AARGHH. Can't get Aq170 started. Solex carb issues??

[RobWales]

I stripped all 3 again yesterday. They are really clean, and fuel can flow easily where I think it's meant to . I know new gaskets might help, but they have very little effect on where the air is moving. I small leak in a bottom gasket might let a little air in an affect idle, or acceleration, but considering they all look ok, I cannot believe they'd totally stop it from starting! I must be missing something fundamental with this!!

Well IMHO the starting procedure seems well wrong, I mean ten pumps?

Have you had the distributor out for a clean by chance? put back in 180deg out?

Just a thought?

This also takes me back..... to my MK11 escort 1600sport with twin Webber 40's hehe

 

[vas]

They are really clean, and fuel can flow easily where I think it's meant to

from the reservoir with the floater on top, to the main jet bottom

and from the other side of the jet to the venturi.

it's been almost 20yrs since I was messing about with carbs, honestly don't remember but should be able to remove the main jet, block the top hole and blow to see air/fuel coming from the venturi holes, right?
if that also is working, the only other thing that'd be wrong is the vacum!

running out of ideas, so I'll shut up and let others step in.

cheers

V.

 

[Feneris]

I have had the distributor cap off, but it's correct. The engine enthusiastically runs when it's got fuel, which should rule our a spark issue.

 

[lenseman]

. . . . I advance the throttle a few times, then the engine starts, it will rev straight to 2000 when it goes, then stops. At times it will hold an idle for 5 or 6 seconds, but never longer. . . . .

You will need to conduct a few more tests?

Firstly, I am not familiar with this specific carb and I think it has been obsolete for a number of years.

When it cuts out, without cranking it over after it stops, you need to see what fuel level is remaining in the float chamber(s). This has to be done before you go on to explore further.

This carb seems to have some sort of instant response device by utilising a 'pump jet'? When the engine dies, are the pump jets still able to spray fuel into the venturi if you quickly manually open the throttle wide? If not I would suspect not enough fuel in the carb float chamber?

Now I am not sure if this downdraft carb utilises an "emulsion tube", if it does, have you checked each of the cross holes and central hole running up the centre. If it does have an emulsion tube, This must be checked but as the fault does not seem to make the engine 'go lumpy' (ie one carb fuel failure) but cut out completely, I suspect fuel starvation to all three carburettors so you need to check the float fuel level. Once it completely cuts out, DO NOT try cranking the engine again before inspection as this will/might give false impression of fuel levels in the carbs.

 

[lenseman]

You might find this pdf file worth downloading as it should assist you in finding your way around the carburettors:

http://www.190slgroup.com/tech/images3/solex.pdf

 

[spannerman]

These were one of Volvos better ideas 'not'! They are always tricky to start as there is no choke, the only way is to pump the throttle a few times to squirt some fuel in then open it about a 1/4 and fire it up, you then have to juggle the throttle until it warms up, as if you drop to idle it WILL stop as you know, and if you go over 2000 it will splutter and fade out.
Had to explain this to customers many a time and usually had to demonstrate the technique. It takes a bit of getting used to as you need to keep it at around 1500rpm to keep it going and have to anticipate which way the engine is going to respond, is it going to die out or rev up.

 

[Feneris]

I've had the top off the carbs several times. When it stops there is still fuel, to the top, in the carb resevoir. If I advance the throttle again, there is plenty of fuel to squirt out of the advance jets. I can also blow down the resevoir vent, and fuel comes straight out of the main jets.

Thanks for the replys and the link to the carb manual. I'm reading it now.

Cheers, Simon

 

[vas]

am I right in saying that you could (therotically at least...) prolong the time the engine runs by sharp blips to the accelerator so that the accel jets pump more juice to the barrels?
trying to establish that it's indeed only fuel starvation that kills the engine

V.

