Will it start with the throttle position sensor disconnected ? (Throttle body not accelerator pedal sensor ) not sure if this would work mind.
Technical Help my Fiat 500 1.2 8V will not start!
- Thread starter Robin R
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Technical Help my Fiat 500 1.2 8V will not start!
Mike1alike
Established member
But I did mention the tension to be measured on both injector's lines, (+) and ground. If there is no voltage, then you can each one of them separately, connecting the other multimeter's connector to a good source like battery terminals. But if there is voltage on the lines, injector's (+) and (-) it means that is no problem there.
Robin R
New member
I cant connect the sensor. Its all in one electricity.
Mike1alike
Established member
I'd say that you definitely need to replace that sensor. That bad reading that it gives... I don't see how you could make it work without replacing it.
All you have to look for now, is the minimum replacing part that you can buy, cause I'm sure there are many experts that would suggest that in this case all throttle body should be replaced.
And technically, the reason the engine doesn't start I'd say it's the fact that it gets flooded. Because the amount of injected fuel is strong relation with the TPS reading. And 100% open means that a lot of fuel goes in.
So to fix it, TPS sensor needs to be replaced.
To manage to start the engine, see if anything modifies in good, TPS sensor to show accurate reading, I think you could press the acceleration pedal, that way you give engine air too, not just a lot of fuel. Or does the throttle butterfly moves according to the false reading and it is already full open when you crank the engine?
All you have to look for now, is the minimum replacing part that you can buy, cause I'm sure there are many experts that would suggest that in this case all throttle body should be replaced.
And technically, the reason the engine doesn't start I'd say it's the fact that it gets flooded. Because the amount of injected fuel is strong relation with the TPS reading. And 100% open means that a lot of fuel goes in.
So to fix it, TPS sensor needs to be replaced.
To manage to start the engine, see if anything modifies in good, TPS sensor to show accurate reading, I think you could press the acceleration pedal, that way you give engine air too, not just a lot of fuel. Or does the throttle butterfly moves according to the false reading and it is already full open when you crank the engine?
Robin R
New member
Throttle is closed at start. Ecu gets wrong values in.
Spark plugs are dry. So he does not drown.
Normally you would think that the ecu would inject extra rich in this situation.
You have 2 different throttle bodies. With one you can get sensors loose, with the other you can't.
Robin R
New member
That's my point disconnect the plug and try starting, whilst it won't rev it may well start and idle given often the sensors are at their maximum resistance when closed ( so will be infinite unplugged ) and gradually go towards nil when fully open, at best it might start?
Robin R
New member
Okay. I'm going to try it tomorrow.
Mike1alike
Established member
Is the fuel pump really working?
The 10 V you've got are on injector's (+) and injector's ground lines, correct?
Mike1alike
Established member
At the TB type you have, seems that there is no IACV so I presume all the air engine gets goes through throttle butterfly. Maybe that's why it doesn't start, because there is no air. Try holding the butterfly a little bit open, with your hands, while someone else helps you and cranks the engine. See if it starts like that.
Robin R
New member
I can hear it humming at ignition. I smell gasoline up front to all that starting. On the rail is pressure. If I take the relay out the buzzing is gone. I can't measure any pressure. Yes I measured 10v on +- plug of injector.
Robin R
New member
There's a potentiometer hidden there I think.
If you push the pedal in during starting, the throttle opens. Have already tested with starting.
Mike1alike
Established member
If there is a potentiometer there (and it should be), it probably stays closed due to 100% throttle opening that ECU misreads, so no air gets to the engine and this is the reason it does not start. You should definitely fix the TPS problem.
Im slightly confused you say the live data says throttle wide open when the butterfly is closed, but you also say it moves correctly when you press the pedal when trying to start?
So is the butterfly potentiometer broken saying wide open but the actuator working correctly as per the accelerator pedal position?
So is the butterfly potentiometer broken saying wide open but the actuator working correctly as per the accelerator pedal position?
But if the ECU thinks the throttle is wide open, why are the plugs dry?
gr J
gr J
Throttle pedal indicates "idle position" to ECU so maybe that's why lack of fuel ECU will be confused if wide open and idle signal?
Robin R
New member
Yes it should be in that black box on the throttle body.
Yes I think so too. I discovered some new things today.
According to the key was only on ignition position 1. Yes it could be the yet battery. Read below.
Yes exactly. Read below.
I don't know.
I think it is controlled differently. Plug throttle body also has 6 pins. Read below.
I don't have one of those, unfortunately. Can't take one out either. Last time was back in school.
Robin R
New member
Today I established two new things.
I borrowed a Snap On reader:
- Throttle position = In progress
- Pedalsensor works perfectly from 0 to 100%
- I wanted to recalibrate throttle = Throttle body, self-learning failed
Then I checked the throttle body plug. These are 6 pins. Cable harness runs directly to ECU. No rodent marks. I did not find those anywhere generally either. Not from underneath either. On the plug was ground and on 3 other pins 5V. But I don't have a power diagram, so no idea where voltage should be. Started without plug. Then I immediately had 3 errors in the ECU. 2x Potentiometer and Throttle body. This was just to test if the ECU responds to this.
A little later I wanted to start again and the engine was starting very slowly. I took the battery out every day and connected it to the battery charger in the evening. So that when I test again I have a full battery. As it looks the battery has not recharged or stored the energy once. The battery is still 12.8V now but apparently has no A or Ah of capacity. The battery tester indicates replace battery. Because the battery is only 1 year old. And the starter motor had enough power every time. Always recharged and on voltage. I assumed that the battery is not the problem.
Now I really have my doubts. Watch this video.
The engine turns quite nicely but won't start. It sounds the same to me. Only since today it is going very slow. I'm going to buy a new battery tomorrow. And the stronger variant with 54Ah. Now a 52Ah is in it. It is now hanging on the charger again. I test it again tomorrow on the battery tester.
I borrowed a Snap On reader:
- Throttle position = In progress
- Pedalsensor works perfectly from 0 to 100%
- I wanted to recalibrate throttle = Throttle body, self-learning failed
Then I checked the throttle body plug. These are 6 pins. Cable harness runs directly to ECU. No rodent marks. I did not find those anywhere generally either. Not from underneath either. On the plug was ground and on 3 other pins 5V. But I don't have a power diagram, so no idea where voltage should be. Started without plug. Then I immediately had 3 errors in the ECU. 2x Potentiometer and Throttle body. This was just to test if the ECU responds to this.
A little later I wanted to start again and the engine was starting very slowly. I took the battery out every day and connected it to the battery charger in the evening. So that when I test again I have a full battery. As it looks the battery has not recharged or stored the energy once. The battery is still 12.8V now but apparently has no A or Ah of capacity. The battery tester indicates replace battery. Because the battery is only 1 year old. And the starter motor had enough power every time. Always recharged and on voltage. I assumed that the battery is not the problem.
Now I really have my doubts. Watch this video.
The engine turns quite nicely but won't start. It sounds the same to me. Only since today it is going very slow. I'm going to buy a new battery tomorrow. And the stronger variant with 54Ah. Now a 52Ah is in it. It is now hanging on the charger again. I test it again tomorrow on the battery tester.
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