Rebuilt Engine Won Idle
 

Hi all,

First timer. Restoring a 1979 SC 3.0 CIS top to bottom.
Diligently followed Wayne's book on the engine rebuild. After the initial 20 minute engine break in (still can't believe it started!), I tried to get the engine to hold idle and I can't. With a helper's foot on the gas I was able to get the timing correct at 950, and the mixture seems good. But even after turning the large idle all the way in, it just dies out.
All new vac lines, rebuild WUR, rebuilt Fuel Distrib, new injectors etc, new MSD ignition and coil.
On rebuild I deleted cruise control and EGR Valve, and added SSI's, everything else basically stock.
It's a home garage with limited (as in none) testing equipment, but I was hoping you guys can give me some pointers on common causes I can check out.
Thank you!
Marc

1979 911SC CIS Petrol Blue Metallichttp://forums.pelicanparts.com/uploa...1616960636.jpg

Wrong coil for the Bosch CD. Requires a Bosch 001
Too many rehabbed parts.
Vacuum leak on oil tank hoses?
Are you vacuumed the distributor at idle, requires high RPM advance
Bruce

As Bruce said..check for a vacuum leak ..did you closed the distributor vac.adv. hose?
also do you have pop off valve behind the air filter ?
The times has to be set on a warm engine otherwise it will be off.
Also your sensor plate is it positioned correctly?That has to be checked on a cold engine or no fuel press, in the system at all.
check and report back...

Ivan
sensor platehttp://forums.pelicanparts.com/uploa...1616967796.jpg

Thanks guys, I plugged the advance vac on the distributer. I thought that no vac was correct at idle. Is that wrong? How do you get high advance then to the distrib?
It's not a Bosch CD. It's an MSD and that is the correct coil pretty sure. It's a MSD Blaster II
By "pop off valve" do you mean the backfire relief valve on the spring hinge right behind the air filter? ? Yes I have that.
I'll check the sensor plate position when cold and report back. Ivan, what is that measurement supposed to be on the plate by the arrow?
Thank you!

the vacc.hose plugs behind the throttle body search for a diagram..
The sensor adjustment is what you see on the picture..left side aligned to the edge...if it off that would also change your fuel mix if you have to correct it...
The valve yes, have you looked if by any chance got stuck open?

Ivan

OK thanks for clarification on the plate. Will check.
Yes, the vac hose from the throttle body to the advance unit on the distrib is connected correctly. But i had it disconnected to do the timing as I thought that was the right thing to do at idle. Will reconnect.
Sorry not sure what valve you are talking about may be stuck open?

look here one of the vac.hose on the left of the thr.body--never mind the arrow

http://forums.pelicanparts.com/uploa...1616969880.jpg

here black and white diagram
https://jimsbasementworkshop.com/CIS/pages/air_vaclines.html

You turned the idle screw all the way in? That LOWERS idle because it cuts off air. Screw it out to increase idle speed.

i was hoping he already did;-))))))))))

Ivan

Ivan, yes I have it connected correctly however on my throttle body there is also a port on the other side that does the same thing as it's above the valve. However to make sure I will switch to your suggested port.
Jeff - Yes I was totally doing that back asswards and will try the other way!
One more question - when I removed the EGR valve, I totally removed it and plugged the hole at the very bottom of the air box where the EGR pipe entered the air box. Does that effect vacuum source? I thought that because it is at the lower end of the air box it does not. Can you clairify?

"i was hoping he already did;-))))))))))"

Ivan you are giving me too much credit !

Off topic but that PBM is an awesome color. Have faith you will get her going soon.

Doyle check that the distributor isn’t one tooth off. Ask me how I know...

Did you perform a vacuum leak test using a cheap homemade smoke machine? Any false air getting into the vacuum side of the fuel injection system will cause idle and running issues.

http://forums.pelicanparts.com/uploa...1617051785.jpg

http://forums.pelicanparts.com/uploa...1617051785.jpg

http://forums.pelicanparts.com/uploa...1617051785.jpg

Did you test the fuel injection system using a fuel pressure gauge to verify fuel pressure and control fuel pressure? A CIS fuel pressure gauge set will cost around $100 and is essential if you do all your own work. Do search for a thread on CIS fuel injection for dummies. It will provide all the info you will need to help test and isolate your issue.

I have an MSD/Blaster 2 setup for my 80SC engine. The coil is red and has to face upright. Looks like yours is black and facing with the terminals facing down. Are you sure you have the right part?