 

[scej]

As spanner man says they where not that good when new. we had a boat with a a pair of these in and you need to keep the revs up at around 1500 until the temp gets up before it will tick over, otherwise forget it.....

watch out for the exhaust manifold as well they clog up real quick

 

[talltim]

sounds as if engine is only running on the fuel being injected by the accelaration pump(s)

Could be

float level too low or float sticking on pivot pin

or

may have a non return valve in the float chamber outlet to the jets stuck open, causing flooding, or closed.

 

[lenseman]

am I right in saying that you could (therotically at least...) prolong the time the engine runs by sharp blips to the accelerator so that the accel jets pump more juice to the barrels?
trying to establish that it's indeed only fuel starvation that kills the engine

V.

and following on from vituvas's suggestion which is good, have you run the engine with any air filter removed?

When the engine cuts out, have you inspected the spark plugs to see what colour the insulator is showing.

New plugs should be a very light fawn-grey if running correctly.

If they are black and when wiped on a cloth, leaves a sooty deposit - [BTOO RICH[/B]

Stark white - running far too weak (engine overheating symptoms will be present.)

Stark white with tiny beads of copper. Far, far to weak with pre-ignition timing errors. (This is most serious and needs to be sorted as soon as possible).

 

[lenseman]

. . . watch out for the exhaust manifold as well they clog up real quick

A very valid point. When I was an RAC engineer, over the seven years I was on the road inspecting difficult problems blocked exhaust pipes due to the silencing material blocking the free flow of the outlet caused similar problems to that which you are experiencing?

 

[Feneris]

SORTED. Posting on my mobile so will give another update with picture later. It was reading the Solex instructions which had cross sections, posted above, that gave it away. The idle jets have a hole in the end, all 3 were blocked solid. I wondered if there should have been a hole, squirting with aerosol carb cleaner and trying to suck air through showed it as solid, I assumed there was no hole there. Took a needle to clear it. Thanks for all replies and ideas.

 

[lenseman]

SORTED. . . . . Took a needle to clear it. Thanks for all replies and ideas.

Nice one.

BTW, you should use soft metal to probe jets. Best to use a strand of copper wire teased out of a multi-stranded flex as you can easily enlarge a jet sufficiently to damage it and cause it to work incorrectly.

You can wobble and poke copper strand through a jet with impunity as the brass is a harder material.

 

[vas]

SORTED. Posting on my mobile so will give another update with picture later. It was reading the Solex instructions which had cross sections, posted above, that gave it away. The idle jets have a hole in the end, all 3 were blocked solid. I wondered if there should have been a hole, squirting with aerosol carb cleaner and trying to suck air through showed it as solid, I assumed there was no hole there. Took a needle to clear it. Thanks for all replies and ideas.

nice, that was quick then
especially with fuel left in there for years and all sorts of muck, cleaning often has adverse results

good luck with the rest of the rebuilt!

V.

 

[DavidJ]

I had this problem a long long time ago with a Sealine 195 with an AQ170. It turned out to be air being drawn into porous fuel pipes. The porosity was so small that no fuel leaked out just air in.
New armoured pipes from Pirtek, I seem to remember, and all was well.

 

[Feneris]

It was a blocked idle jet. So 100% blocked I didn't realise there was meant to be a hole in the end, I thought it just had the side holes. I looked at it, pondered why it looked like it 'should have a hole' in the end; but as all 3 idle jets were closed off, decided it was meant to be that way. Oh well, learnt from that over a couple of days.

Here it is:

I ran the engine briefly, maybe just 15 seconds, but it's clearly right. Because I've had it all apart, I'lll now be studying how to set up the carbs. I bought a carb balancer (Gunson carbalancer) and will now try to learn another new trick!

 

[vas]

I bought a carb balancer (Gunson carbalancer) and will now try to learn another new trick!

3 twin carbs? That's a difficult to master art...
You need a set of good ears, touch and the tool for good measure Just remember if you do it properly and you keep the lines clear, it's unlikely you'll need to redo it for years!

good luck

V.