Technical Punto GT no injector pulse

[Franco505]

Hi to all

Im in the process of getting my gt back on the road after nearly 10 years of owning it .. I was almost ready to get an mot booked when it started playing up the other day!

After cutting out when hot the gt refuses to start. Ive fitted a new crank sensor and checked all the fuses. I have good fuel pressure to the rail and each cylinder is getting a spark. The car runs briefly on easy start.

I carried out an injector noid light test and none of the injectors are triggering / light pulsing...

Immobiliser light on dash goes out after a few seconds as normal.

Blink test shows codes

1256 - crank sensor ( Im told this can be stored from a non start so may be unrelated )

3232 - something about Coolant pressure

Apart from the ECU having a meltdown and not sending the signal Im out of ideas...

It was running fine untill it wasn't

Has anyone experienced anything like this?

Thank

 

[bugsymike]

Hi to all

Im in the process of getting my gt back on the road after nearly 10 years of owning it .. I was almost ready to get an mot booked when it started playing up the other day!
View attachment 474801
After cutting out when hot the gt refuses to start. Ive fitted a new crank sensor and checked all the fuses. I have good fuel pressure to the rail and each cylinder is getting a spark. The car runs briefly on easy start.

I carried out an injector noid light test and none of the injectors are triggering / light pulsing...

Immobiliser light on dash goes out after a few seconds as normal.

Blink test shows codes

1256 - crank sensor ( Im told this can be stored from a non start so may be unrelated )

3232 - something about Coolant pressure

Apart from the ECU having a meltdown and not sending the signal Im out of ideas...

It was running fine untill it wasn't

Has anyone experienced anything like this?

Thank

Would a cam sensor cause that?

 

[Franco505]

Would a cam sensor cause that?

Hi mate, yea I thought that sounded reasonable but I cant for the life of me find the camshaft sensor... Ive even got an engine in bits in my garage and looking at the cam box and camshaft the only "toothed wheel" is the only that the cambelt turns. As best as I can remember there isn't a sensor under the belt cover.... but I could be wrong...

 

[bugsymike]

Hi mate, yea I thought that sounded reasonable but I cant for the life of me find the camshaft sensor... Ive even got an engine in bits in my garage and looking at the cam box and camshaft the only "toothed wheel" is the only that the cambelt turns. As best as I can remember there isn't a sensor under the belt cover.... but I could be wrong...

Unlikely, but some years ago bought a non running 06 Fiat Grande Punto 1.3MJ, long story short involving previous idiots trying to tow start it causing cam chain issues, but at the end of the day the reason it wouldn't start was a corroded wire inside it's plastic sheathing a few mm from the ECU on O/S/F wing. Wire all looked good until gently pulled and plastic just stretched as wire inside rotted through.

 

[Franco505]

Unlikely, but some years ago bought a non running 06 Fiat Grande Punto 1.3MJ, long story short involving previous idiots trying to tow start it causing cam chain issues, but at the end of the day the reason it wouldn't start was a corroded wire inside it's plastic sheathing a few mm from the ECU on O/S/F wing. Wire all looked good until gently pulled and plastic just stretched as wire inside rotted through.

Hmm I mean yea there's deffo the possibility that the wiring has failed somewhere..

Its mad it just cut out and then wouldn't start again or just once briefly for a few seconds.

I guess I could try and check the wiring between the injectors and the ECU and see if there's continuity, but if that test ok then maybe the ECU has failed?!

 

[bugsymike]

Hmm I mean yea there's deffo the possibility that the wiring has failed somewhere..

Its mad it just cut out and then wouldn't start again or just once briefly for a few seconds.

I guess I could try and check the wiring between the injectors and the ECU and see if there's continuity, but if that test ok then maybe the ECU has failed?!

Nothing impossible, but I have never found an ECU to be the cause although many get blamed, often when a sensor or poor connection is the cause.
Can you get good diagnostics on it.
Another thought what is engine code? Is it 176A4.000 age 94-97 with Bosch MotronicM2.7 ECU?
If so I may have pin tables and readings to expect.

 

[Steve gt]

Hmm I mean yea there's deffo the possibility that the wiring has failed somewhere..

Its mad it just cut out and then wouldn't start again or just once briefly for a few seconds.

I guess I could try and check the wiring between the injectors and the ECU and see if there's continuity, but if that test ok then maybe the ECU has failed?!

Hi mate, have you tried swapping the two grey relays over to see any difference, think one is for the pump the other the injectors .
I’d also leave the battery disconnected over night .

 

[Franco505]

Nothing impossible, but I have never found an ECU to be the cause although many get blamed, often when a sensor or poor connection is the cause.
Can you get good diagnostics on it.
Another thought what is engine code? Is it 176A4.000 age 94-97 with Bosch MotronicM2.7 ECU?
If so I may have pin tables and readings to expect.

