31 replies to this topic

[dklawson]

Dan's got a good point. If originality is important to you the rebuild kit could be just the ticket. With a new diaphragm and the Hall-Effect switch replacing the points your rebuilt SU pump would look the part and last at least another 38 years. It's something to think about.

[Gr4h4m]

Dan I'm going to have a look at it. However you can get Q&H pumps for the same price as the re-build kits...

[Gr4h4m]

Doug L I have just seen a pic of your Facet pump that I commented on July last year (Very clean install)

I have installed the same pump I have a couple of Q's

- what is the breather type plastic pipe for on the SU and can I leave it disconnected?
- Do you use a regulator? I have got the low pressure 2.5 - 3 psi as I didn't want too much fuel
- DO you have a safety style cut-out in case of a crash as I have noticed that these pump all of the time, with a constant tick tick (At least you know its running:))

Edited by Gr4h4m, 24 March 2008 - 10:52 PM.

[Gr4h4m]

well I have found out that the plastic pipe on the Su was a breather that goes into the heal board... just rare to find them still connected. I have fitted a fuel pressure regulator....

In my haste I didn't move the black sire on the coil to the correct side and when I went to start the car I burnt out the black wire in the dizzy the one with the spade connection that exits out of the cap. I have a spare so I have swapped it and also the points, condensor and the coil (I wanted a sports one anyway). Could I have damaged anything else? Where do the three wires go on the coil so I can check them for continuity? One goes to the dizzy but I'm not sure about the other two.

Thanks

[dklawson]

Hi Graham, I'm sorry I missed a couple of your posts on this thread.

You've already discovered the purpose of the SU vent tube so nothing I can add there. It's fine to leave disconnected.

So, did you leave your car positive earth or did you switch it to negative earth? Regardless of the car's polarity, the Facet pump should have its black wire connected to "negative" and the red wire should go to "positive". It is my understanding that the Facet pump's metal frame is isolated and not connected to either wire.

I do not have any safety features on my pump. The wiring for my car is stock even though the fuel pump is not. You would never do this on a modern car but my car is now 44 years old and this is an area of the wiring I have not tampered with.

Your car is of comparable vintage to mine so presumably the wires you're asking about will be two white wires and one white/black. The following information is for a car that is NEGATIVE ground/earth. The two white wires go on coil (+). If you're using an OLD coil that is marked SW and CB, these wires go on the CB terminal. One of these wires comes from the ignition switch, the other basically goes off to the fuel pump. The white/black wire goes on coil (-) terminal. The other end of this wire goes to the terminal on the side of the distributor.

I'm not picturing what happened with your coil connections. It might be that you moved one white wire to a terminal shared by the white/black wire. If you did, the second you turned on the ignition (with the points closed) you would have a dead short and the wire in the dizzy would burn out almost immediately. Double check before putting the power back on the coil. Two white wires on coil (+) and the single white/black on coil (-)... for a negative earth car.

If you bought a low pressure Facet pump (around 3 psi nominal), the regulator will not be necessary. A good regulator will cost a lot more than the Facet pump. If you bought the flat, pancake Facet/Purolator pump, you'd be better off without it. They are notoriously inaccurate and I've been told that their pressure settings drift over time. Over here, the preferred regulator for British cars is the low pressure Holley regulator which costs about the same as the Facet pump.

[Gr4h4m]

Thanks for your reply. I have switched to neg earth. Yep the black wire in the dizzy burnt out as soon as I turned the key (I had the wife on fire watch) this casued loads of white smoke. I have cleaned this all out of the dizzy and replaced the points nad condensor.

My car is a Mk2 1970 so a bit newer than yours.

The three wires to the coil are:

Black
White with a brown stripe
White with a black Stripe - This one goes to the side of the dizzy

They are now all swapped over the opposite to when the car was + earth. I was wondering if I could have burnt anyting else out. I will check the locations of the wires tomorrow as I'm not 100% where they are on the coil sat here in the front room.

Thanks for your help

[dklawson]

Graham,

I'm concerned. You implied that the car and its wiring were intact and operating before the polarity swap but the color codes you're saying are connected to the coil do not make sense. I don't have a wiring diagram for your 1970 but Lucas didn't generally change the color codes they used over the years. Therefore, what I see in my diagrams up through 1969 should apply to your car.

Black wires typically are used to indicate ground/earth connections. Perhaps a previous owner replaced a damaged coil low tension wire with a black wire. However, you need to confirm this. If you find a splice, this is a situation where I would correct the wire color now. You should have a white wire between the ignition switch and the coil (+) terminal.

