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I have replaced both vacuum lines with new. The thing is the car is'nt drivable now after the rebuild. Before it was.
Question, With all the things in the way of the bolt on the crank how do you turn the engine to check TDC to see if the rotor on the dist. is pointing in the right spot?
I still think something is amis with the timing. Remember I have the settings set to where it was before and it ran fine. After rebuild and runs like crap. When I sort this all out, if I ever do, I will install the MSD set as well. Heard very good things with that set up. Have to sort this out first though.

Old 04-14-2013, 11:29 AM
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Push in on the fan belt (right side) and turn the motor over with the nut on the alt.
Sounds like you're maybe one tooth off on the dist.
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Old 04-14-2013, 12:27 PM
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Sounds like my experience after the rebuild. Started fine but ran terrible. I found the mechanical advance frozen. Engine had been apart for several months. A little WD40 and a drop or two of oil on the distributor shaft and all was fine.
Old 04-17-2013, 11:00 AM
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Quote:
Originally Posted by pete3799 View Post
Push in on the fan belt (right side) and turn the motor over with the nut on the alt.
Sounds like you're maybe one tooth off on the dist.
I'm leaning that way now, especially after the comment about having to turn the dizzy all the way to the stops to get it to run even somewhat right.

BTW, I machined the adjustment slot on mine intentionally so I could crank it all the way to the stop...in order to get 12 degrees advance at idle (that's with the vacuum retard line connected...so call that 22 degrees once I get above 1500rpms and the vac retard drops off). Then the mechanical advance takes over from there.

In a "normally" timed car, i.e., 1-2 degrees ATDC idle retard, your dizzy should be somethere mid-point in it's rotation adjustment.
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Old 04-17-2013, 11:54 AM
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Back at the shop. There going to smoke the engine to test for leaks. I did check the rotor in the dist. to see if it was off but it's right on the money.
Old 04-17-2013, 04:39 PM
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Well "mark houghton" is the winner. The frequency valve's fuse was blown. Left the shop the first time with it blown. I have never had that fuse go. My hearing isn't all that good for the small noises so I couldn't hear it if it was running anyway. Well now that I know how the car runs when it doesn't work what exactly does the little SOB do? I guess it's just as well as I have the wrench going over the engine with a fine tooth comb now after finding this and the loose manifold nuts. Hoping to have it back soon!
Thanks everyone for the help. This forum is fantastic. Thanks.
Old 04-18-2013, 02:39 PM
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I removed all the lambda stuff from my '87 years ago. The frequency valve is controlled and driven by the k-jetronic lambda box under the driver seat and is connected to it through the lambda harness that runs back through the firewall on the left side and terminates at the multi pin plug on the rear crossmember next to the left side shock tower.

There is a rubber socket on the side of the rear relay panel for checking the pulse frequency or dwell time of the frequency valve with an oscilliscope type meter to check how it's working but I never knew there was a fuse for the frequency valve somewhere.

I'm curious, can you tell me where the frequency valve fuse is?

The frequency valve returns varying amounts of fuel from the lower differential chambers in the aluminum lambda fuel head and returns it to the gas tank through the return line.

By definition it controls another form of hydraulic control pressure that has nothing to do with the WUR and I can explain what happens as it does that if you want to know, but the end result is it changes the amount of fuel injected to make the engine run as lean as possible at all times except for during cold strart and when it's under boost so it can pass emission testing and they could sell these cars in the USA again starting from 1986 on.
Old 04-18-2013, 03:11 PM
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Ha! I win one, finally.

Jim's our resident CIS man having cut his teeth for many years on beemers and such running CIS. Simply deleting that little freakin' valve will mess things up unless you have some major re-turning work done on the fuel head to compensate for it being gone. Not a good thing, since eventually as the years tick by those valves are going to fail all of us.

So, to that hidden fuse.....Must be one that controls all the power to the lambda computer is all I can think of.
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Old 04-18-2013, 04:01 PM
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The fuse holder in the engine compartment. The middle fuse was the problem. Blown. I forgot all about those fuses.
So the frequency valve is another emissions add on? What do you have to change to remove this PITA valve?
Old 04-18-2013, 04:42 PM
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The fuse holder in the engine compartment. The middle fuse was the problem. Blown. I forgot all about those fuses.
So the frequency valve is another emissions add on? What do you have to change to remove this PITA valve?
Beyond my knowledge. Since that freq valve controls fuel flow from the lower differential chamber back to the gas tank, for those of us running open-loop (O2 sensor disconnected) the freq valve will stay at a constant duty cycle...something like 50%...as opposed to modulating in response to the lambda computers' direction as it sees the O2 content of the exhaust gasses changing. Thus, in open loop it's fixed and never changes.
Makes one wonder if a simple flow regulator of sorts - set up to match the flow the freq valve allows when at fixed duty cycle- would suffice and take out the electrical failure potential of the freq valve?
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Old 04-18-2013, 05:35 PM
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The short version is you have to adjust six little 3mm allen head screws under the six 4mm allen head button head screws on the top of the fuel head just a little bit to increase spring pressure on the top of the flexible diaphram disc valves in the upper chambers to compensate for consistant full system pressure that will be in the lower chambers pushing upwards on the flexible diaphram after removing the frequency valve or just disconnecting the plug on it.

