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

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Feneris

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1974 AQ170C with 3 solex downdraught carbs.

A week ago I stripped and cleaned the carbs, as the advance jets were blocked, it started afterwards and I let it idle for just 10 seconds as it's out of the water and I hadn't got the muffs and hosepipe on it.

A week later, it will only run for a few seconds. I've got new fuel, I drained out the old fuel (fuel in tank is 7 months old and had gummed up in the carbs). The resevoirs in the carbs are full of new fuel. The advance squirts fuel into the barrel of the carb. I've squirted carb cleaner through the fuel paths, there is fuel in the main jet. I've got the fuel pipe that feeds the pump, straight into a 5L plastic jerry can with new fuel. No filter or tank issues.

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.

The other way of starting it is to crank it, advance to full throttle, then back, it will run again briefly, no more than 5 or 6 seconds again.

I've persevered with this for a day, it's as if the engine isn't drawing fuel through the main jet, despite it being there. It only runs on the fuel you've squirted in when priming.

Short of taking off all 3 carbs again for another clean, I'm at a loss as to what to do next. It's such a simple system, it should just work!!!

Any ideas anyone ????
 
Feneris said:
1974 AQ170C with 3 solex downdraught carbs.

A week ago I stripped and cleaned the carbs, as the advance jets were blocked, it started afterwards and I let it idle for just 10 seconds as it's out of the water and I hadn't got the muffs and hosepipe on it.

A week later, it will only run for a few seconds. I've got new fuel, I drained out the old fuel (fuel in tank is 7 months old and had gummed up in the carbs). The resevoirs in the carbs are full of new fuel. The advance squirts fuel into the barrel of the carb. I've squirted carb cleaner through the fuel paths, there is fuel in the main jet. I've got the fuel pipe that feeds the pump, straight into a 5L plastic jerry can with new fuel. No filter or tank issues.

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.

The other way of starting it is to crank it, advance to full throttle, then back, it will run again briefly, no more than 5 or 6 seconds again.

I've persevered with this for a day, it's as if the engine isn't drawing fuel through the main jet, despite it being there. It only runs on the fuel you've squirted in when priming.

Short of taking off all 3 carbs again for another clean, I'm at a loss as to what to do next. It's such a simple system, it should just work!!!

Any ideas anyone ????
Click to expand...

Positive the fuel pump is working?
 
hi,

no idea on either motor or said carbs, but you haven't mentioned anything about the fuel pump. Where is it, mech/el? Have you tested it squirts fuel towards the carb intakes?
5sec and then dead could mean there's nothiing coming in to push further the juice, no?

V.
 
I've had the fuel pump apart and it's working great (after cleaning). The solex carbs have a resevoir in them, holding about 40mls each.
 
Feneris said:
I've had the fuel pump apart and it's working great (after cleaning). The solex carbs have a resevoir in them, holding about 40mls each.
Click to expand...

as I said, I don't know the carbs and may be talking bull, but can you confirm that once it dies after the 4-5secs there's still a lot of fuel in the reservoir? Is it a manual fuel pump so when cranking there's lots of fuel coming through it?

nothing else I'd think of

V.
 
theres three carbs

If you have messed up the float levels it could cause a fault, however three carbs means you've created the same problem on each carb ???
I think you'll be taking them apart again to re check things
Did you use new manifold gaskets, an old gasket if re used may let air in, quite often people over tighten the bolts causing the carb base to go out of shape again letting air in, I do think it sounds a bit like their not getting enough fuel through unless you open em right up if air is getting in it could create this sort of fault
Unless of course its an ignition fault in which case, what you do to the carbs wont matter this could even be as simple as the vacuum pipe not connected split or blocked
cheers
Mick
 
I've had all 3 carbs apart again, thoroughly cleaned every part of them. All the adjustable jets and parts have been thoroughly cleaned with carb cleaner. All three are set the same, where adjustments can be made. The resevoirs (hold a couple of minutes worth of fuel, 100ml total) are all full of fuel, so the pump doesn't have an effect, although the pump works fine.

