Fuel system problem, HELP!! updated 31.7.12

Hope someone can help!!!!

I have a 1990 golf gti convertable, all standard engine/electrics.

Over many months I had an intermitent running problem.  Every-so-often I would go to start the car and the engine wouldn't start.  I found that if I 'waggled' the fuel pump relay the pump would kick in to life and all was well.  Never thought much about it and put up with it until the day it did it and didn't start.  I took the relay out and found it had blown and melted the fuse box!!  I bought a new relay from GSF but it hasn't worked, could of popped the first time I tried it with no visual evidence or fuse box is damaged.  I bridged the terminals with some cable and a switch.  To start the car now, I flick the switch and the fuel pump starts and then I turn the ignition and it all runs fine.  Now I have discovered that the cable and switch are becoming way to hot too touch and it has damaged the switch.  

I need to sort the route of the problem as I can see the car going up in smoke!!

One thought I had was that the pump was having to work to hard and was pulling to much power to operate although I have never had a pump do this before.  Normally they get rusted up from a fuel filler neck problem, humm louder and then just pack in?

Any ideas?

Here are some pictures to help.

BTW I am totally skint, that is why it isn't at an auto electricians.  I am very hands on but don't have the knowledge on where to look and what to check.

Hi just wondered if you had any more luck with the fuel pump issue. I have a similar problem but mainly with the relay getting hot and the car having no power at higher revs. i bridged the relay to and the problem was gone but the wire did get hot. I to am thinking new fuel pump and lift pump in the tank

matt

No joy as yet, had no replies on the open forum here but some help on ED38.

This is the plan now, and will be starting more forum posts to catch attention/help.  Need to get the car sorted asap as I need to be able to take the kids out!!

I am going to check tank, lift pump, main pump first to see if there is anything obvious.

Got into the fuel tank and with the aid of a telescopic magnet from tesco for 97p I was able to remove this.  I had changed the filler neck a few years back and cleaned the tank out as best I could.  This must have been what I missed!

Fuel tank lift pump and sender unit.



Filler neck rusty bits!!





Next I will be tackling the pump, hoping to find a small filter on the supply pipe that is full of crap and causing the problem!  fingers crossed!



One thing I was wondering, does all the fuel to the main pump go through the lift pump?  If so, there shouldn't be anything in the main pump as the lift pump filter should catch it all?

Hi, thanks for getting back. I think i have a very similar problem to you then buddy!!
Thats a fair bit of rust in there! As for the main pump i think your right that most of it is filtered thru the lift pump, however small aprticles do get through and over a period of time build up and find there way past the pump and into the main fuel filter.
because the lift pump has been sucking the crap up its struggling to feed the main pump which in tern makes the main pump work harder which causes it to draw more currant. I think this is the reason your relay is melting!!
i would recomend blowing out the fuel lines from the main fuel filter to the tank and replacing the pumps and filter.
This is what i intend to do with mine as its driving me mad.
I hope you don't think im telling you how to suck eggs though, its just what i've gained off here and from the scirocco forum to.
keep me informed on how you get on!!!!

matt

Will keep this updated as I go along.  All advice is welcome as I can't afford to go to the garage atm and need to sort this myself as quick and as cheaply as possible, although I know I may have to replace relay, fuse box, lift pump, pump etc……. hope it doesn't come to that though!!!!!!!

This is link to ed28 thread http://www.edition38.com/forums/index.php?showtopic=461114

Thanks for the link! Im in the same situation tbh need a cheap fix. may just blow the lines out replace the lift pump as you can get them for about 25 quid on ebay and replace the main filter and see how it goes.  good luck mate hope to hear back from you with good news!!!

A little progress………..
 
With the car jacked up at the rear for easy pump access I dettached the fuel feed line to the pump. I had a funnel underneath to catch what came out. As you can see, the cage that holds the pump is rusty. There is a possibility that some of that rust fell into the pot and so I can not be 100% sure that it was all in the pipe and being collected by the filter, but certainly there was some debris. Here is a picture.
 



 



 
The pump did have a little filter just inside the entry which I didn't know exsisted until I started researching this situation! Here is a picture. There were some larger pieces of debris in the filter and this would have certainly been restricting fuel flow. I tapped the pieces into the container with the fuel from the flow pipe from earlier.
 



