milwaukeeshark

Well, I'm back with hat in hand. The vacuum leak that I thought solved my problem has brought me full circle. After clearing what I thought was a plugged WUR filter, my control pressure was running 46-47 psi. My problem of loss of power, breaking up at higher rpm's WOT persist. All injectors, seals and intake runner gaskets have been replaced. My warm control pressure is now in the high 50's. I have cracked the line at the output of the WUR with no change in control pressure. System pressure seems good at 75psi. Anything I can do to confirm the WUR is bad? Anything else that would show these symtoms? Thanks again for the help.

Dennis Wilson

The high 50's reading is alright (on the high end) if the temps were 104F. Your systems pressure should be 5.2 to 5.8 bars, so your 75 psi is at the low end. This could be causing you too run to lean. Try adding a thin shim to the pressure regulator at the back of the distributor. With the high 50's control pressure you should run about 90 psi system pressure.

Dennis

milwaukeeshark

Dennis, the ambient was about 75 degrees. I would have thought I should be in the mid to upper 40's. I've not tried to shim the pressure reg. in the fuel dist. Are the shims fabricated or a purchased item?
Thanks for the help.

Dennis Wilson

At 75 F (cold engine and vacuum applied if # 928.606.109.03) the control pressure should be between 2.25 and 2.5 bar. With the engine warm and no vacuum the pressure should be 2.8 to 3.2 bars. Warm engine with vacuum should give you 3.4 to 3.8 bars. The pressure spec's for your 79 are on page 25-6c and d of the WSM. If your high 50's reading was with a cold engine and no vacuum, the WUR is the wrong part or it's FUBARed.

Dennis

928BC

Replacing the "o" ring (that is actually sqaure) in the wur valve housing might bring the control pressure down 3 or 4 psi and will also insure no vacuume leaks in the upper portiuon of the wur.

milwaukeeshark

Installed an ARM-1 and can easily see I am going lean when rapidly opening the throttle. No matter how the A/F mixture is adjusted, including rich to the point of black smoke on acceleration, the A/F ratio gauge drops into the lean range.

Cold control pressure @ 22 psi without vac. or power
Cold control pressure @ 30 psi with ~400mmHG vac applied
Cold control pressure @ 34 psi with vac. & power connected and engine running
Warm control pressure @ 55 psi after ~5 min.
Cold System pressure @ 75 psi
Warm System pressure @ 76 psi

Pump delivery @ ~1250 ml @ fuel dist. outlet

With mixture adjusted to rich, AF gauge indicates in the mid 14's to 1 at at 4000 rpm but will drop to lean with rapid throttle opening.

What is left? Fuel distributor? Or?

hupp

Could be symptomatic of a sticky fuel distributer plunger. This can be checked by:

-Allow fuel pump to operate briefly to build fuel pressure.
-With key off and with air filter box removed, depress the sensor plate by hand all the way then pull up rapidly
-You should feel the plunger tap the air sensor arm almost immediatly after pulling the plate up.
-These results should be repeatable if the plunger is not sticking.

Could also be symtomatic of a bad distributer -- faulty o-rings resulting in poor fuel distribution to the cylinders. This was the case with my shark about a year ago, which exibited very similar symptoms. It would idle fine, but once the throttle was depressed it would stumble and die. I replaced my distributer with a rebuilt unit from 928 Intl and all is well.

jpitman2

My experience of high warm control was once it gets past 55psi (with a system of 75, which mine was/is) most of your power is gone. Last time I checked my warm control was ~50psi. I also found that waiting 5 mins from start up is insufficient for warm control to be stabilized...couple of times I though I had mine fixed, control was ok, I would go around the block, and find power gone, and control up near 60psi. You need to drive it to heat soak everything to get a good control pressure reading IMHO. I did some cleaning of my WUR by pushing brake cleaner back and forth through the unit with a syringe.
jp83 Euro S AT 50k

