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Ignition and fuel system renewal

Neil Potter


[u]November 2013 - January 2014[/u]

As this is the most recent and most extensive work I've done to the car myself, it's time to record what went on for posterity. Doubtless photos will follow when I can face crawling under the car again!

When the car went in for suspension work to SJs back in the summer, it also underwent a quick tuneup. The result improved the low end torque but didn't cure the hesitation I'd had, on and off, but usually when hot and at about 3000 revs. The temperature would suggest ignition, the revs suggested fuel. Steve suggested I look at the carbs as I'd put new leads and coil in fairly early on.

Now, I knew that the carbs had been "refurbed" back in 2010, but this was by the garage which was also responsible for the drivers side seatbelt replacement (with something which looked like it came from a 1970s van) and one or two other unimpressive repairs. I was keen to get into the carbs and see how they worked, so, armed with Des Hammill's excellent book on Dellorto and Weber sidedraught carbs, I set to work. Off came the turbo plenum, the trumpets, the throttle cable, the choke cable I'd only just replaced, and the fuel pipes.

As an aside, don't you just love the names of some of the things which go on these cars? To tell people your car has a Pertonix Ignitor, or a set of auxiliary venturi, makes it sound very sci fi.

The carbs eventually came off, dribbling petrol over me, and I got my first proper look at the distributor. I'd only ever felt it, vaguely, while replacing the HT leads - a job I'd initially thought was impossible. Now I had access, it seemed daft not to give it some attention too. I knew that centrifugal timing springs rust up and affect the timing, and wondered if this was part of my hesitation problem as well. So the dizzy came off too.

These actually proved to be the least of my problems. They weren't in bad condition internally; some varnish at the bottom of the bowls but not too bad. The choke pistons were very stiff, as I knew. Gaskets looked OK. All the jets/correctors seemed clear and were all original spec. Nonetheless, the carbs were stripped (except for the butterflies/spindles) and sent off to I Cleenz Macheenz near Croydon for a proper ultrasonic soak, while I ordered a rebuild kit from Eurocarb.

The trickiest bit was unscrewing the large brass countersunk screw which fits around the camshaft which works the choke pistons. This needed tapping with a screwdriver and hammer as you can't turn it (the face of the screw is a circle with two notches cut into either side). Watch out for the ball bearings behind the rod weight when you tip out the accelerator pump one-way passage.

When the carbs came back from the clean, expertly packed, they looked great; like new actually. The rebuild was very satisfying work, as I'd taken photos of all the bits as I'd removed them, and bolting it all up again was like making a Lego model. I polished the brass bits and copper-greased the choke piston. Pretty impressed with the quality of these carbs - not that I'm an expert, but there didn't seem to be any gaps or pointless aspects of the design.

One thing you don't get in the Dellorto kit is the sealing washer for the fuel connection. What you want are 2x M12 "Dowty sealing washers" available on Ebay for pennies.

When bolting back to the manifold, put some new rubber O-rings in to the mounting plate - one on either side of each plate, so 8 needed. They're 50mm diameter 4mm cross section. Again, Ebay is your friend.

When refitting the choke cable and the connecting rod, do this before you refit the turbo pipe to plenum. Otherwise you'll be taking it off again or fiddling about with the tiny bolts which hold the connecting rod to the choke cams.

[u][i]Fuel system[/i][/u]
At the time the carbs were off, I'd intended to replace the (original) hose running to them from the fuel regulator. Then I read an article about E10 petrol corroding old rubber, and resolved to take the opportunity to replace all the hoses in the system. I knew the fuel filter looked old, and the Unipart part number was no longer available. Additionally, the tanks were new alloy but the connecting pipe was old, rusty-looking steel, and for some time I'd had a suspicion that rust from the old tanks might still be affecting the fuel filter and pump.

After using the pump to drain the remaining petrol into an illegally-sized jerry can, I set to work.

Be warned, when disconnecting the balancing pipe and hoses, you WILL suffer a small deluge of petrol, even if the tanks have been pumped out and the fuel pump connection is dry. Not a lot you can do about it except have a pan handy.

