HELP: MFI engine starts but no idle

[tref]

Here is some of the background:
- 1972E originally with sporto but now with 915
- car runs OK but smell bad (bad mixture)
- soak inside of pump in solvent, flush, fill with oil
- car runs the same, no change
- added LM1
- start to adjust mixture but no change on LM1, reading full scale.
- now real problem starts (kick myself for touching mixture screws)
- engine starts well with a nice surge but dies right away
- no starting when I disconnect the cold start solenoid
- change fuel filter but it does not help
- kick myself for touching mixture screws
- I am going to check fuel volume and pressure next

Does anyone have suggestions ?

Thanks,
F.

[Zeke]

If you have the manual and know which way the 2 screws go (opposite directions), close them and open them each 6 full turns. That's the base line for beginning the adjustment process if you lose track. If you don't have the CMA manual, leave things alone until you have a better understanding of what is involved.

[tref]

Hi Milt,

I do have CMA and have been through it over time. I know the 2 screw go in opposite direction for enrichning. Do you mean the base line should be 6 turns toward lean or toward rich?

F.

[356RS]

WHAT 2 SCREWS.....STOP. No one has identified the screws that are being played with. So many other things have to be checked first. Start with the MFI check list that's on this board. Go through the list and make sure everything is correct before you think screws have to be turned.

[Zeke]

He was talking about the part load and idle adjustment screws and he knows what and where they are or he wouldn't have been able to post that reply.

F., it's 6 turns from where they stop. I have always assumed that as you went towards the full 6 turns, you are getting more rich. If you read the CMA you can verify this.

I'm only suggesting a way to get back to the baseline.

[356RS]

My apologies. Sorry.

[Zeke]

No need to apologize. I guess my post sounded terse. It wasn't meant to be, only to indicate that the OP was aware.

[tref]

It seems like the mid range adjuster is stuck and does not move correctly so I took the pump off the car and remove the cover to gain access to the adjusting screw. The screw looked damaged, I’m not sure why but as you see in the pic it’s seen better days. Nothing else seems damaged, no aluminum shaving can be seen. I replaced the bad adjuster screw with a spare I have but I have a few basic questions:

- How should I set the adjuster screw before I install the pump? How many turns??
- What could cause this damage to happen?
- May be I turned it too far in but I don’t see how it could have caused this, 6 turns back from full clockwise in does not seems right?

I don’t want to reinstall the pump and guessing how to set up the baseline.

Thanks,
F.

[tref]

I'm talking about item #2 in this diagram:

[356RS]

Well that is not the mid range adjuster. That is the MAIN RACK adjustment. The only way that can get so damaged on the divits is by someone doing lots of adjusting or turning of it. Your new adjustment screw will now have to set the proper position of the main rack. You will need a depth gauge placed on the end of the pump, above the pulley, behind that black rubber cap. If you can give us the pump ID numbers I can tell you the measurement you need to achieve. PS The picture of the screw looks like it must have fallen off at one time because it so bet up. What is the history on this pump?

[356RS]

Oh, I forgot to tell you where the MID RANGE & HIGH RANGE screws are. Look at # 15. The center one is the idle. the two black ones are the mid range and the two white ones are high range. The picture does not show the colors or what they do.

[tref]

Hi Mark,

Thanks for the follow up, the pump is a 1972 E pump with 014 at the end of the pump number. I can get the other numbers off the pump tonight when I'm back home. You are right this is teh MAIN RACK adjustment. The pump was on the car when I bought it 12 years ago and I'm just getting work on it now. I do not plan to touch the MID & HIGH RANGE screws but I will probably have to touch the IDLE one. I do understand what you mean by using a depth guage at the other end of the rack, that makes sense. That depth number is what I need.

Thanks,
F.

[356RS]

The starting point of the main rack, actually the proper name is "control rod" or "regelstange" in German should be between 17.2mm to 18.4mm. This is measured from the surface of the "threaded bushing" or "gewinde buchse" in German that guides the control rod to the tip of the rod in the pump. Be careful when you make the measurement because the control rod is just lightly loaded by spring pressure and can move inward with little pressure from your depth gauge. An easy way to start is to screw in the "cover nut" about 10 full turns on the control rod and then check your measurement. Then you can adjust from there + or - to reach your 17.2 - 18.4mm. Remember this is just a starting point measurement that is done on the pumps before calibration on a MFI Pump Dyno.
One full turn or 12 clicks of that cover nut can change the fuel delivery in a big way. Hope you have a air/fuel ratio meter available. Keep us posted.

[356RS]

F. Don't be to concerned about the measurements of 17.2mm to 18.4mm. That's the wrong information I gave you. Sorry. Those measurements are for the total control rod movement. Early pumps should be 17.2 to 18.4mm and late pumps 19.0 to 20.0mm. What you need to do is just get the "cover nut" about halfway in the middle of the rod. There is only 20 turns of the "cover nut" on the threads. So a good start would be 10 turns in. Like I said, you will need a air/fuel ratio meter for this job.

[tref]

Hi Mark,

Thanks for the info, actually the 1st (wrong) procedure sounded way more cool but I did ~10 turns on the adjuster and reinstall the pump. It now works and idle on it's own . I guess I adjusted it too far lean last fall, probably because I was reading the LM-1 backward. Bigger numbers mean too much air and not too much fuel, doh! stupid me. For some reason the adjuster got stuck and could not come back so it was stuck way too lean.

If the weather is OK today I will get back into the road test and adjustments.

Thanks,
F.

[tref]

Hi,

I went around the block, warmed it up and made a 5 clicks adjustment on the main rack to lean it out, I then leaned out the idle ~1.5 turns. Here's the LM-1 readings:

18 AFR -full throttle acceleration
14 AFR -mid throttle with pressure on brakes
12 AFR -coasting at 45mph on flat
11 AFR -idle
10 AFR -idle (before adjustments)

As I was leaning out the idle adjustment, the idle RPM went up from 850 to ~1200. Another note is the reaction after a blimp on the throttle when stationary, after the blimp the reading slowly goes to 18AFR and back down to ~11AFR all this in a 2-3 second period.

Since I never got to this point in the CMA, I'm not sure how to interpret this.

F.

[356RS]

F.
That's good news. The best way to see good A/F ratio readings is to find a long run up some kind of incline. You need a load better than the brakes dragging. If you find a hill that you can use 3rd or 4th gear and make several runs at 3000; 4000; and 5000 rpm under load for about 10 seconds or so at each of those RPM's you will get a better idea of where your A/F ratio is. Your numbers look a little lean under load.
Get the main control rod adjusted first then deal with the idle last.
The best way to really know your A/F is to put the car on a Dyno.

[tref]

I did a few runs today, the main adjustment was a little lean as you suspected, I did 2 clicks counter-clock to get it richer and the throttle response improved as well. I might still be 1 click away but the mixture under load look OK.

I still have very rich situation at idle, AFR is stuck at 11, I did 3 full turns (~18 clicks) on the idle screw and the AFR is still at 11. The car runs well but there is a solid smell of poor combustion (gas and oil may be), it's so bad that I start to feel dizzy after 10 minutes of driving. There is no significant gas in the oil problem.

Do you have any recommendation beside going through CMA again?

Thanks,
Francois

[356RS]

You probably know this, but remember lean on the idle screw is Counter-Clockwise.

[tref]

Yes I did ~18 clicks counter clock wise on the idle adjuster. I did check the throttles are on their rest screw at idle but I did not check the position of the pump throttle lever, could it cause this type of problem?. Last year I did check the pump throttle rod length and it was right but I will check it again. I might as well check the ignition while I'm at it.

Thanks,
F.