Volvo Penta AQ271C back firing 3000 rpm

[Greg68S]

1990 Carver 2357 Montego
Volvo Penta AQ271C 5.7 V8
Duo Prop

Engine back fires at 2800 to 3000 rpm's. Boat will not climb above 3000 rpm. Just pops and fouls a plug or two each time. But then will idle perfectly at 650 to 700 rpms New wires, plugs, distributor cap & rotor, holly carb equipt w/fresh rebuild. Timing set at 6 degrees per volvo manual. Idles perfectly at 650 to 700 rpm's. What bugs me is that the manual says that the number one cylinder on the cap should be in front at 6 o'clock but its actually in back at 12 o'clock. Plugs are gapped appropriately.
HELP ANYONE. Any and all is appreciated.

 

[Greg68S]

Ignition Problem or timing chain??? Volvo AQ271C

Ignition Problem or timing chain??? Volvo AQ271C

1990 Volvo-penta AQ271C 5.7L V8 GM 350
new parts this year
coil
ignition module (pick up coil)
cap/rrotor
wires
Spark plugs

She ran perfect this past weekend until Monday afternoon. On our way back from lunch we were cruising at 3000 rpm's then began to slowly die out and it ran on what seemed to be 4 cylinders before it quit. I checked my compression and it is good. All of the plugs look good. I have no spark what so ever. Oil is good no water. Fuel is fresh and non ethanol. I am on my second coil. They seem to get extremely hot. So hot that they are hard to hold on to. Is it possible that I may have jumped a tooth on the timing chain? Or is there a resistor somewhere else that should check? I don't believe a coil should get that hot. I'm at a loss. Any input is appreciated.

 

[Walt T]

Re: Ignition Problem or timing chain??? Volvo AQ271C

Re: Ignition Problem or timing chain??? Volvo AQ271C

Are you positive you have the right coil? I'm assuming this is a Prestolite distributor. You might try disconnecting the tachometer and see if that helps. It isn't the timing chain based on what you're describing.

 

[Greg68S]

Re: Ignition Problem or timing chain??? Volvo AQ271C

Re: Ignition Problem or timing chain??? Volvo AQ271C

Ok that's a huge relief I really didn't want to pull this early. Ok so here is what I've got. Just a little history. I bought this '90 Carver 2357 Montego two months ago. I watched it be neglected for 3 years. I had it surveyed and found it to have solid solid bones and some fuel problems. I paid $3500 for it figuring that I was not going to loose out on this one. I drained all fuel from the tank (mostly water), rebuilt the carb, replaced all ignition parts. Coil, plugs, wires, cap/rotor, and the ignition module (pick up coil). The prestolite distributor was paired with a prestolite coil equipted with an internal resistor. Now since then I have changed the oil twice (last record of service was 5 yrs prior) and put 10 hours on her. She ran absolutely beautiful. But I have burnt up to coils. Both coils were equipt with an internal resistor. Now why am I burning them up? Is it possible that I have the wires hooked up incorrectly? Purple is ignition and I have that going to positive.

 

[Maclin]

Re: Ignition Problem or timing chain??? Volvo AQ271C

Re: Ignition Problem or timing chain??? Volvo AQ271C

The wiring diagram for the AQ271 shows an external resistor, page 23. It shows a brown wire with inline resistor from the alternator connected to a purple wire going to the coil + terminal.

You can go to Publication search - Publication Search : Volvo Penta

and put in aq271 for engine type to get a list of PDF's, one of them will be the owner's manual which has the wiring diagrams.

 

[Greg68S]

Re: Ignition Problem or timing chain??? Volvo AQ271C

Re: Ignition Problem or timing chain??? Volvo AQ271C

Ok thanks for the literature reference. I found something. On my coil the wires are paired correctly except for one. My wires are paired equally 3 & 3 between the positive and negative. The positive should has 4 and the negative should only 2.

 

[Scott Danforth]

Re: Ignition Problem or timing chain??? Volvo AQ271C

Re: Ignition Problem or timing chain??? Volvo AQ271C

Disconnect the rev limiter and see if that helps

 

[Greg68S]

Re: Ignition Problem or timing chain??? Volvo AQ271C

Re: Ignition Problem or timing chain??? Volvo AQ271C

I read the diagram incorrectly. There are 4 wires going to the positive terminal of the coil, but I only have 3. There are 3 wires going to the negative terminal of the coil and I have 3. What will disconnecting the revlimiterd do? And also when the boat is at top speed my tach only reads 3200 rpms. which is wrong, it should reading 4600 -4800.

