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Klim,

CIS manifold is set up for CIS injectors, L-Jet is for L-Jet. You appear to be at the 'either/or' crossroads.

I will proffer this: Carl's setup works very well with CIS. And CIS is pretty simple to work on compared to L-Jet, if you're not electrically inclined.

Greg

mulik51

Thanks, I would really like to go back to CIS, but for 800$ I can buy only used stuf. If somebody would sell it to me, then...
Yeah, BTW, back on earth(I mean on L-Jet). What I did with the wires, which go to the ECU from the injectors, I spliced them in the engine bay, and connected to one wire, and then puted that one wire to the ECU. Tell me, is it right?
Thanks,

Klim

Carl Fausett

Kim,

Help me to understand - what year is your 928? Was it ever a CIS car and you are thinking of going BACK to that, or has it always been L-Jet and the previous owner just messed up your wiring?

How did your 928 get this way? What has been done to it?

John..

You can have the whole injector set for $75.00....I will guarantee they all work, but like I said you will have to put new hoses on them.
Personally I would go with the EFI L-Jet, not the CIS. CIS is great until is gets hosed up, then finding parts can be difficult as well as can be tracking down the problems.

Rich9928p

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?

============

Voltage = Current (Amps) x Resistance (Ohms)

You are correct that all the fuel injectors are powered by a switched connection of battery voltage. Fuel injectors have what ever resistance they are designed to have. The amount of current that flows is a result of voltage divided by resistance.

The L-Jet controller provides a circuit "open - close" switch between ground and the fuel injectors. There may be some resistance in the switching circuit, but not too much or the L-Jet controller would overheat and melt.

The period of the injection circuit being "active" is where damage can be caused. The fuel injection pulse signal is only once per 360 degrees of engine rotation and is some fraction of the cycle time.

You should not put ANY STEADY STATE voltage across the fuel injector. If you apply 12 V across the fuel injector for a long time, you will probably melt it because a lot of heat will need to be dissipated and there is no fuel flowing through the injector which acts to cool it.

I guess we should as why would you want to connect injectors to a steady 12V power supply? That isn't the way to test them anyway. A proper test is to remove them and place them in a rig that has fluid pressure and tests for spray pattern and volume out put. There are many fuel injector services that do this and clean them. This isn't a "back yard mechanic" type test.

Below is a diagram from Bosch's L-Jetronic book that may help you understand how the L-Jetronic processes a spark signal as an input and outputs a fuel injection pulse.

mulik51

Thanks Rich. The thing is that I didn't connect them to the ground ever. I only connected the wires which give power to the injectors, and then connected the injectors in pairs to the ECU. Why my injectors are fried I don't know. I just thought that ECU simply grounds it(like relay), not through any ressistance. So I thought that 3Amp is too much, and injectors fried this way. I don't know why they are burnt now... I have one more question, is there any way to check if the ECU still works(check for resistance between terminals, or something like that). Becouse, first, if I fried the ECU, maybe it gave constant ground to the injectors, and this fried them? And second, ECU costs 500$. If I save a little, maybe I will be able to get CIS on it . So is there a way?

Carl, I have Porsche 928 1979 5speed. I checked the engine number, it supposed to have CIS in it. But I bought the car month ago, so I don't know who puted it in there. I see empty places where CIS stuff should be(like two bolts for warm-up regulator). Can you tell me what parts do you have, and for how much will you sell them?

John, let me wait to find out if the ECU is fried. If it is then I will maybe go to CIS(it depends on the cost), but if it is not fried, I will buy this injectors from you.

Thanks a lot guys, I appreceate your help,

Klim

Rich9928p

Thanks Rich. The thing is that I didn't connect them to the ground ever. I only connected the wires which give power to the injectors, and then connected the injectors in pairs to the ECU.

Every time the ignition switch is turned on (and if the relay works correctly) there should be 12 V to the fuel injectors.

If you connected 12 V to the injectors and the L-Jet connectors for the injectors then no damage should have occured. If the L-Jet is damaged and is shorting pins 12, 14 , 32 and 33 to ground, then your injectors could be damaged.

A simple test for the L-Jet module for your problem is to check the resistance between pins 12, 14, 32 and 34 and the ground pin 16. If the resistance is very high to infinite, then it isn't shorted. If the resitance is low or zero, then the switch circuits are shorted. The diagram is the pin numbers for the connector points, you would measure the resistance at the corresponding pins at the L-Jet module.

I have a used L-Jet module, send me a PM if you're interested.

mulik51

Thanks, I will check it tomorrow and tell you the results. BTW, just in case, how much do you want for ECU?

Thanks,
Klim

Carl Fausett

Kim -

I went looking on my spare parts shelf, and I can supply most of the engine parts you need to return the car to orignal in good used parts.
<LI>
8 intake runners with central intake plenum <LI>
1 Throttle body <LI>
1 Throttle Body seal <LI>
2 seal clamps <LI>i
1 CIS Air Metering assembly <LI>
8 recently tested CIS injectors <LI>
8 injector seals <LI>
8 injector mounting sleeves <LI>
1 coldstart injector <LI>
1 warmup regulator <LI>
2 lines from WUR to Fuel distributor <LI>

... for $360 as a package.

You will need a used CIS fuel distributor (I have one I wouldn't trust it) - they are $350 at 928 INTL unless one of the Rennlisters has one for you. You will still need the 8 OEM fuel-distributer-to-injector lines, and a fuel pump, fuel accumulator, and a fuel filter. Then you should be about there.

mulik51

Wow, Carl, wait let me see the parts on 928Intl and I will definitly will buy that from you. Yeah, and where can I find 8 fuel-distributor-to-injector lines? If I will find those, I will feel happy!

Thanks a lot,

Klim

mulik51

Carl, I want to buy this package from you. Are you sure that I don't need anything else but fuel distributor, fuel pump, fuel accumulator and fuel filter?
Thanks,

Klim

mulik51

Rich and John, sorry but I am going back to CIS. Let it be original. Thanks a lot for your help,


Klim

Carl Fausett

Kim - no I am not sure that this is the complete list... - I have never seen your car and I wonder how far the previous owner got in his CIS-to-LJet conversion.

He would have had to have replaced the fuel pump because the CIS pump would have been too high a pressure.... but he might have left the rest alone if you are lucky.

Remove the right rear wheel, and the forward inner fender liner (2 or 2 10MM bolts) Behind the fender liner on your 79 you should see a fuel filter and fuel accumulator... do you? They may still be there. That would save you some money if they were still in the system.

I bet 928 Intl can set you up with the 8 fuel-distributer-to-injector lines. I had a couple sets two months ago but cut them up cuz I needed the fittings!

mulik51

Carl, on 928 Intl there are two CIS fuel pumps, one says that it is mounted in fender. So, in fender one costs 200$(used) and no in fendr costs 100$(used). What is the difference between them?

Klim

Carl Fausett

Go under your gas tank and you will find a piece of steel with two nuts protruding from the other side. Leave those alone, but follow the steel up and rearward to find two 10 mm nuts that hold that piece of steel up and remove those. Now the fuel pump mount/gas tank pan will come down. Is there a fuel pump mounted right there? I think on a 79 there will be. That'd be the $100 used pump, I think - but the guys at 928 Intl now best.

The L-Jet pump runs at about 45 PSI, and the CIS system runs at about 75 psi -the guy that started to convert your car to L-Jet had to have turned down the pressure by removing the CIS pump.

Ask the boys at 928 Intl if they think the ignition-based emergency fuel pump shutoff would have been tinkered with on your car...