KJetronic fuel pressure testing

I have been chasing this problem since I bought my 412; hot restart after sitting about 5 minutes. I finally bought the CIS pressure test kit and done some initial room temp testing. My question is how to test with the CIS pressure setup when 'hot' so I can see what is going on. It doesn't even need to be that hot; drove about 3 miles on a summer day, no traffic, and shut it off. 1 minute later, starts ok. 5.5 minutes...no start. After between 45 minutes and two hours, it restarts (always right after it comes off the tow truck).
I have replaced the rubber bits in the tanks, fuel pumps, check valves, filters, accumulators, injectors and seals, and some of the rubber lines under the hood. Rubber debris from the deteriorated items inside the tank continues to get into the check valves and will take some time to clear. I got what I could out of the tanks but there appears to be some behind the baffles that comes out...very fine stuff.
Anyhow, I bought the CIS fuel pressure test kit, and have run some testing at room temp. Left side pressure is low (40 psi) and drops to 38 psi when the WUR is in the loop. Holds for well over 5 minutes...at room temp.
Right side goes to 80 psi without the WUR,but the check valve has some debris in it again, so pressure bleeds back. Have not been able to check the right side WUR. Manual says if the pressure is high, to check the return line before adjusting the pressure. Not sure pressure was ever adjusted properly after it had some attention before I bought it. But I have to check the return line first.
Is there a video that anyone has done for testing fuel pressures in a 400i or 412 at RT and hot? The Mercedes guy is good to a point, but there is only one distributor and one WUR on an R107.
Thanks.

 

Warm the engine up, then with the engine "off", unplug the safety switch and turn the key "on" = the fuel pumps will run (without the engine running) -- this same method can be used to measure all four pressures without even running the engine (as the WUR has an internal electric heater so will go from cold to hot). Do you have a copy of the Mondial8/QV WSM? It's the best F reference for your K-Jet without Lambda system IMO. If you don't have a copy, you can get a copy here (Chapter D):

https://www.dropbox.com/scl/fi/twng41f9fpi3ipww7q95v/Mondial8qv_workshop_281-83.pdf?rlkey=5sgpj4yz33jepzrec4x8lcwel&st=2o70574q&dl=0

If you've had a lot of debris in the system, it wouldn't hurt to disassemble and clean the fuel pressure regulator sections of the fuel distributors. Also, there is an o-ring seal in the pressure regulator section that can leak and cause the residual fuel pressure to fall too quickly -- see this thread:

https://www.ferrarichat.com/forum/threads/cis-warm-start-troubleshooting.447404/#post-148352872[/QUOTE]

I have copy of the "400i iniezione" booklet.

Clarification on pressures:
Left side,
regulated supply pressure 40 psi
WUR cold 38 psi
Residual pressure 38 psi after 5 minutes
WUR warm not tested
This regulated pressure seems low compared to the ~55 psi it should be at.

Right Side,
regulated supply pressure 80 psi
WUR cold not tested
Residual pressure 0 psi within seconds
WUR warm not tested.
Right side green o ring in the regulator on the fuel distributor appears ok; not stiff,torn or dirty.
I also isolated the cold start injector on the right side and retested the regulated pressure and residual pressure with no difference from that reported above. Issue does not appear due to a leaky cold start injector.
Re the high pressure, the booklet says check the return line before adjusting pressure by removing shims. Need to do that.

What I have done also is install relay circuit with a momentary switch and LEDs to power the pumps if I needed to. Back when I replaced the relay panel and relays, and the burned electrical connectors from the original fuel pumps, I also split out the two fuel pump power wires from the connector behind the battery and installed a heavier, separate connector. My temporary circuit plugs into that connector and allows me to power the pumps if for any reason the LEDs indicate there is not power at the pump and I have a no-start issue. So far, the pumps show having power when I am having the no start issue. (LEDs are powered by a jumper at the pump connector at the tanks). I don't listen to the radio so I pulled it and installed the panel in its place. It is all easily removable. So I have not been removing the safety switch plug on the left CIS distributor to override.

When fuel lines are connected as original, there is a fuel line running between the left and right side WURs. To find out what is happening after the engine is warmed up and I shut it off, I need to have the fuel pressure gage installed while the engine is running and warning up. The fittings in the CIS test kit don't allow the double banjo that is required to have the fuel line between sides. Wondering how that is handled, as I missed it in the booklet if it is there. Also thinking that when the right side pressure bleeds down, the WUR crossover line also bleeds pressure from the left side, and without pressure, remaining fuel in the lines boils and I could get vapor lock on both sides. Otherwise one side would run and maybe get the second side to fire up. BTW, yes, there is spark when I have the hot restart issue.

I will check out the other threads. I'm guessing the Mondial injection info covers a single system, not the crossover / interaction.
Accumulators are not faulty. Originals weren't either; no fuel dripping from the vent line. but I changed them anyhow.
Thanks for the thoughts.

 

I read 55 psi as the correct regulated pressure. I'll go back and read again. Yes, 40 is low.

