2.4L MFI motor running too rich. HELP!!
03-11-2002, 01:23 AM
#1
Racer
Thread Starter
2.4L MFI motor running too rich. HELP!!
Okay here's the deal.. I have been asking for, and receiving lots of assistance from this board over the past few months. My car is now running but running very rich. I tried adjusting the part throttle screw through the fan blades. I tried turning it counter clockwize. No change. Still very rich, blowing grey, black smoke out everywhere. Plus, my screw isn't a screw. It's a very small, thin bolt looking screw. Oh well. So if the part throttle "screw" does nothing (I turned it 4 full turns) what should I look at next?
Scott Harris
1973 911T Targa
1984 944 <img src="graemlins/c.gif" border="0" alt="[ouch]" />
Scott Harris
1973 911T Targa
1984 944 <img src="graemlins/c.gif" border="0" alt="[ouch]" />
03-11-2002, 03:01 AM
#2
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Hi,
the part throttle screw does very little on the MFI setup. It is meant for final fine tuning.
When I had my MFI rebuild the specialist told me not to touch this part throttle screw, because it will change the position of the 3D space cam relative to the follower arm. This means that al the careful adjustment done by the MFI calibration in the workshop can be easily lost, and together with it you will loose a smooth midrange. Full-throttle is always easy to setup, but midrange not!
So , first rule: Do not play with this part throttle screw.
If your engine runs too rich , I would suggest
1. Check the warmup thermostat. Or try even by heating this thermostat with a hairdryer. If you are unsure about the functioning, then you can also open the little cover next to the thermostat on the pump an check that the lever is actuated fully. Common errors are also due to seized thermostat pistons and debris. Do not mix up the order of the thermostat disks!!
2. The right point to change mixture is the main rack screw. This is hidden by a hex (allen?) M6 nut for the pump solenoid. So take the screw out and with a long screwdriver you will get access to the main rack screw.
3. Check the MFI techical section on the Pelicanparts web site, there you find excellent info.
Good luck, and I promise you that the engine will run very well once the MFI is set up properly.
Andreas
the part throttle screw does very little on the MFI setup. It is meant for final fine tuning.
When I had my MFI rebuild the specialist told me not to touch this part throttle screw, because it will change the position of the 3D space cam relative to the follower arm. This means that al the careful adjustment done by the MFI calibration in the workshop can be easily lost, and together with it you will loose a smooth midrange. Full-throttle is always easy to setup, but midrange not!
So , first rule: Do not play with this part throttle screw.
If your engine runs too rich , I would suggest
1. Check the warmup thermostat. Or try even by heating this thermostat with a hairdryer. If you are unsure about the functioning, then you can also open the little cover next to the thermostat on the pump an check that the lever is actuated fully. Common errors are also due to seized thermostat pistons and debris. Do not mix up the order of the thermostat disks!!
2. The right point to change mixture is the main rack screw. This is hidden by a hex (allen?) M6 nut for the pump solenoid. So take the screw out and with a long screwdriver you will get access to the main rack screw.
3. Check the MFI techical section on the Pelicanparts web site, there you find excellent info.
Good luck, and I promise you that the engine will run very well once the MFI is set up properly.
Andreas
03-11-2002, 10:48 AM
#3
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Scott you are going thru the MFI growing pains, just as I did on my 72 E. To see how I finally resolved all my problems just go to the Pelican 911 board and do a search on MFI and fouling plugs. What finally got my problem fixed was getting the Gunson Gas Tester so I could see what my adjustments were doing. Turns out the previous owner(s) had the MFI so far out of adjustment it took approx. 2O clicks to get the rack back in adjustment.
