Problem with throttle valves

[pszemia]

Hi everybody.

Today i got my synchrometer, and i started doing the CMA again.

When i started with the throttle synchronization, i found a problem.

In the first reading at 3000RPM, i got very high reading for my 30Kg/h synnchrometer.

cyl 1 - 19
cyl 2 - 22
cyl 3 - 17
cyl 4 - 25
cyl 5 - 20
cyl 6 - 18

all this with 3 half turns of each screw. I noticed the values are very high, but i continued with the proper adjust of each one. After doing it, i got again the same results

so i made a final test. I closed the screws of cyl 1 and cyl 4, and guess what?, Same readings.

So maybe i though the problem is the throttle stop of each throttle body, or maybe another problem with the valves..

any idea??

thanks!!!

Ariel

[pszemia]

any help?

[BK911]

Sounds like the throttle plates aren't closing all the way. disconnect the linkage between the throttle plates and adjust the stop screws to verify the plates are completly closing. Adjust the linkage so it has barely a little slop (no pre-load) when connected between the throttle plates. Repeat as necessary.

Have fun and good luck!
BK

[DanS911]

Sorry no speaky MFI

[pszemia]

Originally Posted by BK911

Sounds like the throttle plates aren't closing all the way. disconnect the linkage between the throttle plates and adjust the stop screws to verify the plates are completly closing. Adjust the linkage so it has barely a little slop (no pre-load) when connected between the throttle plates. Repeat as necessary.

Have fun and good luck!
BK

They must be completely closed, or some mm open??

thankss

[304065]

They are slightly open so they don't seize against the bore. Here is how to do correlation.

Remove all the throttle rods. DONT MIX THEM UP! Put a piece of tape on the center of each one and clearly mark 1-2, 2-3, 4-5, 5-6.

Start the engine and let it idle. It should not go above idle speed as all the throttles should be at their stops. If it does not idle at 900 RPM, go BACK to CMA and check ignition advance.

Take a synchrometer reading on each. Adjust the air bleed screws. Obviously, IDLE is where the screws make a difference, they bypass air around the closed throttle plate.

Stop and think at this point, are the cylinders balanced? If you cannot get them to balance with normal adjustment of the bleed screws, that means that your throttle shafts are leaking and it is time to have them rebuilt ($1200 or so).

If they are balanced, your next step is to set the rods. Ideally you should be able to snap all the rods back on to the ball pins WITHOUT moving the idle. If you attach one and the speed picks up, then loosen the lock nut, spin the shaft to lengthen or shorten the rod and tighten the nut. You can use light oil on the balls (thanks Grady!) at this point, and use Bosch distributor grease as the final step. Again, if you can't get them to balance out, then either the rods or rod ends need replacement.

OK, now you have an engine that will idle with more or less correct geometry of the rods. You proabably don't have protractors, but if you did, you would find that they are pretty close, within a degree or so. Depends on how worn the ball sockets and balls are.

Now repeat the drill at 3000 rpm, this is really a function of the rod geometry, not the air screws.

Good luck!

[Flieger]

Hello,

I now realize you are the person who emailed me. Looks like you have the right resources. Sorry I cannot help more.

Best of luck with your project. You are certainly taking on a challenge being far from MFI parts and shops.

[pszemia]

Best of luck with your project. You are certainly taking on a challenge being far from MFI parts and shops.

Thanks!!!! it really is, and this forum is like my local shop, a lot of answers, and a lot of people with very good knowledge!

Originally Posted by john_cramer

They are slightly open so they don't seize against the bore. Here is how to do correlation.

Remove all the throttle rods. DONT MIX THEM UP! Put a piece of tape on the center of each one and clearly mark 1-2, 2-3, 4-5, 5-6.

Start the engine and let it idle. It should not go above idle speed as all the throttles should be at their stops. If it does not idle at 900 RPM, go BACK to CMA and check ignition advance.

.....

