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MG MGB Technical - Two fuel pumps??
|Hi, I would like to try and be one step ahead with regard to breakdowns out on the road. If I carry a spare set of points a condensor and a coil, I believe maybe wrongly, that the weakest link after this is the fuel pump. I'm thinking of teeing one into alongside the original one and having a switch on the dash to operate it if needed.|
Question is, has anyone on here done this, and am I being too suspicious of the S.U.pump?
My midget used to give me grief years ago (in my teens)and I've never forgiven it!!
|Quite common. I have small flow through pump between the tank and the SU with a switch under the dash. Put it in as a precaution, but have never had to use it. |
A simple one like this will work fine
|Bruce TD4139 Cunha|
|C Caygill - See the article, Backup Fuel Pump in the Tech Articles section of my Homepage at: http://homepages.donobi.net/sufuelpumps/|
You can ignore the part about the shutoff valve in the fuel line from the tank to the pump. All you have to do to avoid fuel siphoning out of the tank just by disconnecting (or just loosen) the fuel line at the end of the tank. Cheers - Dave
|Highly recommended. My 18 month SU died terminally. One flick of a switch and i was up and running again. Most pumps will "flow through", just plumb them in-line and wire to a DPDT switch. Look at Dave's site. I used a Facet, which is now the primary pump with an electronic SU as back up. Not sure whether i would use a points SU as back-up though.|
|They do fail, but the beauty of the points type is that they can usually be got up and running with a sharp rap - which should then be used as a trigger to do something about it and not keep relying on said sharp rap. Electronic pumps can also fail, usually totally.|
However certain faults could prevent the flow-through scenario getting you on your way again, as opposed to changeover taps each side. Whatever pump you used it would be wise to periodically switch from one to the other ... as long as you didn't wear them both out together ...
Personally I carry a spare, and have been able to change it at the roadside with all four wheels on the ground (chrome bumper car). Why did it fail on the road? Because I ignored the warning signs once too often instead of getting a round tuit.
|All very good replies. Thanks very much. Yes I remember using the jack handle as a beltatronic device to get the old pump working on my midget in my teens. |
|"Not sure whether i would use a points SU as back-up though."|
I would say definitely not! The points depend on a very small sliding action between the contacts to keep the points cleaned. That sliding action and the small amount of arching to keep the film that builds up on the contacts scrapped and burned off. A SU fuel pump that sits idle for long periods of time will most likely not work when it is needed. Even with the all electronic SU fuel pump, I would still switch pumps periodically to insure that it will still start up. I use the SU fuel pump as the main pump and the a little square, make a lot of noise, Facet pump as the backup. Even then, I periodically switch pumps to insure that the back up hasn't fallen off and still works. By the way, if the Facet pump is installed on sound mounts (the ones that are used in the later Midget's exhaust system) makes all the noise go away. Cheers - Dave
|What on earth are you guys doing to your SU pumps that they only last so short a time?|
|Sam - You just got through telling the MGA forum, the problems you went through with your fuel pump and it still doesn't work. The SU fuel pump is not the snap that people sometimes think that they are. The all electronic SU fuel pumps will last almost forever with no maintenance - not so with the points style SU pumps. The points style SU pumps require a minimal amount of preventative maintenance yearly to insure that they will continue working properly.|
Cheers - Dave
|"The points style SU pumps require a minimal amount of preventative maintenance yearly to insure that they will continue working properly."|
I really can't agree with that. I changed the points-style pump on my roadster when that packed up on a trip, done nothing else in 26 years and 60k miles. That only needed the points refacing and diaphragm throw checking, and when I got fed up with the electronic pump (Moprod, not SU)on the V8 going intermittent that was swapped for the roadster pump. That was many years ago, and again nothing since.
An annual burnish of the points *will* keep them working long-term, but it doesn't need to be annual unless you do a very high mileage. I'd expect a minimum of 30k and maybe 50k or more before getting problems.
|Just got my MGB out of storage after 9 years. It's got a points type SU pump. I don't even have a battery in it yet. |
Needed to get the old fuel out of the tank. Hooked up a battery charger and turned the ignition on. At first nothing but after a rap on the body off it went. Turned ignition on and off several time to see if it would restart and it did every time.