03-12-2002, 02:13 AM
#4
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before you get too much deeper, go to the Pelican Parts website, download all the technical articles related to MFI -- particulary the one entitled "Check, Measure and Adjust". read them all very carefully and follow the directions to a T.
first and foremost, make sure your timing, dwell and valves are in adjustment. without this, you are starting from an unknown point and could end up using your MFI system to compensate for other deficiencies.
read the articles THEN decide what tools you need and what screws you need to mess with. otherwise, you could get your MFI so far out of whack that it will take a long time to recover.
also, take careful notes of all the changes you make while going through the system. that way, if you do something that has unexpected results, you can undo it.
i have posted many messages on the Pelican Parts website regarding my "learning curve" on MFI. once you get the grasp of that system, it really isn't that hard. but digging into it without a little background is a recipe for disaster.
any questions, email me at tmctguer@***.net.
first and foremost, make sure your timing, dwell and valves are in adjustment. without this, you are starting from an unknown point and could end up using your MFI system to compensate for other deficiencies.
read the articles THEN decide what tools you need and what screws you need to mess with. otherwise, you could get your MFI so far out of whack that it will take a long time to recover.
also, take careful notes of all the changes you make while going through the system. that way, if you do something that has unexpected results, you can undo it.
i have posted many messages on the Pelican Parts website regarding my "learning curve" on MFI. once you get the grasp of that system, it really isn't that hard. but digging into it without a little background is a recipe for disaster.
any questions, email me at tmctguer@***.net.
03-14-2002, 05:16 PM
#5
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Scott,
You're adjusting the wrong screw. You're adjusting the idle mixture screw, and as you discovered it makes very little, if any difference. You need to adjust the mid-range (also called part-load) screw, the one under the hex bolt that Andreas mentions. You don't need to go through the fan to get at it. (Andreas, the advice your mechanic gave you about the **idle** screw is wrong. If anything, it is the mid-range screw that can severely upset the mixture setting.)
Did you instal an engine tin to driver's side heat exchanger hose, as we discussed?
I'd be careful about which way I turned the mid-range screw. (I don't remember by heart which way is lean and which rich, although I know the idle and mid-range adjustments are opposite.) If you haven't read enough to realize you're adjusting the wrong thing, I worry about which way you're adjusting it.
The MFI system is really very simple. That one screw is **the basic** mixture adjustment. You ought to be able to go from way rich to way lean with no trouble at all. In fact, the ease with which it can be done--a half turn of a screw (that's three clicks) is what gets a lot of people into trouble.
Bob
Y
You're adjusting the wrong screw. You're adjusting the idle mixture screw, and as you discovered it makes very little, if any difference. You need to adjust the mid-range (also called part-load) screw, the one under the hex bolt that Andreas mentions. You don't need to go through the fan to get at it. (Andreas, the advice your mechanic gave you about the **idle** screw is wrong. If anything, it is the mid-range screw that can severely upset the mixture setting.)
Did you instal an engine tin to driver's side heat exchanger hose, as we discussed?
I'd be careful about which way I turned the mid-range screw. (I don't remember by heart which way is lean and which rich, although I know the idle and mid-range adjustments are opposite.) If you haven't read enough to realize you're adjusting the wrong thing, I worry about which way you're adjusting it.
The MFI system is really very simple. That one screw is **the basic** mixture adjustment. You ought to be able to go from way rich to way lean with no trouble at all. In fact, the ease with which it can be done--a half turn of a screw (that's three clicks) is what gets a lot of people into trouble.
Bob
Y
03-14-2002, 08:16 PM
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Hi Scott,
I hope that after all these instructions you will still keep a clear mind...
First, usually MFI pumps do not go out of tune by itself. So if the car was running fine before, but is running far too rich now, without beeing touched by a human beeing, then I would say your problem is just the warmup thermostat. There could be dirt in it or the pin is seized, or simple a house coming from the heat exchanger is gone off.
If you are sure someone has put the hand on the pump and brought it out of tune, then it is more complicated:
1. Set up the throttle-linkage as described in the Pelican article from Lee Rice.
2. If you can turn the adjustment screws of the MFI back to the original positions, then do it now.
3. I said part throttle screw in a message above, but I meant the idle mixture screw. Only the idle mixture and main rack are supposed to be adjusted according to the MFI adjustment manual.