Thanks Paul and Pat,
It's an MSD High Vibration Coil PN 8222 and according to instructions should work with the MSD 6AL-2 Ignition box I have, and can mounted "in any position due to its epoxy potting compound." according to instructions.
I found the link to the thread CIS for Dummies and I'll start testing...

Marc..did you by now unscrew the idle adjustment screw or not yet??

Ivan

Yes, I did back it off the adjustment screw a bit and it idled better for about a minute before it quit. I ran out of time to play around and will get back at it over the weekend for sure.

Have you checked your fuel and control pressures yet?

As Pat mentioned, you need a gauge to check your cold and warm control pressures, your fuel pressure and your residual fuel pressure.

You also want to make sure all ignition components are up to spec.

Let us know the number of the WUR you have and the pressures you get at the ambient temperature you tested. We can then compare them with a chart for a 79.

Until you get a test gauge, you can try loosening the big air bypass screw and see what happens. Loosening it should raise your revs.

I don't know where you are located but here in Toronto around this time of year, your cold start should raise the revs to about 2500 or so at first and then gradually lower them to about 900 after about 4 minutes or so. This will give you an indication for now, without gauges, if your WUR is operating about as it should.

You should also verify your fuel mixture is within range, as this also affects idle speed.

Chart for several WURs. Verify your number with this.http://forums.pelicanparts.com/uploa...1617135296.jpg

Ordered the gauge kit online yesterday, should arrive before the weekend. Will keep you guys posted for sure.
Side question - where do you enter your signatures (and car stats) so they always appear at the bottom of your posts?

click on user pc left corner in light blue

Clarification.........
 

Paul,

Maybe you meant AAR instead of cold start valve? The CSV does not cause the engine speed to increase during a cold start. The auxiliary air regulator does.

Tony

The warm up regulator (WUR) raises the idle on a cold startup and gradually lowers as the bimetallic strip is heated up. The WUR lowers the initial control pressure in the fuel distributor to~2 bar based on outside temperature causing the higher RPM’s. As the WUR is heated the RPM’s will lower to set idle speed because the control pressure in the fuel distributor is raised and will peak at ~3.6-3.8 bar for normal control pressure at idle.

http://forums.pelicanparts.com/uploa...1617165442.jpg

http://forums.pelicanparts.com/uploa...1617165442.jpg

"The warm up regulator (WUR) raises the idle on a cold startup and gradually lowers as the bimetallic strip is heated up. "

NOPE!

I believe we are all trying to help Swazzy with his posted issue by providing a pointer to possible causes for his problem. So, please allow me to expand on my post with some additional comments since I understand that if you increase fuel delivery By the Warm Up Regulator (WUR) that will increase enrichment and that will increase engine RPM's. While the air delivery is initially established by the Auxiliary Air Regulator (AAR) and the vacuum side of the throttle body set by the cold engine at a certain level. I will humbly apologize for my ignorance if I have misinterpreted the functionality based on the technical data on the WUR and the AAR that Bosch engineering has provided in the Bosch Gasoline Fuel Injection System K-jetronics Technical instructions. The WUR and the AAR establishes the increased RPM's at startup (Automatic Choke Function) and the smooth operation at startup. Failure of the WUR or the AAR will effect the initial smooth startup (loss of the Auto Choke Function). It should be noted that any false air leaks in the vacuum side of the throttle body will effect startup and smooth operation once the engine is warmed up. As a side note, I just completed an overhaul of my K-jetronics with Lambda fuel injection system and it functions as designed. I have not disconnected any of the components to mask any issues that do occur with this fuel injection system. It is my opinion that if the K-jetronics system is fully functional and maintained it will provide a very enjoyable driving experience.

http://forums.pelicanparts.com/uploa...1617192199.jpg

http://forums.pelicanparts.com/uploa...1617192199.jpg

Hi Tony.

You are right, of course, that the CSV doesn't raise engine speed, but that isn't what I wrote. Look again very closely at my post. I said "your cold start" not "your cold start VALVE", meaning " happening at a cold start" , not "via the cold start valve".

Anyway, it's funny, I was just sitting at home doing something else and it suddenly popped into my head that what I said may have been misleading, and I was just going into the thread and correct it to point out the function of the AAR v the WUR, but you and gomezoneill beat me to it! LOL. Thanks for doing that, and sorry if I misled the OP. I was trying to help him check on his WUR before he got his fuel gauge, but incorrect info won't help him.

As Tony has pointed out, the auxiliary air regulator (AAR) raises the idle speed at cold start and then lowers it to normal idle speed over time. The WUR changes the control pressure, varying the mixture so it is correct at any given temperature. If not coordinated correctly with the AAR the engine speed could be wrong during the warmup period and beyond.

