1.6 GTi Intermittent complete loss of power when gets hot

[paul mcgrath 2 1 Cars]

Hello,

 

I'm hoping somebody may be able to advise what is wrong with my 1986 205 GTi XU5JA. 

 

The car starts on the button but then after about 15 mins or so it sometimes suffers complete power loss. I put my foot on the accelerator and there is nothing there it starts pinking and power is gone. I end up having to be towed home thankfully it has happened not too far away from my home. I have replaced the coil and the ignition amplifier today replacing the paste on the rear of the ignition amplifier.

 

After fitting the parts i  left it running at the side of the house and  and then tried to rev it. Initially it was ok (as it normally is) i left it running for another 10 mins and revved it again, this time it died immediately. I have recorded the issue and attached to this post.

 

Any help much appreciated.

 

Many Thanks 

 

Paul, 

[PhilNW 46]

I would be looking at fuel pump and pressures.

 

Had similar problem when car (and fuel pump) got warmed up and pump started struggling.

[paul mcgrath 2 1 Cars]

Thanks Phil,

 

I think its definitely something getting hot as its great for 10-15 mins and then its Russian roulette!

 

When the fault manifests itself, If i give the car maybe 2 mins with ignition off, it will give me another 30 seconds. 

 

I was hoping to get it over to Mikeanics in Congleton but it will have to be trailered. I'm trying to not to fire the parts cannon at it although everything is nearly 39 years old on it.

 

The only thing that has been replaced on it is the starter motor and the radio (stolen in 1988 outside Manchester royal infirmary), so i suppose things are going to get tired now. 

 

Believe there is a difference between phase 1 and 2 fuel pumps so its sourcing the correct one i suppose as they don't appear to be cheap and covert procuring is required from mrs mcgrath!!

[PhilNW 46]

Get hold of a fuel pressure gauge (relatively cheap) and insert it in the fuel line just after the fuel pump.

[Thijs_Rallye 89 4 Cars]

Check if the fuel pump is running when you turn the engine over with the starter when the problem had occurred. If the pump isn't running, bridge the tachometric relay and check if the is running pump again. Should be easy enough to hear when sticking your head under the rear seat.

 

[paul mcgrath 2 1 Cars]

Thanks for the advice guys. I will sort a fuel pump gauge out and maybe replace the fuel filter as well. The fuel filter was replaced when i put it back on the road in 2015ish cars probably done around 3k miles from then (if that but it may be ropey) and i was thinking of getting another fuel line off Baker anyway and fitting a gauge permanently within the line across the top of the engine where the yellow arrow is. 

 

I believe the fuel pump is running all the time, as the car runs its only when I try and rev it (or if i'm driving it), put it under load, it cuts out or throws a wobbler as in video. 

 

I have also tested the AFM as the Autodata manual says and that appears to be a bit iffy. I have a video on that which i will try and upload. Hopefully its not that as they appear to be a bit spenny as well. Like i say dont want to start firing the parts cannon at it so will check fuel pressure and status (whether tacho relay is working properly or not) and go from there.

 

Thanks for the advice guys it really is appreciated. 

[PhilNW 46]

1 quick check - do you still have spark when it stops? Pull a plug wire off and earth it to the engine block with a spare spark plug and turn the engine over , should see a small spark and a ticking noise. Careful not to touch the wire/plug  as it has a few thousand volts running through it.

 

Cutting out when revving was one of the signs I found (as the pump had low pressure)

 

Would strongly advise against having a fuel presure gauge under the bonnet, It is not needed when problem solved and too high a risk of a joint leaking above a hot exhaust.

Edited April 21 by PhilNW

[Tom Fenton 1,561]

It sounds very similar to issues I have had in the past with a duff air flow meter. Its worth checking other stuff mentioned as well though.

[paul mcgrath 2 1 Cars]

Take on board all the comments (specially about the fuel pressure guage). I think i do have a spark as the car appears to recover just wont rev!! Although it may not recover immediately it may need 30 secs or more before it will catch again.

 

This is when i took the AFM out and tested it against known good measurements out of Auto data manual. Will try everything before getting the platinum card out!!!!!1

 

I would have expected a nice linear resistance from closed to fully open or visa versa but appears to be all over the place (between terminals 5 & 7) - note i am pushing the flap with a bic pen!!

[SRDT 199]

It's normal, output resistance isn't linear in relation with flap angle. It directly represent the airflow that is pushing the flap. The L-Jetronic ECU is full analog and can't convert flap angle into airflow so the AFM does it and has to be fine tuned for pretty much each engine.

[paul mcgrath 2 1 Cars]

On 4/22/2025 at 8:39 PM, SRDT said:

It's normal, output resistance isn't linear in relation with flap angle. It directly represent the airflow that is pushing the flap. The L-Jetronic ECU is full analog and can't convert flap angle into airflow so the AFM does it and has to be fine tuned for pretty much each engine.

Thats good then thanks for the clarification. ECU temp sensor just arrived so will try changing that tonight and see what happens.

 

[paul mcgrath 2 1 Cars]

Looks like we are trying the fuel pressure next. Got spark, replaced ECU temp sensor last night, runs up to temperature and then bogs down on accellerator. 

 

Can hear fuel pump priming but whether its priming to the correct pressure and volume i dont know. 

[welshpug 1,677]

get the pressure gauge in the line on top of the tank, all the ones in the engine bay on the feed side are plastic with a rubber coating, not so easy to fit a gauge into

[Tom Fenton 1,561]

I have a pressure gauge setup that uses a modified banjo bolt that you fit into the top of the fuel filter, to avoid having to cut anything.

I'd be willing to lend it out with a cash deposit to ensure I get it back.