Once again I need to call on the remaining early 240 and K-jet experts still lurking on this board.

The Car:

1980 242, Stock K-jet, rebuild engine, new wiring harness, all stage zero items addressed.

The Problem:

The car has a starting problem related to how long it has been sitting. The longer it sits, the longer cranking time is required to finally start. After shutting down, a 10 second wait is almost instant start up, a 20 minute wait will require 10-15 seconds of cranking time. A 40 minute wait will require 15-25 seconds. More than an hour wait will require 30+ seconds. All night wait also requires 30+ seconds. It has never completely failed, I've always been able to get it to catch eventually. Once the car starts, it runs and idles perfectly at all speeds, NO indicators of performance problems. It has also never died on its own after starting.

What I've tested:

I've tested for spark during the cranking condition and it's always been strong. I pulled injectors during cranking and noted there was no fuel spray. So I removed the K-jet air bladder, shorted the fuel pumps for continuous run and started lifting the flapper valve. I get a good strong conical spray pattern from all injectors when doing this. So I reassembled the injectors, shorted the pumps and tried cranking. The car still exhibits the long crank times even when the fuel pumps are continuously running. This also confirms the fact that I can hear the pumps run and the pump relay click when I'm cranking normally.

It seems like something is inhibiting any fuel flow during normal cranking. However, because I've confirmed running pumps, good spray from all injectors, and normal driving performance, I'm at a loss as to what else in the K-jet circuit could be arresting fuel flow during start up that seems to be wait time dependent.

Any thoughts?

you won't get anywhere without pressure tests. you HAVE to know line pressure and volume from the pump, along with control pressure with temperature, then rest pressure. a weak or incorrect fuel pump will cause hard starts. can't prove it without testing. good luck, chuck.

Point is well taken. I keep putting that purchase off because I'm always right on the cusp of dumping K-Jet for LH 2.2 or Megasquirt. As soon as I have to consider a large purchase in order to keep it up and running, I begin to think the money would be better spent toward the conversion.

The problem is that any problem I have with K-Jet usually starts with people saying "measure the pressure stupid!".

In this case, I may have fixed the problem. Last night, I disassembled the control pressure regulator to test a theory. The theory was that the CPR diaphragm was getting stuck in the down position after turning the car off, causing abnormally high fuel pressure during starting. What I found was a tiny bit of rust on the spring activated plunger, causing it's actuation to be sticky. That plunger is marked in the red circle below.



I cleaned the plunger and reassembled. So far, I've had normal starts with no extended cranking. We'll see if this lasts.

PS - This particular experience has really showed me just how critical fuel pressure is with K-Jet. Not only does it directly affect the ability to start and run the car, varying pressures essentially shift your fuel "map" all over the place by changing the resistance to motion of the air meter. It's amazing to me the system can function with such a wide range of pressure.

I followed Lucid's link to Amazon. I got the part number for his recommended pressure tester. I did some internet shopping and found it again at TheToolwarehouse.net for 89.95 with a 10 percent coupon if I signed up as a new customer with an email.
My total turned out to be 80.96. I thought this might help take the bite out of your frustration if it comes down to you needing to buy one of these.

I took it as good luck or fate and ordered it. Now I have something to be a companion with the fuel fittings I acquired almost the same way when I helped Rusty at RPR close his business.

I fooled around on YouTube and saw people using gauges. One had a way to drop the plug out of the bottom of his CPR and adjust the pressure. He then had to adjust the pressure at the fuel distributor by shaving or replacing shim washers. He checked the system back and forth to tweak it in. The car he worked on must have been a six cylinder as the distributor was up and out near the grill, lucky him.

Interesting that you took yours apart, you are my kind of man! I figure if something is broke it can teach me one thing before I throw it away and you kept it, WOW!

You mentioned trash but did you see any wear spots. Did you check out the heating element operation and see if the connections were good? I think it has to heat up to reduce pressure as it mimics a hot engine. Same goes for the auxiliary air valve to shut down the amount air or when it is cold it gives the engine more air. You may have a dual problem with all these, the wiring or even the thermal time switch around down there.

You mentioned a computer map. These things work in concert to create a mechanical one that once “dialed in” is very dependable in all those start, warming up and hot running modes. I have had to buy two Air Mass Meters and two Idle Air Controls for my other cars.
On the K-jet so far, one CPR, the new gauge set today and the green books which I have rarely used since 1978. I do make sure that I kept good fuel in the car and drive it and now that has me well over 325k in mileage. The fuel pumps went first, so you got to watch those babies in all the models and in every vehicle made with them. No escaping those even a motorcycle has them today!

Passing another thought from experience are those wires in that harness under the manifold are aged. I had a coolant gauge wire play with me once by shorting to ground and trust me that it can scare you until you realize, it has not turned into a steaming pot for crabs out there!

You might be close enough to the right place that you shook and wiggle it and temporally fixed it. That happened recently to another poster with his instrument cluster as his alternator light bulb kept it from charging the battery. It was a loose connection apparently.

