1980 Fuel issues

[micbrody]

Oops.....I thought that was some else telling their experience.
In any event , to summarize your situation:
1) car only stays running when you manually keep flap open

The airflow meter (besides checking air intake temperature) does two things:
1) actuates switch for fuel pump
2) measures resistance from copper double contact loop (moves with flap) to stationary variable resistance board. The actual measurements are reading two resistances from left and right side of board relative to copper contact, and then based on ECU, knows the position of swing door (hence amount of intake air), and then ECU adjusts fuel delivery timing in injedtors.
IMHO : three possibilities
1) still a funky flaky fuel pump contact in AFM...... Probably not if it runs with manually opening door
2) sticky door. If the resistance to initially open door is high (either dirty, door bent slightly), the cranking of engine start is not enough to overcome this resistance and door doesn't open. The door should be inspected from both intake and output, as part of the door disappears into curved area just after door opening)
3) the initial area of contact on copper swing arm is not making any electrical contact (infinite resistance).
There is a way to adjust swing arm to make contacts with new part of resistor board

[ideashappen]

Clear and concise..... thanks.
I did remove the amf from it's housing to inspect both in and out sides of flap. My question about the flap to either diagnose the physical flap being the issue or eliminating it was the ,what seems to be a curve or arc on both sides. I do not know if that is normal or not.

You said :
IMHO : three possibilities
1) still a funky flaky fuel pump contact in AFM...... Probably not if it runs with manually opening door As I can manually manipulate the flap and have it run I guess that rules this out

2) sticky door. If the resistance to initially open door is high (either dirty, door bent slightly), the cranking of engine start is not enough to overcome this resistance and door doesn't open. The door should be inspected from both intake and output, as part of the door disappears into curved area just after door opening) I took it apart yesterday and the only question about it's free movement that I can see is the seemingly bizarre arc in my picture attached. Other than the arc it seems to move freely without any varied resistance. The first maybe 1/4 -1/2 inch of movement seems to have a little less resistance than the rest of the movement but I assume that is to ensure the fuel pump is properly powered to create enough airflow to push the opening more once engine starts and negative pressure is created.

3) the initial area of contact on copper swing arm is not making any electrical contact (infinite resistance).
There is a way to adjust swing arm to make contacts with new part of resistor board Are you suggesting that I clean all contacts I have access to?


Damn..... I just want to drive my car.... lol

[micbrody]

Nothing looks that bad in your picture . If the "arc" you are talking about is the small curvature of edge of flap, I don't think that would do anything.

I may be wrong, but I recall that car ran fine last year; and now it is having problems, after first drive after a long (I assume) cold winter. I assume that your inspection of afm door movement showed it was not hard to initiate starting moving (you said initial movement with little resistance). As for adjusting afm, I doubt that a wickedly bad contact suddenly occurred (but if so, there is a way of moving swing arm slight up or down on it's pivot point, which leads to contact points to be slightly shifted (hence new).

And since car runs when you manually move door; my best guess (even though you checked it) is that you have an air leak.
1) check to make sure all your hoses are connected and tight. Maybe you forgot to connect brake booster vacuum? Auxiliary air valve hose?
2) maybe big air intake (large plastic to be leaving AFM and going to engine developed a crack with cold/heat cycle . The way I checked was to remove; cover each end with plastic wrap and rubber band/tape; and blow into side auxiliary air port
3) another way is to put screwdriver in AFM and get car running; and then spray all connections and hoses with carb cleaner. If RPMs change, then that is where air leak is.
4) do you check your idle adjustment screw?

[ideashappen]

You are right... I pulled the car out, charged the battery, it started exactly as it should, drove for over an hour and a half, got home parked it. Not a hesitation, blip, or backfire. The next morning.... nothing.

Micbrody Wrote:
Since car runs when you manually move door; my best guess (even though you checked it) is that you have an air leak.
1) check to make sure all your hoses are connected and tight. Maybe you forgot to connect brake booster vacuum? Auxiliary air valve hose? I will triple check this again
2) maybe big air intake (large plastic to be leaving AFM and going to engine developed a crack with cold/heat cycle . The way I checked was to remove; cover each end with plastic wrap and rubber band/tape; and blow into side auxiliary air port Any cracks on this hose I used tape to seal them.
3) another way is to put screwdriver in AFM and get car running; and then spray all connections and hoses with carb cleaner. If RPMs change, then that is where air leak is. Incidentally , I start and run the car by using a small wedge i made that pushes the flapper from the black box control on top. I can always get it to run and idle if I control it from there.I will get some carb cleaner tomorrow and try this trick.
4) do you check your idle adjustment screw? I checked that already.

