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B21 Kjet low idle, no power, '78 242

Frequency valve still not coming on. I decided to do the diag on the o2 system again, ended up at F3, no voltage on the system sensor relay terminal 86 (blue wire), F5 Voltage at aux air valve connector. I checked the blue wire on the fuel pump relay, had voltage. Noticed the relay was very warm, so I popped the cover off and saw this:
OsUrx7il.jpg

Black and crunchy solder directly to the left of the K21 marking, a bit hard to see in the pic.

So F5 told me to "repair wire from CI system pump relay to sensor system relay terminal 86" All the exposed wiring wiring looks fine, and the sheathing isn't damaged anywhere.

Trying hard not to get really frustrated with this CIS stuff, not easy though
 
*loading parts shotgun*...

Throw K Jet in the scrap pile and megasquirt EFI is what I'm starting to lean towards. I don't even know what way to look now. Ya I have to check the timing but since there is an obvious fueling problem why bother till the fuel is sorted out.

Is there a point to doing the fuel pressure test? I already know it has a problem, almost no fuel is reaching the engine apparently. It's not the pumps. The stupid frequency valve isn't working but I can't find an explanation for what it does in simple English. Seems improbable it is causing this much chaos though. My ohmmeter fried so I will get another tomorrow to see if it's good but still...

What should I do next? The only guy who works on this ancient stuff near me retired a while ago.
 
If the frequency valve is not operating then the O2 sensor and control unit are not managing mixture and you will be rich. High fuel pressure out of the Control Pressure Regulator will lean out the fuel.

The fuel pressure regulator in the fuel distributor lowers the appx 90 psi pump pressure to about 70 psi. The CPR regulates that pressure based on engine temp. Feeds about 20 psi (rich) back to the fuel distributor with cold engine. Raises the pressure up to the low 40's (lean) with a warm engine.

My Bertone's CPR was feeding the 70 psi back to the distributor and creating a very lean mixture. It is off to visit the CPR spa in Texas at the moment. They are repairable by DIY efforts but I gave up after having it off and on more times that I wanted to think about.

If the O2 sensor/frequency valve is not operating you are delivering higher than needed pressure to the injectors driving it rich.

You probably have both problems but they will not cancel themselves out.

That's really all the CIS does. Is that simple enough?

Much more info on the CIS system here: http://forums.turbobricks.com/showthread.php?t=289775
 
Thanks for the help! I guess I need a frequency valve and CPR then, gives me an idea where to point the shotgun. O2 sensor is new, but fuel pump relay is obviously a very poor design and I need to buy a 3rd new one, and do the Dave Barton fix (relay to run a relay :grrr:)
 
The relay driving a relay is a great idea.

Lets not pull the cannon lanyard just yet. Measure the O2 sensor operation. If that is moving between 0.4v and 0.8v then verify that the ECM is supplying battery and a pulsing ground to the frequency valve. If you see that and the valve is not vibrating have it cleaned. It is just a fuel injector that any shop that cleans such should be able to do. Because of the semi unique fuel line connector that may be a little more difficult than I said.

After you get that done . . . .

CPRs are a little expensive. $200 for a rebuild, $400+ for a new one and somewhere between for an unknown used one.

You have a pressure gauge in hand now. What is the Control Pressure cold/hot? What is the system pressure. That will tell you where to go next.
 
2turbotoys said:
What should I do next?
Click to expand...

Sit down and breathe for a bit. People keep telling you how to check things out, and you keep saying "nah, I'm going to throw parts at it".

Are you using a greenbook for your diagnostic procedures? If not, find it and read it. I don't know where it may be online these days, with the chaos. The greenbook Kjet section has a thorough description of how to check out the whole system. Among other things, you would use the pressure testing rig. Yes, there is still a reason to check pressure. It is basic to the system.
 
Thanks, I have been using my Greenbooks for the O2 sensor diagnosis. I did put a new O2 sensor in because the last one was very crudded up.

I will test the pressure and report back, and see who around me cleans injectors.
 
Kjet is a mechanical fuel system unto itself. It doesn't need the lambda system to run. Lambda(o2) system is an added on unit to the system to more accurately control the mixture on kjet.

So what you do to approach troubleshooting kjet is to make sure the mechanical fuel injection parts that would be there if it didn't have lambda are good. Then move on to the lambda system.

Otherwise you may have mechanical fuel system problams along with lambda problems that can be very frustrating to get sorted.

I work on this stuff and am not that far from you but I would need help getting to your place to work on the car.
 
dl242gt said:
Kjet is a mechanical fuel system unto itself. It doesn't need the lambda system to run. Lambda(o2) system is an added on unit to the system to more accurately control the mixture on kjet.

So what you do to approach troubleshooting kjet is to make sure the mechanical fuel injection parts that would be there if it didn't have lambda are good. Then move on to the lambda system.
Click to expand...


Excellent advice. Good luck with it.
 
Great point! Helps me focus a bit. I know in EFI the O2 sensor circuit can only change the mix a small percentage, maybe 10% or so. If the fuel pressure test doesn't reveal the problem, I would definitely help get you here and back, plus make it worth your while.

I didn't get a chance to work on it today, which is probably good, so many hours in it with nothing to show made me freak out a bit. Usually that much work ends up with a result haha. Fresh start tomorrow.

Thanks for the input and patience as always guys.
 
I tested the line and rest pressure:
The line pressure is correct at 4.5 kp/cm^2
Rest pressure after pumping the pressure back up, shutting off fuel pump, flipping switch to position 3 = 3 kp/cm^2, Geenbook says minimum is 1.7 so that seems ok also.

Cold control pressure: 1.5 kp/cm^2
Warm control pressure: @ 5 minutes 3.3, at six minutes 3.4 kp/cm^2
I'm not sure if those are good numbers or not. Ambient temp is about 68 deg F if that matters.
 
Warm control pressure is a little low, it should be 3.7. The bimetal spring in the CPR is also affected by engine heat so it may come up to spec on a running engine.

Have you pulled the injectors to check flow and spray pattern?
 
The warm test called for 5 minutes, I gave it 6 and it seemed to be going up still, so it makes sense it would be better on a warm engine. All the other numbers sound good?

I have not pulled the injectors to check that, I guess I should. I don't have a graduated cylinder anymore but can find one I'm sure.
 
You don't so much need one graduated cylinder as just 4 clear plastic bottles so you can run all injectors and compare the volume that they put out. At the same time, you can watch the spray pattern.
 
Ok cool, easy enough.

I guess I'm done with the gauge then? It can't really tell me anything else I assume. I left it hooked up just in case.
 
Leave the gauge on until you're sure everything is working correctly. It's nice to be able to double check the pressure if it starts acting up during further diagnosis.
 
Don't be scared by the awesome screaming sound from the injectors when the fuel starts spraying. Make sure they are firmly attached to the bottles they are spraying in. The fuel pressure is high and will push them right out. They open at about 36psi and full spray is probably about 10psi higher.

If you've never done that test before you jumper fuse 5 to 7 and run the pumps. You remove the intake pipe that comes from the air filter. Then use a long screws driver to raise the plate from the air intake opening.
 
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