A little GTA fuel system story...

Many years ago I bought my first GTA, an Atmo, and after extended wide open throttle sessions, say 20 seconds, it would start to cough and splutter and cut out, untill crusing off throttle for about another 20 seconds, and then it would be back to normal..

Front fuel pump I thought....so I changed it to a Facet racing pump and voila problem solved. The only issue with the Facet pumps is they click when running, and loudly but this wasnt really an issue, the car worked and I was happy, and made good power, just under 180bhp with a few mods.

Now very recently on my turbo GTA, I had the same problem, extended WOT, then cutting out, stuttering, so again I thought front fuel pump. I changed it again for a Facet, click click click, but the problem as alleviated - well some of it. It still cut out eventually. So I changed the rear pump, reg, but the problem was still evident.

Soo, I decided to investigate the whole fuel system, and this is what I found.

First I took off the main fuel lines to the two short rubber pipes that connect them to the tank. These rubber pipes have the internal diameter of your little finger. Now with a full tank of fuel you would expect fuel to flood out when removed. I pulled of the steel fuel line from inside the pipes, and fuel trickled out as if someone had drilled a 1mm hole in a cup - that little.

So I gave them a poke, voila, fuel pissing out all over the place, along with so much black crap. I disconnected the rear end of the fuel lines where they meet the rear tank and blew them out with an airline. Again, mountains of black crap, enough to cover a whole rag. RUST basically.

So then I removed the front tank, again black crap all over the place, like fish food flake sized black rusty crap.

Basically, the steel fuel lines, over 25 years rust internally and any fuel not sent out the injectors is returned back to the tank, so there is 25 years worth of crap circling round the system.

So once all cleaned, replaced, tested etc, I reassembled the whole system, turned the ignition.....

Couldnt hear the front pump clicking...

Tried to the start the car....but it fired up fine! Yes, I realised Facet pumps only click when they are struggling under load, and now it was as quiet as a mouse, but thus made me realised my first car probably never had a pump problem, it was just blocked lines again. Car is now smooth, more torquey low down and a pleasure to drive. Better MPG etc..

I would advise anybody to clean your system, it costs nothing, and all of our cars will have at least 20 years worth of turds swimming around in it. Also the Facet pump upgrade is a must, if your looking to change your pump. Its higher flow and pressure that the original Pierburg (which is now £150 from Renault), and the Facet only costs £40. Its a direct fitment, and the noise it makes when encountering problems is handy.

It also tells you when your close to running out of fuel. When I hear it start to click, I know I have about 5 miles till that tank is empty.

I too have been playing with pumps on my GTA Turbo for a while. I find that I created my own problems about 18months ago when I replaced both pumps, not that I was having any trouble, only that the car had 120K miles and thought they had done their service. I used a Volvo pump at the rear, and replaced the Pierburg front pump with a diaphragm pump similar to the Facet that you used.

It too made the dunk, dunk sound, but at a very fast rate, as these pumps are made to pump to a carb with a needle valve controlling the flow, except in the turbo it pumps into a small tank (swirl pot) above the rear pump with the excess flowing back to the main tank with no restriction.

To shorten a long story it seems this type of pump will wear itself out fairly quickly in this type of arrangement and in my case was prone to seizing after an hour or so, and so drawing excess current and not pumping. This caused a voltage drop to the main pump as they are both fed from the same relay, and made it growl, but the car would run for another 40Klm after the front pump had stopped as it had the 4L of fuel in the swirl pot to run on.

After a wait of 30 mins the front pump would run for a while and I would then get about 15Klm out of the car before it stopped again. On my 30 minute commute to work all would be fine, just don't try and drive it for an hour.

I checked wiring and fuses, replaced all the relays around the computer, replaced the computer, replaced both fuel filters and replaced the rear pump again. I initially found a few points where there was corrosion at joints in the wiring, (the earth for the pump is at the back of the alternator) and the suppressor at the rear pump was corroded badly so I deleted it, and tested for voltage drop at the pump to find it was now fine, of course everything was cold and the front pump ran OK when tested.

After many months I worked out what was happening to my front pump and fitted the original pump. All is well on long runs now. I have bought an American Carter pump, similar to the Pierburg in design, that I will soon fit to complete the tale.