It is baffling to me why this is happening as I have known this car for over 5 years and it never had an issue as seemingly simple but obviously complex.

[ideashappen]

Update.....
I played with the ,I assume, spring that adjusts the tension in the AFM mechanism. I marked where the original position was originally and by turning it to ,again I assume, lessen the tension on the flapper. I managed to move the car both 1st gear and then reverse. I still had to play with pedal as I engaged the tranny. It died once , but restarted. Once I was in a position I liked I killed the engine. Started it again. Mixture was way too rich as exhaust was black and running rough. Then I realized..... duh duh duuuuuhhhhhh the bosch afm terminal wasn't plugged in. Interestingly enough car runs better and has more response to revs if the ECM is not plugged in. Way too rough a run and way too rich but still runs better.

Can someone explain that to me, please?

I am sure I have enough 'sucking' through my afm as I see it move when I give it gas without ECM connected.
So I don't think it is an air intake leak.
Could all of this just be caused by a faulty fuel pressure regulator?

[RRoller123]

Very odd,.... the car should die immediately when the AFM is unplugged.

[micbrody]

I agree with previous poster ; afm plug includes fuel pump contacts inside AFM. Fuel pump should not operate with AFM unplugged (many previous owners have bypassed this AFM fuel pump switch ; it was originally wired this way for safer; if accident and engine off, but keys still ignition (say you are unconscious ), the fuel pump will shut off , preventing potential catastrophic fire).

As to flap opening when loosening spring tension : not a great idea as spring tension is calibrated to keep swing arm movement in sync with air intake; so air:fuel mixture ratio stays the same. So with loosening , the flap swings "easier"; but computer thinks more air intake; thus it sends more gas to engine (lengthens time fuel injectors are open ). The fact that it runs rich confirms this; this also supports hypothesis that engine has new air intake leak (unmetered air)

[ideashappen]

I am 100% in agreement that in theory my car should not start or even that the fuel pump should engage without the ECM connected.

That really confused me and ,with a sigh of relief, I am not the only one to be confused.

This makes it very difficult for me to diagnose what has failed on the car if it does not behave in a manner that follows the typical lines of logic.

I live in a town where I can't just bring it to a mechanic as no one really works on these cars here in Quebec , let alone want to deal with a car you can't plug in to diagnose like all of our stupendous mechanics out there have been trained to rely on.

Any idea how to proceed?
The time is coming where I could actually enjoy the car.

[micbrody]

1) unless you find a mechanic that is knowledgable about L-jetronic fuel injection AND older Fiats, I would not do this yet.....I think this board should be able to help ; and we don't charge $85/hr to mis-diagnose. There is a possibility that the internals of engine are screwed up (valves, piston rings) that are causing lack of suction ; but I am no expert on that; and I doubt this is the cause of sudden problems

2) I would proceed as follows:
A) return spring on AFM to original tension
B) search AGAIN for an air leak. The air leak would explain all the problems . Did you recheck all your air connections? hoses? Did you run car and squirt carb cleaner on all air tubes and connecrions to verify no RPM changes? Did you check hoses to brake booster? Did you check brake booster check valve? (It is a one way valve; it should hold a vacuum in brake booster ; if it doesn't , then maybe bad diaphragm in brake booster , bad valve, cracked hose). Is AAV connections tight? (There should be two vacuum hoses attached to it with 4 clamps)The other way to test AAV and brake booster stuff is to use a clamp/vise grip on tubing to seal off component from engine vacuum source. If car starts, then component has big leak.; did you recheck large air intake hose from AFM to engine. You mentioned that you taped up some cracks already . Maybe new cracks? Tape needs replacing?
B) fuel pump switch obviously bypassed around AFM. If car did not run at all with flap open, then lots of electrical issues to check. Since it does run, I would leave this issue alone until other issue fixed

[ideashappen]

1) unless you find a mechanic that is knowledgable about L-jetronic fuel injection AND older Fiats, I would not do this yet.....I think this board should be able to help ; and we don't charge $85/hr to mis-diagnose. There is a possibility that the internals of engine are screwed up (valves, piston rings) that are causing lack of suction ; but I am no expert on that; and I doubt this is the cause of sudden problems

