Peugeot 106 Race engine potential catastrophe

[Dynion Araf Uchaf]

Hi

please see attached video. I require some help in diagnosing the running fault with my 8v 1600 NA Pug engine.

I took the car to Brands hatch today after a long lay off, I managed three laps.

The car was not running very well from the off in the paddock, really struggling on full throttle to accelerate although ok at lighter loads and lower RPM. It felt like it was being strangulated by fuel.

I have checked - spark - ok, might be a bit weak will check when I get some new plugs
Fuel - definitely got fuel
Long crank to start, feels like it flooding
white smoke out of the exhaust.
video here: https://www.youtube.com/watch?v=aod2OciFED8

a bit of history, last year, I went off, a stone got in the cam belt and jumped several teeth. A leak down and compression test hot and cold was performed all ok.

Did race with it, no problems, change up points exactly the same.
I suspect after todays issues, that I have damaged either the exhaust or intake valves, but tell me otherwise. Best guess at the moment is overfuelling/under sparking but I need some ideas as to what things to go through before I take the engine apart.

Please give your best advice, if you need any more info I'll try to answer.

thanks

[GreenV8S]

Is it using an engine management system that can show you the sensor readings or flag faults?

[Dynion Araf Uchaf]

No unfortunately, Just an MBE unit for tuning only

[stevieturbo]

Dynion Araf Uchaf said:

Hi

please see attached video. I require some help in diagnosing the running fault with my 8v 1600 NA Pug engine.

I took the car to Brands hatch today after a long lay off, I managed three laps.

The car was not running very well from the off in the paddock, really struggling on full throttle to accelerate although ok at lighter loads and lower RPM. It felt like it was being strangulated by fuel.

I have checked - spark - ok, might be a bit weak will check when I get some new plugs
Fuel - definitely got fuel
Long crank to start, feels like it flooding
white smoke out of the exhaust.
video here: https://www.youtube.com/watch?v=aod2OciFED8

a bit of history, last year, I went off, a stone got in the cam belt and jumped several teeth. A leak down and compression test hot and cold was performed all ok.

Did race with it, no problems, change up points exactly the same.
I suspect after todays issues, that I have damaged either the exhaust or intake valves, but tell me otherwise. Best guess at the moment is overfuelling/under sparking but I need some ideas as to what things to go through before I take the engine apart.

Please give your best advice, if you need any more info I'll try to answer.

thanks

So you raced a known problematic engine....not off to a good start .

You say it may be flooding....well the plugs would be wet if it was. So are they ?

how have you checked spark ?

Long crank, did it always do this ? presumably not ? Was this before or after you raced it ?

You say it jumped teeth before, and you did a leakdown test...but you dont say you corrected the timing ?
And compression test ok.....people have varying meanings of "ok". Any actual results ?


Really, back to basics. Compression test, check plugs and their condition "undersparking"....lol, that's a new one.
You could check fuel pressure, just in case there is something odd tank/pump related or something.

And these days, easiest way to verify any fueling on a running engine is with a wideband. They're so cheap nowdays and any muppet can use them. So should almost be considered essential.
But the engine does need to be running reasonably healthily.

Old book...but not a bad book either.

https://www.amazon.co.uk/Automotive-Engine-Managem...


An no idea what you're trying to show with that video, with no audio, and doesnt even seem the engine is running ?

Edited by stevieturbo on Friday 29th May 21:25

[Dynion Araf Uchaf]

stevieturbo said:

So you raced a known problematic engine....not off to a good start .

the engine was checked as far as we could check it, it appeared and performed ok

You say it may be flooding....well the plugs would be wet if it was. So are they ?
yes

how have you checked spark ?
yes,all ok

Long crank, did it always do this ? presumably not ? Was this before or after you raced it ?
no, just today

You say it jumped teeth before, and you did a leakdown test...but you dont say you corrected the timing ?
And compression test ok.....people have varying meanings of "ok". Any actual results ?
timing corrected, compression ok , 200, 190, 190, 200


Really, back to basics. Compression test, check plugs and their condition "undersparking"....lol, that's a new one.
You could check fuel pressure, just in case there is something odd tank/pump related or something.

weak spark, have fuel pressure gauge in car, pressure ok - normal.

And these days, easiest way to verify any fueling on a running engine is with a wideband. They're so cheap nowdays and any muppet can use them. So should almost be considered essential.
But the engine does need to be running reasonably healthily.

Old book...but not a bad book either.

https://www.amazon.co.uk/Automotive-Engine-Managem...


An no idea what you're trying to show with that video, with no audio, and doesnt even seem the engine is running ?

engine not running, wispy white smoke? not it's normal state.

Edited by stevieturbo on Friday 29th May 21:25

[Steve H]

Assuming the engine was hot when you took that video the white smoke looks like fuel vapour which suggests overfueling or a misfire.

When you say the plugs are getting wet, is that after running up to temperature? All of them equally?

One way or another you really need to rule out some basic sensor readings, coolant temp, air temp, throttle potentiometer and (if fitted) map or maf sensors). I would have thought an MBE should allow some live readings but if not then you need a reasonably experienced sparky or setup specialist.

