Cis troubleshooting

[Rich76_911s]

Hey guys,

I've had my turbo for nearly two years, and for most of that time it ran well, but always got too rich under partial boost. I did not have a afr gauge in the car then, but black smoke and hesitation lead me to strongly believe it was rich.

My first attempt to fix the problem was to do no diagnostic work, and just send my wur out to Brian leask for a rebuild and adjustability. Im happy I did it, and I think Brian did a spectacular job. But it didn't fix my problem.

So instead of just spending money wrecklessly I decided to measure my control pressures with a set of Cis fuel gauges.

I found that I was at lest 1 bar low on control pressures for both warm and cold conditions. System pressure was reasonable at 6.7 bar.

But when I put humpty dumpty back together, well humpty wouldn't start.

I towed it to storage and just recently I got the car to start and run for a short while before I turned it off. But it was only 16 degrees out and I think the cold dense air played a role in why it started. When I got the garage warmed up it was a no start issue again.

So that is a long way to get to my question, which is: what other than the wur impacts control pressure?

I've been reading a book on Cis and I think I know the answers to these questions, but I'm stumped so clearly I'm not getting everything.

would idle adjustment impact control pressure?

Would the frequency valve be impacting control pressure?

Could the fuel pumps be inadequate to get control pressure correct even though system pressure was within the suggested range?

Anywhere else I should be looking?

Thanks
Rich

[Rich76_911s]

As a thanks for taking the time to get this far here's a picture of a 918 engine. I wish I got a picture while they started it shooting flames without the exhaust on.

[JFairman]

If you have a Brian Leask adjustable CPR, have you tried adjusting it to raise control pressure?
Might need a turn of the 4mm allen head on the bottom. Brian used to include an instruction manual with them and he probably still does.
Every car is different so it needs to be adjusted for your car.

[Ronnie's.930]

^^^ What Jim said - the fist step would be to adjust the control pressure via your Leask WUR. Also, having an onboard air-to-fuel meter would be a major tuning aid for you.

[timspu]

Is there a chance the WUR is staying in warm up mode? Disconnect the WUR and then check your fuel pressures. Re connect your WUR electrical plug and wait to see if the pressures increase. ( Recommend having a battery charger connected to battery whilst pumps are running)
If pressures do increase then i would adjust the WUR as the previous gents mentioned.
If not then you may have a power supply problem to your WUR.

Regards
TIM

[Rich76_911s]

Hey Guys,

Thanks for the input so far.

I guess my concern with simply adjusting the WUR is that I am "covering up" an underlying problem.

It just seems strange to me that I was running rich before Brian got the WUR (seat of the pants), I ran rich after I installed the rebuilt WUR (AFR gauge recently installed), then after I measured fuel pressure I got so rich it wouldn't start anymore.

I'm confident that Brain set the WUR correctly for my more or less stock engine. So I'm just thinking there must be another factor that is contributing to the low control pressure that I am missing. When push comes to shove I suppose that yes I can adjust the WUR, but I wanted to try and find the root cause of the problem if I could.

[Rasta Monsta]

Dirty/clogged passage in metering head can cause low control pressure. Worth rebuilding if you've never had it done (CIS Flowtech).

FV is separate from CP circuit, and if your system pressure is OK it is not a fuel delivery problem.

[mark houghton]

Originally Posted by Rich76_911s

Would the frequency valve be impacting control pressure?

For what it's worth, no it won't affect control pressure. If the frequency valve were to stop frequency'ing, you would see an extremely lean condition, though.

Lots of good advice already given. Do indeed follow up on Tim's question regarding power to the WUR, to at least take that out of the equation.

[fredmeister]

What AF readings are you seeing when the car is cold started and at idle?

You should see in the low 10's at start up and then it will lean out to low 13's high 12.9's at idle when its fully warmed up after a few minutes. Every car likes a different idle ratio but mine runs good there.

And on cruise I target low to mid 14's.

You need to tune based off an accurate wide band AF ratio gage or you are just guessing.