Good luck!

John, hi again!

my problem besides the throttle valves, is that the car can not stay at idle. It will idle at 900/950RPM, but it turns off. That's the main problem i have, and the first step to start doing all the CMA by myself.

When cold: 5-10 seconds, and then off
when hot: more time, and then off.

it's not instant off, it's like going down RPM and finish stopping.

I have a video of the noise the car makes when it's cold, and i am around 2200/2500RPM.

The "pf pf pf pf" noise, is like failed explosions, and here comes my question if it is because too open throttle valves, or maybe from the intake valves at the cylinder. The noise is 85% coming from the cyl 4-5-6.

The interesting thing, is the noise almost disappear when the engine is hot 180ºF or above.

http://www.youtube.com/watch?v=FxZ_rsNBJtU

I have checked the ignition advance is perfect, 5ATDC when idling, 5BTDC when i remove the advance mechanism (air duct), and around the 35BTDC mark at 6000RPM as the CMA says.

Also i have changed some parts of the engine:
- NEW spark plugs, NGK BP6ES.
- NEW wires, 7" solid cooper.
- NEW airfilter.
- NEW oil.
- NEW oil filter.
- Almost new (500km) fuel filter.


So thinking around, i though the problem could be something related to the throttle, because there is too much air coming, and that's producing the bad air-fuel ratio, and making all that "pf pf pf" noise and also the car turning off.

It's important to add, the car was very very very rich, i used my new gunson and at part-load got readings around 13% of CO, i reduced them to around 4%-5% and also the idle CO wich was too high.

After finishing the first CMA to use as a baseline, i started getting this shutt off problem at idle (earlier i got the shutt off problem when the engine was too hot).



any clues for all this???

THANKS A LOTTTT!!!!!!!!

Ariel

[BK911]

I usually set my CO to around 7 at idle and 3k rpm.

One way to check idle AFR is to disconnect the linkage to the pump and very slowly open the throttle bodies. Ideally the idle will very slightly increase and then die. That means the AFR is barely rich. If the idle increases a lot than it's way to rich. If it dies immediately than it's too lean. This is how I usually set my idle CO. Usually works out right at 7 on the gunson.

[Flieger]

I have heard of similar stalling problems when the fuel lines were routed incorrectly to or from the fuel console in the engine bay. Also, when a non-MFI electric fuel pump was used.

[brantcaulley]

i watched your youtube video,
my car does the same thing.

i cant figure it out either.
i just keep driving it hoping it will go away

very strange.

brant

[pszemia]

Originally Posted by BK911

I usually set my CO to around 7 at idle and 3k rpm.

One way to check idle AFR is to disconnect the linkage to the pump and very slowly open the throttle bodies. Ideally the idle will very slightly increase and then die. That means the AFR is barely rich. If the idle increases a lot than it's way to rich. If it dies immediately than it's too lean. This is how I usually set my idle CO. Usually works out right at 7 on the gunson.

But to do this, should i first check the throttle stops? i mean, maybe they are too much open and there is my problem...

By the way, should i remove the throttle bodies to check the throttle stops? is it complicated???

thanks!

[304065]

Remove the throttle links as I have explained above, then repeat the test.

With the engine at operating temperature, 180F oil temp, you say it runs fine? Then what is probably happening is the hot oil is heating up the MFI pump housing, which in turn is heating the thermostat, leaning out your mixture so the plugs dont foul up and kill the engine.

Remove the throttle links and lean the idle mixture adjustment out six clicks to the LEFT. See if you can get the engine to idle at operating temperature with no linkages.

You can remove the TBs to set the stops on a flow bench, the advantage of the 72 style is they can be more easily adjusted on the car. But I wouldn't go to the trouble of moving them until you first find out whether the correlation can be balanced at idle with the air screws. If it cannot, the TBs are either worn out (more likely, they are 36 years old) or some PO has moved the throttle stops. That is a fairly simple DIY flow bench operation with a shop vac and your synchrometer.

