MFI lost mixture = no start, help!!

[pszemia]

Hi everybody, today working on the car and started to think that maybe my car isn't starting, not because of spark, ignition or air, and just because i have played too much with the part-load and idle screws, that i have made such a mess that the car will refuse to start.

Before any comments, yes, i am a stupid and i have never had to touch the mixture screws until i got the car running and the CO meter on it, but in the desperation (2 months without starting), made me play with them.

The simptom is, engine will turn, but will not catch fire, it sparks, and fuel is coming, the Cold start is working right. Also checked for stating timing with 12v testlamp, so it should run right at that position.

First, i made all the previous check, have fuel with righ rate. Also have spark, and CDI whistling.

The first question is: the spark i have checked (removed cyl #4 wire) is blue/silver but very small. When i connect the wire to the coil directly, i get lot's of spark, so the pertronix is working right. Until today the system was working with points, but i wanted to go back to pertronix to see if they where worn, but i have the same simptoms.

The second and most importatn question is:

How can i set the part-load and idle screws back to a "factory" base line, or something around there so the car can start and then i can go through CMA 3 times, yes i promise it, to get the correct values? i mean something like close all the srews one way or other way and then open X turns.


thanks,

Ariel

[356RS]

Ariel, Sorry to see your still having problems. Sounds like almost everything on your engine has been played with by now. As for the MFI pump "factory base-line" there's none that I know of. I can tell you what the midway point setting of the idle adjustment screw on the MFI pump is: 4 to 5 turns counter clockwise from all the way in. This will be close to a mid range setting on most pumps. I would not touch the other screws in the MFI pump spring capsule. You should change all your spark plugs too, looks like they have been washed out a bit after all the no start issues.

[Flieger]

Maybe you could find someone with a pump taken off a running car who can turn the screws all the way in and count the turns. Maybe Jeff Higgins has already done this in his MFI Pump: Open Heart Surgery thread?

[356RS]

Max, Yes Jeff documented his pump in the "Open Heart Surgery" and lots of good information there. I can tell you that after rebuilding over 20 pumps this year the majority of them have the "High Speed" white screws out about 2 turns from bottom and the "Mid Range" black screws are about 3 turns out from bottom. Every pump is different but this base-line will at least keep it running.

[pszemia]

i know i have played a lot and still no work, but safely i haven't touched the 4 screws (2 black / 2 white) inside the capsuel, so the only ones are the part-load and the idle screw.

when you mean midway, 4/5 turns, that's full turns, right? and the close position of both screws are the same, CW like an ordinary screw? or one CW and the other one CCW?

thanks!

[356RS]

Ariel, The only screw I'm talking about is the Idle mixture screw on the nose of the MFI pump. 4 to 5 full turns CCW from the full in CW position.
Have you also played with the main fuel rack adjustment? The one above the solenoid with the allen head screw covering the hole?

[pszemia]

yes, also played with the main fuel rack..

[356RS]

Ariel, For the main fuel rack, turn the adjuster CW all the way in till it stops. Write down how many turns this takes for a reference. Now turn the adjuster out CCW 7 full turns. Again, every pump is a little different but this should get you in a medium setting and a little toward the lean end. Remember, CCW turns makes it richer and CW leaner. The rack adjustment affects everything from idle to full throttle. And just to be clear, the only real way to get the MFI pump back to factory spec is to have it recalibrated. You can get it close trying to read A/F ratio meters and making adjustments but it takes a lot of time and the rest of the engine has to be all in tune first.

[pszemia]

Originally Posted by 356RS

Ariel, For the main fuel rack, turn the adjuster CW all the way in till it stops. Write down how many turns this takes for a reference. Now turn the adjuster out CCW 7 full turns. Again, every pump is a little different but this should get you in a medium setting and a little toward the lean end. Remember, CCW turns makes it richer and CW leaner. The rack adjustment affects everything from idle to full throttle. And just to be clear, the only real way to get the MFI pump back to factory spec is to have it recalibrated. You can get it close trying to read A/F ratio meters and making adjustments but it takes a lot of time and the rest of the engine has to be all in tune first.

thanks!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

and for the second part, that's why i said, when it starts, i will make 3 times the CMA to keep everything tuned, and more if it's neccesary.

thanks, again. If there is any other advice i will keep it in mind

[pszemia]

Forgot to add the picture of the spark plug and how it looks like. When i removed it had some raw fuel on half of it. But the color seems normal to me, what do you think???

[bkreigsr]

Originally Posted by pszemia

But the color seems normal to me, what do you think???

If that's normal, I'm Steve McQueen. Looks burnt and carbon fouled. Wondering if you might do better with the factory recommended old-school platinum-tipped Bosch or Beru? My mfi loves 'em. Bill K

[BK911]

How about spraying some starting fluid down the intakes? If it doesnt even try to start, it may be something other than a fuel issue. If it tries to run but dies, than it may be a fuel issue.

[Flieger]

Originally Posted by bkreigsr

If that's normal, I'm Steve McQueen. Looks burnt and carbon fouled. Wondering if you might do better with the factory recommended old-school platinum-tipped Bosch or Beru? My mfi loves 'em. Bill K

I thought the copper plugs were the recommended ones. Maybe go one number hotter?