A plugged fuel return line will also cause troubles maintaining fuel pressures. So check for clogged fuel lines and or dirty gas filter.

Fred

[Rich76_911s]

Thanks for the ideas.

The next time I get to work on the car I'll check the fuel filters. This may be a very dumb question but how do you check the return fuel lines?

The afr gauge was reading only 10:1, and I think that is as low as it measures so I could be even below that.

I'll also look into putting a multimeter to the wur power.

[mooney265]

Originally Posted by Rich76_911s

I'm confident that Brain set the WUR correctly for my more or less stock engine.

Don't be confident BL set the WUR properly for your car! Mine was way off from Brian.

You need to start adjusting the WUR to your car. Log every adjustment: cold CP; warm CP; boost CP; and SP after each adjustment. Also remember that your idle screw also affects your cruise and boost AFR slightly. Shannon


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[Reanimotion]

Follow the basic tests on the fuel distributor and injectors as well.
off when it should be
on and balanced flows when pressed lightly
etc.

- a small change on the mixture adjustment at the air plate housing can have a massive effect on fuel quantity delivered.

[DSPTurtle]

You stated that you were one bar low on your cold and warm CP. You will need to adjust your CP to get that one bar back. Then try to start the car. You might not be masking anything. Set the Cold CP according to your ambient temp, and make sure your Warm CP is somewhere around 3.7 and then go do your far data logging.

[jwasbury]

Hi Rich...keep working it.

Do let me know if I can lend a hand sometime when I'm out in PA. Heatwave coming this weekend: two days in a row with high temps above freezing.

[mark houghton]

Originally Posted by jwasbury

Heatwave coming this weekend: two days in a row with high temps above freezing.

Careful Jacob, next thing you know you'll need a row boat to get around. Easy does it on the thaw for you guys.

Here, it's forecast to be in the low 60's the next several days. Will think about all you poor snow bound bastards as I'm letting the ol' girl stretch her legs.

[jwasbury]

Rub it in Mark. Old blue hasn't seen the light of day in over two months. 2nd winter in a row that there hasn't been a single "clean" weekend to go for a blast.

[JFairman]

It's been shorts and t shirt weather in the low 80's here all winter long except for a couple days last month

[Rich76_911s]

Thanks again everyone.

Just trying to get familiar with Cis, and all your guidance on where to look has been a great help.

After I check my filters, and return lines I'll take everyone's advice and adjust the cold pressure up and and make sure warm pressure is close to the 3.7 area. I do have an afr gauge in the car. so that should help as a guide once it is running.

Jacob Id love your help and guidance anytime. I have a lot to learn with becoming a good dyi mechanic, and your experience and knowledge would be great.

As Jacob mentioned we do have a bit of a winter wonderland around here right now, so I may wait to adjust it until it the roads are a bit cleaner and I can take it out and get I properly warmed up.

I think we've seen the last hurrah for winter this week and we are on our way to driving season!

Thanks again and I'll give you an update after I get my fuel pressures closer to spec.

Rich

[Rasta Monsta]

Once you get the control pressure correct, you can actually use the lambda system to set idle mixture...

[Rich76_911s]

Thought I'd give you guys an update.

I adjusted the cold control pressure to be at the bottom end of the range, and got the car running. I had great AFR ratio's but it was running really roughly, seemed to be missing on at least 1 cylinder. So I ordered and replaced all the spark plugs. that #1 cylinder was an absolute biiiitch. Usually you break it free and the plugs just twist out practically by hand, that #1 cylinder gave me hell coming out and going back in. With that said after replacing the plugs the car fired and idled perfectly.

** Stupid question with adjustable WUR's does adjusting the cold control pressure have an effect on the subsequent warm control pressure, and the enrichment control pressure?

Took it out for a little shakedown and fresh fuel top off. In the 3 years I've owned the car it has never run so well. No missing or hesitation as boost built up, just smooth running.

For a bit of IRONY I did happen to get behind this truck on the test drive. If I was a bit sharper I'd have pulled out the Paul's single finger salute, but alas I'm not that quick witted.



YUP that is the CISrepairs.com truck.