 

[Greg68S]

Re: Ignition Problem or timing chain??? Volvo AQ271C

Re: Ignition Problem or timing chain??? Volvo AQ271C

Where is the Rev Limiter? What does it look like?

 

[Maclin]

Re: Ignition Problem or timing chain??? Volvo AQ271C

Re: Ignition Problem or timing chain??? Volvo AQ271C

It is #22 on that diagram. I can't remember exactly what it looks like, sorry!

 

[Maclin]

Re: Ignition Problem or timing chain??? Volvo AQ271C

Re: Ignition Problem or timing chain??? Volvo AQ271C

You may not have it, I have read some posts that indicated it was not always installed even though the wiring diagram in the VP manual shows it. Just follow all the wires from your coil to be sure.

 

[Silvertip]

Re: Ignition Problem or timing chain??? Volvo AQ271C

Re: Ignition Problem or timing chain??? Volvo AQ271C

Because the tach reads low does not mean the tach is bad -- it means the engine is not capable of reaching the desired rpm. If the coil is too hot to hold and you have no spark then fuel, oil changes, filters and the like are not the issue. Spark is the issue and that's electrical. As stated, an incorrect coil or a coil that requires an external ballast resistor (either a separate resistor or a length of resistance wire in the circuit to the coil) is missing. If the resistor or resistance wire are "open" then the engine may start but would not stay running when you released the key.

 

[Greg68S]

Re: Ignition Problem or timing chain??? Volvo AQ271C

Re: Ignition Problem or timing chain??? Volvo AQ271C

I believe I have the correct type of coil. I have read that the rev limiter is problematic in these years. I have also been told by a local mechanic to take it off. After it quits if I leave it alone overnight it will fire right up and run fine. The way it died out this last time suggests to me that it could be the rev limiter. But I won't know what I have until I get there on Saturday.

 

[Scott Danforth]

Re: Ignition Problem or timing chain??? Volvo AQ271C

Re: Ignition Problem or timing chain??? Volvo AQ271C

The rev limiter is a small black box (about the size of a pack of cigarettes), probably mounted on the transom. It is a known failure point. It is supposed to trip at 5100 RPM, however in many cases it limits well below. It has 3 wires in a black sheath. Black, Red, and Grey.

There is no ballast / resistor wire on the 271A, B, or C engines as the original VP distributor is a magnetic trigger unit from Prestolite.

Also, if you are running on the original coil, mine was getting hot. In my case it turned out it had a leak and was loosing oil out the tower.

 

[Greg68S]

Re: Ignition Problem or timing chain??? Volvo AQ271C

Re: Ignition Problem or timing chain??? Volvo AQ271C

So basically this is what I am concluding in my head. Each time the boat has died I have list spark. Each time it has died I had happened in the evening or when I was leaving to go home. So each time I replaced a coil and the engine fired. So really what I'm running into is an intermittent problem that is heat related. Each time the boat has had plenty of timing to cool. So if I were to go and start my boat right now it should fire up. Such is my theory.

 

[Scott Danforth]

Re: Ignition Problem or timing chain??? Volvo AQ271C

Re: Ignition Problem or timing chain??? Volvo AQ271C

As I stated, I would have removed the rev limiter from the circuit and ruled that out. the next thing that could cause the problems you describe about loosing spark is the distributor module itself could be going.

 

[Greg68S]

Re: Ignition Problem or timing chain??? Volvo AQ271C

Re: Ignition Problem or timing chain??? Volvo AQ271C

The module is brand new. That was my second replacement. And the problem still persists. So Tonight I will be removing the rev limiter

 

[diesel1960]

Re: Ignition Problem or timing chain??? Volvo AQ271C

Re: Ignition Problem or timing chain??? Volvo AQ271C

Having similar problems with my Volvo Penta AQ290A (GM350) with installed Mallory Distributor.Can't get more than 3100 RPM,problem with idling.
Check what voltage you have to the coil with ignition ON-before you start engine,and when running.

 

[Greg68S]

Re: Ignition Problem or timing chain??? Volvo AQ271C

Re: Ignition Problem or timing chain??? Volvo AQ271C

What should my voltage be?

 

[diesel1960]

Re: Ignition Problem or timing chain??? Volvo AQ271C

Re: Ignition Problem or timing chain??? Volvo AQ271C

12 V minimum