I think I need to confirm there is 12v at the injectors rather than just the noid light test, that's a job for tomorrow I guess.

Yes its a 1997 punto gt3 I think 176 is the engine code!

 

[Franco505]

Hi mate, have you tried swapping the two grey relays over to see any difference, think one is for the pump the other the injectors .
I’d also leave the battery disconnected over night .

Hi, the two grey ones in this picture here?
I think one is the ECU and one the fuel pump as per the second attached pic. I tested they clicked and measured the coil resistances earlier and they seemed ok but maybe the contact tip is burnt out on one?

 

[bugsymike]

Fingers crossed on the relays, if not this may help.

 

[Steve gt]

Yeah the grey ones this is from the porter manual .

 

[Franco505]

Yeah the grey ones this is from the porter manual .

Mine is similar to that but I have a green box also that has 2 diodes in it ( not shown on your diagram )

Ill switch them over tomorrow and cross my fingers

 

[Franco505]

Fingers crossed on the relays, if not this may help.

Thanks for that ill save them and see how I go!

If I get to the bottom of it ill update the post

 

[Franco505]

Fingers crossed on the relays, if not this may help.

Ive just stopped to have a look at those images, that should be really helpful mate as if there is power to the injectors I can then test the return path to the ECU . Thanks again

 

[Franco505]

So I did a bit more testing today, all 4 injectors had 12.6v unplugged on the live wire. I backprobed injectors 1,2 & 4 ( injector 3 was under the throttle so I left it lol ) whilst cranking and the voltages held at 10.7v. So the power supply to the injectors is fine... I measured resistance between all 4 injector plug ground pins and all 4 were 36kohms.

As these are all separate wires that go to the ECU to trigger the pulse it seems to indicate the ECU has failed internally

 

[bugsymike]

So I did a bit more testing today, all 4 injectors had 12.6v unplugged on the live wire. I backprobed injectors 1,2 & 4 ( injector 3 was under the throttle so I left it lol ) whilst cranking and the voltages held at 10.7v. So the power supply to the injectors is fine... I measured resistance between all 4 injector plug ground pins and all 4 were 36kohms.

As these are all separate wires that go to the ECU to trigger the pulse it seems to indicate the ECU has failed internally

I am still loathe to condemn the ECU, is your rev counter working, you discounted the crank sensor earlier but it may be something simple like that as it often stops the rev counter, does it react when you crank the engine?
Have you got good fuel pressure at the fuel rail?

 

[Franco505]

I am still loathe to condemn the ECU, is your rev counter working, you discounted the crank sensor earlier but it may be something simple like that as it often stops the rev counter, does it react when you crank the engine?
Have you got good fuel pressure at the fuel rail?

Rev counter was fine before it cut out the other day. One thing I did notice when it cut out was the boost gauge dropped to zero just before, and when it started again only briefly the boost gauge was reading zero. This is an electrical signal from the ECU also on these I believe.

I actually fitted a new crank sensor as I thought that was the cause initially, but the coil and spark are fine.
Fuel pressure to the rail is good, pump runs fine etc.....

Apparently the bosch motronic 2.7 it runs ( thanks for the data lol ) can suffer from the injector drivers failing...

 

[bugsymike]

Rev counter was fine before it cut out the other day. One thing I did notice when it cut out was the boost gauge dropped to zero just before, and when it started again only briefly the boost gauge was reading zero. This is an electrical signal from the ECU also on these I believe.

I actually fitted a new crank sensor as I thought that was the cause initially, but the coil and spark are fine.
Fuel pressure to the rail is good, pump runs fine etc.....

Apparently the bosch motronic 2.7 it runs ( thanks for the data lol ) can suffer from the injector drivers failing...

Are you 100% happy about the crank position sensor as the rev counter often takes it's signal from that, if it is kicking to around 2-300 rpm on cranking with starter then hopefully not that.

 

[Franco505]

Are you 100% happy about the crank position sensor as the rev counter often takes it's signal from that, if it is kicking to around 2-300 rpm on cranking with starter then hopefully not that.

I can't say 100% as there's allways the possibility its a dud unit, but its brand new from Ricambio and they are a reputable supplier.

I'll do that test tomorrow to check the rev counter but the fact the plugs fire at the correct moment ( runs on ez start ) would indicate that its ok I guess?

 

[bugsymike]

I can't say 100% as there's allways the possibility its a dud unit, but its brand new from Ricambio and they are a reputable supplier.

I'll do that test tomorrow to check the rev counter but the fact the plugs fire at the correct moment ( runs on ez start ) would indicate that its ok I guess?

I suppose it depend where the injectors get their signal from.