mulik51

Hey. Everybody is defenitly tired of me, with all my L-Jet questions. Sorry, but I want to start HER! So I measured some stuff today. Resistance between Pins # 14, 15, 32, 33 on the harness which comes to the ECU is .004 Ohms. Then ressistance between pins 5,16,17,35 and ground is .004 Ohms. Ressistance between contacts on the Injector #1(I mean contacts on the injector, not the wires which come to it) is .003 Ohms. Ressistance between two wires which come to the Injector #1 is .003 Ohms. Ressistance between injector#1 wires and ground is .8 Ohms. Ressistance between contacts on the injector#1 and ground(just in case) is infinity. The car Porsche 928, 1979(Yes, I know, it should have K-Jetronic, but some stupid guy did transformation), 5-speed. Ignition was turned off, battery disconnected.
So, guys, if anybody knows what it means, is it right or wrong, and what should I measure else, please tell. If somebody would have Porsche 928 1980-1983 in NJ, and would allow me to come and take some measurments I would be really really happy. Becouse I see this car in first time in my life, so I don't really know how it should be.
Thanks a lot,


Klim

Jim bailey - 928 International

Klim the big problem is your car is a bastard , a hybrid , not CIS yet Not L-jet . It starts out with as basic a question as "Is there a power circuit to the fuel injection computer ? " There are several differences between the fuse relay board 78-79 and 1980-84. The only person who could tell you what they did is " some stupid guy " that assumes that the car ever did run since his conversion. For it to have been running I would assume there were several "jumper wires" spliced into the relay board. The engine and engine harness to fuel injection computer is probably fine since both no doubt came from the donor car what probably did not get changed is the fuse relay board . So ohming out the engine harness is probably rather pointless . Can the car be made to run ? sure it just needs a lot of research and thought about what circuits are missing / different from CIS to L-Jet. If you had spark and if the cold start injector the ninth injector is firing in a shot of fuel the car should start and run for a few seconds . Has the car EVER run since you have seen it ?

toofast928

Klim,
Wanna go back to CIS? Why Why L-Injection?? Did it ever run??

mulik51

Hey. The car ran but when I saw the wiring job which was done to my car, I ripped it out(really stupid of me). The wiring was really, really messy.
Don't worry about the relay board. I bought the relay XVI and connected it all by myself.(8 injectors and 2 wires to the ECU) I am getiing the 12V on the injectors, and on the ECU, but the spark plug is dry, so injectors do not open. From my point of view, there are three problems which can be. Bad injectors, bad ECU, and ECU not getting the signal from the tach, becouse I redid all the injector wiring(power and to the ECU), by service manuals, so, now, it must be right. I checked all ground points, they are good too.
So, I have one little question: under what conditions can you burn an injector? What power can it transmit? And what kind of impulse should it get from the ECU?
I thought about K-Jetronic, and later I will defenetly change my system(becouse I want to supercharge my beast, and I heard that for Motorsports 928, Stage 3 Kit, L-Jet does not supply enough gas), but don't want to spend like a fortune for a new system yet(I can't). If it turns out that my ECU is bad, then I am defenitly going back to CIS, but not now.
BTW, to do the transformation back to the CIS, should I get air mixture control unit?(the thing on which you install fuel distributor).
Thanks a lot for your answers,

Klim

2V4V

Klim,

Search the forum, I did a bit of a treatise on the function of L-Jet a coupla weeks ago. Basically, the L-Jet injection pulse is a shaped and modified pulse from the ignition box (term 16) which goes to pinout 1 on the harness. L-Jet manipulates that pulse and modifies it using inputs from Temp I, Temp II, the AFM to come up with the final injection pulsewidth.

Try hooking a tach up to pinout one and see if you get a signal.

I gave you the resistance figures in the last thread for the injectors to ground, if they are .00anything Ohms, you have an injector issue or a harness issue. If the injectors give you the ~2.3 Ohms resistance at the injector, then you have a harness issue.

As Jim said, (like I said when I started this in the last thread) it all depends on what got undone. Assuming it ran before, then it's just (in the words of The Cat in the Hat) a question of 'calculatus eliminatus' - find out what you've not...

Electricity is (a lot) like water. Figure out where the pipe is busted, or hooked up wrong and you solve the problem.

Greg

FBIII

I bought an 83 euro w/o an engine. I put a 84 US 4.7 in it. I used the 84 fuse panel and both front wiring harnesses. It wouldn't start. The injectors were not clicking. In my case I was getting 12 volts to relay 16 through the ignition switch, but the relay did not have a constant 12 volts that was required. I spliced in a wire tothe relay and then it ran. It took me a couple of hours looking at the factory workshop schematics to figure it out.
Fred

mulik51

Hey, thanks a lot. Greg, do you mean that I should get 2.3 Ohms between the injector contacts, the actuall terminals on the injector? I am getting .003 Ohms between them. I saw your post, and looked Rennlist 10 pages back but that still didn't answer my questions.
I am afraid that when I was connecting the injectors, I could burn them. By my calculations, they(injectors), should get up to three amperes on each of them. Tell me, is it enough to burn an injector?(becouse I don't want to buy set of injectors for 350$, and then find out that it wasn't them.) I connected the injectors through relay first, but then tried connecting them without relay(so when the battery was on, injectors were on.)-it didn't change the thing. Actually, when cranking, I am getting some kind of pulse on the wire which should go to the ECU from the injector. But I don't know is it right pulse or not, becouse book says that ECU should ground the injectors. Thanks a lot,

Klim

2V4V

Klim,

If you get much less than 2.3 Ohm at the injector terminals (on the injector itself) they are toast.

