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MG MGB GT V8 Factory Originals Technical - Fuel tanks, EFI and swirl pots
|Lots of discussion has gone on in the past on this issue.|
The one thing everyone agrees on is to use a early style tank with a lote model sender, to get your supply and return lines to the gas tank covers.
However the early gas tanks do not have any baffling or swirl pots in them. I did not think this would be too much of an issue, HOWEVER, now that I finally have my EFI running, I am having problems. After about 5-10min of driving around the car will not be able to accelerate at all and exhibits drastic signs of fuel starvation. At the same time I can hear the HP fuel pump cycling and making noise like it is getting air. My only thoughts are that the return line is dumping into the tank and agitating things, then add in the road motion to further cause issues.
Many of the past threads spoke of using big fuel filters and a low pressure high volume pump to make a swirl pot tank. Have any of you done this and how did it work??
Also, what filters did you use?? All the marine ones I see are fuel/water separators with a glass element which I don't want under my car geting hit by rocks etc. And most are smaller than 1 liter??
ANy help would be appreciated, the cars runs incredible until this problem starts..
|Larry, check your tank first. I have a '71 rdstr & found the original tank had baffles built into it,so the later type tank sender wouldn't fit into the tank. I ended up making the new sender shorter so it would fit. I'd have been better modifying the original sender by soldering an extra pipe thru it for a return. As for the swirl pot, I was able to buy an ally one off the shelf from a hot rod/street machine shop for about $40.I mounted it where the LH battery cradle used to be. HTHs Barrie E|
|Well I already looked inside, it is one big open chamber and the late model sender is already installed with a Autometer fuel gauge sender also fitted.|
I will call my favorite hotrod shop and see what they have.
I was told by a shop owner that the original early tanks were baffled, mine is, but the replacement tanks are not. Some VW's and Volvos used a remote swirl pot. Some even combined the pot and pump in one unit.
|Here is what I thought people were talking about. The bad thing is they are not "cheap", $75-140US!!|
That may be true, mine is a reproduction and I am absolutely sure it has nothing in it.
|Fuel Cell foam will resolve your problem, but it could interfere with the sender.|
|Problem is that requires pulling and cutting open the tank, if I do that I can just put baffles and custom sender, pick-up, return stuff in the tank. NOBODY I can find in WA will touch a tank these days. I have friends that say they have done it before, but I ned a filter added to the system and I have a carb electric pump sitting, so might as well try this set-up 1st.|
sounds odd, it could be that you have a drastic amount of debis in your tank. My tank was an replacment and has no baffles at all, like yours I guess. The later fuel sender, when in place, squashed up tightly to the tank line. The two filters were tight up against each other in the lowest part of the tank. Orrigionally I ran the half inch pick up line up over the axle, through a gauze filter to the pump located at the front of the battery compartment. I found this to be noisy, but not excessivly so. Just enought to be irritating. I relocated to the boot, installed a small high volume feeder pump (pulling though a large filter and feeding a very large filter through a T piece. This filter overflowed back to the tank and the high pressure pump pulled from the bottom of the filter through a T piece, to which the return line from the engine was also connected. Effectly a cheap swirl pot. This worked well but dispite all my efforts to correct, caused a smell of petrol to permiate the boot and any clothing in it.
Now, I made a small box/shelf up to fit behind the rear wheel arch, up in the small dead space under the RHS of the boot. I packed feeder pump, main pump and large filter into it and hold it in place with one bolt and a catch. This works very well. I have dicarded the second "swirl pot" filter and it's T pieces because it made no difference at all.
Details-From late sender a fuel line up over the spring, to a large filter ($20), from filter to small high volume low pressure roller vane pump ($100 Australian).This is located at the bottom of the box and near to bottom of the fuel tank level. From low pressure pump to high pressure pump ($150) thence to engine. The return line runs to the tank "pick up" (now a return) line. I could probaly discard the smaller pump in this location, but for the filter, which is vital.
If the problem was a lack of swirl pot then you would only be experiencing problems on very heavy accelleration and cornering. The fact that it occures after a little time sez it's not this and installation of a swirl pot may not fix this. I would suggest that the real problem can only be solved by removeing and cleaning out your tank, not a nice job. However you could try the low pressure high volume pump with a large filter. The high volume pumps suck a whole lot better than the the high pressure pumps and may be able to deal with a partially blocked filter.
