Strange fuel head issue! After WOT AFR stays at 10-11.5.

[smurfbus]

Before the WOT it would be about 15 on cruise. Also the WOT cuts at about 4300 rpms but I haven't logged yet if it goes super rich before it cuts. I have this 123TUNE distributor so the cuts might be ignition related. I intalled my msd inline but it did not help the cut out.

WCP is at 5bar and vacuum port is plugged so its not the WUR. Its not the cold start valve either as I have a pushbutton for it and engine stalls from too rich if I push it. It idles and run just fine but its just way too rich. Last time this happened I tried to adjust it leaner and after awhile it went super lean like something released again?

Any ideas to try? I have one day to try stuff before another trip elsewhere.

[mark houghton]

Sounds to me like you've got a split o'ring on the IC. Once the boost builds up enough, it's escaping via a poor fitting 0'ring, which will cause you to go pig rich and the engine to falter which may also explain why you're not getting much beyond 4300 rpms.

[mooney265]

This happened to me: due to "dimpled #$%^-ermigiggy" on the fuel head. Only one of my cylinders was running super rich. Someone could chime in on what it's called. Basically, it's a thin piece of metal [when depressed] which controls the fuel flow to each cylinder.

I caught it, because overall my AFR's were down. Went under car with Heat Sensor [laser] and noticed one of my cylinders wasn't hot.

Had car towed and fuel-head replaced.

[smurfbus]

Mark, I got worm clamp thingies on my hoses and it starts spooling early plus a leak would make the idle leaner IMO as it would get extra air through the vacuum leak.

Mooney, I might just buy an inexpencive heat gun for this as it has been on my list for a looong time already. I did test my injectors about 2000 miles ago and it was really nicely balanced. Oh, system pressure is at 7 bar now just for extra info.

[RarlyL8]

Shannon, the dempled diaphragm is caused by fuel spikes. Typical symptom is inability to tune and unbalanced AFR per cylinder. Fix is a fuel head rebuild.

[smurfbus]

If nothing else I might try to lean it out again to normal spec to see if it goes super lean again. If I need to replace or rebuild my fuel head Im done with CIS but I will try to keep distributor and stock IM for the looks.

[RarlyL8]

Smurf you probably have a boost leak somewhere as Mark has stated.

[jsveb]

I don't understand how it can be running rich with a wcp at 5bar. Shouldn't it be way lean?

[smurfbus]

5 bar wcp is for good milage and it was nice. I will do a propane test again to find possible leaks, but I have already tried to find leaks with no success. It idles at 11.5 too and before the WOT run it idled 13.5 AFR. The CO screw works like it should with the c-washer and spring. Last time my car did this the c-washer had dropped so I thought the key that was in there back then had pushed the CO screw lower and resulted as rich, but it does not seem the case as its fine now.

[timspu]

I had a similar issue , after boosting noticed AFR's would be down in the low 12's. If i switched engine off and on Idle AFR would return to high 13's. It would n't do it all the time but caused a real headache when trying to adjust the WUR.
I also noticed when i had the fuel gauge connected in line with the WUR that the fuel pressure would fluctuate by about 0.5 bar when the engine was quickly revved and returned to idle. The mass airflow plate was vibrating. If the plate was steadied the fuel pressure would stop fluctuating. it appears the vibrating mass airflow plate caused AFR's to go rich I have since had my fuel head repaired and this has stopped. (The damper orifice was way over sized) As yet no problem but i am still tuning on the road to get it right.

[smurfbus]

Other symtoms are:
Really hard to start when hot, need to press gas pedal to the floor
Did not cure over night and was at 9afr on cold start

Now I adjusted the co and wcp several times and the best result is wcp at staggering 5.6bar and idle at 16afr. It sounds bad but it idles just fine. Still the afr at low throttle cruise is under 13 but nice 15 at over 50mph and when slightly accelerating.

The metering plate is not vibrating and I still have the filter off but now its going back.

The soft cut out is still at about 4300rpm but it goes lean when that happens so it might be misfiring. I do have my spark wires kind of in a mess at the distributor, could that be the cause?

Using a butane torch was about useless. Aiming it at the metering plate did not make much difference and either did disconnecting one of the small hoses on the TB.

I managed to make 40 mile test drive at the twisties and it was quite ok but the cut out is annoying. I need to get rpms on my lm2 again later.

BTW, Im really liking the hand throttle! I can accel to 80 mph with it!

