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MG TD TF 1500 - switch for fuel pump (td mkii)
|Have a 52 td mkII that(as you know) has two fuel pumps.One clicks with the ignition and the other is wired directly to a toggle type switch located in the glove box. The entire wiring is extremely scary, but have a wiring loom from British Wiring ready to install(also the subharness). The loom is not setup for the second fuel pump. Anyone have any thoughts as to how I might correctly wire this, where should the switch be located or should it be wired in tandem with the other pump. Also, any digital pics would be helpful that shows the correct location of the loom(both under the bonnet and under the dash). To say the po owner trashed the wiring is a major understatement - by George it has construction wirenuts throughout. Been through the archives - taking the seats out does appear to make sense. I am somewhat leary of my abilities under the dash but am going to tackle the job anyway well aware of the risks - again pics would be a great help. My home email address is "email@example.com". Thanks in advance for your thoughts and help.|
|TW - I am looking for some picture that I have of the fuel pumps for the TD MKII, but I am not sure that they will show what you are looking for as they were taken to show the plumbing rather than the wiring. I can tell you this much, the pumps should be wired in parallel. I don't know if this means that the power lead from the harness goes to one pump and then a jumper wire goes between the two pumps or if the power lead is 'T' somewhere behind the firewall and each leg goes to a pump. Either method would work fine. The main consideration is that the two pumps whould be powered up at the same time. Obviously the PO had wired the pumps as a primary pump, withthe second pump being used as a switched back up. While this set up will work, it is possible that you could experience fuel starvation with just one pump trying to supply the MK II engine (although the early TF used the same engine and just a single low pressure pump with no problems that I know of).|
If it is any consolation, every MG I have ever owned (quite a few over the past 40 years) have had the wiring in total dissaray from the previous owners. My contention is that the only thing wrong with Lucas electrics is previous owners. Good luck - Dave
|Thanks Dave, I am still flying by the seat of my pants as this all new to me. I will eventually find a workshop manual that will surely help with many questions. I hate to tie up the board when a little sluthing will uncover the answers. As previously mentioned, this is my first classic and I would like to do things as right as I can.|
|To the best of my knowledge, limited-inpaired-etc. as it might be, there is no switch involved. They are both hot at all times with a jumper across the end terminal. Plumbing has one going to the front and one to the rear, with the balance between the carbbies. The front carb has a double fitting as at the rear on a std TD/TF.|
|To tw hager --- I have dual fuel pumps on my TD just like Mk II's but I only have one running. It is one that has been made electronic (no points). The other is my backup. I made up a jumper so they could be run at the same time if it was needed for any reason. But it never has been. The spec for the pumps is 30 gallons per hour, no way is a TD engine going to consume 30 gal. in 1 hour.|
So my conclusion has been that the two pumps were for reliability in a racing situation.
One time I had to switch to the other pump because the electronic pump didn't want to supply enough fuel. When I took the electronic pump apart it was full of gray powder which my restorer friend tells me came from the gas tank. When it was boiled out, apparently the old varnish in the tank doesn't come out but changes to this powdery substance which will stay in the tank for a while then decide to come loose all at once. I've been running with the electronic pump two years since that happened and have not had another problem, nor have I installed the fuel filters I bought right after it happened.
I hope this story helps you decide what to do with the wiring of the two pumps. Failed fuel pumps are one of the common causes of "T" series not getting you home, the extra pump with it's own fuel line from the tank is insurance that just by suppling 12 volts to the second pump you will get home OK, (it's a great feeling).
|R. K. (Bob) Jeffers|
|My TF has a switch on the backup pump to turn it on and off. I like that setup as I can't see any point in running two pumps at the same time. It just akes an extra wire run from the switch back to the pump. I have a toggle switch mounted in the under dash shield but I think it would be better to use the aux switch as I don't have fog lights.|
|Good grief Bob, what kind of a pump do you have on your TD! Even the double ended, low pressure pumps used on the Rolls Royces, with both ends pumping at once only put out 24 gallons per hour. The standard Low Pressure pump used on a TD puts out a maximum of 9.6 gallons per hour, so combined, the two pumps would only put out 19.2 gallons per hour. I will agree that 19 gallons per hour is a bit of overkill for a TD (by almost an order of magnitude). |
Dave C. I agree with the switch in the case of the TF to use the second pump as a back up, I do the same on our MGB where the fuel pump is a bear to change out on the road. The TD MKII however came with two parallel pumps that were designed to work at the same time (still overkill in my estimation, but they were designed that way). One caveat regarding your back up pump (and Bob's also). If the back up pump is a points style pump, it may not work when it is needed because of the points filiming over due to disuse. I would suggest alternating use between the two pumps to keep any film build up burned off of the points. Bob, in your case, I would suggest using the all electronic pump as the back up in that it doesn't have any points to film over. Cheers - Dave
|Dave Dubois --- Maybe I am remembering the specs for another pump? But I thought that's what Lawrie Rhoads told me. I work closely with him on WW motors.|
I hadn't thought about the possibility of the backup pump getting it's points filmed over. The reason I hooked it up the way I did was to check the reliability of the electronic pump. I have had several other converted pumps quit on me. This one seems OK but I don't know what the difference is.