If you’re in the Staffs area I could probably help but if you were testing at Brands I guess that’s unlikely?

[stevieturbo]

Steve H said:

Assuming the engine was hot when you took that video the white smoke looks like fuel vapour which suggests overfueling or a misfire.

When you say the plugs are getting wet, is that after running up to temperature? All of them equally?

One way or another you really need to rule out some basic sensor readings, coolant temp, air temp, throttle potentiometer and (if fitted) map or maf sensors). I would have thought an MBE should allow some live readings but if not then you need a reasonably experienced sparky or setup specialist.

If you’re in the Staffs area I could probably help but if you were testing at Brands I guess that’s unlikely?

The engine isnt even running when he took the video......like really ?

[Steve H]

There’s a lot of vapour there, if that was turned off on a warm engine I wouldn’t expect that so I’m just trying to look for reasons for it. .

[Dynion Araf Uchaf]

Did some further investigation today. Removed all spark plugs can confirm spark on each. However turning the engine over without the plugs in sends out a torrent of fuel from the bores. I have now removed the injectors in order to get them inspected and repaired. I suspect they are knackered. It should be a fine mist but is more like a garden hose.

If they come back with no issues noted then a) I’ll be amazed and b) I’ll have to look a little harder.

Also don’t turn the engine over with one of the sparks grounded, I can tell you that that provides more adrenaline than any racing does. Thank the lord for my spare fire ex!

[Steve H]

Very unlikely that it’s the injectors, much more likely that the ecu is triggering them for too long due to an internal fault or, most probably, a sensor issue.

Conventional petrol injectors rarely fail to the point where they give such severe symptoms.

[colin_p]

An often forgotten but simple piece of the puzzle when stuff like this happens is a duff fuel pressure regulator.

Assuming it is a basic vacuum actuated mechanical one then substituting it should be quite cheap. Vac line to it ok? Fuel return hose ok?

[Dynion Araf Uchaf]

Steve H said:

Very unlikely that it’s the injectors, much more likely that the ecu is triggering them for too long due to an internal fault or, most probably, a sensor issue.

Conventional petrol injectors rarely fail to the point where they give such severe symptoms.

2 of the injectors are ok, 2 not, so that rules out the ECU.

[Dynion Araf Uchaf]

colin_p said:

An often forgotten but simple piece of the puzzle when stuff like this happens is a duff fuel pressure regulator.

Assuming it is a basic vacuum actuated mechanical one then substituting it should be quite cheap. Vac line to it ok? Fuel return hose ok?

FPR has a gauge attached to it, it is showing 60psi which is normal. So don't think it is that, but as it is easy to change I'll review it once I know the outcome of the injector inspection

[colin_p]

Dynion Araf Uchaf said:

colin_p said:

An often forgotten but simple piece of the puzzle when stuff like this happens is a duff fuel pressure regulator.

Assuming it is a basic vacuum actuated mechanical one then substituting it should be quite cheap. Vac line to it ok? Fuel return hose ok?

FPR has a gauge attached to it, it is showing 60psi which is normal. So don't think it is that, but as it is easy to change I'll review it once I know the outcome of the injector inspection

It is the return pressure that will cause the injectors puking fuel issue, does the gauge show that or just inlet pressure?

[stevieturbo]

Dynion Araf Uchaf said:

2 of the injectors are ok, 2 not, so that rules out the ECU.

Although ecu faults are very rare....no it doesnt.

And you cannot do a spark plug test if the plugs are not grounded.

Which cylinders were full of fuel ? What was the sequence of events that lead up to you determining they were full of fuel ?

Edited by stevieturbo on Saturday 30th May 18:08

[Steve H]

Yep I’m with Stevie on that, some ECUs fire in pairs so while it does rule out most of the sensor options it makes the ecu a possibility.

[Dynion Araf Uchaf]

colin_p said:

It is the return pressure that will cause the injectors puking fuel issue, does the gauge show that or just inlet pressure?

just inlet.

[Dynion Araf Uchaf]

stevieturbo said:

Although ecu faults are very rare....no it doesnt.

And you cannot do a spark plug test if the plugs are not grounded.

Which cylinders were full of fuel ? What was the sequence of events that lead up to you determining they were full of fuel ?

Edited by stevieturbo on Saturday 30th May 18:08

the plugs were grounded which is why the chuffing thing caught fire. I was caught out by the splash back of the fuel coming out of the bores. I just wasn't expecting it ( at least to that extent) although I did have the foresight to have my hand held fire ex to hand. My heart is still pumping!

cylinder 1 and 4 were very wet, the others were much less wet.

2 of the spark plugs were sat in what looked and smelt like fuel when I pulled them out, the plugs were wet and black once I removed them.

I've done a bit of online research into the MBE ecu and they do fail, but I am going to check everything else before I go down that route as ££££.

[colin_p]

Dynion Araf Uchaf said:

colin_p said:

It is the return pressure that will cause the injectors puking fuel issue, does the gauge show that or just inlet pressure?

just inlet.

In which case I'd say my FPR punt is well worth investigating further.

[stevieturbo]

colin_p said:

In which case I'd say my FPR punt is well worth investigating further.

it really isnt.