Would a car start if the multiplug to the MAP sensor was disconnected?

If it does, how would it effect the running of the engine?

Thanks.

 

It all depends on the car's ecu and it's software.
If the software is smart enough to see the map-sensor is defective and then uses a replacement value the car can start and run.
Otherwise it would lead to wrong fuelling.

 

How about on an L8 ecu on a 4x4 cosworth?

I have an Ahmed Bayjoo chip and an MSD chip that i can put in if that makes any difference.

 

Standard L8 tries to calculate a replacement boost based upon the throttle signal.
The function will probably also be in the tuned chips. But if it uses a 3-bar map-sensor I don't know if it has been adjusted for that map-sensor.

That is assuming the signal wire from the map-sensor does not have a form of short circuit that prevents the software of detecting the loose connection. AND, of course, the throttle signal MUST be valid.

What's your problem?

 

I'm getting a supply voltage of 5V to the sensor, but when the ignition is switched on i only get 0.4V, not 2.2V as it should be.

I think the car is overfuelling and this is why the car is not starting.

I've checked everything else and it's all spot on. Throttle resistance included.

 

2.2 volt would mean a 2-bar sensor. That is correct?
You are measuring voltage with key on, engine off?
What is the signal voltage when the map-sensor is disconnected?
Have you checked the ground? Common for Map, TPS, ACT and ECT to ecu pin 11.

When the voltage is that low, the car is probably under fueling when cranking.
With 0.4 volt the L8 with not try to calculate a replacement value.

 

Ok. Yes, key on engine off is giving 0.4V. When the map is disconnected o'm getting 5V. Would you check the earth against the. +ve on the battery?

 

It is a.3 bar map sensor

 

I had a faulty new 3bar the other day doing the same thing

 

A 3 bar sensor is supposed to give around 1.55 volt at key on, engine off.
That value doesn't change your problem. It's just good to know.

5 volt on the signal line with the map-sensor disconnected is false. It should be Zero.
So, your either measuring the feed, or there's a short circuit somewhere.
The readings are very contradictive. With the map-sensor connected the signal is way too low, with the sensor disconnected it's way too high.
Maybe it's time to get some professional help?

 

Ok, that doesn't sound promising.

Over the weekend i tried starting with the map sensor disconnected, it wouldn't start. I also tried turning down the fuel pressure, it still didn't start.

Do you know of somewhere i could send my ecu to get it checked over?

 

this link will help you alot
http://www.bigturbo.co.uk/

 

Are you completely sure you're measuring the signal line? I think you're measuring the 5 volt feed (power supply).
Measure ALL 3 pins with the map-sensor connected and disconnected (of cource with key on). And report back with some reference to which measurement is which. 1,2,3 or a,b,c or left,middle, right.

Do you still have the standard 2-bar map sensor?
Connect it electrically and measure all 3 pins just like above. Of course you cannot start the engine.

 

2 is earth

Disconnected i'm getting +5V on 1 and 3

Connected i'm getting +5V on 1 and +0.42V on 3

This is with the ignition on

 

How did the op get on after ???