This has the main advantage of not wasting any money as you will need such a pump if you eventually buy a swirl pot (or go the cheap "big filter T piece route) and it will be useful even if you don't as it will make the high pressure run a lot quieter.
Just a thought, is your temperature sender OK? Could be the computer thinks the engine is cold when it has warmed up after ten minutes ie too rich.
If the filter clags up then it back to tank cleaning, which you might have had to do anyway so effort wasted
|Actually you could just chuck all this in the boot for a trial.If it works you could then either put up wiht the petrol small or make up the box/shelf or whatever. Just buy the low pressure high volume pump some T pieces, filter and fuel line. Shouldn't take more than an hour to join it all up and a relatively easy job.|
Well I had the same concerns, as it does happen right around the time the engine reaches temp to switch modes. The problem is just before I start to have problems I can hear ther fuel pump making noises and changing pitch/rpm like it is cavitating. I did pull over one time when it got real bad and popped the hood. FP was 40, but then I whatched it go 40, 20, 0, 20, 20, 20, 40, then she stalled. durring this time, my adjustments to my adjustable regulator had NO affect, this told me she was either boiling fuel, or getting air. I felt all the fuel lines and none of them were hot at all. When the car stalled I unhooked the fans to make sure I saved the battery, I would say she sat less than 2min, so no way she cooled off. When I refired she ran as she does when cold or not driven and I proceeded to flog on her the last 3 miles home with no problems what so ever. THAT is what pointed me to fuel issues, it only takes a couple bubbles to make these inline pumps cavitate out.
I am wonderign if the Fram HPG-1 fuel filter is big enough and properly fitted for this purpose? IT is just like a remote oil filter, I just don't know it's volume and do not htink it has a way to vent back to the tank?
My plan for the system was main tank, LP/HV pump, filter/swirl pot, HP/LV pump, engine, return to main tank. One big circuit. I just worry that if the LP/HV gets air off and on, it will eventually fill the filter with air and the same problem will arise again?
I have an unbaffled tank running with an external inline Bosch fuel pump to a hot-wire EFI. No swirl pot.
I never have a problem with normal driving until I get below 1/3 tank and then only on right hand turns. As the nipple on the tank is on the passenger side, I recognize that it is un-porting. However, it only gives a minor interruption in power, not stalling as you experience. Therefore, I think the pump is easily capable of recovering from "cavitating".
Also, fyi, the pump is located well above the bottom of the tank and I only have a small filter just before and just after the pump.
I think you may be chasing something else.
|I was worried about this same problem when I built my MGBV8. I solved it by using a 1989 Range Rover 20 Gallon fuel tank. It has the swirl pot and pump built in. I cut the trunk out and dropped the tank through the floor so there is about 3 inches of tank in the truck. So you do loose some luggage space. I added a small spare tire from a Saab to help. The 20 gallon tank is nice with the V8. I know this doesn't help you with your OE tank. Maybe this info will help someone. I have photos of the tank conversion on my website in the fuel section.|
|Here's a real stupid idea, do you have the tank vented?. You say that the problem starts after a few minutes and sounds like the pumps are having problems, could it be that there is a vacuum forming in the tank? |
There must be less fuel returning to the tank that came out as the engine is using it so I asssume the tank must need to be vented.
|Here is a typical filter and mounts, $33.|
|Today I let her run for a good 10+min in the garage got nice and hot (to rule out it being a ECU issue). When I pulled out she ran great for the 1st couple minutes THEN started acting up again, quicker than usuall. I was at 1/4 tank though and she did the more classic smooth loss of power, but under that the pump was freaking out and she was bucking like usual when she misbehaves. SO I still am leaning to Fuel slosh.|
BUT, I have thought about venting also, and more and more I am thinking that could be a big part or all of it.. I may try that later today or tomorrow.. get it running to when it acts up then pop the cap off the tank and see what happens. THAT would be a great and simple fix!! In fact I think I need to test that today.