Going with the thought of fuel supply/accumulator from another thinker/tinkerer, I know that the in-tank fuel pump has to work even more so if you are at or below a half a tank from full. I know you jumped the pumps on and you would think that would cover filling the lines but when you crank and have to start worn pumps, you need good current flow. I was just thinking out loud and trying to help with ideas to look for.

Also, did you listen for the frequency valve to buzz that I mentioned in one of my other postings.

Well I’ll buzz off of here to hide and watch what happens.

Phil

I may still by the pressure gauge, but I put a feeler out locally and a guy in my area offered to loan the use of his, so we'll see how that goes.

A K-Jet troubleshooting guide I have suggests the most common failure of the CPR is clogging of the passages. They are indeed very small orifices. I blew mine clear with compressed air, perhaps something got back in there. I checked the resistances of the heating coil and it was within spec printed on the coil itself. Another advantage of taking the thing apart!

The frequency valve does indeed buzz during cranking and running.

My in tank pump is the HD version brand new and confirmed working along with the main pump.

My big clue in all of this is that car runs perfectly once started, but fails to fire the injectors when cranking. That really narrows it down for me to a starting component. Fuel pressure has got to be good while running. I just need to pressure test while cranking to see if it is too high or low and go from there.

Sounds like a good plan too me! Got-to have buddies and those with tools are assets.
Phil

Fixed! The problem ended up being two fold. My CPR was indeed out of spec; providing 35 psi of cold start pressure instead of 22 psi. The bigger problem though, was that my system could not hold rest pressure after being shut off. In fact, it would bleed down to 0 psi within 20 seconds of stopping the car. Thus, the fuel in the injector lines would boil off in the heat soak and I'd get vapor lock trying to start the next time around. A new fuel pump accumulator fixed that, and now cold and warm starts are no sweat!

Great to hear back on this one. I was fairly sure your CPR was twisting things somehow as that flap moves so easily. Did you adjust it or have to replace it?

You make me feel better that I sprung for the injection gauge set!

Phil

My CPR was providing a starting pressure that was TOO high, meaning, the air meter had too much resistance to upward motion and leaned out the starting quite a bit. The higher the fuel pressure, the leaner the running, which is the funny thing about K-Jet. Higher pressure increases the resistance to motion of the flapper, so that to get the same amount of fuel, you need more air flow.

A dead cold CPR that allows too high pressure means the spring is not pressing hard enough on the closing valve initially. It could also mean your overall pressure is too high to start with which overcomes the CPR, but then you'd have other running symptoms. I was told that there really isn't a way to adjust the CPR, so I put in a tested used one that provided the proper pressure after confirming my main pressure was correct. The side benefit of a proper CPR is that I get a nice high cold idle speed like 1200 RPM. That feels much better on a cold morning start.

Yep that car is working correctly now, enjoy as it sounds like you got it dialed in! Should do good for a long time just keep good and clean fuel in there.

Phil

Looks like the CPR rebuild earned me 6 perfect starts in the last 24 hours, but this afternoon I returned to long cranking times. I tested that I was getting 12V to the CPR, and did the injector test again. It's confirmed that while cranking, the injectors aren't firing. Then all of a sudden they come to life after 30+ seconds.

I have a hard time believing a pressure problem could be so bi-modal in its occurrence, but I'm out of electrical ideas. If it were pressure, I would imagine it was too high during starting. What else besides the CPR could I swap out if this were the case?

"I have a hard time believing a pressure problem could be so bi-modal in its occurrence, but I'm out of electrical ideas. If it were pressure, I would imagine it was too high during starting. What else besides the CPR could I swap out if this were the case?"

My thought here is that the CPR pressure is on the high side (or line pressure on the low side) resulting in too little pressure at the injectors, which need about 45psi to open.

I think this gets corrected (sort of) during your long cranking episodes because the heater in the CPR finally warms the bi-metallic spring enough to reduce the Control Pressure to where the fuel flow to the injectors can get above the 45 psi threshold.

A test that might confirm this guess work would be to leave the Key ON for say 3 to 4 minutes, then see if cranking time is reduced by the heater's effect.

EDIT: Just realized that voltage to CPR/WUR heater normally comes from Fuel pump relay 87B (Blue wire). Easiest way to test my hunch is to pull the Pump relay harness plug from the relay and jumper +12V from the Red wire terminal 30 (always hot) to the Blue wire terminal 87B.
NOTE: The Frequency Valve will probably buzz! If it bothers you, unplug the Lambda relay (on fender rail) for the warm up test period.

After the 3 to 4 minute warm up, reattach the Pump relay harness plug and try starting to see if cranking time is reduced.


--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

Another thing that effects rest pressure is the Fuel Accumulator.

It's under the car next to the fuel pump.

First..what is the ambient temp as the time to taske to start gets longer?

are you in Calif or Fla? where it makes no diff?

I'm in Oregon, but the problem seems to span 45 degree outside starts and my warm 65 degree garage without changing.