If those allen head spring pressure adjustment screws are not adjusted a little tighter after removing or disconnecting the frequency valve to compensate for full system pressure in the lower chambers then the diaphram with it's 6 metal discs will be pushed higher into the 6 upper chambers partially closing off the 6 small valve like orifices in the top of the upper chambers leading to the injector lines and the fuel head will inject less fuel leaning out the AFR.

Those 3mm allen head screws are the same ones used to adjust fuel flow to the injectors to balance the flow from them equally when you know you have 6 equally flowing good fuel injectors.

If I dug up a bunch of pictures I've saved to show the parts I'm talking about and tried to tell you how they work and told you how to adjust the allen head screws while doing an injector flow test into 6 plastic bottles until the fuel flow to the injectors and AFR's are where you desire I would be giving away part of what CIS Flowtech does to modify these fuel heads on a test bench to flow more fuel when running higher boost with better cams and headers.
Larry wouldn't like that.
Old 04-18-2013, 06:09 PM
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I'll add that the reason the frequency valve can vary the amount of fuel pressure in the lower chambers up and down in relation to system pressure by returning some of that fuel to the gas tank is because the fuel feeding the lower chambers has to flow through tiny orifices leading to them from fuel that is at steady high system pressure.
Anotherwords the frequency valve that is just an inline electronic fuel injector can bleed off some of that fuel in the lower chambers and return it to the gas tank faster than it can flow through the small orifice from system pressure to replenish it.

That is the same reason the control pressure/warm up regulator everyone calls a WUR here can change hydraulic fuel control pressure pushing down on the control plunger in the middle of the fuel head while the air flow meter linkage is trying to push it up from the bottom.
The fuel feeding the control pressure chamber above the control plunger has to flow from system pressure through a tiny orifice so the CPR can easily vary that hydraulic control pressure up or down by returning some of it to the gas tank.

This is why you need two big fuel pumps to feed 930 CIS.
This crazy mechanical fuel injection system has to return fuel being used as hydraulic control pressure to the tank for it to flow and inject more fuel to the constantly flowing injectors at high fuel pressure into an intake manifold running around 15 psi higher than atmospheric pressure.

The euro fuel heads only have one hydraulic control pressure circuit returning fuel to the tank and the aluminum lambda fuel heads have two seperate hydraulic control pressure circuits returning fuel to the tank.
That is why the lambda heads run at higher system pressure than the euro heads.

Because the lambda heads have the more flexible synthetic diaphram between the upper and lower chambers they are capable of flowing alot more fuel than the euro heads after they are modified and adjusted.
They also weigh alot less and don't rust inside like the euro heads. When modified they are much better if you are after more fuel.
Old 04-18-2013, 07:23 PM
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There are 2 easy ways to eleminate the Lambda system, swap out to a Euro fuel head or swap out to a modified USA head. I handle both and keep them in stock. The modification on the USA head eleminates the second port allowing it to function like a Euro head. As Jim stated the USA head is then capable of producing greater flow than the USA. I have never seen an engine that needed that much flow but it is available.
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Old 04-18-2013, 08:56 PM
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Quote:
mark houghton said: BTW, I machined the adjustment slot on mine intentionally so I could crank it all the way to the stop...in order to get 12 degrees advance at idle (that's with the vacuum retard line connected...so call that 22 degrees once I get above 1500rpms and the vac retard drops off). Then the mechanical advance takes over from there.

In a "normally" timed car, i.e., 1-2 degrees ATDC idle retard, your dizzy should be somethere mid-point in it's rotation adjustment.
Car runs beter than before. Very good now but.....

While I was playing around with the timing , and other things, trying to figure out my poor performance I noticed by mistake how well the engine ran with more advance than 26 and when the boost came in it was quite a rush! but not knowing what the safe limits are I quickly set it back to stock. So I have a few questions. I know this has been asked a bunch of times and have read this in other posts but wanted to ask in my own way to make sure I get it.