Thanks for that link, I saw that once and then could not find it again. I just wonder if it will have enough fuel capacity to work as a swirl pot? I am wondering also if I should have a vent in the filter, if the carb pump is putting out air to the filter, the filter would over time be full of air and the same problem happen.. Also is there any way to see if the filter empties for the bottom?? most filters go in and out from the bottom, so the air will still be getting to the EFI pump pick-up.. Fram makes the same set-up, model HPG-1. It is 3/8" in/out and rated to 90gph I think.
Keep the ideas coming folks, They are all usefull and give me more things to test and rule out!!
|I have ally tank (built by me) baffled horizontally and vertically, the fuel pump is Holley blue (noisy, very noisy) the filter is Bosch, free flow for injection system, the sender for the gauge is the early MGB model, Aeroquip hose with Freeflow fitting, the tank is vented by 8mm hose. In engine bay I have Holley regulator and Holley carb of course. No problem.|
|Does anyone have the part number for that Bosch Inline pump?? During testing this afternoon the pump made some ugly noises and I think the cavitation is taking it's toll on it.|
I had around 2 gals in the tank and she would hardly get down the street to the gas station, I now know my limit for pushing it before pulling in for fuel!
I FILLED the tank completely and it runs is great now. I ran it a good 15min after filling it, and ran it very hard and had no issues. I think the carb fuel pump and swirl pot are gonna be added next week, see if that helps.
|Larry-I too think you have a problem seperate from your tank.|
1st check for a vent. 2nd, check your thermostat to see that it is 195'. You will run rich until your system reaches that temp. Check your sensors- fuel & water temp.
When driving last night, the car was running fine, but was running out of "poop" around 3500 RPM. As this is a very new installation I got very concerned until I realized I had less than 2 gallons of gas & was driving a lot of curves. A fillup cured the problem.
In theory, the simplist install is an early tank, late model sender, using the tank line to a stock SU or equal pump to a swirl tank & then a high pressure FI pump to the fuel rail with appropriate filters./ The sender provides a tank inlet for the return line.
After reading this & other threads about tanks I decided that it was less complicated & more dependable to have the tank modified to include a swirl pot & new 1/2" outlet & just use a single FI pump. I had Glenn Towery do a tank for me & used a truck filter between the tank & fuel pump. I got a fuel pump & filter from a Volvo 240 Turbo. This comes as an assembly of pump & filter mounted on a steel plate with rubber isolators & was easy to mount to the side of the battery box with good accessability with the wheel removed. The turbo pump will suck gas, other Volvo pumps will not & require gravity or an auxillery pump.
|I know it is a pump/sucking air issue after todays testing. Soon as I filled the tank 100% she ran great, she was already full hot and had been acting up badly until I filled her up. Mine will NOT run with only 2 gals in it as tested today.|
So I am gonna do the carb, swirl pot EFI pump routine. All I need is the filter to put it all together.
|It just can't be a lack of swirl pot. I've done some strenious driving on a few litres no problem. May be it the large filter prior to the high Vol pump|
The filter needs to be fed from the bottom otherwise you get a vapour press' build up
Bosh part no.
I got mine through acompany called Petroject
Their stock no- 0580464070
the Bosh bar code on the box has this no. above it
0 580 464 070.001
So I guess thats it. Cost $140
The smaller low pressure pump is made by Pierburg
and is called a "universal autosuction rollervane pump which may be used universaly".
It developes only 0.5 barr but is able to draw up to 0.5 meter comfortably (they claim). It does draw through a large EFI filter up into the boot OK.
If your not using this feeder pump then you need a low resistance to flow gauze filter 14001 ,cost $15.
This filter needs to be fed through a 1/2" fuel line from the bottom, thence to the HP pump, which needs to be located level with the bottom of the tank. This means you need to place the filter in a loop of fuel line to ovoid vapour bubbles forming in it.
Better to use a feeder pump, the usual size fuel lines and a decent filter (which the feeder pump is easily able to draw through). This does away with all that gravity feed set up, its attendant prob's and leaves you free to put the pump where you like. Also the large filter (about 500ml) serves as a reserviour which probably explains wh
When I initially set up my EFI fuel system I made a mistake that gave exactly the symtoms you describe.