The white/brown wire is equally disturbing. This is typically used for an oil pressure warning switch. The proper routing of this would be: White wire from ignition switch to the warning lamp, white/brown wire from the other side of the lamp to the oil pressure switch. When the oil pressure is below about 20 psi, the switch and it allows current to flow through the lamp. I can think of no situations where a white/brown wire should be on the coil. Really look at this aspect of your wiring. Determine where the other end of this wire goes on your car. IF indeed you find the other end of the white/brown wire is on the oil pressure switch, every time you switch on the ignition you will have a dead short between coil (+) and ground. Again, I can think of no reason in the original factory wiring that the white/brown wire should be on the coil.

The basic wiring should go like this: Switched power coming from the ignition switch going to coil (+). If you have an electric fuel pump, some wiring schemes use a second coil (+) terminal for the fuel pump wiring connection point. Thus, there may be two white wires on coil (+). The only other low tension wire on the coil should be the white/black wire going to the side of the dizzy.

[Gr4h4m]

DK I have been out at the car this eve and recorded the wires. These are there positions now, they were reversed before I changed to neg earth

Coil +
Black wire (Which has a white cotton overbraid it had just worn off a bit.
Beige (I said white before but they could have faded over the years) with a brown stripe

Coil -
Beige (I said white before but they could have faded over the years) with a black stripe this goes to the Dizzy.

The car is very very original I can't see there being any wiring changes I might have misslead with the white, but it could have faded over the years.

[Gr4h4m]

Oh I found I was using "R" plugs I have swapped them for my old ones but still no joy the can has started three times in god knows how many try's. It must be something broken

[Dan]

I agree with Doug, white/brown was only ever used for the oil pressure switch. It emerges from the loom in the same location as the coil wires but that doesn't mean it should run to the coil. Look at the rear of the speedo, if the warning lamp connection is white/brown take the other end off of the coil! Something is amiss with the wiring.

Get the meter out and check that this black-with-a-white-cover wire is indeed an ignition supply.

[Steve D]

Have you tried a different coil. It may have a break down after you wired it up the wrong way round.

[dklawson]

The coil really should not have been affected by any wiring mistakes. In normal operating mode is connected with a full 12V across it. Even if a mistake were made, you could not have exceeded 12V or run current through it in an unexpected way. If the polarity on the coil is connected wrong, you have reduced spark potential but it's not going to burn the coil out.

I feel better now about the black wire since you say it has the white cotton braid on it. As Dan suggested, disconnect the "black" wire from the coil, turn the ignition switch on, and measure from the free end of the black wire to chassis ground. You should find +12V if the "black" wire is the live feed from the ignition switch.

Since this is a relatively early car, you may still have a 25D4 distributor. I think the following also applies to the 45D but others will have to confirm it. There should be two fabric covered high-flex wires inside the distributor. One goes from the spade lug connection through the dizzy housing to the moving arm connection of the breaker points. The second high-flex wire goes from the breaker plate to the dizzy housing. You mentioned that one wire burned out when the wiring was wrong. Go back and look for the other. If the second wire is missing or burned through you'll have intermittent earth/ground connections for the points and may have trouble keeping the engine running.

Since you've replaced one of the high-flex wires, make sure your connections are right inside the distributor. If you have a 25D4 distributor, there are insulating washers for the points that must be in the correct locations. If they aren't assembled in the correct order they create a short that renders the points ineffective and make it impossible to start the engine. On the 45D distributors I have a friend who had problems with the forked spade lug on the condenser wire. If the condenser wire lug is incorrectly positioned it can create a short to ground that also prevents the coil from firing.

[Gr4h4m]

Have you tried a different coil. It may have a break down after you wired it up the wrong way round.

Put a new one on incase the old one was burnt out I was getting strange reading on the multi meter

[Gr4h4m]

DK its a 25D. I will check the inside again.

[dklawson]

Put a new one (coil) on incase the old one was burnt out I was getting strange reading on the multi meter

If the coil was working before, there's no wiring mistake you could have made that would damage it.

What do you mean you got strange readings on the multimeter? Remember that to measure the resistance of a coil you MUST disconnect the low-tension wires. For a normal coil you'll see a nominal 3 Ohms across the low-tension windings. The resistance between either low-tension terminal and the high-tension spark plug terminal on the coil will be on the order of several k-Ohm (and vary from manufacturer to manufacturer).

Depending on your multimeter, getting either of these readings MAY take several seconds. Resistance measurements are made by passing current from the battery in your meter through what you're trying to measure. (That's why even with an analog meter you can't measure resistance if the meter has a dead battery). Since the coil has a ton of inductive coils in it, it MAY take your meter a number of seconds for the reading to stabilize (it's effectively charging up the coil a bit).

Footnote: For example, one of my meters has a function to measure capacitors. The larger the value of the capacitor, the longer it takes to read. I am not exaggerating when I tell you that for caps near the top of the meter's measurement range I may have to wait 10 or more seconds for the reading to stabilize. The coil is a large inductor and MAY behave similarly with your meter.