Now you can turn the main rack clockwise by 3 ticks each time until the engine will starve on giving full throttle at about 3000rpm. Then the engine is too lean and you can turn counter-clockwise again, but now you go only 1 click each time until the starving under full throttle disappears. This should happen after 1-3 ticks.
This is only a rough setup, and fine tune with CO tester at lower rpm also, should give 5 - 8 % CO for best running, 2 - 3 % CO according to manual.
4. If after all the above steps you are still not satisfied or if you are sure the idle mixture and or intermediate range springs are out of tune, then download the MFI repair manual addon,
<a href="http://www.pelicanparts.com/techarticles/911_MFI/Bosch%20_More_MFI_Repair_Instructions.pdf" target="_blank">http://www.pelicanparts.com/techarticles/911_MFI/Bosch%20_More_MFI_Repair_Instructions.pdf</a>
here you get instruction of how to adjust these springs:
4.1: Take off the stop magnet, and insert instead a gauge. Set the gauge to 0 mm
4.2: Go to page 4 of the manual, and you see that there are 3 major steps involved.
These steps are
A: Control spring preadjustment,
B: Full load values
C: Part load values
As you can see there are adjustments to make for different throttle positions (defined by the angle of the trottle lever (0, 8.3,16 and 29.5 degree) and different rpm.
Start with the Control spring preadjustment, for this the pump must be rotating at 2000, 400 and 800 rpm. It is easier to do so on a fuel injection test stand!
Then remember the gauge, which is there instead of the stop magnet! Let the pump run at 2000 rpm and adjust the control arm such that with fully actuated throttle lever the gauge is 7 mm more inwards. Adjust...
repeat for the different lever angles (0,8.3,16 degree) at rpm (400,800,2000) and adjust with spring 1 (idle mixture) springs 2 (black) and springs 3 (white)
Check the full load values and go on with the partial load adjustment. As you can see from the table (C) the 3 springs act all at a wide rpm range, but spring 1 is used to adjust almost closed throttle, springs 2 at partially open throttle and springs 3 at quite open throttle.
5. If you are still not satisfied with how the engine is running after all the adjustments done under 4. then I advise you to send the pump to a specialist. This is what happened to me, and after a long time of trial I decided to have the pump reassembled and readjusted by a specialist.
I can recommend
Turati & Cipponi
Corso Europa 49/A
20090 CUSAGO (MI)
ITALY
Tel. +39 0290119353 Fax. +39 0290394711
price is about 350 Euro + shipping for a reassembly and readjustment ( is this too cheap to be true?). The pump comes back with new bearings,sealings, repainted, etc.
Send in also the injectors, so they get Ultrasonic cleaned as well.
(I can help you getting you in contact, if language is a problem!)
The above mechanic has experience with Bosch since about 1935 when the father opened the Bosch workshop, now the sun is in his 50s already, but he learned his trade in the late 60s on the Porsches. They also do pump overhauls for the Mercedes 2 cyl pumps and for the Mercedes 300 Sl gullwing.
It is his recommendation not to touch the idle screw except for less than half a turn. Otherwise the whole pump adjustment might go out of tune and position 4 (see above) has to de done again.
Good luck after all
Andreas
Daedalus Software
Andreas Langhoff
via Pontaccio 23
I - 20121 Milano
Tel. +39 028051278
Fax. +39 335 0302345
<a href="http://www.daedalussoft.com" target="_blank">http://www.daedalussoft.com</a>
I hope that after all these instructions you will still keep a clear mind...
First, usually MFI pumps do not go out of tune by itself. So if the car was running fine before, but is running far too rich now, without beeing touched by a human beeing, then I would say your problem is just the warmup thermostat. There could be dirt in it or the pin is seized, or simple a house coming from the heat exchanger is gone off.
