its back!!!!..(if it had actually ever gone...)

[B-Hive]

Hi all

Recent aborted trip to Sydney (300km) revealed a hidden/recurring running issue with the GT.

She has been running brilliantly around the city, but the moment I hit the highway.. sitting at 110km/h ....no problems until any decent up hill grade that would have the car baulking, missing and eventually losing most power. If I pulled over to slow it would correct itself...until the next incline...it gradually took longer and longer to "correct" itself as I pulled onto the hard shoulder..

New fuel pump ...float has been checked and rechecked.. full tank of fuel..

Any suggestions???

[Philip Chidlow]

Water in the fuel tank?

[Gibbo2286]

Fuel pipe too near to something hot or carb needs a heat shield, causes fuel to evaporate/gasify.

Or air leaking into to tank to pump pipe causing starvation on hills.

Or filter on pick up pipe in tank choked with crud.

[BX Meteor]

or even crud in the in-line filter (if there is one)

basically you're running out of fuel flow when you reach a certain power requirement, you should find the same issue if you try to go at say 120 or 130 or 140 or 150 or 160 kph (honest officer, I was only trying to find out when my engine became starved of fuel)

[mds141]

Ignition coil packing up?

[B-Hive]

thanx guys

fuel tank pick up filter is clean

not 100% sure its a power related thing as if i gas it on the level it seems to show no issues,, but of course this could be disguised by the revs sucking the fuel rather than the pump providing it (via the return line)

coil swapped out an wiring/movement checked..

i dont think its over fuelling by a sticking on needle valve,, maybe its under fuelling by a sticking off needle valve. just guessing now

almost certain it is an incline related issue...but not really sure about how a carb and it venturies/float chamber level work in respect to the carb on an incline

[BX Meteor]

/\ depends on the incline of course

carb recon kits have been suggested on another matter in Mick's blog here where I've also put the complete solex carb overhaul.

Do you also have problems when going fast into and out of corners, often one side more than the other ?

If yes then you definitely need a carb recon kit.

If no, and if you are 100% certain that it is only on inclines and under no other conditions, then you need to adjust the float level again. The float level provides the correct pressure for the venturi to pull the correct mizture off the jets into the air flow. It is literally the height of the fuel in the float chamber that gives the slight pressure to the jets.

One other idea I just thought of: maybe its a problem with the auto-choke, the choke flap might be closing on an incline due to not having the water system bled. Try driving absolutely flat out for several miles (I'm being serious), if you then feel the power coming and going, it's the auto-choke. There are two venturi's in the carb, the seond one starts tp open when you put your foot more than half-way down. The auto-choke closes off the second venturi leaving you with only about half power, I have experienced this flat out on motorways in the past, you can feel the choke flap closing and opening all the time, bloody annoying (I've disabled the choke-flap from closing on my carb).

I put more info in Mick's blog here (I put other useful forum links and a possible source of recon kits in the UK, might be somewhere similar in Aus)

[B-Hive]

Thanks every one for your comments and suggestions..

Just thought I'd let you know that I am pretty certain that I have finally cracked the mysterious issue..

It seems that its all related to the modifications/pollution control that got fitted to the GT when it entered the country.

Basically it had a bizarre arrangement that had a metered t-joint feeding fuel from the pump to the carby as well as the re-routed fuel return to the tank. It must have worked SOME HOW when the car was new. but I deduced that going up a long incline needing reasonable fuel (above 100km/h) that the fuel in the return line was syphoning back to tank and thus fuel pressure was compromised but the air in the line.

Long story short... I drilled out the proper (blocked at manufacture) return port on the carb and attached a pipe to which i attached the return line..

Result...so far ...big big smiles...GT going stronger and harder than ever with out a murmur of hesitation...

Helps me get over the annoyance that someone tried to steal it the other night... ruined my door lock,, bashed the interior light (..couldnt find the off position... heheh) ..Think the only thing that saved her was the fact that I dont actually have an ignition switch any longer but a push to start button..BUT you also need to know which other switches to flick to get it to start...