Again, the engine will enthusiastically start and burn the fuel that's been put in by advancing the throttle several times. It just will not keep running though. If the revs go to 2000 and stay there, it stops. If I bring it straight back to idle, it stops.

As far as I can tell, it's just not drawing fuel though the main jets. I've not replaced the gaskets, all look ok. I could imagine small issues from reusing the gaskets, but at the moment it's just fundamentally not working.

When it starts on the fuel from priming it, it roars into life, it's not a struggle to start. Just to keep it running!!!
 
you dont mention mixture enrichment while cold, choke or starting jets.

air cleaner / chamber fitted?

hold hand over air inlet to restrict flow & richen mixture
 
I don't know how the choke system works as it doesn't have one!

The carbs are Solex 44pa1.

There's no clever auto choke either. I'm trying to google for info, not getting overly far though!
 
having had it all apart, hav the mixture adjustments been put i n a midway position?

there must be some type of mixture enrichment, if no choke, some supplementry starting jets, might only be on one carb?, not unless the race engine method is used, a rag in the air intake?
 
Again today, cannot get it to run for more than a few seconds. It still enthusiastically starts from the fuel you've primed it with, and stops. I'm close to paying a mechanic.
 
The carb resevoirs are always full. They have a vent pipe upwards, I put a tube over the vent and blew down it, fuel came out of the main jet straight away.

The pressure difference between the venturi and the static air pressure is what should get the fuel moving.

It just doesn't seem to!!!! So confused by it!
 
Whip a carb off, blow into the fuel inlet, you should be bale to gently blow air through the carb, keep blowing, turn it upside down, you should not be able to blow any more, this will tell you if the float and needle valve are working in the carb.
 
The float in the resevoir, and the 'shut off valve' that is closed by the float rising, all work correctly and shut off when the resevoir is full.

Are there any moving marts between the removable banjo bolt that holds the main jet, and the central 'column' in the venturi, that hols the emulsifier??
 
OK,

I think it's safe to assume that fuel is pumped, stored in the tank, banjo, floater etc are ok.
Somehow and on startup a wee bit of fuel moves to the engine and is burnt.

Now digging into my twin delorto 45s days in my T-reg Lotus elite, I'm pretty sure there's an accel pump in there. When pulling the accel cable, do you see the top jet dumping stuff in on top of the venturi?
Maybe just maybe this bit works, but the main jets are blocked/messed up?
I guess it's not difficult when cleaning the thing to push dirt into areas you shouldn't and block the whole thing solid...
I also assume that it was working alright/anyhow better than now before you started the operation, right?

Other than that, you're right it's hairpulling stuff! :(
good luck

V.
 
Thanks for the ongoing ideas, there is an acceleration jet, when I advance the throttle, the acceleration jet on all 3 carbs gives a good squirt of fuel into the carb barrel. This is what the engine is running off of.

When it starts, at time it's revved up to 3000rpm (I try to avoid this as the oil is cold), I'd have thought there would be good suction through the carb at that point to draw fuel through the main jets.

Maybe I've missed something fundamental about starting. To start it, I fully advance and retard the throttle up to 10 times, then crank it at 1/5th open. It then goes. If I advance it just once, the engine will start briefly and burn that fuel. Advamce it 10 times, it will start and run for longer, but stop all the same.

I had to strip and clean all the carbs as old fuel had gummed them up. None of the advance jets worked, all were blocked. Although after I first cleaned them a week ago, I started the engine and it ran for 10 seconds, at idle, before I stopped it as there was no water feed.
 
Last edited:
ok, so you basically run on the accel jets and not main ones. :(
3-5secs make sense...

I guess another strip is in order, check routes bb I think mentioned how, and make sure you have no air leaks that would render the suction of fuel impossible.
I think a set of new gaskets is a must, as I guess they are now rather hard and brittle, right?

I think you'll get it eventually, just a matter of clearing the fuel paths to the jets and ensuring vacum is there to suck the fuel in.

V.
 
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!!
 
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