theduck
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 posted on 29/6/13 at 06:48 PM |
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Twin 40s fitted, won't start
Ok so fitted my twin 40s to my 1600 pinto after sorting out the throttle linkage, however I can't get it to start. I assumed that the jetting
and venturi sizes would at least run, but if they are well out (and judging by Venturi too small?) could they stop it starting completely? Venturi is
30 and I expect I need 34.
Or... My timing was set as a best guess to get the engine started on a weber 34ich and really needed final adjustment. Could this need tweaking
instead or should it be good enough if it was good enough to run with the 34ich on?
I've managed a couple of what sound like almost starts but it does almost immediately after letting off the starter
Thanks in advance.
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britishtrident
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| posted on 29/6/13 at 07:49 PM |
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Nothing to do with venturi size they don't come into startup & idle
(1) Check there is fuel filling the float chambers.
(2) Clean the idle (more correctly slow running jets).
(3) Check the cold start mechanism piston valves are closing properly.
(4) Check the firing order and condition of spark plugs -- ie. check they aren't wet with fuel.
(5) Check the ignition timing (for first start this should be 5 tto 10 degrees BTDC and check spark.
(6) Give the throttle 2 pumps and immediately try to start while applying a tiny amount of throttle.
If it doesnt start after two attempts on the the next attempt use the anti-flood procedure don't pump the throtlle but s-l-o--w-y press
the throttle all the way to the floor and after a couple of turns of the starter bring the trottle back to approximately 1/4 open.
If all else fails as long as the engine isn't back firing try a squirt of Eezystart
[I] What use our work, Bennet, if we cannot care for those we love? .
― From BBC TV/Amazon's Ripper Street.
[/I]
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wilkingj
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| posted on 29/6/13 at 08:06 PM |
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Squirt a bit of propane gas down each inlet, then try to start. If it runs or coughs and runs even for a short while, then you know its the carbs, ie
not the ign timing, or the valve timing etc.
This method is always easier with a single carb!
Have fun..
1. The point of a journey is not to arrive.
2. Never take life seriously. Nobody gets out alive anyway.
Best Regards
Geoff
http://www.v8viento.co.uk
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theduck
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| posted on 29/6/13 at 09:12 PM |
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Will check floats and clean and check jets sizes tomorrow.
How dominate the ignition timing? As I said before was a case of fiddling and best guess. If its just setting no1 cylinder to tdc on combustion stroke
an then moving crank backwards 10degrees I can do that.
You've lost me at the cold start mechanism piston valves though...
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Mr Whippy
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| posted on 29/6/13 at 09:36 PM |
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On the 40s I had there was a link on the back which was for a choke cable, it closed a port or something as there is no normal choke butterfly on
these carbs.
Pump the pedal a couple of times and turn it over, you should smell petrol in the inlet or take a plug out and it should also smell of petrol. If so
then chances are its the ignition, get hold of a strobe light, you need that anyway to set the timing up well and it should flash when the engine is
turn which indicates you have a spark.
My guess is you have the timing out by 180 degs, if it starts spitting and banging while trying to start that is the cause. Double check everything.
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theduck
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| posted on 29/6/13 at 09:50 PM |
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Timing has not been touched and was running yesterday on a different carb.
What 40s did you have? Weber or dellorto? I have dellorto and not spotted anything for a choke cable?
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Mr Whippy
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| posted on 29/6/13 at 10:01 PM |
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Mine were weber DCOE's which have a cold start feature. It looks like yours don't.
Here's a web page that describes cold starting (near the bottom). Do you have an electric pump? It's an awful lot to fill up with a
mechanical one
Links
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theduck
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| posted on 29/6/13 at 10:06 PM |
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Just been reading that.
I'm using the original pinto mechanical pump.
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Mr Whippy
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| posted on 29/6/13 at 10:13 PM |
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Hmm I'd recommend going electric otherwise your going to be cranking it over for ages, at least with electric pumps you can hear the carbs are
full as the ticking stops and from that will know exactly how much you have primed with the pedal pumps
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rusty nuts
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| posted on 30/6/13 at 07:35 AM |
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As has already been suggested a quick squirt down the inlets often helps getting an engine started, I tend to use brake cleaner rather than gas
because it's more controllable . Have the plugs got wet due to overfueling, double check you haven't knocked off any wiring etc.I would
have thought the mechanical pump would work OK but it will take a lot of cranking to prime the carbs
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britishtrident
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| posted on 30/6/13 at 07:57 AM |
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The main reason for priming with Eezistart (ether) is it burns over a much wider range of air/fuel ratios than petrol or propane/butane.
Brake cleaner will also work.
Mechanical fuel pump is not a problem.
[Edited on 30/6/13 by britishtrident]
[I] What use our work, Bennet, if we cannot care for those we love? .
― From BBC TV/Amazon's Ripper Street.