If you are sure someone has put the hand on the pump and brought it out of tune, then it is more complicated:
1. Set up the throttle-linkage as described in the Pelican article from Lee Rice.
2. If you can turn the adjustment screws of the MFI back to the original positions, then do it now.
3. I said part throttle screw in a message above, but I meant the idle mixture screw. Only the idle mixture and main rack are supposed to be adjusted according to the MFI adjustment manual.
Now you can turn the main rack clockwise by 3 ticks each time until the engine will starve on giving full throttle at about 3000rpm. Then the engine is too lean and you can turn counter-clockwise again, but now you go only 1 click each time until the starving under full throttle disappears. This should happen after 1-3 ticks.
This is only a rough setup, and fine tune with CO tester at lower rpm also, should give 5 - 8 % CO for best running, 2 - 3 % CO according to manual.
4. If after all the above steps you are still not satisfied or if you are sure the idle mixture and or intermediate range springs are out of tune, then download the MFI repair manual addon,
<a href="http://www.pelicanparts.com/techarticles/911_MFI/Bosch%20_More_MFI_Repair_Instructions.pdf" target="_blank">http://www.pelicanparts.com/techarticles/911_MFI/Bosch%20_More_MFI_Repair_Instructions.pdf</a>
here you get instruction of how to adjust these springs:
4.1: Take off the stop magnet, and insert instead a gauge. Set the gauge to 0 mm
4.2: Go to page 4 of the manual, and you see that there are 3 major steps involved.
These steps are
A: Control spring preadjustment,
B: Full load values
C: Part load values
As you can see there are adjustments to make for different throttle positions (defined by the angle of the trottle lever (0, 8.3,16 and 29.5 degree) and different rpm.
Start with the Control spring preadjustment, for this the pump must be rotating at 2000, 400 and 800 rpm. It is easier to do so on a fuel injection test stand!
Then remember the gauge, which is there instead of the stop magnet! Let the pump run at 2000 rpm and adjust the control arm such that with fully actuated throttle lever the gauge is 7 mm more inwards. Adjust...
repeat for the different lever angles (0,8.3,16 degree) at rpm (400,800,2000) and adjust with spring 1 (idle mixture) springs 2 (black) and springs 3 (white)
Check the full load values and go on with the partial load adjustment. As you can see from the table (C) the 3 springs act all at a wide rpm range, but spring 1 is used to adjust almost closed throttle, springs 2 at partially open throttle and springs 3 at quite open throttle.
5. If you are still not satisfied with how the engine is running after all the adjustments done under 4. then I advise you to send the pump to a specialist. This is what happened to me, and after a long time of trial I decided to have the pump reassembled and readjusted by a specialist.
I can recommend
Turati & Cipponi
Corso Europa 49/A
20090 CUSAGO (MI)
ITALY
Tel. +39 0290119353 Fax. +39 0290394711
price is about 350 Euro + shipping for a reassembly and readjustment ( is this too cheap to be true?). The pump comes back with new bearings,sealings, repainted, etc.
Send in also the injectors, so they get Ultrasonic cleaned as well.
(I can help you getting you in contact, if language is a problem!)
The above mechanic has experience with Bosch since about 1935 when the father opened the Bosch workshop, now the sun is in his 50s already, but he learned his trade in the late 60s on the Porsches. They also do pump overhauls for the Mercedes 2 cyl pumps and for the Mercedes 300 Sl gullwing.
It is his recommendation not to touch the idle screw except for less than half a turn. Otherwise the whole pump adjustment might go out of tune and position 4 (see above) has to de done again.
Good luck after all
Andreas
Daedalus Software
Andreas Langhoff
via Pontaccio 23
I - 20121 Milano
Tel. +39 028051278
Fax. +39 335 0302345
<a href="http://www.daedalussoft.com" target="_blank">http://www.daedalussoft.com</a>
