Still got really annoying fuel problems, seriously need help!!! :(
Turbo Mini Forums

Hello I posted a message a while a go about my fueling problem, during the few weeks I have tried some of the suggestions.
The setup I have:-
* standard mini tank with fuel return fitted (a non enlarged fuel outlet pipe)
* Brand new Bosch fuel pump (metro turbo)
* 8mm Copper microbore fuel line
* A not that old (replaced last year/maybe 6 months) fuel pressure regulator (FPR)
* Fuel filter clear in line between the regulator and the carb
* Fuel pressure guage T'ed off after reg. before the fuel filter

My problem is that when i am sat at idle it appears that there is no fuel in the filter but the guage says there is 3.5psi. When I first drive it up to boost then pull over the additional fuel pressure encourages the air through the system and the filter will fill up. However, when i continue driving the fuel pressure will slowly die away until it reads 0psi and then it will use up the rest of the fuel in the filter. Strange thing is when the pressure dies away it still follows boost pressure of the turbo.
If i link the input of the FPR to output the fuel flows though it fine, so I think that my fuel lines are free of blockages. I am thinking about buying yet another FPR as it is now one of the oldest parts of the system? But since it follows the boost pressure it seems like it working.
My main problem is I am seriously losing interest in my car it seems that no matter what i change there is always the problem.

I am tearing my hair out as I type!

Please, please HELP!

As a first step I would suggest getting rid of your fuel filter between reg and carb and then have another try to see what happens. It sounds like the air in the filter is causing you a problem.

i have the very same problem ive taken fuel filter out and problem still there. have a look at my previous posts. very good advice will be found let me know how you get on.

have you checked the hoses/pipes for kinks or anything?

when the pressure drops to zero is there still plenty returning to the tank via the return pipe?

this shoud then point to a "before or after" regulator problem

i have changed regulator got a brand new one,rebuilt carb,tried t piece trick,brand new fuel pump,new ignition module,all pipes are ok,even tried mpi tank and problem still there work this one out.

I am pretty certain that there is fuel returning after it drops to zero psi. I cant check at the mo because my car is at my parents as they have off road parking.

Speedyminidave I feel for you man! This is completely killing me spent an absolute fortune replacing bits that have done nothing to remedy the problem.

Its just not fair :(

not sure but could it be the outlet pipe on std mini tank being too small ? wheres turbo dave when you need him???

I thought that, its the only thing i havent changed!

But I dont understand how it is doing what it is if it is that though? (Whoa, an interesting sentence there!) Well I guess that is why I have the problem he he:)

Well i have not driven it until it dies (recently). Before I removed the filter from before the fuel pump and replaced it with a filter in the supply line from FPR to carb, replaced the fuel pump and checked the fuel lines I used to break down on the way home from work if it took a lot longer than normal ie heavy road works crash etc. But since then I have driven short distances and found the filter emptying.
After i had replaced the pump there was no fuel in the filter, and when turned on the pump it didnt fill up. You could see a very small amount of fuel going in to it from the FPR but it still started and ran.
I have taken the petrol cap off to see the fuel returning but I cant run with it off as the fuel returned would spray everywhere (return is quite high in the filler neck. As far as noticing a difference I dont think so.

Don't take this the wrong way, but it could be you're looking too heavilly at something that isn't the real problem..
The only time is seems to have cut-out is when everything is nice and warm; this could suggest the ign module is breaking down for example...

You say there is no fuel going past the filter, yet the engine runs. This is unlikely - engines need fuel to run (which must coem from somewhere).

So what happens if you take the pipe off that goes between the fuel pressure outlet and the carburettor? Does anything come out?

I'll ask this once aswell. Are you 100% sure your fuel system is plumbed in correctly using the diagrams on these pages?


Personally, I'd set your plumbing system up like so:

1) Connect your pressure gauge to the outlet of the FPR.