[/I]
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theduck
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| posted on 30/6/13 at 02:54 PM |
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Right, jet sizes are
Idle jets - 50 / 7850.1
Emulsion tubes
right bank of each carb 7772.5
Left bank of each carb 7772.1
Main jets 115
Pump jets 40
Dave Andrews site suggests
34mm Chokes
140 main jets
7772.10 emulsions
180 air correctors
40 pump jets
40/7850.1 idle jets
7848.1 aux vents
Not sure which bits the air correctives and aux vents so haven't checked them.
Idle jets, some contrasting advice. Dave Andrews suggests 40s, but des hammills book suggests 45s with a 50 being only slightly too large.
Now the concerning bit is the 7772.1 and 7772.5 mixed emulsion tubes. Although the recommendation is 7772.10 by dave Andrews further reading suggests
7772.5 should be ok, and obviously cost effective as I only need 2.
The main jets are smaller than they should be but right for the chokes, so should be ok.
So... What to replace and what to keep? I'd like to reuse as much as possible to keep costs to a minimum so am thinking 7772.5 emulsion tubes an
maybe some smaller idle jets, probably the 40s as that's what dave Andrews suggests. I'll look at main jets and chokes when I fit a 2.0
cam
Also what the best way to clean the existing jets? They look ok but as they are out might as well clean them up.
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theduck
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| posted on 30/6/13 at 04:07 PM |
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Spark plugs are black as night. Think the smaller idle jets are deinitely needed.
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theduck
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| posted on 4/7/13 at 05:44 PM |
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Still wont start,list of things done
Fitted correct idle jets
Set timing to approx 8degrees advance
Checked spark on all plugs and all sparking in correct sequence and not 180degrees out
When removing plugs tonight I notices two things
1: plug 1 was black, all others were wet
2: header 1 was warm, all others stone cold
Would others agree that sounds like an air leak on 2,3 and 4?
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alfablack
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| posted on 4/7/13 at 05:54 PM |
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Hi are the choke levers on the top of the front section stuck on witch would over fuel your engine giving similar results
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theduck
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| posted on 4/7/13 at 06:10 PM |
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Genuinely thought there wasn't a cold start circuit until you just describes where they are. Missing have levers attached so missed them.
However, they move freely and just quickly disassembled and they move freely inside as well. As throttle pulls toward back of the bay and the chokes
naturally sit to the front as I assume this is the correct off position.
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alfablack
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| posted on 4/7/13 at 07:21 PM |
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Hi that seems ok. they are very sensitive to float heights and vibration
are you using the misab plates in-between the carb and manifold ie the bonded alloy and rubber. not the plastic spacers with
O-rings. and the thackery washers are not done up tight you have about 1-2mm gap in the washer
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britishtrident
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| posted on 4/7/13 at 07:22 PM |
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quote:
Originally posted by theduck
Spark plugs are black as night. Think the smaller idle jets are deinitely needed.
Simples don't pump the pedal.
[I] What use our work, Bennet, if we cannot care for those we love? .
― From BBC TV/Amazon's Ripper Street.
[/I]
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omega 24 v6
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| posted on 4/7/13 at 07:24 PM |
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Will it start and run on light throttles?? If yes then possibly at idle the butterflys on 3 of the cyls are closed and no air is getting in. If so
then no bang either. You'll need to balance the individual butterflies.
If it looks wrong it probably is wrong.
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theduck
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| posted on 4/7/13 at 07:25 PM |
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Put old carb back on and it runs.
Was using O rings with Thackeray washers done up tight...
Would not start at any throttle level.
[Edited on 4/7/13 by theduck]
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alfablack
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| posted on 4/7/13 at 07:26 PM |
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the other thing is before you turn it over put the battery on charge. once charged take of charge for about 10 mins before turning over. in mean time
take out your plugs and get the ends nice and hot with a blow torch if one is about not to hot to melt the end put them back in using gloves and a
socket then wind it over getting ready to catch it on the throttle usually works
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alfablack
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| posted on 4/7/13 at 07:29 PM |
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you really need the misab plates a lot better and the thackery washers should not be done up tight as this is used as anti vibration absorber
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theduck
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| posted on 4/7/13 at 07:40 PM |
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So plan of action is to set ignition timing properly while the 34ich is on and to strip the carbs and make sure floats are set right and give
everything a good clean. Then put back together using misab plates instead of the O rings.
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alfablack
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| posted on 4/7/13 at 07:48 PM |
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that's a starting point. and then a little bit of fettling
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theduck
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| posted on 7/7/13 at 07:59 PM |
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Checked the float levels and they were way out. Set them correctly, cleaned and rebuilt and...
IT WORKS!!!
Have to use the cold start valves to fire it up so will be ordering up some proper levers but it works and sounds amazing! Will get a video once have
sorted it out properly.
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