Minimum number of sensors to start an engine?
Minimum number of sensors to start an engine?
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Discussion

Dynion Araf Uchaf

Original Poster:

5,177 posts

253 months

Monday 20th June 2022
quotequote all
I am currently toward the end of an engine swap in a Peugeot 106 Rallye, from 8V to 16V.
It is a race car and runs an MBE ecu, with custom air craft spec wiring loom. Generally this loom does fit the 16v engine, except for the TPS which is a completely different style of connector. I am getting this replaced tomorrow.

The engine does turn over and the injectors are firing ( wet plugs), its a different style of coil but still wasted spark and the connector from the old loom to new coil is the same.

All the other connectors that are available are in place and connected, however a few are missing as they are deemed not necessary to run an engine, e.g. oil level.

I am assuming that once the TPS is connected, I'll have all I need to start the engine? Or am I missing something? YOU can take it as read that it'll be difficult to start not least due to the wrong map in the ECU.

Does anyone have any pointers I need to look at to help solve the inevitable non start.

(I have checked that the coil/tps won't fry the ECU), which is why it's being wired up by a professional.

tia.

M4cruiser

5,203 posts

180 months

Monday 20th June 2022
quotequote all
Hello
Although I'm not familiar with that engine, my first thought is camshafts, and location of the cam sensor.
I feel the change from 8V to 16V may confuse the computer's inputs from crank and cam sensors?
Is it multi-point injection or single point?

Dynion Araf Uchaf

Original Poster:

5,177 posts

253 months

Monday 20th June 2022
quotequote all
M4cruiser said:
Hello
Although I'm not familiar with that engine, my first thought is camshafts, and location of the cam sensor.
I feel the change from 8V to 16V may confuse the computer's inputs from crank and cam sensors?
Is it multi-point injection or single point?
it has one injector per cylinder so single point.
Not sure it has cam sensors, just runs of the crank sensor (it's a mid 90's engine) Inputs are limited as not so much emissions.

Krikkit

27,938 posts

211 months

Monday 20th June 2022
quotequote all
Are you running a TU5J4/TU5JP4?

If so it needs the crank sensor for rotation (iirc front of the block, near the oil filter). No camshaft sensors on those engines.

Dynion Araf Uchaf said:
it has one injector per cylinder so single point.
Not sure it has cam sensors, just runs of the crank sensor (it's a mid 90's engine) Inputs are limited as not so much emissions.
This is multi-point injection - SPI is where you almost have a carb at the top of the engine, then feed each cylinder from a single injector.

Dynion Araf Uchaf

Original Poster:

5,177 posts

253 months

Monday 20th June 2022
quotequote all
yes it has a crank sensor, not sure if JP4or not.

Chris32345

2,141 posts

92 months

Monday 20th June 2022
quotequote all
Normally both cam and Crank sensor's if fitted

Maf if fitted unless you want it to run terrible

Throttle position if electric throttle body


Steve H

7,584 posts

225 months

Monday 20th June 2022
quotequote all
If you have wet plugs and a spark I wouldn’t count on the TPS fixing the job.

Sounds like over fuelling, have you plugged into the ecu and checked it’s seeing engine temp?

For an aftermarket setup you would typically need at least rpm, throttle and engine temp to make it run but intake temp and a second load measurement (MAF or more often MAP) are also often used.

Is the map in the ecu set up for a similar engine?

GreenV8S

31,023 posts

314 months

Monday 20th June 2022
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The minimum would be crank, cam and a can of easy start to take care of the fuelling.

That's enough to prove you have airflow, compression and ignition in some sort of order.

Steve H

7,584 posts

225 months

Monday 20th June 2022
quotequote all
It wouldn’t need cam, it has wasted spark wink

Dynion Araf Uchaf

Original Poster:

5,177 posts

253 months

Monday 20th June 2022
quotequote all
Steve H said:
If you have wet plugs and a spark I wouldn’t count on the TPS fixing the job.

Sounds like over fuelling, have you plugged into the ecu and checked it’s seeing engine temp?

For an aftermarket setup you would typically need at least rpm, throttle and engine temp to make it run but intake temp and a second load measurement (MAF or more often MAP) are also often used.

Is the map in the ecu set up for a similar engine?
It is almost certainly over fueling, the map on it is for an 8v with large injectors so I expect the standard ones are pushing out too much fuel. I have all the other sensors but it sounds like I should disconnect the fuel pump and chuck some east start down it and that might work?

