Pump and circumstance

Well, I think you can probably guess that the photo to the left will tell that there’s a story for you this time! That was the scene last Sunday night on a wet M4 near Heathrow. For a couple of weeks, although the car seemed mostly to be running fine, there had been a slight suspicion in my mind that it was slightly down on power, just not quite 100% there. It was just that subtle feeling that anyone familiar with old cars will know. (The same way you spend ages trying to hear that quiet, intermittent, unusual noise as you drive along only to find it’s the kids in the car in front with their stereo turned up too loud…) Anyway, all seemed basically fine, I’d been in London for the weekend, had spent much of Sunday morning walking round Finsbury Park thinking that maybe one bottle between two people was too much port (or maybe better port is the key!) and was quire frankly looking forward to getting home. So you’ll understand I was a little put out when the engine simply stopped going round, without warning, while in the middle lane of the M4 at 70mph. Luckily there was no one in the inside lane and I had sufficient momentum to get onto the hard shoulder without coming to a halt in the carriageway. (Unlike a V8 Aston that had been causing a huge tailback a few weeks ago while parked in the fast lane.)

A quick look see revealed nothing obviously wrong – nothing on fire, no fluid leaks, electrics all OK. I tried the engine again and it turned fine, but would not fire. A closer look see revealed there was no fuel in the filter. We have a winner! However, connections to the pump were all fine, and without any tools or meter to check for power, and given the rain and traffic (and the small fact that I had no real knowledge of how a pump really worked anyway) it was a easy decision to call out a friendly orange RAC van. He got there in about 15 minutes and admitted he’d never heard of Bristol cars – he thought he was coming to a motorbike.

However, he tested the power to the pump, which was fine, and with two people present it was easier to both try the engine and listen to the pump at the same time. The engine did fire this time when asked, but the pump was erratic and it died again. The tow truck took another 20 minutes to arrive, so we sat in the van waiting out of the rain while I did my best to re-educate the RAC man about Bristol Cars!

Being a Sunday night I wasn’t sure where to have them take the car – I’m not a great mechanic so was uncertain about having an immobile car deposited at home, but I didn’t want to just dump it outside Spencer’s. However I did then learn about a nice thing the RAC will do that I hadn’t known about before, which is that they’ll take you and the car home, then come back in a day or two when you’ve had a chance to book it into a specialist. So they took me and the car home, where I had a chance to read the long entry on the subject of the 410 Fuel Pump on the BOC Wiki. I did have a chat with Spencer the next day and though he couldn’t take the car any time soon as the workshop was almost overflowing, he did explain that the SU pumps are pretty simple to take apart, so I popped down to Burlen Fuel Systems in Salisbury who have taken over the manufacture of SU pumps and carburetters. They supplied a pair of overhaul kits (it’s a twin pump – two pumps on one housing) and I set to on the kitchen table to strip them. I don’t recommend this – even with no petrol in it, it still had a definite arome d’essence!

It’s a simple enough task to replace all the points, seals, diaphragms, and so on in the pump. Some parts are clearly built to a lower budget than the originals, and I decided to reuse the original brass spacers instead of the new plastic ones. I did put in the modern capacitors though to replace the much larger originals. Anyhow, all went back together simply enough, refitted to car, fired up, it ran beautifully for about 30 seconds, sputtered and died. Hmm. Definitely still had power to the pump, but tried shorting across the points and it still wouldn’t pump. The coil did get very slightly warm to the touch after a couple of minutes with the power going through them, and the people at Burlen had pointed out that it is possible for the coils in the pump to burn out or short. So the next day I called him back to find out how to diagnose a failed coil, but he said though it is possible it is very rare. Far more likely a poor earth, points not correctly adjusted, or a misconnection internally. With nothing better to try, I stripped them down again, found nothing obviously amiss, set them up from scratch again, and this time before reconnecting it I tried it with a direct connection to the battery, and that worked fine! So once again, refit to car and fire up. Amazingly, this time it ran and didn’t splutter and die, but kept running. Sweet. And the petrol fumes had gone from the kitchen by now so I could even have a cup of tea in peace!

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