Fortunately through all of this I found all of my fuel system to be devoid of any gunk buildup anywhere, from the tank back. The filters were clean, as I opened them up looking for a possible answer to my problem.

So my advice is to not fit a diaphragm style front pump to a GTA turbo.

I guess GTAs may be a few years behind DeLoreans in suffering fuel system problems. It's amazing how heavy the fuel filter can be if it hasn't been changed in years, though the DeLorean usually suffers from fuel that has been left to go stagnant in the tank and tar-like deposits build up that start to dissolve into a sort of sludge when soaked in fresh fuel (as the car is put back into service after anything up to 20 years with fuel sitting in the tank). I've cleaned out a few tanks in my time, oh yes.... I highly recommend a good glug of Mr Muscle, or whatever other caustic cleaner you can get hold of, topped up with water and left to sit for several weeks, then drained. Obviously don't let this get anywhere near the engine... I usually work with the tank removed from the car.

(just fired up #'3 DeLorean today - first time since 1987!)

Well which one then ?
Do you see it on the trolley ?Can you point at it please ?
http://www.fuelsystem.co.uk/web-facet.pdf

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... :IT&ih=014
Wiv one of these attached ?
http://cgi.ebay.co.uk/Facet-Straight-Fi ... dZViewItem

Off out to find a nice quiet road to test the latest Adapt settings
I'll expect an answer on my return .........................

SS503

To shorten a long story it seems this type of pump will wear itself out fairly quickly in this type of arrangement and in my case was prone to seizing after an hour or so, and so drawing excess current and not pumping. This caused a voltage drop to the main pump as they are both fed from the same relay, and made it growl, but the car would run for another 40Klm after the front pump had stopped as it had the 4L of fuel in the swirl pot to run on.

After a wait of 30 mins the front pump would run for a while and I would then get about 15Klm out of the car before it stopped again. On my 30 minute commute to work all would be fine, just don't try and drive it for an hour.
.

This is EXACTLY to the letter what I had before I cleaned out the pipes before the new Facet pump (but also on the original pump, and another pump I used before going to the Facet). And almost exact to a certain time, about an hour too. I would know it would be about to fail, as it would start ticking really loudly, and then tick faster and faster, and then cut out and stall the car. Then it wouldnt run till about 15 mins later, and then do the same thing about 20 mins after again.

Once I sorted the flow into the pump its been fine, and Ive used it as a daily driver ever since, and you can't even hear it now, except when the tank is running low. Maybe it was just a problem with the brand of pump you used, or it wasnt enough pressure/flow rate.

One thing I noticed about the GTA setup, which can't help, is where the pipe runs from the tank, it goes down towards the front filter, and then up over the transmission tunnel, and then down the pump. Would be easier if it was kept under the tunnel straight into the pump rather than fighting against gravity.

The best idea is to completely ditch the two pump setup, and run the highpressure pump at the front as it is on the A610.

Fortunately through all of this I found all of my fuel system to be devoid of any gunk buildup anywhere, from the tank back. The filters were clean, as I opened them up looking for a possible answer to my problem.
.

This is EXACTLY to the letter what I had before I cleaned out the pipes

Have we got a contridiction here guys

SS503

Ta Muchly !!
I'll get one on Monday ..
Guess what ?I've got an idle issue on the Adaptronic again once warm after a damn good boooooosting
I've put another valve back on to try ......

Hi David,

Could you satisify my curiosity with reference to your two quotes below:-

just under 180bhp with a few mods.

This is the pump I used. Think it was the SS503. Made nigh on 180bhp on an atmo.

The second one was posted on the 10 Dec 08, and I did pose the question to you about how you achieved the extra bhp. Unfortunatally you must of missed it, as I never received a response. But now you have made the statement again, I am still interested in how "nigh on 180bhp" was achieved. The implication appears to suggest, especially in the second quote, that the pump change made the difference, in the first quote you added that a few mods were done.
I am sure there are other Atmo owners who would be interested in this apparantly simple mod, which would give approx 12% more bhp. I look foward to your help in this matter.

Regards

John

More fuel plus a bit more advance on ignition, be wary of the oil getting thinned out with running rich.

