Solved the ignition problem I asked about awhile back on these forums, thanks, I put the Pertronix unit in and it fired right up......now the next issue! After it runs smoothly for awhile, it will start to miss and bog, tailpipe emits black smoke and plugs are a velvety black, swap in a new set of plugs and it will run for awhile and then go back to running rich. Car sat for awhile, oil was diluted with gasoline from the high school shop class that had it more than likely cranking it over and over attempting to start it. (changed oil with new filter). Any ideas?

3 diagnostic test:

First one is to check the Cold Start Valve. It is on the intake. I has a 6mm hex plug test port.
With key on , engine off, take the test port hex plug off and see if any fuel is coming out the port.

Test two:

Warm car up and see if intake air ceases to enter Injection pump at the little air filter. It should shut off when car coolant is at normal temp.

Test 3:

When warm, take rod off pump at ball socket and give the car a little gas at pedal.. Does the car rpm speed up with this test?

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A Dalton

Test 1- good, no fuel comes out. Test 2-no air being drawn in when warm, tiny air filter looks clean and can blow through it easily. Test 3- yes, when I disconnect the rod from the injector pump and press the gas pedal, it will rev up and "pop" back through the intake. Also seems to idle smoother when disconnected.

If the rpms go up with pump rod disconnected when you increase the throttle plate , the air/fuel mixture is too rich.

First test is to turn the air bleed [ idle screw] in and see if the rpms drop and can you stall the car by turning that in??

The problem is most likelynthe pump shims, but do that test first

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A Dalton

is that the large knurled screw w/spring tension on it that goes into the intake and is located on the passenger side of the valve cover?

Yes

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A Dalton

I screwed the adjustment until it stopped and it will still run, very slowly, but it didn't stall. It also seems to run better. You are on to something here!

OK


Take the rubber snout off the intake that goes to the air filter..
Now, get the car at a nice idle and cover that front of the intake so no air can get into the intake. All air at idle must go thru that screw I had you adjust.

So, with that test , the rpms should not change [ or hardly at all]

Just do that test ....I think someone has adjusted the air flap instead of the pump , which is big No-No on MFI system

Give me those results, but don;t touch any adjustments yet

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A Dalton

no change in idle with the intake covered

OK

So we are on the same page, you are telling me that you block off the front of the intake and the rpms stay regardless of your block/no block??

..and you do this test when you know that the car is warm enough that there is also NO AIR being drawn into the Pump filter port?

IF yes, than you should be able to stall the car with the air bleed screw ..if you can't , then you have an intake leak b/c all air at idle has to go thru the AB screw....first suspect would be brake booster...

Are we on the same page here and what are the idle RPMs

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A Dalton

Yes, barely a change in idle when I blocked the intake, idle dropped from about 875 to 800 I'll have to check for vacuum leaks now, pull the hose off the booster and plug it then run the car, plus looks like vac lines have been butchered so I'll use my CD from MBZUSA to clean that up, then see what happens. I'll get back on it next weekend, unbelievable what this shop class "fixed", guess that's why they wanted to get rid of it, looks like the adjustments for the throttle flap have been played with, here's a couple pictures of other butchery maybe you can tell me what these things are. It would be a shame to part this car out, it's got a very solid body, 125+ lbs compression on all cylinders, came from CA. Any idea where I can get the rubber parts I need?

Attached Thumbnails

       

OK

All those parts are avail...

Anyway...someone has fooled with it , but I am going to give you some basics so you know what you are checking and how stuff works. Knowing and understsnding the whys of a system makes it easier than following steps from someone else. Then common sense takes over.

The throttle plate has to move in unison with the pump lever..they are a mechanical connection for fuel and air at the correct angles..meaning it is a mechanical system, like an old type-writer.