 



 
I then attached the fuel supply back to the pump and dropped the car back down. Going under the bonnet I disconnected the main fuel filter on the 'out' end. I used the switch which is in place of the relay to prime/run the pump and cought the fuel that came out, this was clear. I replaced the filter with a spare I found in the garage.

I tapped the fuel that was in the filter into a clean container. As you can see, it was full of the fine rust particles.
 



 
I pulled the filter paper out. The clean white part was nearest the outside and furthest away from where the fuel enters the filter. If the rest of the paper should be the same colour, the filter was full of the small particles of rust!!
 



 
I then ran the engine for about 1 minute befoe I could feel the switch cable that replaces the relay, getting hot. The pump did sound alot quieter though. It was never really loud but I had to go under the car to hear it. The engine still runs fine with no spluttering.
 
Mate is lending me a volt meter and so I can get some current readings.
 
The plan is to then change the fuse box as I haven't ruled this out as the problem yet. The first sympton of the problem - the engine not starting, was solved by wiggling the relay. It seemed like it had a bad connection. Since it melted I will replace it along with the lifter pump and relay.
 

One question though, Which is the fuse for this curcuit and what is is rating? Should this not have popped first, thus saving the relay and box??

i think you have got to the bottom of the problem, next step replace the fusebox because it is knackered! the fuse should be rated at 15a, i bet someone bodged a higher rate fuse in there because it kept popping rather than doing what you have done and fix the issue!

i think you need to go back thru the system though and clean everythign out thouroughly. look further back under the car and you should find a plastic fuel reservoir, that is probably full of rust too. if the reservoir is missing, then this is also goinf to be a problem for the main pump, any tight corners and it will run dry and start to eat itself. the main pump MUST have a constant supply of fuel as it lubricates the internals.

 i would drop the tank so you can give it a really good clean, but thats your call. you might get away with the old 'magnet on a string' trick to get the worst of the rust out.  once you are sure everything is clean at the tank end, take the fuel return hose to the reservoir and point it into a container. take the feed hose off your fuel filter, and point that into a  container too. bridge your relay so it blows a good volume of fuel into the bucket to ensure any residual crap in your feed line is flushed out. then reconnect the feed and repeat the process to flush anything out of the return line into the bucket. if this is clear, good you have been lucky! if not you might have a damaged metering head, plus your injectors could be clogged too. reconnect it all then keep an eye and see how it behaves though.

"rubjonny" said

i think you have got to the bottom of the problem, next step replace the fusebox because it is knackered! the fuse should be rated at 15a, i bet someone bodged a higher rate fuse in there because it kept popping rather than doing what you have done and fix the issue!

i think you need to go back thru the system though and clean everythign out thouroughly. look further back under the car and you should find a plastic fuel reservoir, that is probably full of rust too. if the reservoir is missing, then this is also goinf to be a problem for the main pump, any tight corners and it will run dry and start to eat itself. the main pump MUST have a constant supply of fuel as it lubricates the internals.

Thanks for all replys and help.  

When you mention a plastic fuel reservoir, do you mean the accumilator?

Checked the fuse and its a 15A. There is a slight sign of the plastic melting.  Anybody know why it can get so hot and not pop???

Here it is……….

no the accumulator is after the fuel pump, its there to smooth out fuel flow and hep maintain pressure after shut down. the accumulator goes before the fuel pump, its a square plastic tank which maintains a reserve of fuel before the main pump. if you dont have one then you need to fit one as the main pump will eventually die!

Bit of progress/success!!!

Found a fuse box in the garage and its the same part no as the blown one and so I have changed it and put the relay in that I got from GSF when the original blew.  Whilst box was out I cleaned up the earth 'crown' terminals as some were slightly corroded.  Started her up and she runs fine! yippee!!

Put a lower 10A fuse in to hopefully protect it but this felt hot after 10mins.  Put the proper 15A fuse in but I could be imagining its getting warm, not sure!!

How can I check if the problem is fixed now after clearing the fuel filters, cleaning the earth terminals and replacing the fuse box and relay?

I haven't ruled out the thought that it could have been a fault on the relay or fuse box, because of the intermitent starting/ waggling of the relay over the months.

just keep an eye and see how it goes, they will get hot there isnt much you can do about it unfortunately!