Logo
FULL SITE MENU

AQ171C will not idle

M

moresparks

Regular Contributor
"Hi Guys, I would be grateful

"Hi Guys, I would be grateful if your collective wisdom could offer a couple of pointers on My Volvo Penta twin solex carb AQ171C.
The problem is the engine will not idle.
It starts no problem but once the revs go below around 2000 it just dies even when warm.
I have replaced the fuel filter and spark plugs and cleaned all the linkages etc. I have checked both the throttle levers are actuated at the same time and both carbs have fuel squirted into them from the accelerator pump nozzle. I have also made minor changes to the air /mixture and idle screws with no discernable difference.
I have not dismantled the carbs yet and with repair kits being around $70 for each carb, I just wondered if there was any other area I should look at first that I may have overlooked.
If it is synchronising, is it o/k to adjust whist the engine is revving around 2000?
If one of the carbs is faulty is there an easy way to determine which one?
Thanks in advance."
 
"I would start verifying that

"I would start verifying that the idle mixture is properly adjusted and that the carbs are properly synchronized. You may want to get hold of a Uni-Syn vacuum gauge/flow meter for the synchronization part.

I haven't done this for awhile, but I seem to recall that when synchronizing with a Uni-Syn tool, you get better results if you do it at idle or close to idle speed. Then, you check again with higher RPM that the vacuum (flow) is still identical in both carbs.

After you have done the synchronization and adjusted the idle mixture, you should be able to set the idle speed. At that point, verify that the ignition timing is what it should be.

The Seloc manual has a chapter explaining how to synchronize the Solex downdrafts."
 
"Hi Stephen,

I have an AQ14

"Hi Stephen,

I have an AQ145B which I believe has the same Solex carb set-up. I had the exact same issue that you are having and I went the same route as you..new wires, plugs, rebuilt both carbs, but I still couldn't keep it running at idle. Finally, I found that my timing was off because the timing belt had skipped a few teeth. Of course, in your case it could be the carbs (they're not hard to rebuild), but checking your timing is easier and if your belt skipped, you probably should tend to that. An easy test: Bring your #1 piston to TDC, is the rotor pointing to the #1 cyl wire? If not, you will need to make timing adjustments and/or replace your timing belt."
 
Hi guys … thanks for your comm

Hi guys … thanks for your comments it is really appreciated. This engine is new to me so this forum is great for giving me the confidence in attempting these checks myself.
Hoping to undertake simple vacuum leak and “hiss” tests this weekend which may give a further clue. I have the Seloc manual so this helps in checking the synchronizing and timing.
 
Hi Guys – just had a quick loo

Hi Guys – just had a quick look over this weekend and I may have an air leak in one of the carburettors. I initially set up the carbs using the basic initial settings as explained in the Seloc manual. Spraying carb cleaner around the carbs whilst it is running certainly made a difference to the engine revs. Although this on its own is probably not conclusive as some may have found its way into the bowl. However when I tried to listen to the vacuum using a rubber hose (“hiss” test) the engine died on the first carb test but made no difference when listening to the second carb. I assume this to be because I restricted the air flow slightly but other comments would be welcomed.
 
"One thing to check is the con

"One thing to check is the condition of the core plugs on the head. I went through a process of elimination trying to get my AQ151 to idle properly, rebuilding carbs, replacing with a Weber etc and some of the issue was around perforated core plugs causing a vacuum leak. Something to bear in mind."
 
"Hi – Just an update.
The car

"Hi – Just an update.
The carburettors have been stripped, cleaned, gaskets replaced and re-fitted. I did not see anything untoward and it didn’t make any difference.
A couple of extra checks, all spark plugs are black and sooty possibly because the air/fuel mixture is too rich. If I partially block the air flow into the throat of the carburettors it runs not too bad but the throttle control has very little effect to lower the revs. Removing the partial block from the front carburettor made very little difference but the engine stalls if you remove the block from the rear carburettor (the one with the vacuum valve)! One other worry I spotted the occasional very fine droplets of water blown out but I am not sure where they are from but it appears to be below the intake manifold."
 
It seems to me that your idle

It seems to me that your idle mixture needs readjusting. Did you try to set the idle mixture and synchronizing the carbs as per Seloc? It would appear that the carbs need the idle mixture screws open about 10 turns as initial setting in your engine model.
 
"Hi – thanks for speedy your r

"Hi – thanks for speedy your response. I have to confess I am a little unsure of the idle mixture settings as the Seloc manual mentions an initial setting of 1 ¼ turns but that appears to be for the earlier carburettor. I will try the 10 turns as you suggest, this setting has been nagging me for a while now."
 
"This is a second posting of b

"This is a second posting of basically the same question, I just wanted to be a little more clear on what I am asking. I have a volvo penta AQ125B and I have the outdrive in a barrel and running the engine, I would like to know if someone can tell me how I can tell if the outdrive is picking up the raw water and if it is circulating through the engine like it is suppose to. This is the first I/O I have ever owned and don't want to burn it up. Thanks ahead of time for any of the help anyone can give me on this."
 
"Mark, it is not considered po

"Mark, it is not considered polite to hijack posts with other topics.

I have replied to your original post. Please feel free to ask further questions, but in your own threads.
happy.gif
"
 
"Hi…
Well things are startin

"Hi…
Well things are starting to look much better; I made a couple of not to scientific adjustments and manage to get it too idle, albeit still a little rough. Now is the time to get the synchrometer and coffee container on them for final tuning. It still seems to be delivering far too much fuel as the throttle control is not very responsive at low revs but that may be adjustment of the throttle control lever.
The water droplets appear to be completely unrelated as it looks like a water filter to pipe connection leak. Just another job to put on the list!"
 
"So, in other words, you are m

"So, in other words, you are making progress.
biggrin.gif


Hopefully, after you sync the carbs you may be able to adjust the idle mixture and the idle speed in a more scientific way....
wink.gif
"
 
I do feel I am making progress

I do feel I am making progress but more important than that is trying to understanding the machinery.
I owe a big debt of gratitude to this forum as a short while ago I would not have attempted these tasks. It does give you the confidence to try and after all you cannot call a mechanic if you break down 5 miles out.
Thank you and have a good week.
 
"Hi – still no joy I think its

"Hi – still no joy I think its time to bite the bullet and call the mechanic I am afraid. No amount of adjustment of the air / fuel mixture screws has any effect so maybe there are other problems that need checking.
There is a solenoid on the second carburettor that presumably shuts off air to the idle circuit, does anybody know how this works and cannot it cause the poor idling? There is no mention in the Seloc manual as far as I can see.
Thanks."
 
"Hi - just an update.
I had a

"Hi - just an update.
I had a mechanic check the timing and for vacuum leaks etc but it looks like it was the fuel pump the main culprit. However all idling nicely now.
But ….. frustrations … frustrations … The gear shift is locked solid cannot shift into forward or reverse now, am I allowed to swear? I checked the shift before it was launched and all was o/k so now it is a case of arranging a lift out to check the linkage and cable etc.
All the same thanks for you assistance guys."
 
"I was able to check the shift

"I was able to check the shift linkage on my drive with the boat still in the water. Its a matter of geometry. With the drive tilted all the way up and the tide in a high state, I was able to lay on the dock and reach the cover on the leg and get to the shift linkage mechanism."
 
Back
Top