So, when you push down on the pump rod , watch the throttle plate movement..there should be no delay in it's movement..if there is , you have wear at the ball sockets and the bushings at the cross bar on top of the engine..but , if they are fairly tight, that will be OK for next adjustments.
The throttle plate MUST be completely closed at idle. The little screw you see on that throttle adjustment is not an idle adjuster..it is only a throttle plate STOP adjuster so that the throttle plate does not stick or wear out the housing. So, the adjustment for that is to get it so the throttle plate comepletely closes and just sticks a hair at closed position. It is best to do this with the ball link disconnected. Then with the rod re-installed, if the plate is not the same , you adjust the rod so no changes occur in that throttle angle setting. 75% of the cars with MFI I see have had someone fool with that adjuster , thinking it controlled idle to solve an idle complaint..they could not have been more wrong.

Now we discuss the real idle mixture setting and rpm procedure

The rpm and a/f mix for idle are done with a combination of the air bleed srew and the fuel adjuster knob on the back of the Inj Pump. Mind you that all ignition timings have to be factory BEFORE ANY of these pump adjustments are made. [ I assume you have addressed that with the new Pert Ign.]
With throttle plate at stop and car at warm idle with correct timing, turn the AB screw for max rpm...Not too lean, not too rich..find that smooth spot and read the rpms...if the rpms are too low for normal setting w/warm engine, the pump has to be richened...this is done with the knob on the back of the pump..Turning it CW , looking at the knob face, just like looking at a clock face..[I only mention that cuz I get asked " looking from front of pump or back ?" stuff ,, all adjusters are looking at the adjuster]
Here is the trick and "Warning" on that knob:
The knob is spring loaded and has to be pushed into the pumps adjuster screw slot in the pump in order for it to turn the adjuster screw. The reason it is spring loaded is b/c it can only be turned when the engine is NOT RUNNING !!!!..if you push that adjuster into the screw slot with engine running, you will be very sorry. The spring keeps the knobs screw blade out of the adjuster slot with the engine running...once the engine is stopped, then and only then can you make this adjustment. The adjustment is made by pushing the knob into the pump and turning it until you feel it drop into the screw slot in the pump..you then hold it in that slot and turn it..as you turn it, you will feel/hear some locking 'Clicks'..these clicks are the detents to hold the adjutment in place when you release that knob. Each click is a 1/6th turn of the knob [ 60 degrees]
This adjustment richens the fuel CW and leans fuel CCW..and you start by turning 2 clicks each time ...so, if the rpms are low , you add more fuel...if they are too high , you lessen the fuel...and each time you do this [ a couple of clicks at a time] , you go back to the AB screw and smooth the idle out again.
You do this several times until you get a nice smooth idle at approx 50 rpms
more than you are looking for. Than you drop that last 50 rpms off by richening the mix by slightly closing the AB screw..that will give you the correct A/F mixture at idle.
You should then be able to take the ball links off w/o any rpm changes, or cover the throttle plate intake w/o any changes , and stall the engine [ or make it very rough/slow] with just closing off the A/B screw...then you know you are cool .... all this can aslo be done with a gas analyser, but this system procedure works fine if you don't have that equip.
You can aslo get a better feel for the AB screw tweaking if you use a vac gauge at that trans modulator port. You want max/smooth vac when adjusting AB each time. [ or a good ear of exhaust notation]
As you can now see, the idle rpm and Mix is the results of you combining the correct air and fuel adjustments seperately until that corrct balance is attained..it take some tweaking and experience but very do-able and actually some fun...I can do them by ear in my sleep, even if I slept !!
[ Shatner....]

That is just idle mix..do that and I can go into higher rpm adjustments...if any of this is cloudy, just ask.
These MFI are simple once you know what the adjuster do and why..

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A Dalton

thanks so much, appreciate all your help, sounds like you've worked on a lot of these, I will get back on it this weekend.

Like I said........ In my sleep, if I slept .

from the Shatner commercial where they kidnap the tourist couple in the Van....funny skit

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A Dalton

Thanks.. Not that this is my thread but this is really useful to try and learn the MFI on my 250SE.... Which is running much better since you and a few other people helped me with my fuel delivery problem a couple of months back, but I'm sure this will come in handy.

Bryce

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Bryce

http://www.classicjalopy.com