Petza914

Today's update

Peter DeJong of Twin Turbo 928 fame graciously came to the house today with his CIS gauge set and knowledge of the K-Jet system from working on other comparably equipped 928s to try and help me resolve my running issues. From what we could tell, all the electrical plugs, fuel lines, and vacuum lines are connected correctly.

I learned a good bit about how the CIS system works, actually learned to use my CIS gauge set that I bought a while back, and we discovered something that we think may be the culprit with the running issues, so I thought I'd share that here for additional input from the group.

Testing the fuel pressure from the pump with the engine off and the fuel pump jumpered, we're seeing 145 psi of fuel pressure on the gauge. We thought this reading was a bit high, so disconnected his gauge set and connected mine, and got the same reading, so a lack of fuel pressure to the WUR doesn't seem to be the issue. I don't know if Carl bumped up the fuel pressure at the fuel distributor because of the supercharger, but will be talking with him tomorrow about this.

With the supercharger out of the equation (air feed disconnected from the K-Jet metering plate), if we set the mixture in the 12 - 12.5 AFR range and the idle around 85-950 rpm when the engine is idling, we would get a repeatable fluctuation where the car would idle well, then stumble as the AFR got rich, like around 10, then recover and go back to 12.5 for a few seconds, then stumble again at 10, and so on. It would stay running like this for almost as long as we wanted it to.

So we hooked up the gauge set to monitor the return pressure from the WUR. When the car was idling well at around a 12.5 AFR, the pressure on the gauge was around 130 psi, then it would start falling and when the engine started stumbling (and the AFR would drop to 10), pressure was only around 48 psi. It would keep repeating this cycle as you can see in this short video I shot.


I reconnected the supercharger and the car exhibited the exact same behavior. If I hold the revs at 2,000, the AFR would get lean, like to around 14, and if I moved up to 3,000 the AFR would go full lean to 18. If I played with the mixture screw to where at 2,000 and 3,000 RPM I had good AFR #s at around 12.5, then at idle the AFR # would be around 10 and I could visibly see both the exhaust coming out and a stream of smoke coming from my crankcase ventilation setup under the car. But with this setting on the mixture screw, the idle at 10 would hold steady and not do the fluctuation dance shown in the video. So I decided to try and drive the car this way to see what would happen.

It runs and would stay running at idle just like it did in the garage, but if I'd try to accelerate hard, it would go full lean still on the AFR gauge to 18 and start missing. I could never get the boost needle to go above zero before it would get fully lean.

I know the AFR idle setting of 10 is way too rich, but based on the above tests and results, what do you guys think the problem is. Did my WUR somehow go bad and it's not metering the fuel to the motor correctly or is there something else I should be looking at.


2 other things, testing the vacuum advance and retard of the new distributor, neither would work. Peter discovered that the arm that goes on the pin and pulls the distributor was disconnected. He fixed it once but I came off again in the next round of testing so I took it apart and discovered the arm was actually a little bent, which is what was allowing it to come off the pin. I straightened the arm and reconnected it onto the pin and using a Mighty-vac tester, was able to both advance and retard the timing depending on which port I was connected to, so that problem now seems to be fixed.

Also, the clutch action is very good - smooth and the new friction discs don't grab and shudder like the prior Spec units even when trying to start of on an incline, so looks like I have that problem rectified too, which will make driving the car much more enjoyable, providing I can get the motor running right. Still hoping to get the car ready to make the Rendezvous event in Atlanta in a few weeks.

Thanks for any guidance or suggestions.

j.kenzie@sbcglobal.net

Hi Pete,
It sounds like fuel pressure is not being regulated properly. Does K-jet have a separate fuel pressure regulator or is it part of the fuel distributor?
Glad you fixed the distributor. I was lucky. When I tested mine with the Mityvac, it worked right away.
Sounds like you're making progress.
Good luck,
Dave

Petza914

To my knowledge, fuel pressure is controlled by the spring in the fuel distributor and there is not a separate pressure regulator. The WUR sees full pressure from the fuel distribututor, then modulates that pressure based on temperature back to the fuel distributor for what then gets sent to the individual injectors. I might need to do another pressure test at the input of the WUR with the car running (instead of just the pump running) to see if the pressure coming in is fluctuating or if it's just the pressure going out that's fluctuating. That may pinpoint my issue to either the Fuel Distributor or the WUR. But I still don't understand why either of these is having a problem that wasn't there before the engine swap.