[pszemia]

got some good news here..

Today i spent some time with my porsche..

following john advices, i disconnected the throttle rods and found something interesting...

I've been working some time ago with the pump rod distance to the cross shaft, which had bad length and some other supplements to keep the pump "richer" in idle.

I found that the throttle rods where too short and not allowing the throttles to reach their stops.

So, i adjusted them so each throttle reach their stops and then the car was idling very well for some minutes with the engine cold, the sound is too different, not so loud as before, it's a biggg progresss for now.

But another problem appeared...

After turninng off the engine and then back on, i couldn't get fire again, tried 2,3,4 times and nothing.

But i don't want to deep in this problem yet, because the car has been sitting for 6 months, without reaching high speeds, and the battery is not well charged (i tried to start with the help of another and no fire) and maybe the car needs some high speeds and use to get all clean of dust and old fuel it could have...

I think, as i said, get the car to the track, use it for some hours and then, see if the problems are corrected..

aahh.. i forgot, the air bleeds aparently are working, because as i touch them, the sound of the engine changes a little bit, but i can't feel a noticeable difference in the RPM values at the dashboard.

thanks!!!!

Ariel

[pszemia]

tomorrow i'll be working with the car again..

any advice???

thankss

[pszemia]

back from tests, got some new results and found a big problem that i've solved.

Looking at all the cables that goes from the 14 multi-pin connector, and found something interesting..

The Cold start injector was getting power from the yellow cable (12v switched i think), so maybe that's the problem of overflood i was getting, and making my car to die after a short or long run, and also the bad idling.


So, i removed that cabel, and connected the original one (grey-white i think it was) that was hanign in back of the fuel filter.

But i found also, the microswitch was also getting to both of their connection 12v from the same source as the CSI, so i take out those cables, but now i don't know where i can take the "power" to the microswitch and then to the Shutoff solenoid.

thanks!!

Ariel

[Flieger]

The RPM Transducer receives 12V (ignition-switched) power. When the distributor/tachometer wire signal says the engine is above 1500 RPM or so, it sends power to the microswitch. When the throttle arm contacts (closes) the microswitch when you are off the accelerator pedal, the fuel shutoff solenoid is activated. This pushes the injection pump main rack past full lean and shuts off fuel flow. The engine then slows in RPM. At the point that the distributor says the engine is below 1500 RPM, it opens the circuit to the microswitch and the solenoid retracts, allowing idle fuel flow to keep the engine from stalling.

I think your wiring was correct in using 12V switched power.

[pszemia]

flieger, i understand what you say, but mine was very bad wired, as i show in this diagram:



Yellow cable:

The yellow cable is on coming from the 14-pin connector to the other side of the engine with a lot of cables.

It was cut in the middle and linked with a new cable from the middle of it running to the CSI and to both ends of the microswitch (yellow cables)

Brown cable:
This cable comes from the middle of the 14-pin connector cables behind the alternator and there is one grey/white (i think this was the combination) with a spade connector. This was connected directly to the stop solenoid.

Following the wirings, i found this one had to go to the microswitch and not to the stop solenoid directly, am i right?

This is how i have the cables now (don't pay attention to the colors):



The grey/white cable from the 14-pin connector, connected to the microswitch.

A new cable from the microswitch to the stop solenoid.

The CSI is now connected to the original cable, which was behind it (have to test the cable yet).

is this ok???

THANKS!!!

[Flieger]

That last diagram seems correct to my logic. Where does your RPM/Fuel Shut-off Transducer Switch connect into this?

I hope Grady can provide some definative answers here...

[Flieger]

Here are some thread you may find helpful:

MFI resources: Ultimate MFI resources thread

RPM Transducer repair: For MFI Gurus. . .and friends of Warren . . .

search results for "MFI resources thread": http://forums.pelicanparts.com/search.php?searchid=2976636