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AQ 151 Will not idle

V

vern

New member
"Recently rebuilt both Solec c

"Recently rebuilt both Solec carbs, using Sierra 18-7000 kits. Discovered years of sediment in carbs after the front carb float value stuck open and flooded the engine so much I had to replace the plugs.

After rebuild, I cannot get the engine to idle (or run at any constant RPM). As long as I pump the throttle, I can keep it running, but at a constant RPM, it dies. I've noticed that the front carb does not appear to be getting fuel thru the idle jet, unless throttle is advanced (accelerator pumps both work great), while the rear carb shows a constant mist.

I have replaced the fuel pump and cleaned the steel fuel line and fittings. I have even swapped the carbs around and the front carb always acts the same.

I know I am missing something here as I have read thru many of the posts on these types of issues, but they all point to the fact that the engine needs to idle to be able to tune and sync the carbs. I used the settings as outlinned in my Clymer Volvo shop manual and I have downloaded the Op manual mentioned in several of the posts.

I know it's a DUH kind of thing, but I am not seeing it. Thanks for any insight."
 
"Get hold of a uni-syn tool &#

"Get hold of a uni-syn tool (vacuum flow meter) to properly synchronize the carbs (the Seloc repair manual and the uni-syn instructions tell you how to do it), then re-adjust the idle mixture and idle speed."
 
Thanks.

I have the tool on

Thanks.

I have the tool on order and should recieve tomorrow. Wasn't sure if that was the only problem I had.

We'll see what the weekend brings!
 
"If the front carb act the sam

"If the front carb act the same after the swap, most likely they are not properly synchronized. Please post again if the problem persists after synchronizing the carbs."
 
"Hi guys, please excuse my con

"Hi guys, please excuse my confusion here, but how does one sync carbs when the engine will not idle? This problem sounds like the fuel is not reaching the front carb at all and that the rear carb is attempting to support all combustion. Could the line servicing the front carb be blocked? What number of turns did you use on the air/fuel adjustment screws? New style initial setting is about 8 turns and about 2 for the old style. New style needle goes into carb at 90 degrees, old and about 45 degrees, or so the Seloc manual states.
I'm about a day away from attempting to start my 151 after carb rebuilds
so please keep us posted!!! Tom"
 
"Tom, it would be mighty diffi

"Tom, it would be mighty difficult to plug-up one of the fuel lines. I suspect that the front carb butterfly may be completely closed because of the way levers 8 and 13 are adjusted respect each other; this is probably the reason why it makes no difference swapping carbs. If it was my engine, I would start making a rough setting of the idle mixture, then increase the idle speed so that the engine does not stall, then synchronize the carbs until the uni-syn tool indicates identical vacuum/flow on both of them, then do a final adjustment to the idle mixture and idle speed."
 
"I agree Eduardo, the fuel blo

"I agree Eduardo, the fuel blockage would be a stretch but if I read Kevin's post alright, the rear carb performs somewhat. And I agree that it would be better to be a little too rich rather than too lean to keep the fire burning.
I would be interested in knowing what carb base Kevin has, perpendicular or 45 degree fuel/air screws. I intend to get a handle on these carbs; they are said to be simple so they should be right down my alley
Tom"
 
"Hello All,
At the end of las

"Hello All,
At the end of last season I had a similar problem to that described by Kevin (the front carb seemed to be doing little or no work with the rear carb taking on all the duty). This resulted in the engine stalling in the 900 to 1500 rpm range. At the time I had decided to install an electronic ignition module and to re build the carbs.
I have today started up my AQ 151 and after setting the linkage rod clearances, idling speed and mixture screws as described in the volvo manual, the problem disappeared and the engine is working beautifully. (syncing with uni - sync to follow). Here are some of my observations during the carb re build:
1)stripped both carbs and removed all external paint as the carbs were to be re painted later on.
2)carefully faced all mating faces using 2000 grit emery paper over a face plate.
3)cleaned the underside of the top part of the carbs with a fine scraper (this cannot be faced on the faceplate due to design of casting)and then checked for proper seating with main body using a 0.001" feeler gauge.
4)cleaned all parts including carb bodies and bases etc. in alcohol in an ultrasonic bath.
5)on re assembly, removed the fine mesh filters around the banjo bolts supplying fuel to each carb. Instead of these an in line fuel filter was installed in the fuel line, just prior to the rear carb.
6)the re build kit came with two copper washers for the needle valve. The thicker washer was used to get the same height of the valve relative to the housing as before the re build.
7)the metal plate between the carb base and the manifold has to be installed in a particular position. Observe the markings on the plate('front/ top' for the front carb and 'rear / top' for the rear carb.
8)changed the tiny 'o' ring on the mixture screws to ensure tight seal with base (not included in kit).

Please excuse the long post, but one or more of these actions seems to have cured the problem. Hope this helps."
 
"Thanks everyone for all the h

"Thanks everyone for all the helpful hints.

First, I have an '87 AQ151 with dual Solec 44 PAI downdraft carbs. Application is on 14x64 houseboat.

This past weekend, using the Clymer Volvo manual and the Op manual d'loaded from Volvo, I adjusted the carb linkages as El noted. It wasn't off much, but enough to cause the previously noted problem. Set the idle screws per spec and fired it up. It was now running well enough to allow me to adjust the idle screws for a smooth idle at approx 850-900RPM. We were able to cruise Sun and Mon and it ran well, althou I did have some stalls at idle while docking after the Mon run in.

Hopefully that will be better after I use the Uni-Syn to sync them up. I have the tool, but waiting for the Seloc manual which I should have this week.

Thanks again"
 
Just an FYI I rebuilt my carbs

Just an FYI I rebuilt my carbs with OEM kits and I had same issues. Took boat to a repair shop and after many hours and money it was the OEM carb kits had to have new holes punched out of the gaskets to feed for idle? They were just not the same as the old ones. So much for OEM parts saying there the same?
 
"Hi Warren. What was the carb

"Hi Warren. What was the carb kit number you bought and what carbs do you have? It is good to have this information on record for future searches and solutions.

Thanks, Tom"
 
"Hi,After having converted my

"Hi,After having converted my VP AQ151C to HotSpark electronic ignition and also completely rebuilding the Solex PAI44's last winter,I have finally launched the boat for the season and carried out some sea trials.
I can now safely say that I am absolutely satisfied with the result and I would recommend this conversion. Starting is unbelievably easy (no need to pump the throttles)and idling is very smooth with plenty of power at WOT. There was however one small snag. The tiny 'O' ring which creates friction between the mixture screw and its housing thus prevents the screw from coming undone and also air leaking into the carb (late model PAIs)had perished. This had not been replaced as it did not come as part of the kit. After a few hours running the mixture screw rotated due to engine vibrations and the original setting was lost resulting in uneven running and low performance and finally the engine stalling at idle. This was temporarily fixed by winding PTFE tape tightly into the undercut where the 'O' ring normally sits and re setting everything.
Does anyone know where to get replacement 'O' rings for the mixture screws?
Thanks,
Lawrence"
 
"Lawrence - If you cannot find

"Lawrence - If you cannot find a replacement, send me your mailing address and I'll send you my spare. Hopefully I'll not need it after I replace my carbs. However, I think I saw a similar sized o-ring in our local hardware store. I think they are out there.

Tom"
 
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