The L-Jet cars use "low-Z" or "peak-and-hold" injectors. (pick the nomenclature that you like). Basically, they use a surge of current (~1 millisecond) to push the pintle open, then the ECU backs off on the power, because you don't need as much juice to keep it open as to open it.

Yes, the injectors are always "hot" and are grounded by the ECU. The shaped ignition pulse determines how long they are grounded for.

If you applied a steady 3A current to them for any length of time at all, I would not be surprised if they fried.

Greg

mulik51

Oops. The thing is that when I looked at the wiring diagrams, there is one wire which gives power to ten wires(8 injectors and 2 ECU). Becouse I have 1979 car, they were not connected. I heard that for injectors and ECU you need a steady power, like from battery. So, then there were my calculations, assuming that L-Jet was made by Germans, and the injectors harness is original, injector should be able to hold up to what the harness can hold up to. So, the wires which come to the injectors were like 1mm thick, from physics, it means that they can hold 4Amp. So, I connected 12Gauge wire, becouse it can hold 35Amp for this ten wires. Looked right to me.

So, Greg, are you saing that I need to apply really small steady current to injectors, becouse when injector needs to be fired, ECU will send more current to it?
But whrere will the ECU get the power, if they (injectors and ECU) get power from one source?(Assuming that my wiring diagrams are right).
And becouse I fried the injectors is there a chance that I fried the ECU?

So, the big question is, what steady power should I apply to the injectors not to fry them?

Thanks a lot,
I don't know what I would do without your help, guys(definitly would go back to CIS),

Klim

Carl Fausett

Miulik -

I know I am biased, but for my money, I'd definately dump L-Jet and go back to CIS if it were me. You'd be driving your car instead of working on it. CIS is mature technology and is very trouble-free.

...and why did you look at our Stage 3 kit for your car? (I oughta take that thing off the website) the Stage 1 and 2 kist are meant for street use and we fuel
them fine. Stage 3 is for racing only - wrong kit for your application.

I've got a supercharger kit for your car in CIS at just $4,295 and it is available on payment of $179 a month. CIS. Rock-steady. Dyno'd it in front of god and everybody at the Wichita 928 OCIC convention.

2V4V

Klim,

If you wanna go back to K-Jet, Carl can help you better than I can. Either K or L, Carl has a slick kit.

I'm gonna skip another paragraph on actual v. technical electrical flow and just cut to the chase....

One wire going to each injector is wired directly to the "+" that comes off term 87 on relay XVI.
The other wires are wired down to 4 pairs of 2 injectors then fed to the ECU. The ECU then provides the "-". The amount of "-" is regulated by the ECU, not by the size of the wires. If you hook the injectors directly up to "+" and "-" you will get fried injector. Period.

You have to limit the flow of current through the injector. That's what the ECU does.

You don't have to "do" anything to power the injectors. Hook them up directly to term 87 on XVI. Then hook the other wires from the injectors up to the ECU. Remember, they must go into the ECU as 4 pairs, do NOT start hooking them up in parallel to save wire or something, you'll reduce the ohm load of the injectors and fry them or the output section of the L-Jet or both.

If your .000x ohm reading on the 2 terminals on the injector is correct, you've already fried them.

Greg

mulik51

Allright, cool, now I definitly know that I need to buy new injectors.
Greg, is there a way to check if the ECU works and is not fried? Becouse if I need to change the ECU and L-Jetronic injectors, then I better go to CIS.

Carl, when going from L-Jetroinc to K-Jetronic, I assume that I need to change 8 injectors, by warm up regulator, new fuel pump, fuel distributor, new fuel rails, fuel accumolator, new air-filter box. Is that it, or I need to get something else?

Thanks a lot,

Klim

John..

Jim, you are wrong, there is only one real "Bastard" 928 and it has L-Jet . On a more seroius note though, conversions like that can be tricky for sure.

Mulik, if you need a set of stock L-Jet injectors, I have a fine used set from the turbo conversion. They need new rubber ends, but 1 hour with a hack saw and some fuel hose and you'll be in business. Drop me a line if you want them. I also have some other L-jet odds and ends avaialble if you might need them, like the stock regulators and a few lines. I also have a full L-Jet brain if you need one.

Carl Fausett

Working from memory, you need:
Intake manifold "shoe" w/throttle body and fuel distributer
CIS intakle manifold
8 CIS injectors
Colstart injector
Warm up regulator
Aux air valve
CIS fuel pump (much higher pressure than L-Jet)
CIS accumulator and filter.

I have some of these parts used, if you are interested. The expensive "Euro" intakes and throttle body are not needed if the goal is supercharging.

mulik51

John, how much do you want for them? I may be interested.
Carl, what is the difference between CIS intake manifold and L-Jetronic manifold. I don't get it, do I need to change throttle body? What parts do you have? (Right now I can spend 800$ on either L-Jetornic or CIS, whatever will get my car running for this money)
Thanks a lot guys, my e-mail is: mulik4@yandex.ru. Just in case.

Klim