Another GTI wont start!! HELP!!!

Hi All!! Looking for a bit of advice!

My 1981 1.6 Gti stalled last weekend when I had it out for the first real drive of the year. The car suffers an high idle when cold so was allowed warm up properly and only lasted 15-20 mins on the road.  The car would crank but wouldn’t fire, and I ended up having to get a tow home.

Iv checked the relay and the spark and both seem fine. Spark a little yellow, but don’t think this would cause it not to fire. I don’t think a rusty system is the cause either, most replaced a few years back so should still be fine.

The plan is the change the fuel filter next on the off chance that its clogged up with cr*p, then fuel pump, but after that, I have no idea where to look next!!!

I do think the fault is something to do with fuelling, was hoping it was a relay or something straightforward but no such luck!


I have read about lots of similar problems, but most seem to be sorted by either a relay, or changing a lot of the fuel system components.

Any advice on where to check next or potential issues would be massively appreciated – wouldn’t you know this would happen the day I drop my daily in for a timing chain replacement!!

Thanks!!

Chris
 

Next logical step would be to measure the fuel pressure, hot and cold starts.

I bet you're going to say you don't have a fuel pressure gauge? If so, then just let the car cool and see if it starts ok cold. If it does, then it points to a mismatch between hot fuel pressure and injector opening pressure (or, the amount of fuel supplied by them in this scenario).

paul_c said

Next logical step would be to measure the fuel pressure, hot and cold starts.

I bet you're going to say you don't have a fuel pressure gauge? If so, then just let the car cool and see if it starts ok cold. If it does, then it points to a mismatch between hot fuel pressure and injector opening pressure (or, the amount of fuel supplied by them in this scenario).

Yep your right, no gauge! Tried to start it last night, stone cold and no luck. Still sounds the same, cranking but no bite. I do have a problem with hot starts, think it's down to the fuel accumulator. 
Will be doing the filter and pump tomorrow because I have the bits at home. Hoping itl do the job but I'm not convinced. 

I thought it was only hot starts you had issues with.

If its both (ie won't start at all now) its worth checking the fuel pump relay. Its possible to get some wires, or a paperclip or something, and bridge the relevant connector to completely replace/bypass the relay for testing purposes.

If that works and it doesn't cold start, check the 5th injector AKA cold start injector, since this is an easy check to do.

paul_c said

I thought it was only hot starts you had issues with.

If its both (ie won't start at all now) its worth checking the fuel pump relay. Its possible to get some wires, or a paperclip or something, and bridge the relevant connector to completely replace/bypass the relay for testing purposes.

If that works and it doesn't cold start, check the 5th injector AKA cold start injector, since this is an easy check to do.

Thanks for the replies  

Yep wont start at all now!

Nope both hot and cold starting problems!!! Its an ongoing work in progress so I didn't really mind these problems.
 I did have a look at the relay and it is clicking when the ignition is turning on. I know the old ceramic fuse board has known problems with the fuel pump relay overheating, I cant see any evidence of it melting. Presumably the relay clicking once when the ignition turns on is it priming?
Will look at the fifth injector tomorrow!

Excuse my ignorance! First mk1 project

I have no idea if  a clicking relay is a reliable diagnostic test of a relay. I do know that removing it then bridging the connections with a little piece of wire, is.

paul_c said

I have no idea if  a clicking relay is a reliable diagnostic test of a relay. I do know that removing it then bridging the connections with a little piece of wire, is.

Well then ill bridge it just incase! Worth checking it before I start replacing bits

So I bridged the relay and the car still wouldn't fire. Changed the fuel filter and fired first turn of the key!! After a face full of petrol I realised new copper washes were a must! Quick trip to the local motor factors for a rummage through their fuel filters, finally found 4 that would do the job. Took her for a quick blast through the mountains and all was perfect.
A bit of rust in the old filter that will need further investigation but Nothing massively concerning. Will look at tank and pipes after the summer!  

Best to take a look at the filler neck now not wait till after the summer, take the filler cap off and shine a torch down there and look for any rusty holes as they are usually at the top as that is where the mud sits, if there is any holes fix the problem/replace the filler neck ASAP as dirt and water will kill the injection system and will just keep causing problems.

It's not a hard job to check inside the fuel tank, take the base of the back seat out and undo the 3 screws holding the cover on then undo the 2 fuel lines and electrical connector and twist off the fuel sender and you can see inside the fuel tank.

mark1gls said

Best to take a look at the filler neck now not wait till after the summer, take the filler cap off and shine a torch down there and look for any rusty holes as they are usually at the top as that is where the mud sits, if there is any holes fix the problem/replace the filler neck ASAP as dirt and water will kill the injection system and will just keep causing problems.

It's not a hard job to check inside the fuel tank, take the base of the back seat out and undo the 3 screws holding the cover on then undo the 2 fuel lines and electrical connector and twist off the fuel sender and you can see inside the fuel tank.

That's not a bad idea, didn't realise checking the tank could be so easy!!Will get a stick and go fishing!!
The neck looks good, no major corrosion or holes that I can see of. It was one of the first things I checked when I saw rust in the filter, and thankfully it doesn't seem to be the cause.

Thanks for help!  

Magnet on a bit of string/rod and fish out what you can then clean the magnet and drop it in the tank to collect any more rusty but just don't drop the magnet near the float for the fuel gauge incase it sticks to it. Not sure if there is a filter on the tin top fuel tank as there is in the Cabriolet with a lift pump so may be worth looking into some sort of filter on the end of the fuel pick up? 

mark1gls said

Magnet on a bit of string/rod and fish out what you can then clean the magnet and drop it in the tank to collect any more rusty but just don't drop the magnet near the float for the fuel gauge incase it sticks to it. Not sure if there is a filter on the tin top fuel tank as there is in the Cabriolet with a lift pump so may be worth looking into some sort of filter on the end of the fuel pick up? 

That's very straightforward alright, can the magnet be left in the tank? same concept behind magnets in some auto boxes? Great idea  
I have a list of bits to get done at the weekend ( seems to be every weekend!!) so will add this on.

Thanks for the advice mark1gls        

Yep leave the magnet in there to collect any other bits as I said in my last post, it's a metal tank so it will stick.
The hardest bit is twisting off the fuel sender, if it's a metal one then you can get a socket set T bar, a blunt flat bladed screw driver or similar tool and on one of the ridges on the edge tap the fuel sender around till it's lose, it's like a bayonet connection so only needs to turned 1/4 turn to get it out, remove it care fully as the float and other thing's attached to it.

Have some rag handy when you remove the fuel lines as some petrol will come out but should stop then use the petrol soaked rag to clean gunk of anything you like as petrol is a great cleaner!

Don't forget which fuel line went where as one is a return line and the other the intake.

mark1gls said

Yep leave the magnet in there to collect any other bits as I said in my last post, it's a metal tank so it will stick.
The hardest bit is twisting off the fuel sender, if it's a metal one then you can get a socket set T bar, a blunt flat bladed screw driver or similar tool and on one of the ridges on the edge tap the fuel sender around till it's lose, it's like a bayonet connection so only needs to turned 1/4 turn to get it out, remove it care fully as the float and other thing's attached to it.

Have some rag handy when you remove the fuel lines as some petrol will come out but should stop then use the petrol soaked rag to clean gunk of anything you like as petrol is a great cleaner!

Don't forget which fuel line went where as one is a return line and the other the intake.

Thanks for the advice!! Will definitely be giving it a go at the weekend.