Carl Fausett

Hmmm... its a bid of a head-scratcher to be sure, but we're missing something. I'm wondering about the air flow meter - in "the shoe" as we like to call it. That disc rises and falls according to a taper machined into the walls of the shoe. Would you check the taper in the 4.5L air flow meter with that of the 4.7L air flow mater? Push the air flow meter disc down with your fingers and photograph the wall of the meter on both and please post them.

Because the 300 HP motor had larger valves, larger runners, and higher lift cams - I would think the increase in air flow would require a different air flow meter calibration. Meaning: taper and shape of the housing. Specifically near the top, where it effects idle and tip-in. I have also published before that I thought the fuel distributor for the 300 HP K-Jet was different than the 220 HP model. I have been told I was wrong on this a number of times, but still, I have been unconvinced.

Back in the day the hot setup on your VW Rabbit with CIS was to install a build-up of tape on the inside rim of the air flow meter to narrow the bore of it at the top, above the plate. This narrowed the opening, making the velocity of the air passing through the meter faster and as a result, drawing the plate down deeper, enriching the fuel mixture. Analog stuff. Memories.

Carl Fausett

...about my last post... I am reminded that many guys (including myself) have swapped the M28/11 cams, intake, and heads on to their M28/01 motor with no trouble or tuning issues at all. So I might be wrong to send you down the road to obscure stuff when it is more likely something simple we have overlooked.

Have you tried adjusting the control pressure via the screw I placed in the bottom of your WUR?

Petza914

I have not and did not know my specific WUR you installed had an adjustment screw on the bottom. This is exactly the type of tip I was looking for.

As a reminder (in response to your prior post), I have the base 4.7L engine onto which I installed my complete K-Jet fueling setup from my 4.5L as well as the cams from the 4.5L into the cam towers from the 4.7L.

I don't have the L-Jet fueling setup from the 4.7L motor where I can compare the shoes. The 4.7L is not a not a Euro, just the US version with higher compression.

I reused my WUR, my fuel distributor, but installed brand new Bosch injectors and new stainless fuel lines. The lines from the WUR to the Distributor are Greg Brown versions. The lines from the fuel distributor to the injectors are not his.

So, going back to the fuel pressure at the WUR. The inlet pressure with the engine off and the fuel pump jumpered is 145 psi. I did not do a test where I monitored this pressure with the engine running. The outlet pressure with the mixture screw set so that AFR at idle is around 12-12.5 is what you see on the gauge in the video. With an inlet pressure of 145 psi, how should I adjust the pressure screw you referenced in the bottom of the WUR? Can the WUR be unbolted from the mount and adjusted while the engine is running or does it have to be removed, adjusted, and reinstalled to be tested?

Here is a photo from inside the shoe. If you can't enlarge it far enough via Rennlist, let me know and I'll email it to you.




Let me know what other tests I should perform. Thanks.

Carl Fausett

Don't do anything rash just yet... I am not sure you DO have an adjustable WUR. I am looking through your old invoices to see if you ever bought one. If you do look, the bottom of it will look like this:

Petza914

My Build Parts Invoice shows a "Used 086 Warm up Regulator" and I remember you telling me we installed the one that had altitude compensation, which I assume is the purpose of the 2nd vacuum line port that some others don't have. Would this mean you also modified the bottom to make it adjustable?

Carl Fausett

I can't find an invoice where I charged you for modifying your WUR, so I may have sold you the one off my K-Jet race car that already had been modified. If you can slide a small mirror under the WUR you may be able to see without removing it.

Petza914

Does it just remove by taking out the 2 side bolts? Mine has flex lines on it now so I should be able to get a look at the bottom if removal is that simple.

Carl Fausett

Yep. Two bolts, that's it.

Petza914

Carl, here's the info you had sent me about the WUR that's in the car:

Petza914

Had what I think may be a Eureka discovery this evening.