Pat,

I've found with my engine, a too rich mixture can also cause the engine idle to decrease. This is why I think Swazzy should have his mixture setting checked, as well as trying to vary the air bypass screw setting.

You are indeed correct........
 

Paul,

I misread your post. You are indeed correct.

Tony

Thank you all for continuing to comment. I have a lot to learn!

Very rarely is Tony ever wrong. HE'S THE MAN.

Ok heres the latest and again very appreciative for feedback:

Ivan, I did have to make a slight adjustment to the sensor plate but not much.
The bigger issue now is I did the fuel pressure test. the bad news is I'm so new at this that I did not know that the whining noise while I was doing it was probably the injectors flooding the engine.

The results of the test were not promising either:
WUR Ohms seemed good at 25.7 at 65 degree F temp.
System pressure seemed ok at 72 PSI, and the rest is downhill -
control pressure reached about 15 psi
about the same with warm control pressure - 15 psi although maybe I did not leave it on long enough after I plugged the WUR back in.
lastly there was essentially no residual pressure. dropped to zero in about 10 seconds.

Question are -
How do i resolve injectors that are spraying fuel when they should not be?
Where is the cold and warm fuel pressure, and why does the residual drop so quickly?

Frankly I'm hoping I'm doing something so completely incorrectly that it's not a difficult fix.
I suppose I should add that on the initial break in of the engine it ran fantastic as I varied the revs from about 2200 to 2800. for 20 minutes....

Appreciate the help,
Marc

If your injectors are spraying with the ignition on your sensor plate maybe set wrong also the enrichment screw maybe set too rich. Best figure it out before you ruin your engine. Pull the injectors and use cans or jars so you can see the fuel delivery and post a video.

You may want to check fuel volume delivery. Is it possible there is a clamp on a fuel line, or a cap was left in a hose during assembly and/or installation.

Thanks, heres more info:
I tested the injectors as gomezoneill suggested. They indeed spray when pump is on however they will go off if I push down on the pressure plate. After confirming this, i removed all spark plugs and turned the engine over a few time and pushed the gas out of the cylinders. There was some but not much.
What is the adjustment on the mixture control unit that will put the FD in the closed position when the sensor plate is properly flat?

did you do any adjustment on the sensor plate with the engine cold or the system completely empty??? looks like you have it wise open if the injectors are spraying..
as mentioned in another thread today...
http://img.tapatalk.com/d/14/05/29/yzyne4ah.jpg

I made a slight adjustment with the engine cold and no pressure in they system. Is this the only adjustment to be made on the mixture control unit? It seems like the position where the plate rests correctly does not fully engage the plunger/valve in the fuel distributer to shut off the lines to the injectors. It also feels like there is some resistance in the up/down movement of the plate as it operates the plunger/valve. I do not believe this is normal, right? BTW the FD and WUR have been rebuilt, of course they could still be problematic.

Fuel distributor...........
 

The FD plunger might not be fully going down by itself. Inspect and test the movement of the plunger. As suggested earlier, pull out all six (6) fuel injectors and place them in suitable containers.

Test run the fuel pump. There should be no fuel delivery from any injector/s when the FD plunger is at rest or down. If you get premature fuel delivery:

• The mixture setting could be too rich.
• The fuel injector/s could be leaking.
• The o-ring/s inside the FD could be defective.
• The FD plunger is stuck up high.
• You may have a leaking FD.

Any of the above could be the culprit. Test and verify.

Tony

Well..you have a obvious problem.The movement has to be absolutely free smoth....looks like your fuel distributor pin is getting stuck

Ivan

The Following is from the CIS Service Guide and will provide you with the correct way to connect the pressure gauge and test your fuel pressure, control pressure and residual pressure. Due to limits of posting JPG's I will follow this post with another with 3 more JPG's


http://forums.pelicanparts.com/uploa...1617498397.jpg


http://forums.pelicanparts.com/uploa...1617498397.jpg

http://forums.pelicanparts.com/uploa...1617498397.jpg


http://forums.pelicanparts.com/uploa...1617498397.jpg


http://forums.pelicanparts.com/uploa...1617498397.jpg

Here are three more JPG's of the CIS Service Manual.

http://forums.pelicanparts.com/uploa...1617499131.jpg


http://forums.pelicanparts.com/uploa...1617499131.jpg


http://forums.pelicanparts.com/uploa...1617499131.jpg