CU engine - Mechanical Pump - Engine cutting out

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BOXY
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CU engine - Mechanical Pump - Engine cutting out

Post by BOXY »

Hi all. It's been a while but I've broken my van again. 

Yesterday after spending a couple of weeks camping in Cornwall, the AA had to relay me home. The van started fine at the Lizard and drove fine as far as Truro. I stopped and put 45ltrs of petrol at a Shell garage and headed off towards St Austell. Three miles later the van back-fired twice like a shotgun and the engine stopped. I coasted into a side road and let the van cool down in case the start-stop traffic in and out of Truro had got the engine a bit warm. 

After a couple of minutes I turned the key and the van started and idled so I drove 30-40 mtrs up the road to turn around and the engine cut out again half-way through the three point turn. I started the van again and the engine ran long enough to get back to where I'd started. At this point, I'd decided it was a fuel issue so called the AA and started to look for any thing obvious while I waited for them to arrive.

Fuel filter - new - fitted two weeks ago along with new fuel lines.
Fuel lines - all ok, no leaks or kinks.
I un-clipped the fuel line from the filter and got a sleeve full of petrol so I guess the tank outlet wasn't blocked.
I tried the van again and it started and ran, I could even rev it to the red line, but as soon as I tried to reverse it, it just stuttered to a halt.
Another hour went by whilst I waited for the AA to arrive and I started the van a couple more times in case the Cornish pixies had fixed the problem, but despite starting and idling, the van refused to go anywhere in gear if the throttle was pressed.

The man from the AA didn't bring a magic wand and thought that the fuel pump was probably the problem, so he ordered a flat-bed to get me home.

So later this week I'll pop off the fuel pump and check the push-rod first. How long should it be in a genuine CU mechanical pump? And what else should I check whilst the pump is off, or before I take it off? 

Update - Took the pump off and measured the old push rod was only 0.5mm shorter than the new one. Would this small a difference in length make a difference?

Pushing the lever by hand end up spraying the petrol into my face. Doh! I hooked the pump up to my motorbike petrol tank and manually pumped petrol through a clear pipe into a jerry can. The only thing I could see wrong with the pump was the drain pipe  had gone AWOL but the hole was clear so I added a short piece of nylon pipe as a replacement. I refitted the pump but the battery was a bit too flat to get the engine started. It still turned the engine over slowly so I popped off a fuel pipe to one of the carb and fuel was pumping to the carb.

I've got the battery charging tonight ready for another try at the weekend. Is there an easy way to check for water in the petrol?








 
2ltr Aircooled CU with twin Solex's & originally a 009 dizzie, but now back to standard.

colinthefox
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Re: CU engine - Mechanical Pump - Engine cutting out

Post by colinthefox »

BOXY wrote: 16 Jul 2021, 18:29 Is there an easy way to check for water in the petrol?

Pump or drain some fuel from the tank through the normal outlet of the tank into a glass jar. Let it settle for  few minutes, and any water will show up as globules (or a layer if there's lots of it) in the bottom of the jar. Water doesn't mix with petrol, and is heavier so sinks to the bottom.
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Re: CU engine - Mechanical Pump - Engine cutting out

Post by davidoft1 »

backfire suggests ignition not fuel pump, do you have access to another distributor to try?

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Re: CU engine - Mechanical Pump - Engine cutting out

Post by BOXY »

Well, I've learnt an important lesson. Even when I sure I know what the problem is, I should still systematically check everything. I convinced myself and the AA man it was a fuel problem. The way the van would start and run and then stall, shouted fuel issues. I even convinced myself the back firing was caused as the mixture weaken off as the fuel ran out.

This week I started to check out the ignition system. Using BigHerb's patented Hall sensor diagnostic method it turned out the dizzy is the likely culprit after all. 

If I'd checked the dizzy out whilst I was waiting for the AA I could have found the fault, fitted my old 009 dizzy and made my own way home. Doh!

On the bright side I've now got a clean fuel pump with a new push-rod, and I've found all the other bits of spare ignition gubbins I stashed in the garage when I originally fitted an electronic dizzy.
2ltr Aircooled CU with twin Solex's & originally a 009 dizzie, but now back to standard.

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jospanner
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Re: CU engine - Mechanical Pump - Engine cutting out

Post by jospanner »

BOXY wrote: 24 Jul 2021, 17:46 Using BigHerb's patented Hall sensor diagnostic method it turned out the dizzy is the likely culprit after all. 

Whats the BigHerb method?
'81 2.0 Aircooled CU with 4 speed box

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BOXY
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Re: CU engine - Mechanical Pump - Engine cutting out

Post by BOXY »

Pull the plug off the dizzie. Pull the king lead off the centre of the distributor. Push a piece of wire into the middle of the dizzie plug (the green wire on the loom). Turn the ignition on. Hold the free end of the king lead near the engine block. Touch the end of the wire against the engine block. You should get a fat spark jumping between the king lead and the engine block. This spark proves the amplifier, coil, and idle stabilizer are all working. I found it easier to use a wire with a bullet connector crimped on the end I touched to the engine block as it allowed me to get a good contact with the block.
2ltr Aircooled CU with twin Solex's & originally a 009 dizzie, but now back to standard.

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