2) Remove the pipe between the top of the FPR and the plenum. Rig up a bicycle / foot pump such that you can put pressure into the top pipe on the FPR.

3) Turn on fuel pump. Adjust pressure after loosening off the locknut by screwing the screw in/out. Set pressure to 3psi first. Leave running for 10 minutes. Check if pressure has changed.

4) repeat above, but set pressure to 7/8 psi - again leave for 10 minutes continual running to see if the pressure changes.

If the pressure stays the same, so far so good.
If it drops, either the regulator is faulty or (more likely) the fine gauze over the original outlet on the tank is restricting the outlet. My engine ran fine for 3/4 years before this became a problem - I made a new outlet tube.
If the pressure rises (unlikely from wht you've said) the return is restrictive.

If the pressure stays the same, wind it back to 3psi and apply a 'pressure signal' to the top pipe on the FPR. You should see the pressure at your gauge increase, and decrease as you operate your hand/foot pump. If it doesn't, then you have a problem with the regulator.


Do the above tests, and see what happens...

I didn't take it the wrong way I understand that I have become slightly neurotic about the empty fuel filter.
I know that fuel comes out of the FPR supply to the carb as I have checked it in the past before i got the guage.
I am pretty certain that i have the FRP, fuel supply & return lines and carb connections all right, but I will check them again.
I will try the testing method you sugested, possibly tonight, to see if I have any joy.
Sounds like a pretty bomb proof procedure thanks a lot.

If it is the FPR can you buy a diaphragm and sping kit? Or will I have buy the whole FPR? Its just that mine still looks brand new lol

those plastic filters are still flowing even though they dont look full. confused me a few years back. must be air locking in them

i have taken my fuel filter out because mine used to be half full and thought this was the problem but obvuiosly not. i did put an mpi tank in a few weeks ago it seemed to be better could drive the car a bit further than normal but seemed to be over fueling but problem still there but not as bad though.

is the fuel thats returning back to the tank supposed to come out with force if it is mine doesnt if i turn pump on before starting up you can hear it trickling out is this normal.

well, it should in theory come out with a smilar force to that coming out of the pump, minus whatever restriction is generated by a 3psi pressure restriction (not that much).

Dave, I'd sugest that you put a pressure gauge into your return line at the FPR. This should show ZERO psi. If it shows even a little pressure, your return line is restrictive and you'll suffer from overfuelling.


If there isn't a restriction, it suggests that your pump is struggling...




EDIT - just read you have the MPi pump... These are pretty quiet in operation.

Edited by turbodave16v on 5th Apr, 2005.

when i did the conversion i used 10mm copper pipe on return when it come to entering the boot floor from underneath my bro in law whos a plumber said it would be best to use 90 degree elbows and a few straight lengths there are three elbows at present then rubber pipe on to tank i wonder if theres too many bends causing restriction not sure.

Have you considered running long lengths of flexi temporarily from the pump to the FPR and back to the tank? Just to prove that the problem is not down to the solid fuel lines underneath the car?

Ok I have tested the system and this is what I found relative to the numbers that turbodave used in his post:-

3) I ran the pump for at least 10mins and it were very small tremors now and again on the needle but stayed pretty much exactly on 3psi.

4)Same amount of time was given and the pressure was set to 7psi. After a few minutes the pressure gauge showed a pulsing effect and the needle moved between 6 and 8 psi for the rest of the time. You could also feel the pipe pulsing from the fuel return and so was the fuel returned in the tank.

I am not sure what this proves, but, I did not check the air signal test as i could not secure the bike pump enough to get a test working. However, when driving even a zero psi on the guage when i accelerated and the boost comes in the guage would rise with it suggesting that this part of the system works. ( Will redo test after adapted the tank so can try harder to get this test to work then!!)

I have removed the tank and will replace the outlet and return pipes as a matter of course now. I understand that this cant hurt and I think while I cant drive it might as well!
I am unsure what i should do about the replacement outlet pipe should i try and get a gauze? what shape should it be? etc.