2) I would proceed as follows:
A) return spring on AFM to original tension
B) search AGAIN for an air leak. The air leak would explain all the problems . Did you recheck all your air connections? hoses? Did you run car and squirt carb cleaner on all air tubes and connecrions to verify no RPM changes? Did you check hoses to brake booster? Did you check brake booster check valve? (It is a one way valve; it should hold a vacuum in brake booster ; if it doesn't , then maybe bad diaphragm in brake booster , bad valve, cracked hose). Is AAV connections tight? (There should be two vacuum hoses attached to it with 4 clamps)The other way to test AAV and brake booster stuff is to use a clamp/vise grip on tubing to seal off component from engine vacuum source. If car starts, then component has big leak.; did you recheck large air intake hose from AFM to engine. You mentioned that you taped up some cracks already . Maybe new cracks? Tape needs replacing?
B) fuel pump switch obviously bypassed around AFM. If car did not run at all with flap open, then lots of electrical issues to check. Since it does run, I would leave this issue alone until other issue fixed

Thanks for the response..... Here is an update:
I have been busy and haven't been able to play with it much (not to mention it is damn cold here).
After I did the air leak tests as suggested a couple of times by micbrody.... I found there to be no discernible difference in the RPMs as I sprayed not just 1 but 2 cans on every conceivable part of the engine, I decided to do some serious digging to find someone to help with the diagnosis.
I found a mechanic in Montreal who works on these cars all the time and owns, with his father, a Garage dealing solely with older import cars such as mine. We had a conversation lasting no less than 30 minutes.
He seemed to be very knowledgeable about this Injection system and my car year..... He believes at almost 90% the AFM is the issue given the variables laid out to him.......
Interestingly enough when we discussed the fact that the car runs with the AFM unplugged from the ECU he said that it was specifically designed to do that. He referred to it as a "Limp Home" provision and said the car system was designed to run without the AFM plugged in case of this very issue. He also said that the reason for the system to run rich while the AFM is unplugged was to safeguard the Catalytic Converter from damage from too lean a mixture of fuel, which seems to make sense.

Now I have to find an AFM from somewhere....... if anyone has one or knows where I can get a used one that works I would be very grateful.

Once I am able to swap that part out I may very well be able to close this thread.
Any feedback on what the mechanic said would be appreciated.

[micbrody]

Hmmmmm

I am not an expert on this, but I have not read anything on "limp home" modes. I did a google search, and found later cars with limp home. I just re-read section on L-jetronics and there was no mention of "limp home". However, in two separate places it mentions the "safety circuit" of fuel pump contacts in AFM (If key in ignition RUN but engine stops drawing air, the fuel pump contact opens in AFM and shuts off fuel pump.

I did come across another possibility when reading manual.

The throttle position switch

The purpose of this switch is to tell ECU whether driver is actively trying to ask for fuel (acceleration) or has decided to slow down (coasting). In active mode , the ECU is more aggressive with with fuel delivery; in coasting mode, it shuts down fuel delivery to just maintain idle, thus saving fuel and emissions .

Maybe switch is stuck in "acceleration mode", and ECU is flooding engine, even though throttle plate not allowing matching air intake.

There is a procedure to test and adjust switch. Very easy if you have an OHM meter.

[RRoller123]

No limp home feature on this old version of L-Jetronic that I have ever heard of. If you unplug the AFM connector, the car immediately dies out.

[ideashappen]

No limp home feature on this old version of L-Jetronic that I have ever heard of. If you unplug the AFM connector, the car immediately dies out.

Fair enough....... in this case, would you think that the ECU may be the culprit?

[RRoller123]

Did you check the proper operation and adjustment of the TPS or Throttle Position Sensor? Instructions for checking and adjusting it should be in that manual the you were sent. If it is bad and is always telling the ECU that you are always at idle, then the car would probably never accelerate and would probably die (overly lean out) when you open up the throttle/air supply.

[micbrody]

I suggested the TPS a few posts ago; however, if it was sending a signal that throttle was at idle, the car should start and stay running. My theory is it's out of adjustment where the ECU is receiving a signal from TPS that car is wishing to acclerate, and ECU lengthens the fuel injection time; but because there is no matching air intake, the engine floods out and stops