Here's what I put on:

Fuel filter - Mann Filter WK830/7 about £6
Fuel pump - [url=""]This[/url] generic lookalike from Ebay, £40 and works fine
Balance pipe - alloy tube 25mm diameter, I think it was 55cm long, but I had to cut it down a little about £15 I think with the beading added
Balance pipe grommets - 38mm diameter £pennies
Hose clips - JCS Hi-Grip stainless £1.40ish each but worth it
Hoses - a few different diameters and grades, all nitrile and SAEJ30R9-or-higher compliant:
Tank to balance pipe [url=""]25mm marine reinforced fuel hose[/url] which is very heavy duty and hard work to bend to fit. Not totally happy with it to be honest, but it is secure and does the job. The alternatives I could find weren't as ethanol proof, but I probably could have looked harder.
Tank to pump 12mm
Pump to filter 7.6mm
Filter to fuel pipe 9.5mm. This one could have done with being narrower at the filter but I couldn't get the 7.6mm to fit onto the pipe. The larger pipe is secure at the filter.
All the rest are 9.5mm

I also replaced the plenum to purge pump hose, although it didn't really need it. 9.5mm hose was really tight on the plastic connector to the plenum.
Not much fun grovelling under the car in a cold garage in winter, but I'm happy with the results. The old pump and filter were full of rusty flakes, so I'm glad to have replaced. Check the fuel pressure once you've replaced the pump and/or filter - the new pump had much more oomph and I needed to reduce it down by adjusting the regulator. The old balance pipe was pretty rusty on the outside but not too bad inside, so could probably have been repaired. Worst part was getting to the old hose clip on the top of the fuel pipe - tricky access. Once all the petrol has gone just cut off stubborn clips with a Dremel rather than muck about trying to unscrew them.

Have to say, I'll be happy never to see the distributor again. I haven't ruled out going for a crankcase sensor/coil pack/programmable timing option in the future purely to avoid ever having to go near this again!

I sent mine off to Martin Jay, the "Distributor Doctor" for a refurb. Took a while (6-8 weeks) and isn't cheap at £230, but it comes back like new and you know it's done properly. You also get a cool graph with the timing curve shown. I was tempted by the Aldon Amethyst device, but wasn't sure I wanted to trust my engine to it and you still need a distributor sparking away under the carbs, so it didn't seem quite right to me. I have been more-or-less keen to preserve originality where possible.

At the same time, I bought a Flamethrower coil to go with the "new" dizzy and the Pertronix Ignitor which was already fitted. I'd heard that the Lucas gold coil (mine was new) wasn't always to be relied on.

During the travails with the dizzy, I refitted it without the carbs (easy), and with the carbs in place (OK). It's much harder with the plenum backplate/trumpets fitted, and I found it impossible with the plenum in place. It's easier to remove the cap first, then guide the dizzy out trying not to snag the vacuum capsule or knock the rotor. I managed to knock off one of the terminals on the oil pressure sender, requiring lots of swearing and some soldering to repair.

[i]Flamethrower coil causes problems[/i]
These bad boys are expensive but top quality. You can gap your plugs an extra 0.1mm due to the extra voltage, which intuitively is a good thing. BUT, what I found (the hard way) is that they don't work with the standard Lucas rev limiter fitted to my Esprit. Don't do what I did and assume that your intermittent spark from the coil to the dizzy is due to the electronic ignition failing. I thought I'd managed to fry my Petronix at some point (although I removed it and it tested out OK on the bench), and ended up destroying it trying to fit an Accuspark module to the Pertronix baseplate. That plan failed, and I ended up with a new Aldon Ignitor I shouldn't have had to buy.

Most irritatingly, I'd got it running OK without having connected up the rev limiter, then put the plenum back together, made gaskets etc, before finding it barely coughed when I tried it all out having connected up the limiter. So as well as getting an unrequired Ignitor, everything got dismantled again for the sake of the rev limiter not liking the coil.

So, having got the new Ignitor, and before I worked out the rev limiter problem, I ran into another problem. Although the Pertronix and Aldon ignitors seem to be the same product, the module is positioned differently on the baseplate and the magnetic collar fitting on the rotor shaft IS NOT THE SAME. The magnets are in different places, as I found out after yet another frustrating attempt to get the car to fire up with the new ignitor and (stupidly, in hindsight) the old collar.

EVENTUALLY, I got it fired up again and connected up the rev limiter with the engine running. It killed it pretty quickly, and so the module is now in the "posterity" box. Oddly enough, if you unplug the wiring from the module but keep the wire connected to the coil the rev counter works...

[i]Job done[/i]
It's relatively easy to set the timing at 10 BTDC at this point. Then you can balance the carbs (no substitute for the Morgan Carbtune I think) and have a go at setting the mix using a gas analyser.

I then went for a spin and found my throttle cable had got sticky over winter. BUT, the car ran well, never missed a beat, and somehow I've managed to fix the hesitation issue which has plagued me for ages.

Happy with the results and the knowledge that my fuel and ignition systems shouldn't require attention for a long time.

I'd advise anyone thinking of doing similar to try to do the carbs and dizzy separately, so you can rule out problems with one when troubleshooting issues with the other. I reckon a starter button in the engine compartment would be a good investment too.


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