Steve H

7,584 posts

225 months

Monday 20th June 2022
quotequote all
You don’t need easy start, you need to see which part of the system is overfueling.

Dynion Araf Uchaf

Original Poster:

5,177 posts

253 months

Monday 20th June 2022
quotequote all
It’ll be the injectors due to the way it was previously mapped.

Steve H

7,584 posts

225 months

Tuesday 21st June 2022
quotequote all
Or because you haven’t got sensors connected. ……

Are you able to connect to the ecu with MBE software?

996Keef

435 posts

121 months

Tuesday 21st June 2022
quotequote all
Has it got the same number of teeth on the trigger wheel as the original engine


Dynion Araf Uchaf

Original Poster:

5,177 posts

253 months

Tuesday 21st June 2022
quotequote all
Steve H said:
Or because you haven’t got sensors connected. ……

Are you able to connect to the ecu with MBE software?
No unfortunately. I have downloaded some trouble shooting guides specifically for the MBE ecu that focus on battery voltage, spark, and crank sensors. My main concern is whether I can get any spark and there is a process to determine that
https://www.sbdmotorsport.co.uk/wp/wp/pdf/Helpful_...

I'd like to try to get to the point that I know that everything works so that the mapper just has to map and not fault diagnose. I don't want to be told that the coil is knackered whilst spending £100 ph.

There a company called odified that can repair ecu's if the drivers for the coil are knackered. However as it is basically the same system I am swapping into, I hope that is not the case.

Finally, I have realised that the throttle body rotates the other way to the previous one, that means that the look up table for throttle position is 'upside down' so that might completely stop any chance of getting it started. But so long as the coil/injectors work I can live with that.

Dynion Araf Uchaf

Original Poster:

5,177 posts

253 months

Tuesday 21st June 2022
quotequote all
996Keef said:
Has it got the same number of teeth on the trigger wheel as the original engine
I've re-used the old flywheel as it was lighter, so yes!

GreenV8S

31,023 posts

314 months

Tuesday 21st June 2022
quotequote all
If you don't know where the fuelling is then fit clean plugs and start the fuelling to zero and work up slowly. When you start getting signs of life you know you're getting close. And in the meantime the easy start will confirm everything else is OK.

Dynion Araf Uchaf

Original Poster:

5,177 posts

253 months

Tuesday 21st June 2022
quotequote all
Got a man round to wire up the TPS. Once he’d worked out that I’d pointed him to the wrong connector he wired it up pretty quick and it fired off almost straight away. So it runs…
Got some other issues to sort, but the key thing is it can now go and get mapped.

Steve H

7,584 posts

225 months

Tuesday 21st June 2022
quotequote all
Dynion Araf Uchaf said:
No unfortunately. I have downloaded some trouble shooting guides specifically for the MBE ecu that focus on battery voltage, spark, and crank sensors. My main concern is whether I can get any spark and there is a process to determine that
https://www.sbdmotorsport.co.uk/wp/wp/pdf/Helpful_...

I'd like to try to get to the point that I know that everything works so that the mapper just has to map and not fault diagnose. I don't want to be told that the coil is knackered whilst spending £100 ph.

There a company called odified that can repair ecu's if the drivers for the coil are knackered. However as it is basically the same system I am swapping into, I hope that is not the case.

Finally, I have realised that the throttle body rotates the other way to the previous one, that means that the look up table for throttle position is 'upside down' so that might completely stop any chance of getting it started. But so long as the coil/injectors work I can live with that.
The TPS will most likely have three wires, an earth, 5v feed and signal. If you were to swap the 5v and earth round you will most probably invert the signal which may be useful?

Have you checked if there is a spark while cranking? I’d assumed you had already confirmed this but may have missed something.

In any case getting the SW and appropriate lead to talk to the ECU will be completely invaluable so I would suggest that’s where you need to go first.

Dynion Araf Uchaf

Original Poster:

5,177 posts

253 months

Tuesday 21st June 2022
quotequote all
Steve H said:
The TPS will most likely have three wires, an earth, 5v feed and signal. If you were to swap the 5v and earth round you will most probably invert the signal which may be useful?

Have you checked if there is a spark while cranking? I’d assumed you had already confirmed this but may have missed something.

In any case getting the SW and appropriate lead to talk to the ECU will be completely invaluable so I would suggest that’s where you need to go first.
See earlier post. It runs! (Like a bag of ste)