I've been reading the green books on the cold start system, and I'm wondering if the hard starting is the control pressure regulator. This lowers the fuel pressure during starting to reduce the flapper motion resistance and increase fuel flow. If this were not working, I could see the system getting into a lean condition, or not fire the injectors at all, which is what I observed during the testing today.

Any thoughts?

"Any thoughts?"

Like "porkface" says below, I think you need to start by measuring Line and Control fuel pressures. That means a special gauge setup for around $100.

You won't find any much cheaper than THIS ONE for $102 with free shipping. To me it's essential for K-Jet ("CIS") troubleshooting


--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

Hi there.

I have a question for you.

If you use the gauges and a problem is observed, can any of the components allow external adjustment or is it all about just replacing them?

Many years ago, I changed out my control pressure regulator that turn out it was not the problem. I still have it in a box and as a back up for a long, long time!

I am only aware of the fuel distributors Allen screw for idle mixture or Co2 adjustment.

I had a chance to buy the setup from RPR when he closed. He still wanted $25.00 more than the one you posted. His reasoning was it is a factory one. I passed on it because it was in a cardboard “parts” box, it had been a rental tool and he could not answer the same question, as he only sold parts.

I did buy three nice large metal “parts” boxes of cotter pins, electrical connectors and fuel injection hose fittings.
It has several sizes of ring nipple fittings, swivels, copper washers, nuts, a few hollow bolts and such.
I have no idea how many cars they will fit as they are from a company called Metric Man in Lakeside CA.
Probably out of business as a Google does not come up with anything for me.

If I should find some more “mad money” would you add the gauge set to the fittings box for the one car? You say it is important and I trust you advice!

Thanks, Phil

Hi Phil,

I haven't done any K-Jet work in about 8 years now, but here's my take on pressure testing as Step 1.

You ask: "If you use the gauges and a problem is observed, can any of the components allow external adjustment or is it all about just replacing them?"

Off hand I can't think of any needed external adjustment that might be discovered by a fuel pressure test. But for me, knowing that the basic fuel pressures are in spec is a confidence-builder that eliminates a lot of guess work. For example:

"Many years ago, I changed out my control pressure regulator that turn out it was not the problem. I still have it in a box and as a back up for a long, long time!"

Finding good Control Pressure values in the first 15 minutes of trouble-shooting makes the gauge worth it in my book, vs buying and storing an unneeded part costing as much or more than the gauge.

I used to get a lot of stuff from RPR about 20 years ago, before I knew there were suppliers closer to upstate NY. Always got good service, and the RPR catalog is an excellent resource that I'll always treasure.


--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

At first I thought you were losing rest pressure from a bad check valve on the main fuel pump or the in tank pump was not operating. I read onward to the part that you lifted the fuel distributor air flap.
How did you do that?

I recommend you double check how easily it lifts. It should be so easy to fly upward, that if a slight breeze or breath of air from an air hose directed towards it from underneath, it would be like a bird feather in the air. No binding what so ever! The distributor could be gummy or the plate needs to be adjusted to the center of the bore so it will not be sticking.

Is the rubber bellows connecting the two without cracks or any looseness when clamped up? You want good air draw from the engine to pass under it.

The next thing would be the control pressure regulator but you say it runs fine so I blew that off as you would need to have gauges to verify that it isnot doing anything when cold.

Hope I helped,
Phil

Thanks Phil. To answer your question, I removed the rubber bellows to test the injectors. Once that is gone, you can manually lift up on the flap to fire the injectors. When the car has been sitting a little while and the fuel pressure drops, the flapper is very easy to move up and down (like a bird feather as you said). No binding at the bottom end, and I measured for a centered rest point when I had the whole car apart. I did notice, however, that with fuel pumps running and pressure built up, increased force was required to lift the flapper, perhaps a pound or two. I took this to mean the fuel pressure itself affected the flappers resistance to motion, which is why K-jet is so sensitive to fuel pressure in the first place. Given that the car drives perfectly once running leads me to believe this resistance must be normal. If it were binding in that state, the car shouldn't run, or run very very lean.

The rubber bellows is in good condition, very supple and soft with no cracks. This went through a vigorous inspection when I rebuilt the car.

Another thought!

What is your frequency valve doing?
It should be buzzing while cranking and stop very shortly after you stop cranking every time. The frequency valve varies pressure in pluses and effects mixture.

There is a relay on the left fender of my 1978 Lambda model. It turns on that valve and connects the 0-2 sensor signal to the ECU. Two separate circuits in a single throw. Do not know if they still use it on your car?

When I had a bad one it was very intermittent and would cause hard starting. Drove me nuts for a while and I just happened to notice not hearing the frequency valve and that gave me a clue.

Corrosion had crept up from terminals and into the crimped bottom side. I found a new one and coated the bottom with clear finger nail polish to seal it. Easier than a spray can and stopped having to wipe off or tape the terminals.

I saw where a poster is thinking about the thermal time switch. I thought of that but cannot remember how that engaged the cold start injector? You might trace or think about how it may affect things.

Thanks for posting back as it is good exercise for a muscle with no limbs.
Phil