Lee, the idle stuff behaves very oddly when in any of the modes that use lambda correction, regardless of the setting telling it to ignore below a certain RPM. If you're running lambda, switch it to open loop and the idle will suddenly stabilise. I don't get it either.

Fortunately through all of this I found all of my fuel system to be devoid of any gunk buildup anywhere, from the tank back. The filters were clean, as I opened them up looking for a possible answer to my problem.
.

This is EXACTLY to the letter what I had before I cleaned out the pipes

Have we got a contridiction here guys

?

I didnt quote that bit did I?

Hi David,

Could you satisify my curiosity with reference to your two quotes below:-

just under 180bhp with a few mods.

This is the pump I used. Think it was the SS503. Made nigh on 180bhp on an atmo.

The second one was posted on the 10 Dec 08, and I did pose the question to you about how you achieved the extra bhp. Unfortunatally you must of missed it, as I never received a response. But now you have made the statement again, I am still interested in how "nigh on 180bhp" was achieved. The implication appears to suggest, especially in the second quote, that the pump change made the difference, in the first quote you added that a few mods were done.
I am sure there are other Atmo owners who would be interested in this apparantly simple mod, which would give approx 12% more bhp. I look foward to your help in this matter.

Regards

John

Modified exhaust, fuel pump and and adjustable fuel pressure raised, ignition timing advanced.

When I first got the car it made dead on 161bhp, after the mods 176 IIRC on the same rollers.

Hi David
Thanks for the info, it makes more sense now. I was a bit concerned, especially with your quote in Dec, with no mention of mods, that some Atmo owners might have got the impression that with just a higher pressure fuel pump, it could increase the bhp from 160 to "neigh on 180". I am sure you will concur that this clearly will not happen by its self, and in fact it could be quite dangerous, as if the pump pressure was such that it overcame the force of the float on the needle valve in the carbs float chamber, it would cause it to fill and overflow via its breather, and send fuel over the hot engin, with disastrous consequences.
Regards
John

To shorten a long story it seems this type of pump will wear itself out fairly quickly in this type of arrangement and in my case was prone to seizing after an hour or so, and so drawing excess current and not pumping. This caused a voltage drop to the main pump as they are both fed from the same relay, and made it growl, but the car would run for another 40Klm after the front pump had stopped as it had the 4L of fuel in the swirl pot to run on.

After a wait of 30 mins the front pump would run for a while and I would then get about 15Klm out of the car before it stopped again. On my 30 minute commute to work all would be fine, just don't try and drive it for an hour.
.

This is EXACTLY to the letter what I had before I cleaned out the pipes before the new Facet pump (but also on the original pump, and another pump I used before going to the Facet). And almost exact to a certain time, about an hour too. I would know it would be about to fail, as it would start ticking really loudly, and then tick faster and faster, and then cut out and stall the car. Then it wouldnt run till about 15 mins later, and then do the same thing about 20 mins after again.

Once I sorted the flow into the pump its been fine, and Ive used it as a daily driver ever since, and you can't even hear it now, except when the tank is running low. Maybe it was just a problem with the brand of pump you used, or it wasnt enough pressure/flow rate.


The best idea is to completely ditch the two pump setup, and run the highpressure pump at the front as it is on the A610.

The pressure and flow rate were fine on the low pressure pump feeding the swirl pot, only that because the pot feeds back to the main tank when full the diaphragm style pump will beat its heart out, at high beat rate, prematurely wearing it out, compared to if it were feeding a carb with the pumps' output controlled, by the needle valve, and so a much slower beat.

Certainly I didn't use a Facet pump, but one of a similar type, possibly of less quality. The gravity flow of fuel was certainly fine to the front pump, and in my case at least there is no gunk in the system blocking it up. By putting the original old pump back in the front everything is now fine.

only that because the pot feeds back to the main tank when full the diaphragm style pump will beat its heart out, at high beat rate, prematurely wearing it out, compared to if it were feeding a carb with the pumps' output controlled, by the needle valve, and so a much slower beat.

Just for clarification, on the Atmo, excess fuel not required by the carb is also sent back to the main tank via the antiperculation unit. So as you say, a diaphram pump will beat its heart out even in the Atmo. I personally would stick to rotary pumps for these installations for all the reasons given above if you want reliability. Fit larger delivery ones for modified engins if necessary .