Orrigionaly I set up a loop of fuel line that conained a large filter, the HP pump and the engine. I fed this loop via a T piece, with the old 1800 carby fuel pump, which drew from the tank. I figured that the carby pump would keep the filter topped up (just like a swirl pot) and any addittional fuel the HP pump needed could be drawn from the filter.
What happened was the engine would run great for about 10 minutes (untill the engine warmed up) and then splutter and stop. After a wait I could then start up again for another 10 min's or so. What I believe was happening was that as the fuel circulated it warmed up and the vapor pressure increased, of course. When the vapour pressure was high enough the old carby pump would stop kicking over, as if it had filled the carby up, like it's designed to. I know the vapour pressure of petrol is about 84KPa at 38 deg Celcius, not to be ignored. The engine would run until it had used the half litre of fuel in the filter, then stop. After the vapour pressure had reduced in the circuit the carby pump would then kick over and fill the filter.
Sorry for the long winded response, but it might help you.
|HEH No problem with the long response. Not like mine are not huge!!|
I know it sounds wierd, I had NOO problems with the Carb set-up using the same tank, maybe it is the EFI pump I have, maybe a combination of things. But like I said once I FILLED the tank 100% she ran absolutely great. That tells me it is definitely a fuel supply issue, whether the tank is not vented properly, the fuel sender is making goofy air bubbles in the tank, or pure fuel slosh in the tank I don't know but all the signs point to somethign with the tank/pump set-up I have now.
I will see if I can get a cheap inline EFI compatible pump someplace to try out. Mine made some BAD noise when it was cavitating earlier, so I may have killed it with all the dry running it has been getting
|I have used a later 90s model Jaguar pump with success on a 80s Land Rover Defender EFI conversion. I bought the pump at Advanced Auto Parts. I am at the beach this weekend and the part number is at the office. I will post the part number tomorrow. It is an inline pump and cost me around $60 US. I used a carbureted fuel tank in the Defender and it had no problems.|
That would be great. I am HOPING that my inline will make it once I get it properly fed at all times, but I would like to have a spare on hand in case it decides it is done on a road trip.
I will of course keep everyone updated via the website. It hasbeen badly neglected of late do to "real life" and working on the car, but I hope to begin making more steady updates again.
I assume you've mounted the pump as close to the tank as possible, and at bottom tank level ?
Bosch pumps are notoriously poor 'suckers' I made the mistake of mounting mine originally behind the battery, with low pressure feed over the axle, it suffered the same symptons as yours once the tank reachd 1/3 full.
You might find the att. web site of interest. It shows all of the different fuel pump part numbers and maps them to 'their' pump model. By sorting on 'their' pump code you can see what other cars have a suitable pump for your application. HTHs
|larry, did you say the tank was vented properly? i saw someone else suggested it and i know i did not have mine done initially and i would come home from driving and the tank would actually be compressed from the presurre of being sucked in and than expand again as it sat. on the electric external pumps, i have tried 1/2 dozen of them, including the most expensive one ssold thru summit an djegs and i get a lot of noise when the gas level gets below 1/3 or after they heat up, i have made a change based on what the ricers use for their cars, even though most of these pumps are made to push not suck, and mine is mounte dbelow the tank less than 1', i am addig another of the same pumps in the engine bay and on the sam eline, it reduces the tasking on the single pump and drastically cuts down on the noise, i have seen it work on othe rcars and i assume it will on mine but willknow for sur ehtis summer, jim|
|Here is the part number to the Jaguar pump I used in the Land Rover EFI conversion. It is E8002 in Airtex, or Master brand. Good luck fixing your little problem.|
Thanks for the part number!! I might just go grab one of those and try it, or at least keep it for a back-up pump. I see a bunch on Ebay, so will whatch there as well, just need to get some specs to see it will flow enough for this motor, but I bet it will be fine.
I just found a possible solution to this issue which would work well for all of us EFI guys. It is a multi faceted solution that will cover BOTH issues we have discussed with one system. It can be bought "off the shelf" or built for 1/2 the price or less by yourself.