Earlier today I was reading some CIS information that had been shared with me by Ron Borras and one of the articles was "Playing with your K-Jetronic Warm Up Regulator, or WUR". In this article, the author (who isn't listed) states that "if your control pressure is high, you need to find out if if is due to incorrect calibration of the regulator, or a blockage in the system somewhere".

Well, based on the manual, my control pressure was way high - 145 psi vs the around 90 it should be at the top of the range, so it got me thinking about blockages in the fueling system. Though I had installed a couple of Greg Brown's fuel lines, I actually don't think I was able to install the right lines in the right places and a couple of those lines had little adapters with small holes in them, and though I'm sure they were fine (since all of Greg's stuff if first rate), I decided it was time to start eliminating variables, compared to how the car used to run. Before the engine swap, it would start immediately and run perfectly with a rock solid idle, great responsiveness, good AFR numbers, etc. The fuel distributor and/or the WUR don't just go bad when being removed from one motor and installed on another, so I decided to go back to the original hard fuel lines. I was initially just going to run the 2 from the Fuel Distributor to the WUR, but decided that still leaves too many variables, so bit the bullet and started taking stuff apart again, including removal of all the fuel lines.

The stainless injector lines I had installed had different end connectors for the injector side than the OEM hard lines, and I figured because of that, is why each one had a small o-ring inside. Here's a picture of the #4 line I didn't use in its original form because it sticks up off the injector and interferes with the heat exchanger for the supercharger, so for #4 I had reused my OEM hard line. (Note: Greg's version of these stainless lines have 90 degree ends, probably have the stainless sections coatedlike his others to not abrade themselves or other things they contact, and I would guess the ends can be tightened independently of the line rotating also like his others, all of which would make his much nicer than these).




Well I took the first couple lines off the injectors and saw this squiggly black stuff drop down onto my pristine cam towers, so the next few I was more careful about as I took them apart...

Here's the Eureka moment








I don't know what those o-rings were made of, but they certainly weren't fuel resistant, and essentially disintegrated and exploded in the injector inlet. In fact looking at the taper inside the fuel hose, and how that would mate with the injector, they probably didn't need to be in there at all, but each line had one.

So the blockages they surely caused is why I think whenever I'd try to give the motor some fuel, the AFR gauge would go super lean and why when using the mixture screw to try and enrich it would be able to do that at idle when the demand for fuel volume was very low, but not under any load since I'm sure I had a very compromised flow through the injectors. The sad part is that these were brand new injectors and the way the o-rings disintegrated into tiny pieces, I'm sure they are now completely full of rubber debris and ruined so I'm going to have to throw them out.

Tonight I moved the new tension rings and sealing washers from the new injectors over to the old injectors that I had removed when the 4.5L was running perfectly, and have now reinstalled them. I was going to reinstall the hard fuel lines, but they look crappy compared to the rest of the engine, so I decided to mask off the ends and use some high temp engine paint to freshen up the outside of them.



I'll reinstall them on Wednesday when I return from a business trip and see where things stand.

My theory is the super high fuel pressure was being caused by the fuel distributor not being able to push any fuel through the injectors which then backed up through the WUR outlet line and effected the WUR inlet line pressure as well. The surging witnessed in the video was because once the pressure built up high enough, it was able to push some fuel through the clogged injectors, but once the pressure subsided a bit, the car got no fuel and wanted to die, but just before it would, the pressure got high enough again to force more fuel in.

When I tried to drive it around the neighborhood yesterday, any time I would give it any gas it would go full lean - of course it would without any fuel getting through the injectors...

I'm glad I didn't make a bunch of changes to the fuel distributor or the WUR as my gut feeling is that this was the primary running issue and once the correct fuel lines are reinstalled, it will just be a matter of tuning with the mixture screw, idle screw, and timing and then I'll be back in business.

Fingers crossed....

j.kenzie@sbcglobal.net

Good job, Pete. That sure looks promising.
Good luck,
Dave

Chris Lockhart

Wow! Those O-rings have seriously turned to sh*t! Glad you found it Pete.