1800 wont start when warm

Tips and help requests for your cars mechanics. points gaps, timming settings all those sorts of things

Re: 1800 wont start when warm

Postby 1972nail » Fri May 17, 2019 5:18 pm

reb78 wrote:My new one is a dlb102. Is this ok to use?


Should be OK.
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Re: 1800 wont start when warm

Postby reb78 » Sun May 26, 2019 5:54 pm

So. Had a play today. The new coil might have made a marginal difference to the warm start issue. But theres a flat spot on acceleration until it seems to catch and she’s still hard to start when warm. Checked the points and plugs and cleaned the distributor.
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Re: 1800 wont start when warm

Postby reb78 » Sun May 26, 2019 5:55 pm

Put a timing light on it and got the timing set to 9 degrees - she runs sweet with the vacuum line blocked but really quite rough with it unblocked and linked to the air filter like normal. Annoyingly, as we did the distrubutor bolts up, the timing moved so had to fiddle quite a bit to get it right.

We then changed the condenser just because I had one and that helped a fair bit.

Any more ideas?
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Re: 1800 wont start when warm

Postby HC Fairley » Mon May 27, 2019 8:52 am

reb78 wrote:Put a timing light on it and got the timing set to 9 degrees - she runs sweet with the vacuum line blocked but really quite rough with it unblocked and linked to the air filter like normal. Annoyingly, as we did the distrubutor bolts up, the timing moved so had to fiddle quite a bit to get it right.

We then changed the condenser just because I had one and that helped a fair bit.

Any more ideas?


Had this problem with mine back at the start, had to hold the choke on to get rid of the flat spot, solved this by blocking off the vacuum line like you've done. Long term problem was a dodgy vacuum advance unit. Try changing it and see how you go. I drove mine for over a year with the vacuum line blocked and the timing advanced :imsmiling:
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Re: 1800 wont start when warm

Postby reb78 » Mon May 27, 2019 11:52 am

This might fit with something else I noticed - I sucked on the line to the vacuum advance unit when the engine was running (I was just checking the pipes were all intact) and it made no difference so this could confirm your suspicions?

What advance unit am I looking for on the 1800 engine?
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Re: 1800 wont start when warm

Postby HC Fairley » Mon May 27, 2019 12:09 pm

I'm not sure which Vacuum Advance you need, someone more knowledgeable than I will have to aid you on that front. The only reason I have a working advance unit now is because i swapped my distributor out for a new one with a working vacuum after I bent the shaft on my old dizzy. Like I said, I drove 7-8,000 miles over the space of a year with the vacuum blocked off and the timing advanced but I appreciate it is more satisfying having the thing working correctly.

I'm not sure how this would make the engine harder to start when warm though ? Or has this been solved with the new condenser ?
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Re: 1800 wont start when warm

Postby ADRIAN » Tue May 28, 2019 9:10 am

The Zenith 36IVT carb has a flat spot as standard. Thats because this carb does not have an acceleration jet. There is no cure that can be done for this "characteristic" . Every 36IVT has the flat spot, so replacement of the carb wont cure anything. Only replacement with an alternative carb will solve the flat spot. A common conversion at the time was the DCD Weber downdraught, that sits on a special C & T manifold. Unfortunately, you cannot find these manifolds now. (C & T = Conversions and Tuning) You could use a Weber 34 (from Bedford CF van) which are very good, but this carb is taller and the air filter on the top, may catch on the underside of the Viva bonnet.
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Re: 1800 wont start when warm

Postby edgoose1 » Sat Jun 01, 2019 10:30 am

Try running without the air filter. I remember once the wrong size was fitted. When warm it expanded and the engine died, as could not breath
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Re: 1800 wont start when warm

Postby 1972nail » Fri Jun 07, 2019 6:15 pm

I was tidying up some spares in the garage today and came across a NoS vacuum advance unit for a 73 - 76 1800 distributor. It is a 6 degree unit part number 7953413. It was fitted to a NoS distributor I am using for a project that doesn't need a vacuum advance unit. It has a bit of surface corrosion but it's not bad.

PM me for further info if you need it
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Re: 1800 wont start when warm

Postby reb78 » Mon Jun 10, 2019 11:41 am

ADRIAN wrote:The Zenith 36IVT carb has a flat spot as standard. Thats because this carb does not have an acceleration jet. There is no cure that can be done for this "characteristic" . Every 36IVT has the flat spot, so replacement of the carb wont cure anything. Only replacement with an alternative carb will solve the flat spot. A common conversion at the time was the DCD Weber downdraught, that sits on a special C & T manifold. Unfortunately, you cannot find these manifolds now. (C & T = Conversions and Tuning) You could use a Weber 34 (from Bedford CF van) which are very good, but this carb is taller and the air filter on the top, may catch on the underside of the Viva bonnet.


I was just re-reading this. When I look in the carb and tweak the throttle from under the bonnet, there is a jet of petrol that squirts out that is combined with movement of the throttle - I assumed this was an acceleration jet? Haynes says that the carb on this engine is the 36IVE I think (if that makes a difference)?
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