Thanks for your help so far it felt good to do something to sort it out with out spending money yet he he!

This pulsing this not quite right I think. It could just be a hysterisis from the spring in the regulator, but it must have started somewhere. Also, why after a minute or so of being steady...

It is pointing towards the gauze in the outlet on the tank being partially blocked.

I've removed the standard 'outlet' tube from my own tank when I sufferd from problems a few years back. The standard outlet is also 1/4" which is a little smaller diameter than the 10mm pipe on the metro pump inlet - ie a restriction!

so then:
1) Drain and remove tank.
2) Remove sender unit. Also familiarise yourself with where the existing pipe runs inside the tank.
3) Flush out tank a few times with water
4) Cut the existing outlet off flush with the tank. Now get a 10mm drill and 'drill' the remainder of the tube out, retrieve it from insode the tank.
5) Pop down to B&Q and buy a 1m length of 10mm steel tube (?3-4).
6) Bend this to shape in a vise. Basically, you want the end of the pipe inside the tank to be around 2" up from the lowest point of the tank. Use the old pipe as a template if reqd.
7) Cut the pipe off such that it'll protrude 1" or so from the tank - so you can get a hose on it.
8) Weld into place - make sure your welding doesn't leave pin-holes mind!

As you can see, I didn't bother with a Gauze - the reason, I wanted to get it done fast and easilly. Gauze would need to be soldered onto the pipe - and i didn't have any gauze the right size, or an engineers soldering iron.
I figured that leaving a 2" gap at the lowest part of the tank is sufficient to prevent (most) crap getting sucked up. If you have the time and tools - fit a gauze mind!

As regards the fuel return, mine is rearwards(as it's installed in the car) of the breather. The return needs to be positioned such that it won't obstruct the filler neck (or petrol pump nozzle). If you don't mind noise, put a 90degree bend in the pipe and point it down. A much better solution however is to aim the pipe at a shallow angle to one of the sides of the tank to soften the velocity of the fluid. This makes a big difference believe me!
The size of the return pipe is up to you - basically keep it simple!

This post is pretty good reading, with the results verified by Harry. Note the use of either a larger diameter return pipe, OR a restrictor fitted just before the plenum is reccomended for correct fuel-regulator operation.
http://www.turbominis.co.uk/forums/index.php?p=vt&tid=1456


Hope that helps!

Edited by turbodave16v on 7th Apr, 2005.

Just a thought, if it is your gauze partially blocked up with shite, as a quick attempt to see if it helps you could drain the tank and then blow compressed air into the fuel outlet to blow any crap out of the gauze? Then try the 8psi test again?

Good plan tom - might give a fast answer...

Then again, how effective is back-blowing gauze with air? Usually it dislodges some, but not all of the crud. Using a hosepipe would be better as you're using the lower viscosity of the water (compared to air) to shift the crud (the air will escape through every little unblocked piece of gauze before doing any work).

End of the day, even the 1/4" outlet, without any gauze, is too restrictive...

Edited by turbodave16v on 7th Apr, 2005.

i have no gauze, avonbars motorsport fuel filter with 10mm outlets running to 8mm copper lines, i also use flexi till it gets under the car has been working for 6 months no probs, sorry if this has been said/advised only skim read!

Aye, water would probably be better, especially if you've got a pressure washer handy.

back to the problem again did my fuel tank today i did as turbodave says went to b&q got a length of 10mm tube cut outlet of tank drilled 10mm hole through removed old pipe in tank bent a new piece to shape exactly the same as old one welded into position no gauze so then put tank back in connected pipes as they should be job done ha ha started her up oh she would not fire so disconnected pump then she started as soon as i connect pump back up she cut out could this be overfueling altered regulator did not make any difference loads of smoke out of exhaust sorry if its longwinded but really getting me down now