How do I "tune" the K-jet?

Order the Charles O. Probst book (Bosch Fuel Injection & Engine Management). Start there and then you can post up specific questions as you go.

There are several experts on this site that can help out once you get down to diagnosing specific issues.

 

You very much need to go to Steve's great website and download everything that pertains to your car. You need the WSM for the 308GT4, 308GTSi 308GTS QV,328 GTs etc. the service updates and anything else that you find there that applies. All the information is there for the K-Jet. I am not sure but your car may have the K-Jet with Lambda or maybe even the KE-Jet. I don't know 328s but everything you need is there:

http://www.ferraridatabase.com/The_Downloads/Downloads.htm

 

Hey, Lester Is yours running badly?

 

Does the idle oscillate?

 

I got this book and I've read it cover to cover twice. Great book. Having said that I have not touched my injection except to change one leaky injector seal.

My uneducated opinion is that it sounds more like ignition. Stabbing the brakes and engine dying is more like a vaccuum issue. IMO this is what makes these cars fun. They are old and may have many small issues that are victories when we find them. The Bosch K-jet is a known reliable system on averages. Our ignition system is less so on averages. My tech feels it is one of the weaker points on the car and suggested if I'm not worried about originality and I have a failure in that system that going after market will make the car run smoother and with more power than I could ever imagine. I have replaced my wires, extenders and plugs and the car runs good and has for the last 20K miles.

I do have to say it runs great after several hundred miles on the highway. Also just my opinion, good gas and a long highway drive is the best tune up for the Kjet.

As Soucorp and I believe others have suggested, get yourself a timing light and put it on each wire and see what kind of blink you get out of each wire. For this purpose get one of the timing lights that doesn't require a battery connection.

 

I'm not expert on things technical, so please take this with a grain of salt. But I recently had this problem with my 88 328 and took it to my mechanic. After ruling out the Warm-up regulatory, he discovered that one of the vacuum lines was breaking down and had small holes in it. New line, and the car apparently sounds much better (havent had a chance to pick it up yet). Obviously I dont know whats going on with your car in particular, but a potential area to check at least with respect to the idle oscillation.

 

Check vacuum line to ignition and fuel pump operation.

Feedback through shifter is a bad miss...clean spark plugs too.

The only electronic variables on a warmed K-Jet are lambda probe (if buzzing...it's good) and TPS (only for WOT).

The only K-Jet pressure adjustment is at WUR. There are adjustments to each CIS injector line (should remain untouched).

Skips caused by fuel sys could be: bad fuel; dirt in pressure regulation network (causes springs/seats to stick), or; throttle/sensor mechanicals. Most likely is bad fuel.

 

Does it smell bad (running rich)?

Stalling when you chop the throttle and hunting idle can be symptoms of rich running.

Doesn't help with the miss though. Definitely rule out ignition first before messing with the injection system. When the are set right they tend to stay that way, so better to make sure everything else is right before you monkey with it.

 

I had hunting idle and stalling at lights on my 328. It was dirt in the warmup regulator diaphragm valve.
But, I would not suggest diving straight into the WUR as many other factors could cause rich running. There is nothing really adjustable on the K-Jet other than the idle mixture but you would not want to adjust that as a workaround for a possible different issue.
It might be worth checking that the air sensor flap is returning fully when you press on it.
A control pressure gauge will reveal this type of K-Jet issue and that would be the place to start if there are no other more obvious causes of running rich.
This was my WUR adventure: http://www.ferrarichat.com/forum/showthread.php?t=351408

 

Ooops

Absolutely not.

Hey Lester,
Having a PhD from the KISS school of Automotive Technology, coupled with nearly 30 years of hands on actual Ferrari experience, here's where I'd start; the number one fuel injection problem with a 3x8 is the ignition system. Pull the plugs, distributor caps, wires, spark plugs extenders and inspect them, first. Once all of the ignition problems are addressed, then, if need be, we can look at the injection system.

 

Exactly, look when you shouldn't have to look, but know that you should. (I don't tell many folks this, but I used to enjoy working on the Lotus cars... HA!)

I would inspect the extenders closely (looking for burn-through holes) and measure their resistance. The ignition wires are notorious for problems, as well. The front bank is a bit of a nuisance, but no real big deal. Without know the basics, much time and money can be wasted in the diagnostic process.

Have fun!
David

 

Doesn't mean one wire isn't bad. Don't take anything for granted. The wires connect into the caps by a small screw that pierces the center of the spark plug wire. If not a good connection it will be a problem. With a miss like you are having, I'd probably use an ohm meter on the extenders as well just to rule them out and as they will already be off the car. And while you're in there...... since all the plugs will be out, why not do a compression test so you have a baseline.

And not too much blood sacrifice, only a little bit from about half your knuckles.

 

Cleaning spark plugs is easy and reach-able. Pull each wire carefully, one at a time; clean it at the spark plug end; pull the extender and clean it (checking for resistance short is good); if extender removes with wire, separate and clean; pull each plug and inspect first (better yet, take a pic of each and show us all; this will help the advice; identify the cylinder numbers too...recall 1-4 is rear bank and 5-8 is frnt bank, also labeled 1-4)...then clean plug and ensure proper gap. When reconnecting, use anti-sieze on the plug threads, ensure a good connections throughout (PV makes a good point here) and use dielectric grease (silicone) on the connections at the plug and at the extender. I haven't done the wire breakdown at the distributor, so ask for advice for that.

I wouldn't recommend a compression test unless you fully understand the procedure and the analysis; you will need to be able to run the starter remotely with fuel pump off and throttle open; you would want to do dry and wet test for each cylinder; this isn't as easy as it seems. Spend some time reading on this before trying DIY. Leak-down test is also possible here.

Also, for some, cleaning fuel injectors has helped...do a search on this.

 

The Basic Set up on every QV and 328 and mondial I have worked on has been the following.

After a full tune up on the ignition system or confirm all is fine. You need the following tools.
CIS injection tester- The fuel gauge with the cut off valve. This installs into the banjo line at the warm up regulator. This is important, if this is off you are screwed. LM1 wide band 02 diagnostic tool. 3mm allan wrench. basic tools.
1. Take stone cold pres. readings. Fuel and Sys pres. I have a chart I use. Some guys try adjusting the WUR but I just replace them. CIS Flow tech is great source. FYI make sure you have 12v at the warm up regulator. Get your wiring diagram out.
2. Rest position on air flow sensor plate. We always have to adjust these. Makes a huge diff. In the book also and easy to do. Always needs to be lowered. Acess hole is a tight fit next to a fuel line to Fuel Dist but it can be adjusted on the car with everything in place but air cleaner housing. Very important
3. Car warmed up read preasure reading for control pres. Book gives great breakdown.
4. Remove and unplug O2 sensor. Ferrari rec this being unplugged for mixture setting. Install LM1 Wide band O2 sensor in 02 sensor port on car. Warm up car and adjust mixture to 13.1 or a little richer. Sometimes I run a little leaner if the car likes it but I have gotten cold and hot start problems. They seem to really haul ass lean but start and idle better richer.

This method has been done on 8 cars so far with excellent results and only 1 WUR replaced and no other special parts needed and All 8 cars run perfect.

This CIS system is really good if set up correctly.
Larry at CIS Flow tech is the go to man for CIS stuff. I give him the credit. Google him as he will always give tech advice.
Joe Frazar
Savannah, GA