[JFairman]

Sometimes I wonder if the higher volume of fuel flow from 044 fuel pumps is just too much for the tiny little fuel pressure regulator in the CIS fuel head.
That little piece of overpriced junk is probably the worlds smallest fuel pressure regulator ever made... It's hardly adjustable and all fuel pressure regulators regulate fuel pressure by returning some of it to the fuel tank.

Ever taken that little thing out of the fuel head and seen how small it is?
Pelican Parts - Product Information: 928-110-920-01-M14

Throw two high flow motorsports bosch 044 fuel pumps made for racing at it.. and can it actually return enough of the excess fuel to the tank to keep 930 CIS running normal?
I don't know... Maybe Chris at Turbokraft knows the answer to that.

[smurfbus]

Who knows, I might just try to lower system pressure 7bar to 6.5 for a test. It did how ever work fine for some time and after that car was not used for about 15 months so maybe the fuel head is dirty or corroded. I did use some fuel system cleaner a week ago, maybe this started at the same time.

[smurfbus]

Well, it was not the system pressure. Although it was too high (over the gauge scale) removing all the washers got it to 6.2bar but the fluctuating AFR remained and so did the 4000 rpm cut out. I also have the wcp at crazy 6.5 bar so it stays over 11AFR also on light throttle. Accel and over 50mph is fine.

Next I will try an spare ignition distributor from Jbp

[smurfbus]

The fuel line bursted under the car on a short testdrive. Saw a line behind the car and was able to take a quick u-turn. Fixed that yesterday with a ptfe line. The bad hose was aeroquip 3/8 and the ethanol had softened its inner layer.

Did not help the rpm cut and either did a spare stock distributor that JPB kindly shipped to me.

Can a MSD6 unit behave like this when it goes bad? Cutting rpms when on full boost at around 4000-5000. I tried to easily accel on second gear but it did not rev over 5000?

My wideband started acting up so now I have no clue if the readings have been correct when I have been diagnosing this problem. With this iroc bumper I cant replace the sensor like I could with the stock bumper so that a big booper.

Im also going to try third set of spark plugs. My new set had one of the plugs crack the plug white ceramic frame and Im not sure the old bosch plugs gapped to 0,8mm are ok any more.

[RarlyL8]

Wow sounds like a cascade.
The crazy high WCP is indicative of a dimpled fuel head diaphragm. Do you have a Euro unit -016 or -037? Those are less forgiving of pressure spikes than the later -145. If this does turn out to be the issue (or one of them) the source must be corrected or the damage will repeat. Typical sources are a blocked return line or faulty fuel accumulator. If your fuel lines are failing they could definitely cause this.

[smurfbus]

The FH is alumin. Actually after the new fuel hose I had problems with the AFRs so I set the wcp lower and lower and now its at 3.6 and system pressure is at 6.2

The new problem is now off idle jumpiness which shows as 18-20afr and goes away if I press the cold start button so it is lean and not just misfiring.

I just swapped my 123tune distributor back with msd and tightened all clamps again and the car seems a bit more happy. Inthink it revs now to almost 5000 and sometimes even higher. No problems on 4th gear WOT but revs were only up to 4000.

Next I will put my J&S and go do some more WOT runs.

Does the MSD really need battery negative? I have mine grounded to rear seat bolts so they should be same as battery terminal.

[smurfbus]

Ok, took a 50 mile test drive and the car runs fine except the off idle weakspot and the now 5000rpm limit.

What controls the off idle fueling? My metering plate does not vibrate but could adjusting its height affect the off idle fueling?

[RarlyL8]

So what was the problem? The fuel lines?
The metering slits and piston height govern off idle enrichment until the vac drops to positive pressure. Yes the metering plate height is involved but it will typically vibrate if off spec. I'm sure you know not to tap the pin in too far if an adjustment is needed.

[smurfbus]

Not going to tap the pin if its fine when not vibrating.

There might have been a leak in the fuel line for some time, only now it totally bursted. But it still has the 5000 rpm cut off thats driving me nuts ( cant figure it out)

I need to test another set of plugs and possibly try a bigger cap too. Now the wideband went totally blind so I need to replace that too which is a pita. I hate the quater panel screws.

I also need to check where the AIC-1 cells place now that there is no leaks in the fuel line.

EDIT: one more oddity, I need the press the pedal to the floor to get the car started easily. If I dont give ot throttle I need to crank for 10 seconds if it even starts.