|R. K. (Bob) Jeffers|
What is a WW motor?
|Good point on the points Dave D. My switch on the under dash shield gets kicked on once in a while inadvertently :-) But I think that pump might be pointless, (pun intended).|
Interesting on the stock two pumps for the TD. That means when one goes out you probably wouldn't know it until the second one stops anyway or can you hear both running? I guess one could get out and feel if they're both working. I kind of like my setup.
|Bob - If your present electronic pump is the SU all electronic unit, they have become very reliable. They apparently had some start up problems with them, but they appear to have worked out the bugs. I put one of their kits in a fuel pump that I have been using in our MGB and it has performed flawlessly for about three years now. Being a Hall effect circuit, it depends on a shading piece to counteract magnetic fields and if that becomes loose and changes position, the pump will fail, but there no longer seems to be a problem with that happening. The only other thing that will stop the pump is a burned out swamping resistor in the coil, which is why I recommend not installing a filter between the fuel tank and the pump. If the filter clogs, it will stall the pump in a current on condition which, if power is left on while the pump is stalled, will burn out the resistor.|
Dave C. - I doubt that a person could tell that one pump was not working, although the two pumps working together would give a somewhat syncopated beat since they are not synchronized together. Most people would never hear the difference and can't hear the pumps anyway while driving. That is why I question the need for the two pump to be used at the same time anyway. I think that in other than conditions where the car is racing, the extra fuel volume is not needed. Using the second pump as a backup makes more sense to me as long as the back up pump is not one that will fail due to filming of the points. The backup pump that I put in our MGB is one of the little, square, run all the time, make a lot of noise, Facet pumps that are all electronic and completely sealed. They run about $40 at NAPA and can be hidden under the car. Anybody interested in installing a back up pump can read my article at: http://www.custompistols.com/cars/dave/BackUpFuelPump.htm
Please note that this article is written to MGB owners, but applies equally well to T series cars. Cheers - Dave
|Dave Dubois --- No, my elecronic pump is one of my designs altho it is a modified SU. I use an infa-red interupter type module, and put a small piece of brass on the toggle mechanism to interupt the beam. The first one I built is the one on the TD and has worked flawlessly. All the rest of them that I built failed the first time the weather turned hot. Still have not figured out what I got right on the first one and not on the rest.|
I understand that the people who bought SU did for a time offer a kit to convert to electronic, but I didn't manage to get one of those kits.
|R. K. (Bob) Jeffers|
|To John, Ct. --- WW motor is Windscreen Wiper Motor.|
Sorry if I used too much abreviation.
|R. K. (Bob) Jeffers|
|Bob - The conversion kits are still available from Burlen Fuel Systems <http://www.burlen.co.uk/>. The part number is EPK 12N (negative ground) and EPK 12P (positive ground). They are however rather expensive, around $80 after shipping. They are very straight forward to install and work very well. The pump runs a bit faster with the modification and while it still has the tick, tick, tick of the SU pumps, it is a bit subdued from the pumps with points (most of the ticking of the pumps comes from the toggle throwing over). Cheers - Dave|
|Quote David D"The backup pump that I put in our MGB is one of the little, square, run all the time, make a lot of noise, Facet pumps that are all electronic and completely sealed. They run about $40 at NAPA and can be hidden under the car."end|
Yep, that's what I've got and I can tell when I bump the switch on that it's running due to the loud noise. A very good backup though.
I find the stock pump seems to be pretty reliable if you drive the car frequently.
|Dave C. - A points style SU pump will last for many years if it is used regularly. If you want to tame the noise on that little Facet pump (your are right by the way, it is an excelent little pump) is to get some sound mounts for it. They are available from Pegesus Racing <http://www.pegasusautoracing.com/advcat.asp?CategoryID=AIRFUEL>|
Scroll down to Fuel Pump Accessories and then down to mounting kit. Cheers - Dave
Thanks for the link. I've got some of those isolaters/shockmounts in my airplane parts supplies. They're used for instrument panel mounting. Guess I'll have to "do the mod". Thanks.
This thread was discussed between 24/02/2006 and 26/02/2006
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