Mark, You said you set the timing at idle to 12 deg. with the vacuum retard hose attached. This is with a stock distributor and vacuum pot? So once the vacuum stops above 1500 RPM you have a timing of 22 deg. because the vacuum retard in the pot releases as there is no longer any vacuum to hold the plate thus a total of 22 deg asuming there is 10 deg of retard in the pot. 12 + 10 = 22 advance. The the counter weights in the dist. take over and add how much more? for a total timing say at 4000 RPM? Must be more than 26 deg right? And you do this with out using WMI like JFairman? Just wondering as I have read other posts like this with ign running more than 26 total timing and are geting good results. I'm starting to understand all of this and want to know just how much safety is built in with a total of X deg. running 93 pump gas w 10% Alcohol I'm going to put my my t vac on the outer port and add .8 bar of pressure to see how much advance is removed with my stock set up. I know this subject has been beat to death but I need to understand what other pelicans are running and not blowing up there engines. More advance is fun!
Old 04-20-2013, 11:28 AM
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The outer pot on the '87 distributor is vacuum advance when vacuum is applied to it and boost retard when air pressure from the turbo is applied to it. You'll see that when you hook a mighty vac to it and test it.
The inner pot is vacuum retard when vacuum is applied to it and when air pressure is applied to it nothing happens, it does nothing. You'll see that with the mighty vac test.

Mark and I have a similar timing setup with the distributor slot machined over so we can advance the distributor static timing farther to 12 -15 degrees btdc which is farther than the slot allowed origonally. I had to also remove a little aluminum from part of the housing near the fan housing area to turn the distributor that far because it was hitting something limiting the travel back there.
We both use the MSD 8762 boost timing retard box to retard timing along with the origonal boost retard working.
This way timing is around 12 to 15 degrees btdc at idle and with centrifical advance and vacuum advance working timing increases to around 35* btdc by 4000rpms.
Then when boost comes up both the inner vacuum pot and the MSD 8762 pull the timing back to around 18* btdc in response to the air pressure.

I don't have a good timing light that has the dial back funtion on it that is compatable with the multiple sparks from MSD ignition and the pulley only has 0 and 26* btdc marks on it so I have to guess or borrow a timing light with the dial back retard function to know what timing is above idle. I should file some marks into the pulley someday so I can see what timing is with my regular old timing light.

It's kinda hard to describe how all this stuff works in text with a keyboard but once you've done it and learn it all it makes sense.
The purpose is to have a little more power and drivability around town below 3000rpms.

If you were rebuilding the motor and wanted better low speed drivability it would be good to do the timing curve modifications and increase compression to around 8:1, enlarge the intake ports, and use a smaller and more efficiant turbo that comes on earlier and doesn't boost over .8 or .9 bar with SC cams and headers with a free fow muffler.
Henry at Supertech does something like that.

Last edited by JFairman; 04-21-2013 at 06:31 AM..
Old 04-20-2013, 12:33 PM
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JFairman wrote: Mark and I have a similar timing setup with the distributor slot machined over so we can advance the distributor static timing farther to 12 -15 degrees btdc which is farther than the slot allowed originally. I had to also remove a little aluminum from part of the housing near the fan housing area to turn the distributor that far because it was hitting something limiting the travel back there.
We both use the MSD 8762 boost timing retard box to retard timing along with the original boost retard working.
This way timing is around 12 to 15 degrees btdc at idle and with centrifugal advance and vacuum advance working timing increases to around 35* btdc by 4000rpms.
Then when boost comes on both the inner vacuum pot and the MSD 8762 pull the timing back to around 26 to 28* btdc.
MSD 8762 controls the boost and you have modified the distributor ignition curve or did you just modify the slot only?

I have been looking at the MSD 6AL-2 programmable that will control the boost and the ignition curve with a locked distributor which I'm sure your familiar with.

So your running 35* BTDC @ 4000 RPM and this is only possible with WMI? If so what is the safe limit with out a WMI?

I ask all this as the wrench installed a new vacuum pot on the distributer and set timing to 26* BTDC @ 4000 RPM and the dizzy is turned almost to the end of the slot. It runs great but I think the port closest to the dist. body is adding a lot of retard because I checked the timing at idle just to see where it is and is around 2*BTDC with the retard hose plugged in. I'll check this all out tomorrow in detail and let you know where it's at. I am surprised that it's not near the middle of the slot as you mentioned a few posts back with a stock setup.
Old 04-20-2013, 04:48 PM
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"MSD 8762 controls the boost and you have modified the distributor ignition curve or did you just modify the slot only?"

