Air Flow Meter or Double Relay?

[ecalmus]

I have an 81 Spider. I have a problem with the double relay clicking repeatedly. It seems worse when you first start the car. The car runs fine when it has warmed up, despite the clicking.

I was reading Brad's fuel injection manual, where he talks about the relay clicking due to improper adjustment of the chrome rod in the AFM. I removed the AFM cover, and the rod seems to be working properly. How do you adjust it?

Can something else in the AFM cause the double relay to keep clicking? Could it be a bad double relay? Where else should I look?

Thanks much,
Ed
Fiat hobbyist since 1995 (and still fixing it!!)

[divace73]

the chrome rod, makes and brakes the fuel pump, I'd be swapping the relay over first, it's usually the first source when problems arise...usually...

[bradartigue]

I was reading Brad's fuel injection manual, where he talks about the relay clicking due to improper adjustment of the chrome rod in the AFM. I removed the AFM cover, and the rod seems to be working properly. How do you adjust it?

It is not the double relay, or at least it is very unlikely. Something is causing it to click and that something is probably the AFM...

The rod holds the contact open when no air flows through the box. When air moves the flap the contact closes. Sounds great until you consider that air is kind of irresponsible at idle and likes to make that door flutter. This flutter makes the rod hit the contact and opens and closes it over and over, hence the click. That click is wearing out your double relay and turning your fuel pump on and off over and over; "it ain't good."

The first thing to inspect, since you already have access to the top of the AFM, is if the anti-flutter spring is intact. This little, circular spring is in the left bottom corner of the AFM if you orient it with the plug facing up. It creates resistance against the flap flopping around.

The second thing you can try is to simply increase your idle speed by about 50 RPM. To do this, set your idle by the book (in my book it is in the FI section) here it is briefly: remove the screw, clean it, clean the orifice, replace the o-ring if necessary, reinstall, get it somewhat idling to get the engine hot, then completely seat the idle speed screw; loosen the accelerator linkage stop screw. Adjust the idle so that the car idles on the stop screw only at 800-900 RPM (700-800 on automatiques). Lock the stop screw. Increase the idle speed by 50 RPM using the air bleed screw. Are you using the car's tachometer? They are notoriously low. If you are still clicking use the procedure above to set the stop screw at 850/950 and increase to 900/1000 with the air bleed screw.

Finally, you must have some sort of air leak that causes the vehicle to idle off of the leak, and when you adjust idle you're actually relying on "false air" and not air from the AFM, which means your door never opens enough when idling, and you can't get it far enough off the switch to stop the normal flutter. You have to go on air leak hunt.

[surfingfreeman]

Hi Ed
I had a similar problem see below:
"Hello All
I have a 1982 FI Spider that I have been having very sporadic loss of power problems with. The problem usually happens while on the freeway and usually only lasts for a second or 2, I usually downshift and the engine power kicks back in. I'm wondering if it could be a fuel filter or fuel pump problem, I also thought perhaps a loose connection to the AFM? There has been the occasion when the car totally looses engine power and stalls and will not start for up to 15-minutes. I have only owned the car for a little over a year so do not have a complete maintenance history for the car. Oh I don't lose any electricals in the car when the problem occurs. Thanks for any advice.
Mike"
I ended up changing the double-relay, which didn't seem to fix the problem, so next I changed out the fuel filter which seems to have resolved the problem. In an attempt to see what kind of MPG I was getting I was running the tank very low to calculate the MPG, further I was told that with Californias addition of ethanol to our gas formulation can have the effect of causing an accumulation of particulate matter in the gas tank which then gets passed thru the system to the fuel filter and can cause sporadic loss of fuel to the fuel pump, not sure this would cause the rapid opening and closing of the double relay. Anyways changing both the double relay and the fuel filter took care of my problem. Best of luck.
Mike

[bradartigue]

