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Runs at high rpm then dies coming down

J

jscc24

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I have a volvo 4cyl that will

I have a volvo 4cyl that will not idle adjusted timing cleaned carbs it will still only run higher rpms then stalls when you decellerate
 
"What engine model do you have

"What engine model do you have? When you say "carbs", I assume you may be talking of an AQ140, and AQ151 or an AQ171. Chances are that you may just have to adjust the idle speed and idle mixture and/or synchronize the carbs."
 
I am sorry that was a miss typ

I am sorry that was a miss type and I am not sure of the model however I believe it a 140hp 4cyl if thats any help
I feel like a fool I should know these things
Thanks again
 
"Hello All,

Well, I was pos

"Hello All,

Well, I was posting in another thread relating to essentially the rebuilding of a top half of an AQ131A, the project is essentially finished; engine runs great except....

...something about the timing. I get it set, runs great throughout the RPM range and then just decides to run poorly. I'll lose about 1000 RPM's and 10 knots. When I idle it back down to check the timing, the timing will have changed by a degree or two, or worse yet, it will correct itself and I won't be able to tell what happened.

It's almost as if one of the spark plugs quit firing; and naturally there's a drop in speed. It won't correct itself until I drop down to an idle for a little while or actually reset the timing with a timing gun. The firing order is 1-3-4-2.

This just started yesterday (8/10/07). All other times over the past few weeks, the engine has run great.

If anybody has any ideas on how I can get the timing to quit changing, I'd be most grateful.


Thanks,

Chris Robbins


FYI:
New Pertronix Ignitor Ignition Module
New Pertronix Flame-Thrower Ignition Coil
New Bosch Distributor Cap
New Bosch Platinum Plugs .028
New Starter
New Mando Alternator
New Osco Exhaust Manifold
New VP Thermostat
New VP Exhaust Outlet
New Head Gasket
New Exhaust Manifold Gaskets
New Intake Manifold Gasket
New Valve Cover Gasket
Rebuilt Cylinder Head"
 
"Chris, you may want to try ga

"Chris, you may want to try gapping the plugs at 0.032-0.035 and see if you notice any difference. This is from the Pertronix website: <font color=""0000ff"">"The Ignitor has no set specification in which the spark plugs should be gaped at. Every engine responds differently to spark plug setting. In most cases increasing the factory recommended gap by .005 improves the engine performance."</font>

Also, you may want to consider taking your distributor to a shop where they can check the advance curve and correct it if necessary.
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You can also try to hook-up a volt meter between the (+) of the ignition cold and ground and see if there is a drop in voltage when the drop in RPM happens."
 
"Now that you mentioned the vo

"Now that you mentioned the voltage, It does drop down to around 12.7 or so when this occurs. It usually puts out around 13.6 when at cruising speeds. Does this mean anything special?"
 
"Just wondering if you had a l

"Just wondering if you had a low voltage problem, as described in your Pertronix instructions.


http://www.pertronix.com/downloads/ignitor12vneg.pdf


Also, it could be a fuel related problem, like the anti-syphon valve in your fuel tank starting to act-up and occasionally restricting the amount of fuel reaching the carb. Or that the fuel pump is not pumping as much as it should. Or that the carb is overflowing and creates a very rich mixture. To troubleshoot some of the above possible fuel problems, you can run the engine from a jerrycan and see if the symptoms clear. You should be able to make a temporary arrangement where you can switch from the fuel tank to the jerrycan without stopping the engine. Or even easier, just check that the anti-syphon valve is not stuck and that the fuel pump delivers fuel at 2-4 psi."
 
"Okay, so I should try the fol

"Okay, so I should try the following:

Widen spark plug gap to .032-.035;
Check anti-siphon valve in fuel tank;
Replace fuel pump (been meaning to do that anyhow);
Rebuild carburetor (been meaning to do that, too);
Pull distributor and take to shop;

One question though, if I do need to take the distributor for service, what kind of shop should I take the it to? I've never had to have a distributor worked on before.