[Zeke]

Originally Posted by 356RS

Ariel, The only screw I'm talking about is the Idle mixture screw on the nose of the MFI pump. 4 to 5 full turns CCW from the full in CW position.
Have you also played with the main fuel rack adjustment? The one above the solenoid with the allen head screw covering the hole?

Originally Posted by 356RS

Ariel, For the main fuel rack, turn the adjuster CW all the way in till it stops. Write down how many turns this takes for a reference. Now turn the adjuster out CCW 7 full turns. Again, every pump is a little different but this should get you in a medium setting and a little toward the lean end. Remember, CCW turns makes it richer and CW leaner. The rack adjustment affects everything from idle to full throttle. And just to be clear, the only real way to get the MFI pump back to factory spec is to have it recalibrated. You can get it close trying to read A/F ratio meters and making adjustments but it takes a lot of time and the rest of the engine has to be all in tune first.

Just remember that the adjustment screws for the rack and the part load turn opposite to bottom out. 356RS has given you the correct procedure, I just wanted to make sure you caught the difference.

[pszemia]

and if i add that those sparkplugs got no kilometeres, but a los of starts?? hahaha

milt, i double caught it!, this weekend going to continue working with the car and post news..

thanks everybody!

[RSTarga]

I know you are in Buenos Aires. Bosch should have a repair facility down there. Mercedes used these same pumps both on their cars and on their diesel engines. Try talking to them and see if they can rebuild your pump and test your injectors. It's worth a try as these thing are very difficult once you've lost your way.

[pszemia]

thanks for the advice, yes i can search for a diesel bosch repair, and last week i was drivnig around and found one near home, so maybe i'll go there to check it out.

For the tests:
idle screw was 5 turns out, so i left it there.
main rack was about 5 turns also, so i moved it to 7 turns out.

then tryed to start but no luck, i think i've done like 25 starts, but no luck. Got some sporadic fire but nothing, and then I found 1 problem.

I was 2 hours trying to start with the cross-shaft to pump rod dissconected, yes i am a dumb. So i think i have flooded the cylinders with fuel because as soon as i tryed to start with ALL the rods connected, it will refuse again.

I removed one sparkplug to check and it was half wet, so maybe that's why it wouldn't start, as far as i know wet sparkplug = no start, right?

From another side:
I removed one hard fuel line to check if there was fuel and it was positive, as i was removing the screw some fuel dropped out and then i tried to start the engine (with cdi dissconected, safety first) and when the engine was cranking there was some fuel drops coming from the hard line, so i assume the pump is working ok.

The other thest i did was to remove the #4 injector to check for fuel spray, and i tried it for 3 periods of 4sec and i never got fuel spraying for it. I don't know if it was because there was no right fuel quantity in there (because of the drop when the hard line was removed) or if it is definetly stuck and no fuel is coming from it.

And last and final test was for spark at sparkplugs, i got spark in all of them, but the spark is very weak or tinny or if it is ok, i can't tell the difference, but it's like a tinny spark.

remember that i have started the car with this CDI and coil (MSD new one) 4 months ago, and it was untouched.

i have made an orientation picture (red is the spark):



Thanks, Again!

[pszemia]

HELLO EVERYBODY!!!!!!!!!!!

I went to work on the car yesterday and guess what???.. THE CAR STARTED, i can't belive it, i jumped like i have won the world championship

This was my yesterday steps:
1. Took out sparkplugs from 6 cylinders for 2 days for gas evaporation.
2. Check for spark directly from coil with telegraphic test --> beautiful blue spark
3. Installed all 6 new NGK BP8ES sparkplugs.
4. Checked for dizzy at Z1 and TDC of cyl #1 --> OK
5. Tryed to start --> explosions but no start.
6. Removed points and installed pertronix.
7. Tryed to start --> START!!!!!!!!!!!!!!!!!!!!!!!!!

When it started, it was idling like a champ but at 1200RPM (idle screws are too open 6 half turns)

After 10 minutes at 3000RPM it suddenly stoped, and i said, oh my god, what's going on in here...

No start, but the engine will crank. I went to the fuel station and bought 20liters, filled with it, and no start either.. so i said, mmmm.. let's check everything again.
Fuel pump, running.
Battery, ok.
whistling from cdi, NO noise, so i sad oh, i am in trouble. So i took it out, and checked the 12v for voltage and i got no 12v at it when the key is at ignition, so remembering all the stuff i have learned here, i recheck the 14 pin connector, and there was the problem, one leg was kind of dirty, so some WD40 on it plus a metal brush, reconnected, 12v, and whistling again

So, now i have the car running again!

I think my main problem was:
1) when i took out the hard fuel lines to replace the intake gaskets, and the car refused to start, i started touching the idle and the main rack screws and i lost the way.
2) the sparks where getting wet, i think because of bad timing, or poor ignition due to lack of fuel on them. That's why i replaced them.


Again, thanks everybody, and now start with the CMA again, to get it tottaly working !

[Flieger]

Wonderful news! Good work. Best of luck on tuning and I hope you can start enjoying the drives soon.

[dicklague]

good for you and glad you put in a Pertronix.......that is a great upgrade!!