brought it to Houston from Holland. Because it is more than 25 years old, the car is now exempt from Texas emissions testing so I am trying to identify the function of the added-on items that I plan to remove (air pump, cats, charcoal canister, etc.) There is a single electric fuel injector laying under the spider with hoses on both ends. The input of the injector is attached to the control pressure regulator and the output end connects to the fuel distributor at the fuel return line (to fuel tank). This single injector seems to bleed fuel pressure from the control pressure regulator to the return line when activated by a relay under the pod. Does anyone know what the function of this bypass setup is and what activates the relay?

Jim V

If there was/is an O2 sensor installed it this system or one similar:

http://www.neutronics.com/bosch.html

The valve fine tunes the control pressure for emmissions.

Rich9928p

If it ain't broke, why fix it? You could open up a can of worms that will cost more to fix.

Clean air is something that we should strive for. If we can each reduce the crud that is spit out of our 928s, we can help. Older engines produce many more times the pollution of newer engines. An out of tune engine spits out much more crud than a good runing engine. We **** and moan about the IM240 smog test in the metro Phoenix area. But it FORCES people to tune up their cars because many people just drive them till they drop.

The catalytic converter is a fantastic device for reducing pollutants and doesn't consume much HP at all as it does it. I do not understand why people feel the need to strip off pollution control equipment if and when it is no longer required by their locality (and also in many cases when it isn't). I don't believe that the federal requirement for pollution control equipment ever goes away.

In Europe, people are putting catalytic converters on cars that didn't come with them and their governments give them tax breaks. Here in the US many owners are taking them off for the fun of it.

John Struthers

Steve,
Dennis Wilson the fuel system Guru will probably post in depth -this reply is just to bump the post up to the top of the list-.
But, if memory serves -and to be honest, not that well lately- you are describing the cold start system. What signals the relay for the cold start is well out of my zone of knowledge but I'd guess either a signal from water temp sensor, or the O2 sensor unless they devised a mechanical timer of some sort, or a warm-up regulator to get the engine into a warm idle I admit I'm lost...
If you don't get a response from Dennis or other exalted fuel demi-God's I'll roam thru the parts book and my 'NEW' set of 928 pubs in search of a rightous answer.
For what it's worth you early model folks are either blessed or damned, depending on point of view. What, with no O2, mechanical injectors, a WUR, on one hand and NO computer to fry or confuse you and your engine with bad inputs/outputs on the other hand...
I almost bought that Gorgeous Green 78/79, Euro, auto up in Cleveland last month and would have joined the ranks of the early model members myself. Had I done so... my mission was to camp out in Dennis's front yard until Dennis pounded some early model fuel system knowledge into my thick skull -it was actually planned with Dennis in advance-.
I was a bit concerned as rumor has it that sheep skin seat covers in Oklahoma are usually still breathing -sweating & nervous maybe, but, still breathing- so in a way I was glad that the Euro bid got out of control.
She was pretty though still have it as my screen saver... sigh...

ViribusUnits

Steve, that sounds like Jim V is correct.

The cold start injector on your car should be bolted to the front of the throtal body.

SharkSkin

The cold start injector is on the front of the plenum. The extra injector described by Steve, IIRC, is a primitive positive-feedback mixture control. I don't know the "proper" term, but it has to do with adjusting the air/fuel ratio in response to O2 sensor output via the brain. You don't want to remove it.

ViribusUnits

K-jetronic was origionaly not made to include that injetor. If you retune the car, you can probably remove it for no real gain. Me? I'd leave it, reinstall the O2 sensor, and brain, and enjoy the better fuel milage.

Dennis Wilson

The "injector" is actually a frequency valve. It fine tunes the fuel system based upon the signal from the O2 sensor. Porsche didn't put these on their cars until 1980. On the 924 this sytem with a cat was so effective they were able to omit the air pump. Besides reducing pollution, it will keep your engine from running too lean which can do nasty things to head gaskets and aluminum heads.

If you want the best performance, delete the smog pump but keep the O2 system and cat.

Dennis

SharkSkin

Thanks Dennis... freq. valve...

Also, if you are worried that your cat is plugged(or know it is from the vacuum test) there are units available that will have little or no impact on your power output. I've skimmed http://www.randomtechnology.com looking at their stuff but have no experience with them.

Normy

The frequency valve and the cold start injector are two different things on the big K...

The cold start injector pulses fuel into the intake for a set period of time upon cold start up.

The frequency valve is a device controlled by the computer via inputs from the O2 sensor that opens and closes so rapidly that it makes a buzzing sound, hence its nickname the "buzz valve". Essentially, it varies fuel pressure to a minor extent in order to maintain close control of emissions.

Neither device has anything to do with horsepower. Neither hurts either. Some stupid turbocharger systems have made use of the cold start valve in order to provide the extra fuel that a boosted engine needs. It is not a good idea and it didn't work in the end-

I don't know much about the K-Jetronic installation on M28 engines, but the notion of an injector "tacked on" to the intake plenum makes me believe that you are dealing with something that some idiot has rigged. Listen, if it works...deal with it. Drive the car, but be carefull about removing anything and do the research to find out what it actualy came with. This website is your biggest ally in this respect!

N!
'85 S2 5 Speed

SharkSkin

What I was referring to must have been "tacked on" by some idiot in Stuttgart who really did a great job of making it look original. You can see mine here... the fuel line wraps around the oil filler and you can see the banjo fitting just below the crossbar. Just above the crossbar you can see one of the two allen bolts that hold the injector to the plenum. Damn ricers!

Normy

OK Dave.....I can see it clearly now. Whatever you say-

B safe-

N

PorKen

What's the vestigious casting on the right underside of the L-Jet plenum? It's in the shape of the cold start injector base.

When I deleted my L-Jet cold start plumbing, I moved the cold start injector to the front, like on the K-Jet, but I was considering drilling out that unused casting to install the injector there instead.



umc276 had a good idea to wire the cold start injector to a high-intensity-washer type pushbutton under the pod, in order to delete the cold start sensor as well!

Normy

"umc276 had a good idea to wire the cold start injector to a high-intensity-washer type pushbutton under the pod, in order to delete the cold start sensor as well!"


Well, thats great...but I've got an idea: what about some elbow grease and a $2 bottle of aluminum jelly from Wal-Mart for polishing up those intake tubes~

Normy!
'85 S2 5 Speed

SharkSkin

PorKen, take a look at my EGR hookup, red circle in the pic below. Is that what you're talking about?



Normy, many of these older cars are very rough looking under the hood. For example, the pic that I posted earlier in the thread... it was the first pic that I ever took under the hood, before I ever touched anything other than the usual fluid & other under-hood checks that I did as part of the purchase process. Things are looking MUCH better under there now. Looks like your shark is just about perfect... others are just getting started, capisce?