I did modify and shorten the centrifical advance curve by bending the vertical steel tabs that stop and limit the centrifical advance weight outer travel inwards about 1/8". I also ground some metal off the sides and outer edges of the centrifical advance weights to make them lighter. Then I polished them to make them pretty and finished looking while equaling their weight even though you can't see them installed. It just makes me feel good.

That has a similar effect as putting in stronger advance weight springs but none are available unless you take apart many BMW and Mercedes mechanical distributors and test the springs... The same diameter housing distributors including points and condensor units including ones that spin the other direction all use the same advance weights, but different springs.
So I made the advance weights lighter to delay the centrifical advance curve a little and then advanced the static timing to 12 to 15* btdc so final centrifical advance is the same as it was stock.

"So your running 35* BTDC @ 4000 RPM and this is only possible with WMI? If so what is the safe limit with out a WMI?"

Yes, but that is only with full vacuum advance and full centrifical advance together and only at steady low load cruise on flat level roads like the interstate in Florida.
WMI is not spraying during steady cruise on flat level roads because there is no boost happening then.
When accelerating timing will stay there until boost starts comeing on.

If you remove the vacuum advance hose during steady no load 4000 rpms then timing is at 26 to 28* btdc just like when in nuetral while you're back there with a timing light on the pulley. It sounds like you may be forgetting about full vacuum advance on top of full centrifical advance. Thats when you have around 35* btdc

Under boost there is no vacuum so there is no vacuum advance but there is always centrifical advance.
The distributors vacuum retard and the MSD 8762 both work at the same time to gradually pull timing back to around 18* btdc when boost comes on. That way vacuum retard is pulling timing back to a safe level.

I set the adjustable pressure switch for the WMI so it starts spraying at .7 bar to help reduce the chance of detonation between .7 and 1.1bar
WMI is overrated by the places that sell it but it helps especially when the mixture in the WMI tank is around 70% methanol and 30% water. It's kinda fun to experiment with it and watch the AFR gauge when it comes on and the 930 intake manifold being a flat plenum with 6 holes leading downwards to the intake ports works good for WMI distribution with little laminar flow wetout and dropout on the manifold walls unlike the Carrera manifold with all it's length and twists and turns.

If I think of it I'll take a picture of my distributor tomorrow and post it so you can get an idea how far it's turned in the lengthened slot. I have a stainless steel washer and nylock on the stud but you'll get an idea.
Old 04-20-2013, 06:17 PM
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This timing stuff will make your head spin and keep you awake at night trying to understand it. I think Jim did a good job explaining, as well as can be done with a keyboard.

I do not have WMI and I think I'm ok without it because when on full boost all the extra timing I added at idle has all been shaved off by the MSD 8762 and by the boost retard to the vacuum pot to where I'm left in the normal timing safety zone for these cars (maybe a degree or two more, but I don't have the means to test the actual under-boost timing). WMI becomes critical when running higher boost numbers, higher timing advance, higher compression ratios, and/or crappy lower octane gas...or any combination of those.
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Old 04-20-2013, 08:15 PM
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Quote:
Originally Posted by mark houghton View Post
This timing stuff will make your head spin and keep you awake at night trying to understand it. I think Jim did a good job explaining, as well as can be done with a keyboard.

I do not have WMI and I think I'm ok without it because when on full boost all the extra timing I added at idle has all been shaved off by the MSD 8762 and by the boost retard to the vacuum pot to where I'm left in the normal timing safety zone for these cars (maybe a degree or two more, but I don't have the means to test the actual under-boost timing). WMI becomes critical when running higher boost numbers, higher timing advance, higher compression ratios, and/or crappy lower octane gas...or any combination of those.
Belive it or not with all the good posts by yourself and JFairman and all the rest of the gang I am starting to understand this and will definatly invest in a MSD setup this year.
All I was able to do was to check how much advance I have when I pull the retard side hose at idle. Timing mark 2deg BTDC with hose attached and 15-16 deg BTDC with the hose removed. So I'm getting a little more than the expected 10 advance with the hose pulled. Didn't have any help today to opperate the throttle to check the rest with the my-t-vac. Stay tuned. Car is running good though. Have to put the a V1 on the top of the list to buy soon.
Old 04-21-2013, 03:41 PM
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Try driving it with the retard hose disconnected and plugged with a little bolt or something. The car is going to have alot more pep leaving from a stop.
Vacuum retard is gone above the transmission in nuetral 1500 rpm throttle position anyway so you won't hurt anything.
Vacuum advance will work the same and so will boost retard.

FWIW, I took a picture of my distributor slot area today to give an idea where the stud is positioned in it after lengthening the slot for more advance and all the other stuff I've done to it.

Old 04-21-2013, 04:12 PM
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