Thanks,

Chris"
 
"Chris, you should definitely

"Chris, you should definitely check the anti-syphon valve, but I would not replace a good fuel pump: if the pressure is good, I would keep it. Rebuilding/cleaning the carb is also a good thing to do (make sure the fine filter is clean).

Regarding the distributor, you have to find a shop that can check the advance curve. They usually install the distributor in a machine that makes it turn at different speeds and it makes a graph (a curve) showing what the advance is at different RPM and then compares it with the design advance curve. Sometimes they have to change the springs and some other internal components in the distributor in order to get a curve reasonably close to the design curve. This is one of the most neglected tests, and many people have had ignition problems for years (even leading to detonation and engine damage) without realizing that their distributor was acting-up. It is not even uncommon to find brand new distributors with the wrong advance curve.

You can always have a first look at the distributor and make sure that the weights are not seized and that the springs are not broken. For that, you have to lift the cover below your Pertronix module."
 
"Okay, thanks. As for the dis

"Okay, thanks. As for the distributor shop, I meant what type of shop would I look for, not what are they capable of. If I do a search for "distributor shop" in google I'm sure I'll be overwhelmed with wholesale distributors and shops. To be more specific, am I looking for a machine shop, starter/alternator repair, etc...

Thanks,

Chris"
 
"So, here I am still WORKING O

"So, here I am still WORKING ON the boat instead of RIDING IN the boat. I pulled the anti-siphon tube, it was clean. Widened the gap on the plugs to 0.035. I would love to see if that makes a difference, but now the engine won't start. Got a click on at the solenoid but no crank. I figured the battery was low because I left it on for a few days (the ignition was off, whew...) Charged the battery up, no change. The starter and solenoid are brand new, so I thought maybe it might be the relay. Bought a new one, put it on, solenoid clicked once and then the whole system died. No outdrive tilt, no tilt indicator light, no power to the instrument panel, no panel lights, not even a click at the solenoid. For all practical purposes, it seems as if the battery was taken out of the boat. Of course it hasn't, the bilge pump, blower, horn, depth finder, stereo and nav lights all work like a charm. So, I put the old relay back in, no change. The 40 Amp circuit breaker didn't trip and the giant inline fuse is intact.

Ideas anyone?

Thanks,

Chris


New Osco Exhaust Manifold
Replaced Cylinder Head
New Head Gasket
New Exhaust Manifold Gaskets
New Intake Manifold Gasket
New Valve Cover Gasket
New VP Thermostat
New Timing Belt
New Accessory Belt
New Pertronix Ignitor Ignition Module
New Pertronix Flame-Thrower Ignition Coil
New Mando Alternator
New Starter
New Bosch Distributor Cap
New Bosch Platinum Plugs .035
New Starter Relay"
 
"How is the ground between the

"How is the ground between the engine block and the (-) of the battery? Also, check the line between the 40 Amp fuse and the ignition key and instrument panel."
 
"The ground is good. I cleane

"The ground is good. I cleaned all contacts a couple of weeks ago. As far as the 40 Amp fuse, did you mean to say "circuit breaker", and if so, what am I checking for? I have a multimeter, but electronics is absolutely not my strong point.

With the battery turned on, I have power going from the battery to the starter solenoid, from the solenoid to the the 40A breaker.

Attached to the 40A breaker is the 12VDC lead going to the fuse panel behind the steering console. Everything connected to the fuse panel works as it should. Also attached to the breaker is the power lead to the 30A Ignition Relay and the lead for the tilt motor with it's 20A inline fuse. The tilt motor is not operating and there doesn't appear to be power going to the ignition relay (I pulled the plug off the relay and checked for voltage coming in, there wasn't any). The tilt motor is dependent on the ignition being switched on.

The question now would be, of the three items getting power at the circuit breaker, why are two (relay, tilt) not working and the third (fuse block) is? This is quite confusing. I'm assuming that I don't have power at the ignition switch because the relay isn't receiving current.

As a side note, I don't think I have current going to the coil either. Multimeter reads 0.00 on the + side of the coil with the battery and key on."
 
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