928BC

MJ I just had the pressure gage on my system on the weekend. When I nailed the throttle(eng. nice and warm) i did notice a decrease in pressure from 50 psi to 44 psi and then back to 50psi(very quick change), which was the same as when i tested it warm with vac. applied(eng. vac @ idle) 50 psi. And with the vac. line removed(lower line) 44 psi. I belive this is the fuel enrichment for open throttle. I was into the system because I was running a little lean. Spark plugs were totaly clean with a bit of white spots, and a little rough @ idle, performance was fairly good. when I first checked my control pressure warm it was 53 psi. and the upper chamber on the wur was not holding vac. I opened it up, cleaned it with out opening up the diaphram plug, replaced the o ring. End result was 50 psi and no leaking upper chamber, I still wanted to test out what a lower control pressure would do so I tapped the diaphram plug out .035" and ended up with a control pressure of 44 psi.
Runs great a little more power and no hesitation. the starts seem to be much better warm and cold.

jpitman2

Well done! Can be tricky to fix wur that way. Watson gives warm control around 45psi. Now get mixture adjusted back to spec. If you cold idle isnt high enough the extra air valve may need work, but thats relatively easy. Hot start problems will usually come back to accumulator failure/leakage - BTDT.
jp 83 Euro S AT 50k

SMTCapeCod

Interesting stuff, love the CIS posts when you knowledgeable folks chime in!
Interesting in part because-

- My system pressure was running about 75.5, I saw that was at the low end of the adjustment range and subsequently found the .5mm washer wasn't installed on the system regulator. INstalled it to raise the pressure a smidge (guages were already off), and the car ran better.

- Also because I thought my '83 was without a fuel accumulator-- I'll have to root around some more in the fenderwell, I guess!

- Time to refit the guages yet again and plot out my warm up cycle, I suppose. For a while I"ve been happy that its running fairly well, and intent on not 'poking it with a stick'. Guess its time to try to nail the tune....albeit with some trepidation...

SMTCapeCod

Interesting stuff, love the CIS posts when you knowledgeable folks chime in!
Interesting in part because-

- My system pressure was running about 75.5, I saw that was at the low end of the adjustment range and subsequently found the .5mm washer wasn't installed on the system regulator. INstalled it to raise the pressure a smidge (guages were already off), and the car ran better.

- Also because I thought my '83 was without a fuel accumulator-- I'll have to root around some more in the fenderwell, I guess!

- Time to refit the guages yet again and plot out my warm up cycle, I suppose. For a while I"ve been happy that its running fairly well, and intent on not 'poking it with a stick'. Guess its time to try to nail the tune....albeit with some trepidation...

928BC

I'm kind of thinking that over time, wear and tear on the engine(175000 km on my shark) will require a lower pressure to achive a fairly good running engine. WSM states 3.4 to 3.8 bars warm system pressure, maybe on a tight new engine. That pressure range didn't seem to be cutting it on my worn engine(it's not burning blue or knocking or anything just well broken in). I've read of another rennlister using fairly low control pressure. JP I did readjust the mixture, but with out a co2 gage(unfortunatly). At a temperature of 6 deg. C. this morning it started very smooth with a rpm of 1600 going down to 850(no need to go back into the aav). warm start is right on.
SMT you must have a fuel accumulator somewhere unless a PO had removed it, like in my case.

I was a little hesitant at first to "poke it with a stick", but now i've been into every thing on the cis system(accept fuel dist. rebuild) and It sure is neat how it works. The system imo is built to take a part and calibrate as required.

Dennis Wilson

Robbie,

The CIS is very stable even in old age. Had an 80 924 with over 300K miles and the CIS never missed a beat. Just remember that they are matched mechanical components that normally tolerated wear extremely well.

SMT,

The accumulator should be inside the front cover of the right rear wheel well.

Dennis

928BC

Good point Dennis, and thanks a ton for your input to the forum I have learned alot from you and other cis guys(JP,Hupp,Sean79,928fixer just to name a few) thru the archives!