I may have some exciting news soon...(exciting for me at least)

Anyway road trip here I come (again....)

[mat_fenwick]

Glad you've (hopefully!) found the problem. If you struggle to fine a replacement interior lamp over there I'm sure I have one. Should be fairly light to post it.

[Dickster665]

I have a similar car to 2BXORNOT2BX a 1985 Aussie Spec BX19 GT that I am very slowly tidying up to be functional transport.

I have decided to replace the fuel hoses (engine end) as part of this process and when I took them off to measure the the internal diameters to buy new ones I found a screw forced into the return hose that goes to the fuel tank effectively blocking it. So I suspect the previous owner had some difficulties with the correct funtioning of this system similar to those that frustrated 2BXORNOT2BX.

Does anyone out there understand the anti-pollution systems that Citroen used on carburettor BX models enough to tell me whether this modification will have any adverse effect on the running of the car or shorten its life? I understand that this modification negates some elements of the pollution control system but as we have no car roadworthy test (MOT) in South Australia I will be able to use the car with this set up it will just be a bit more smelly.

The metering 'tee' fixing mentioned by 2BXORNOT2BX has a branch for 7mm I.D. hose that leads to the fuel pump, a branch for 7mm I.D. hose that leads to the carburettor inlet and the final branch has a 4mm I.D. hose attached that returns to the fuel tank. The ratios in diameter suggests to me that it is designed such that the resistance to fuel flow to the carburrettor is significantly less than that to the return path to the fuel tank. So the return path only comes into play when the carburretor is satisfied in terms of fuel supply. How this benefits the environment I am not sure.

The carburretor is a Weber 34 DRTM.

Thanks for any assistance.

Cheers

Dicky

[B-Hive]

hello

Nice to hear yet another member from Oz.

That "Tee's" metering needs to be absolutely spot on and even then it gives grief.

My advice would be to dispense with it entirely, and to drill open the carb's fuel return port on the top of the carb. Being an Oz spec it would have been blocked at manufacture. I had no end of problems (as this post can attest to) until I did the mod to revert the fuel return system to its original (non pollution spec) layout.

I even used an exact metered carb jet in the old return line system to replace the broken Tee, but I still had problems going up hills as I think the fuel in the return line ran back into tank which subsequently starved the engine of fuel.

Aside from that I have left the pollution gear as is, for fear of creating more problems if I was to remove it..

Having said that there is a temperature sensitive valve that controls the amount of ignition advance to the dizzy. This was not functioning, as such I was getting no vacuum advance at all. The vacuum also goes through a maze of other pipes in the pollution gear, in conjunction with the air conditioning cut in/out damper.. Basically I have had to dispense with any vacuum advance for the moment and manually advance the timing..

BTW I am heading to Adelaide shortly to have another attempt to bring back the TRS. If you are free I'd like to catch up and see your GT..

[Dickster665]

2BXORNOT2BX

Thanks for your advice I will proceed with the carb conversion. Below you will see a picture of your new car that I copied from Aussiefrogs. Is this what the carburettor should look like post conversion?



I am glad that your pollution control system is still in tact as three of the small diameter hoses have become detached in my engine bay and your ability to be able to tell me where they go will be invaluable. I will post some photos later if you don't mind assisting me with this.

It would be nice to meet up if you have enough time while you are in Adelaide. I will PM you my details.

Cheers

Dicky

[B-Hive]

Happy to assist where ever I can ...

Yes this layout on the TRS for the return is as it should be for a proper fuel return.. Drill only a hole size that would match the inner diameter of a return hose .. This ensure less chance of accidently mutilating the top of the carb as well as ensuring it wont leak..

After you have drilled the return port you'll need to fit a small length of outlet pipe, (the snugger the better)_ and then seal it in place with an application of some fuel and temp resistant gloop...I used Quik Steel which works very well...

Interesting the TRS appears as though this is its' original setup... Maybe the dreaded Tee piece mod was only for the GT..

This is a quick pick of my "mod" or should I say "un-mod"