I don;t have a chance ot get to fully into it right now,but it was a source given to me by a Ford Bronco driver I work with and is what most of the EARLY bronco drivers do when they convert thier rigs to Ford EFI, so I know it will work for me no problem.
|Well Larry, why must you leave us hanging?? I feel like I just left the theater after watching the bad guys sneaking up on Hoppy. "To be Continued"...|
|Sorry guys, I realised I was late for work and had to cut it short, PLUS I have not tested the system or even got all the parts in hand yet. THis gets long liek I alwasy seem to do..|
The bronco guys have issues due to extreme terrain. This is two-fold. As we all talked about, the EFI pumps can't pull fuel well AND the bronco guys often uncover thier fuel pick-up's due to trail angles which EFI pumps and systems don't tolerate. SO when they go EFI they have both issues to deal with.
Thier solution is dual pump system using what they call a accumulator/filter. MUCH like what many here have said with the marine filter idea.
A LP/HV Carb style fuel pump pulling fuel from the main tank and sending it to the filter/accumulator, from there out to a EFI pusher pump and the engine. The key part here is the accumulator/filter assembly. IT is a remote oil filter base that is modified two ways. The outlet of the fuel filter is ported to the bottom of the filter element rather than left at the top. That way any air that gets in is not sent to the EFI pump. Since the carb pump is high volume, it will be feeding more fuel than the EFI pump can use, SO they also vent the top of the filter mount to let the air and extra fuel flow back to the fuel tank. That way if and when the carb pump gets air, it goes into the filter then gets vented out the top and back to the main tank.
The link here is to the tech write-up, it also has links to the website to buy the unit.
I have emailed the gentleman that wrote the article and he said in the 2 years he has run the vehicle he has not yet had EFI fuel problems and he HAS heard is carb pump pull air from the main tank with no affect on the EFI system. The nice thing is we can use inexpensive items to fix this problem as most of them use generic fuel pumps. I just ordered my filter and base locally for around $35 after tax. I will do the modifications myself. I already have a carb fuel pump and obviously the EFI one, so my system SHOULD be done mid weekend.
I will keep you all posted onthe outcome.
|Take a look at the second filter mount down (PER-1221)|
This is a fileter mount that takes two filters, twice the capacity!
|And you didn't have to spend the $400 on the RV8 tank! Way to go Larry! |
I will stop by and check it out soon.
MOST of those filter bases are made by www.tdperformance.com then the other Mfg get them, maybe tag them and resell for even more $$ THe onle I got is TD#1028. The issue I see with the dual filter mount as well as the 90* mount like I use for my oil filter on the MG is that you don;t have a good place to tap the port in to let the air out.. plus it is just darn HUGE!!
I figure if these bronco guys can do rock climbs and be 30* off horizontal for 3min getting over something I think it will be just fine for us...
FYI - I looked at my tank it is a 65-77 tank if that helps anyone. Was purchased at MOSS I believe.
Good point regarding the size of the filter carrier. Will you be using 6-AN fitings? 6-AN hose is 0.34" (approx 5/16") internal diameter, is that big enough? How about 8-AN to the engine and 6-AN on the return?
Not sure if this is what you are planning, but you might want to take a look. It sounds like what your Bronco fans are referring to. Low pressure/high volume pump to an accumulator and an overflow return. Accumulator is always full and bottom feeds to the high pressure EFI pump.
You could probably use some steel tubing capped top and bottom with a couple of bungs welded in.
Hope this is useful,
|I did some reading and found that VWs, Audis and other cars with Digifant injection used a low pressure transfer pump to a remote, combination high pressure pump/surge tank assembly. Also, take a look at this site and scroll down to the fuel pump/surge tank.|
Call me frugal but I refuse to pay the overpriced rates for pretty , soft, alum bits like AN when a simple heavy duty steel JIC flare fitting will do it just as good. So I use 3/8" JIC on 99% of my fuel system. Costs I think about 1/5th as much as AN stuff, and I don't have to have a special wrench to install it without marring it up.
Same idea but they incorporate it in as a filter as well. You can buy the kit fro,m BC's for $70 or build it yourself with a drill, and tap for a little less.
I JUST got my stuff in and this filter is HUGE!! I would say it hold between 20-30oz of fluid, based on sheer size.
I will let you guy know late this weekend how it goes. I have to get the old pump back in, move the EFI pump, do wiring and hosing, plus modify my filter base for it's new use and then mount it...