Hi Ed
I had a similar problem see below:
"Hello All
I have a 1982 FI Spider that I have been having very sporadic loss of power problems with. The problem usually happens while on the freeway and usually only lasts for a second or 2, I usually downshift and the engine power kicks back in. I'm wondering if it could be a fuel filter or fuel pump problem, I also thought perhaps a loose connection to the AFM? There has been the occasion when the car totally looses engine power and stalls and will not start for up to 15-minutes. I have only owned the car for a little over a year so do not have a complete maintenance history for the car. Oh I don't lose any electricals in the car when the problem occurs. Thanks for any advice.
Mike"
I ended up changing the double-relay, which didn't seem to fix the problem, so next I changed out the fuel filter which seems to have resolved the problem. In an attempt to see what kind of MPG I was getting I was running the tank very low to calculate the MPG, further I was told that with Californias addition of ethanol to our gas formulation can have the effect of causing an accumulation of particulate matter in the gas tank which then gets passed thru the system to the fuel filter and can cause sporadic loss of fuel to the fuel pump, not sure this would cause the rapid opening and closing of the double relay. Anyways changing both the double relay and the fuel filter took care of my problem. Best of luck.
Mike

To elaborate on why this would cause the pump issue - if the filter is so restrictive as to cause a serious reduction in pump pressure then the engine will continuously struggle to get fuel and cause a continuous flapping as it dies, enrichens (as the flap closes), then dies again (as the flap opens). Therefore the flap is flapping around and turning the relay on and off, fighting the pump.

It is as plausible as anything on these old bastards.

[surfingfreeman]

Thanks for the explanation Brad, gives a great visual of what might have been going, now I have a ton of electrical questions for you! Thanks
Mike

[ecalmus]

Thanks for the insight, Brad. I will try the things your suggested. They all make sense considering what I have done so far and the symptoms.

The car starts correctly, but then idles very low until it warms up. I have replaced the hoses on the AAR and the brake booster, and I have replaced the fuel filter. I have been adjusting the idle with the car tach, so I will re-adjust that and see if the clicking is minimized. Then it's carb cleaner spray to look for additional leaks.

Thanks again,

Ed

[ecalmus]

Still struggling. I reset the idle, and sprayed carb cleaner around to see if I could find a leak. No change in the rpm. The relay is still clicking at idle, and the car is surging like it is starving for gas. Since I have the top off the AFM, I am able to watch the chrome rod and see if it is opening the fuel pump contacts. It is not. Is there anything else that could be telling the relay to shut off the fuel pump? Should I try a new double relay?

Thanks for all the help.

Ed

[spider2081]

Do you have a volt meter or trouble light?
If there is a poor connection supplying voltage to the dual relay it could make the relay intermittent at idle. If your car is Idling less than 1000 RPM the alternator output may be marginal.
Can you measure the voltage at the switch contacts in the AFM?? It should be about 13VDC with engine running and measure the same at both contacts. If this voltage is intermittent or changes with the relay clicking I think the problem is either the power relay contacts in the dual relay or the connector under the dash that has the large brown wires in it.
The dual relay also gets power from the ignition switch.
There is a resistor in the dual relay that is prone to over heating and being a problem. The relay can be opened and visually inspected for overheating or discoloration.
I guess what I am getting to is I would not just buy an expensive relay just to see if it fixes the problem. I would look at the ignition switch connector, dual relay and socket, brown wire connector, AFM connector, and measure your cars voltage to see if your alternator is putting out 13.75-14.6 volts DC.

[ecalmus]

You were right on. I finally determined that the problem is the connector on the AFM. Cleaned the terminals and plugged it back in - problem solved. Thanks for the help.

One more question. I noticed the PO had pulled the plug on the AFM bypass screw. Is there a way to adjust the AFM air bypass?

Best,

Ed

[bradartigue]

Pulled the plug; if so then you should see a flathead screw top inside of it. If it is open to the atmosphere (draws air from the top when car is running) then literally put a cork in it.

That air bypass does very, very little. It is a fine tuning for CO levels, and if the O2 sensor is working it does nothing because the O2 sensor overrides its impact.

You were right on. I finally determined that the problem is the connector on the AFM. Cleaned the terminals and plugged it back in - problem solved. Thanks for the help.

One more question. I noticed the PO had pulled the plug on the AFM bypass screw. Is there a way to adjust the AFM air bypass?

Best,

Ed

[surfingfreeman]

Nice group effort to fix the problem!

[amcfall]

Anyone have suggestions for getting the AFM open? Have attempted to take it off but don't want to break it.

Thanks!

Andrew