That is only the second pump I have ever had in the car. Bought the car in 1978 and only changed the pump in the early 2000's. I always just put new points and a condenser in followed with setting the diaphragm exactly as described in the workshop manual.
I'm with Paul on this one.
|I've owned, at least 10, SU pumped vehicles since the late 1960's. I have never had an issue with a pump until the recent failure of a very youthful one. |
My previously acquired pump, an electronic SU, has given 12 years of faultless service, (tempting providence!!), When did Burlen take over manufacture from SU?
Annual maintenance is preventative. I've no doubt some cars would last many years without an oil change and many brake systems would still stop a car with ancient fluid in, doesn't make that a rational for no maintenance. Some 40 a day smokers live to be 90 or Russian roulette might not blow your brains out at the first spin of the chamber! But go down that road at your own peril!!!!
|difficult to beat one of these at the price. i carry one.|
it will push or pull, meaning if main pump fails you can put it in the engine bay and connect it to existing pipes.
|Hard to predict what will fail to leave you stranded at the roadside. I ran a 79 GT as my daily driver for 15 years & have had a 72 roadster for 18 years as a fun car. In all that time/miles the su pumps have never failed me. I have to give the roadster one a tap at the beginning of each summer after its been sat all winter asleep but that's it.|
I've been stranded at the roadside twice. Once was a bad rotor arm on the 79 & the other was a water pump that sprang a catastrophic leak on the roadster. I've had lots of other issues of course but none that had me unable to limp home.
|I've mounted a Facet pump in the engine compartment. Iv'e tried it and it pulls fuel through the S.U. pump fine. Also the S.U.pushes fuel through the Facet pump.|
However I've decided to have the Facet pump in situ and ready for action with a wire a on crocodile clip in case of emergency.
So I'll just swap the fuel pipes over, clip the 12v supply on and away I'll go...thats my theory anyway.
|Many people overlook the fact that Facet pumps (or copies of Facet, which most of them are now) have double the pressure an SU needle and seat is designed for. A fuel pressure regulator is recommended.|
Besides the fact that 'Facets' are very noisy.
Why not have a spare SU if you think it is needed.
I stand to be corrected, but I was under the impression that the Facet type pumps were available in several pressure and flow ratings
If you mount your Facet type pump on a pair of them little double ended rubber mounts they are quite acceptable noise wise
|An excellent alternative pump is the Webcon. The low pressure model is designed specifically for carburettor applications with a pressure output of 2.5 - 4.5 psi. I had one on my Lotus Elan and it performed, and sounded, just like an SU pump. It certainly didn't clatter away like the Facet cube.|
|You are not wrong Willy. The Facet "cubes" are rated between 2.5 and 7 psi, depending on specification. Pos-flows start at 1.5psi and the cylindricals max out at 8psi. Burden reckon the SU viton tipped valves can handle 4 psi max, all metal ones less than that. Higher flow rates are usually accompanied by higher pressure, hence the need for a pressure regulator.|
|Willy, looks like I am wrong about being able to get lower pressure Facets. Many years ago when I fitted one I don't think their range of pressures was as good at it is now. I just checked their website and found this information. I still hated the noise despite rubber mounting so I just bought an electronic SU for my V8.|
|The Facet Cube pumps come in the following range that will work with the MGBs 1 - 2psi, 2 - 3.5psi, 1 - 1.5psi. Their Posi Flow pumps come in the following range 1.5 - 4.0psi, 2.5 - 4.0psi 1 - 2psi. See the charts at: http://www.facet-purolator.com/index.php I have one of the cube pumps in our MGB as a backup at the flip of a switch - so far I have not needed it after having to change out a pump on the side of a major North South highway many years ago. Cheers - Dave|
|I've just fitted a Posi-Flow 60107, as a primary pump for my V8 roadster. It gives 7 - 10psi and max 40 GPH but does need the pressure regulator. The first one I fitted didn't work "out of the box" which is slightly worrying. But having fitted the replacement, supplied very quickly by "Fast Road Cars", the upside is it is reasonably quiet. In fact on cotton reels it is only slightly noisier than the SU!|
This thread was discussed between 29/08/2016 and 16/09/2016
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