504 Hard to Start

geodon

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Fellow Frogger
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I have a 504 2L motor in my 404 ute that I'm prepping for a RWC & red plates.


It has the dual throat Solex carb. with a manual choke & a 123 distributor set on advance curve no6.

Carb has been reco'd 12 months ago but has only been operating continuously a week or so. It had to go back as the needle valve was not cutting off fuel; the plugs literally dripped fuel when I removed them to have a look at what was going on. I thought THAT was the reason but it's still recalcitrant. It won't go at all with continuous cranking and a bit of pedal. I get a better result with short bursts & it seems to fire with no pedal & half choke when I let go the starter.

Before I launch into investigative mode, is there a preferred starting procedure for this motor?

Is it prone to flooding too easily?
 
Nothing special about starting a 504 engine. Are the spark plugs sparking? Have you still got the old distributor to try?
 
Nothing special about starting a 504 engine. Are the spark plugs sparking? Have you still got the old distributor to try?

Don't know about the plugs sparking but I have an HT inline device that measures how far the spark will jump & the 123 is delivering prodigiously- FAR more than the old unit.

I could try a new set of plugs I suppose but they are new and I don't see how a bath in petrol could have degraded them.
 
From my experience, the 2L 504 engine is a well sorted engine and not particularly prone to flooding or anything else.

Before doing anything else, I would check the timing very carefully.

What about fuel quality? Is it clean and newish? If the carby was reco'd 12 months ago and the needle and seat was getting stuck then maybe there are other carby issues? That the spark plugs were/are very wet suggests that the fuel pump is doing its job properly.
 
geodon,
Remove and clean out the idle jets, accessible from outside the carby. A Weber conversion would compliment the ignition set up.

PS. Are the choke butterflies fully open when warm/hot ?
 
A Weber conversion would compliment the ignition set up.

That is exactly my feeling as well. I've fitted Falcon Weber carbys to a few XN square port engines and have had good results every time.

EDIT: Grab the carby end of inner throttle cable which you harvest the carby.
It makes the conversion to the XN easy. You can join the Weber cable to existing pug cable with a double screw electrical connector. Solder it afterwards if you don't feel comfortable with screw fixings.
 
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What is the internal resistance of the ignition coil? The 123 requires a ballast resistor if it is high, check the tech manual.
 
Timing is dead on 8 degrees BTDC as measured with a strobe light.

Coil is a brand new Bosch GT40

I'll replace the plugs Thursday & check they are sparking before they go in.
 
If the plugs were new then it probably isn't them. I'd check for spark as you suggest and, if there is plenty of spark and the petrol is good, then start thinking carby. If the needle and seat were sticking there could well be other things going on with it.
 
the 123 is delivering prodigiously- FAR more than the old unit.

This happened to me once, and the problem was that the spark strength was OK previously, but with the new, higher voltage setup, the spark plug insulators couldn't handle the higher spark and it jumped across them. The insulators are an often forgotten part of 504s and 505s.

You may well get spark at the plugs but some of it will short out.
 
This happened to me once, and the problem was that the spark strength was OK previously, but with the new, higher voltage setup, the spark plug insulators couldn't handle the higher spark and it jumped across them. The insulators are an often forgotten part of 504s and 505s.

You may well get spark at the plugs but some of it will short out.


I think I just "heard the penny drop".

Copper HT leads are not recommended for the 123 as the higher voltage can cause misfires due to leakage.


What about those loooooong, un-insulated steel springs carrying the current from the ends of the silicon leads to the plugs? I know they reside inside a bakelite tube but there is potential for leakage.

It's time to set up the 4 plugs out of the motor but hooked up to the leads in a darkened workshop. Then crank the starter & look for sparks.

I added new points, rotor & cap for the old distributor to an order from Der Franzose so I'll have a standby.

Has anybody else used a 123 on a 504?

I had to get one for the Big 6 because The Prince of Darkness stopped making distributor caps for it. It has performed flawlessly.
 
Sounds like a plan and it sounds like Beano could be on the money.
 
I have used a 123 in my 404( essentially same engine) since restored in 2014

It works perfectly well with Bosch GT40 coil, although 123 recommend a more powerful Bosch coil ( about to go in)

I have not had any issues with shorting from the spring contacts in the tube, but this may have just been dumb luck

Have you changed over the petrol and cleaned out the carby - modern unleaded is PITA if left standing for months a) can go off and won’t go ‘ bang’ on request and b) leaves deposit in carby etc which can block fuel passages

Best wishes

Andrew
 
Those bakelite spark plug insulators break down with heat and age...I have seen it happen many times.

People often look everywhere but there.

Which is not to say that the other ideas put forward here are not correct. Andrew's suggestion about the petrol could also be the go, if the car has been sitting for some time with the same petrol.
 
To start my 504 (single solex) I simply pull out the choke and turn the key. I don't touch the accelerator pedal.

I recently had the tappet cover off (to retorque head bolts after a head change) and I had to stretch the accelerator cable so I could remove the tappet cover.

After reassembly, the car would not start. Would crank over, but not fire. I first of all thought I had put the plug leads back on in the wrong order, however it was clearly suffering from a gut full of fuel after pulling on the accelerator cable.

Also, as part of the cylinder head change over to a series 1 505 head, I installed the 505 style solid spark plug extensions and leads. I still run the standard Ducellier distributor with standard points/condenser.

Car runs so much smother with this change over to 505 solid spark plug extensions and leads.
 
To start my 504 (single solex) I simply pull out the choke and turn the key. I don't touch the accelerator pedal.

I recently had the tappet cover off (to retorque head bolts after a head change) and I had to stretch the accelerator cable so I could remove the tappet cover.

After reassembly, the car would not start. Would crank over, but not fire. I first of all thought I had put the plug leads back on in the wrong order, however it was clearly suffering from a gut full of fuel after pulling on the accelerator cable.

Also, as part of the cylinder head change over to a series 1 505 head, I installed the 505 style solid spark plug extensions and leads. I still run the standard Ducellier distributor with standard points/condenser.

Car runs so much smother with this change over to 505 solid spark plug extensions and leads.

I concur with your starting procedure for a cold engine.

What about hot?

Runs so much smoother?? When I do fire mine up, the exhaust note is splashy with sporadic misfires, as if the mixture is too lean. But it doesn't respond to the mixture screw.

Fuel is fresh BTW
 
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