You are right about the size of the Wix 33281 filter, I estimate it holds 23oz of fluid. How do you plan to fasten the 5" (approx) long by 1/2" diam pipe into the filter mounting? Do you think epoxy will hold it?
|I got a piece of Alum tube while getting my fittings, we took the base in back and got one that was a tight fit. I got about 7 " then cut it once I had tapped it up in as far as I could..|
I THINK I finally have all the fittings I need, and found my extra low pressure 3/8" hose for the return. Any luck I can do the filter and EFI pump mounting when I get home. MAYBE drive it to a local mustang BBBQ tomorrow!!
|I should clarify, by tap I mean tap, as in gently with a BFH until it would go no further. (not blocking ports)|
|Well AFter an initial test run yesterday I will say IT WORKS!! I still want to keep running it more and more, but it seems to have solved the problem!!|
I ran it around the block for a good 10min with 3/4 tank and had not a single stumble or problem, I then took heron the freeway and ran her to a local Mustang BBQ, no problems. She made a little noise when I fired it up in the parking lot to show people, but I let the Fuel pumps rum for a min bepofre leaving and the system cleared itself, and the trip home was great!!
I will get a page written up on what I did and then post a new thread here when it is done.
|For the record (and those who take on future conversions):|
A fan shaped nozzle (a little like a guitarist's plectrum) attached the uptake tube inside the fuel tank will ensure that the pump can not suck in air from above and can happily get fuel from the last couple of litres - on a strait run !
Foam can be a mixed blessing - melted by some fuel - frequently blocking filters and needing some special baffling to allow for fuel uptake - not recommended by the specialists.
The larger of the two fuel filters used by the RR,RV8 and SDI holds about a pint and acts as a pretty good swirl pot for normal road use - WITHOUT a second pump.
The Bosch HP pump (number above) will draw fuel into this provided both pump and filter are primed.
If space is a concern, Landrover significantly reduced the size of the post-HP pump filter in the mid 90s. The feed to the HP pump can be redirected from the tank through the bigger filter and then to the engine through the new smaller filter recommended.
In the SDI the large HP filter was situated in the engine bay. Pretty dodgy practice with so much fuel but the much smaller filter now recommended is the same size as many other inline filters in engine bays. U Pays your money and takes your choice...
I personally favour the 20 gallon RR tank conversion mentioned above. The high volume/LP pump has invariably been the weakest link in the MG powertrain. A second pump is not always needed. The two filters/one HP pump is the cheapest solutions.
Sorry I was away when Larry re-started this thread.
|All good points RMC, but for pure simplicity and bang for the buck the system I am using is the best, hands down.|
I WILL agree that using a stock MG pump might not be a great idea though. A used Holley blue, red or any HV pump will work great. THat Bosch may be working well for many people but the inability to pull fuel is an inherent trait of HP EFI inline pumps.
I would thinkg that if you had to buy a HV pump and this kit also, you could get them all for $150, less if your a good deal finder...
|ake a look at this EFI pump, it appears to be fully self priming and can operate above the tank.|
|That is a great pump. But they are $350+shipping the places I have looked.|
|The ideal solution is to get someone to weld in an "intank" style of pump. |
Then again all you really need is to get them to put in an acess hatch, a flange with some threads tapped into it and a lid. You can then do as you like as the bosh pumps may be immersed in petrol. Maybe use a polyproplyene cutting board (which are very cheap) as the lid. You could then put your electrical connections through this (use a tight screw), attach a small container underneath for the pot, and you're done.
Or maybe the Range rover pump is small enough to fit through the sender hole? From the manual that pump appears to be fairly thin, and the sender hole is fairly wide. I see no reason why the pump need not be on an angle instead of upright.
You could reshap the top attached hatch a little and then all you'd need do is poke it in there, problem solved. No swirl pot, but if the uptake is in the correct location then no problem.
Does anyone know the maximum diameter of the rangerover pump? because if it does fit then this is the best solution for money spent by far and away.
|Most intake pumps are small enough that with some finagling they may fit. the other issue though is making room for your fuel sender to swing freely.|
Maybe it is different in other locals but I could not find a single shop that would touch a fuel tank out here. :-(
This thread was discussed between 17/04/2004 and 29/04/2004
This thread is from the archive. The Live MG MGB GT V8 Factory Originals Technical BBS is active now.