 

Steve, not trying to argue, just understand. Page 5 of the 400i booklet shows 0.5 - 3.8 bar for the regulated pressure between the fuel dist and WUR. Unregulated from the pump and to the lower chamber and cold start injector is 5.5 bar. Upper chamber is 5.4 bar. Pressure to the injectors is 3.3 bar. The only one with what appears to be a range is the regulated pressure. If it is actually a range ("0.5 - 3.8 bar"), my interpretation was that 40 psi was within that range. 80 psi was completely unregulated.
I think the tests so far show that both fuel distributors should be rebuilt. I want to make sure they are adjusted properly, so want to understand the correct settings if different from above. I could send them out and get them rebuilt, but then I don't really learn anything.
Thanks for your help and patience.
I had asked about videos; has anyone done them for the Ferrari 400i/412. There are some excellent ones for Mercedes, but it is the single CIS setup and doesn't hit on unique areas such as the tied together WUR pressures. I am interpreting that there are no CIS related videos specific to 400i and 412.
Again, thanks.

 

Thanks, I will check that. I can hear a "dung... dung..." sound when I shut down. Figured it was the check valve again.
Did find that the cold start injector also does not get any momentary power on hot restart. Otherwise, this has been on the back burner for other projects. Just getting back to it.

 

Lots going on...finally got back to this for a little bit to check for the possible blockage in the return. From the CIS back to the tank is clear; blowing compressed air into the line results in bubbles in the tank (audible). From the WUR return line connection point to the CIS to the CIS port for the return line to the tank there is no flow with 90+ psi air supplied to the WUR return line connection point on the CIS. My interpretation is that would indicate that the CIS pressure regulator is the blockage. Pulling it out, nothing appears wrong; all o rings appear to be intact and nothing was jammed. No foreign particles.
What would result in this behavior of the regulator? It looks pretty simple, and not easy to adjust incorrectly after it is shimmed.

 

What did you do for the leaking line? I think that is now my last issue. Visually confirmed it.

 

OK, follow up to my investigation...turns out there were several things going on at the same time, but the root cause of my original problem was the curled line from the fuel pump to the tank cover plate leaking at the fitting to the cover plate. When I replaced the fuel pump and check valve several years ago, I disturbed the end at the banjo fitting. Suspecting that, I put a clamp on the end. The other end appeared sound; a factory shrink fit without any clamp. Now, investigating again, I found that it only leaked when compressed, so when I tested it outside of the tank, it did not leak.
I used a Racetronix FFT-208B in-tank corrugated fuel line. It is 5/16" ID (8mm) and 280mm long. The corrugations keep the line from kinking at the bends, and the material is intended to be submersed in fuel. I bought several different lengths, from 230mm to 360mm since they were only about $5 each. You can also buy the clamps from them. I used some from a Harbor Freight kit with a nice rounded edge and 7mm hex head bolt.
Reinstalled the pump package tonight and after more than 4 hours, still had 8 psi in the line (5.2 bar to start, dropped to 2.9 bar with the key off and held for longer than I stayed and observed it. Checked it a long while later after dinner and it still had pressure. Previously, it would drop to 0 in less time than it takes me to type this line.
Other things: The o rings on the cis distributor regulator were no good, although I previously reported that they "looked OK" one stuck and caused the fuel pressure to climb past the top of the gauge range. regulation was not right, and when I pulled the assembly to check, and then reinserted it, the o rings dragged. Next removal, the larger green o ring had disintegrated. With new o rings there on both sides, I now found the pressure on the left side was regulating much too high. I removed a .004 shim and brought it down to within 1 psi of the right side.
I replaced the WUR on the right side with a rebuilt one from K Jet Specialists in Tanah Merah Australia.
As part of my troubleshooting, I installed check valves in the short section between the steel lines to/from the tank, and the cis distributor. I could have left them in place, but they added back pressure, which would make the pumps work harder, and they decreased the flow when I tested that.
A photo of the assembly with the new line is at the link below (if it doesn't load as a photo).
https://photos.app.goo.gl/o49JL496Re9JpB3z5
I also had to repair the clip on the plastic fuel pump basket, which you can see on the left side of the basket in the picture. This fix actually worked out great, as it is thinner than the original plastic, so it fits through the tank opening better.
Thanks for the inputs and manual downloads. On another reply, I will load some additional K Jet testing and troubleshooting guidance I found that was very helpful, even though it was written for 4 cyl VW Golfs. The explanations and photos were great for K Jet novices.

 

These three links I found to be very helpful for me.
Not Ferrari, but same basic Kjet.
https://tasteslikepetrol.net/2020/02/bosch-k-jetronic-basics/
https://tasteslikepetrol.net/2020/02/bosch-k-jetronic-part-2-testing/
https://tasteslikepetrol.net/2020/02/bosch-k-jetronic-part-3-tuning-and-fixing/

 

I bought a kit for the entire CIS distributor from K-jet Specialists in Australia. I had not / have not rebuilt the CIS distributor but figured if I needed it, I have it, and knew I needed the o rings. I have seen a kit for just the regulator pieces on eBay, but I have gotten a couple of shipments from Colin (in very good time, despite Customs and distance) that are excellent quality.
Shims...I was lucky that I had one shim about .004 thick that I removed. The remaining shim more closely matched the thickness of the other side. That brought the pressure down to within one psi of the other side. I have read of someone starting with a small copper washer and carefully sanding it down to the thickness they needed. It does not take much thickness change to change the pressure quite a bit.