Volvo 5.0GL won't rev above 2k RPM

[AZChapBoat]

I recently bought a '98 Chaparral 240 Signature cruiser. It only had 360 hours on it & the previous owner said he filled up the gas tank once/year. It wasn't running above 3k rpm the first day I ran it but by the end of the weekend, after putting some hours on it, rpm's would periodically 'surge' and finally got up to running at about 3,500 rpm. I decided there were probably engine deposits and bad fuel in the system so I got some zMAX Marine Fuel Formula treatment & added to the tank the 2nd weekend. For the first 15 or so minutes with the throttle all the way down, the boat wouldn't go above 2k rpm but then just snapped out of that and was fine and ran up to 4k rpm and pretty well the rest of that day. Last weekend, the boat would not go above 2k rpm at all under a load but will rev full rpm's in neutral (so I don't think it's the throttle cable) no matter how long I ran it. Talked to a mechanic and he said it was running in engine protection mode, but this is the the GL which is not fuel injected & isn't supposed to have the protection mode. Temp & oil pressure gauges are normal and the engine sounds fine, except like there's something holding it back. Outdrive looks fine and props spin freely. Mechanic can't get to it for at least another week so this weekend I'm sitting at the dock if I can't find the solution. Since the problem started immediately after I put the fuel treatment in the gas tank, I'm thinking it could be a fuel system issue and should start by replacing the fuel filter and cleaning the carburetor filter. Any ideas?

 

[chris600uk]

Re: Volvo 5.0GL won't rev above 2k RPM

It certainly sounds like the fuel filter to me.

I had a car that did that once and nothing seemed to be wrong, except one day when I tried to drive it over 50 mph it seemed to die on me, and when I slowed down a bit it ran just as before.

Fuel starvation.

A little plastic fuel filter solved the problem, the old one was clogged.

Chris.

 

[cr2k]

Re: Volvo 5.0GL won't rev above 2k RPM

Very much a fuel issue. Old fuel bad. clogged filters bad. water in fuel very bad.

Also could be a fuel pump issue.

One more thing to check is the spark plug wire routing on the port side of the engine. Make sure wires are NOT running in order from front to back. Due to firing order there are adjacent cylinders firing and one wire can cause induction in to 2nd and "kill" this cylinder. Can't remember which ones off hand. Check firing order and you should be able to figure this out.

New fuels only have life of 90 to 120 days then start to go bad.
Ethanol in gasoline will dissolve aluminum tanks depositing alum. granules in fuel system clogging them.
Have good filters and change often.

Start with the filters in line and at carb if so equipped. Then check fuel pump pressure.

Carb orifices could be corroded from water in fuel too.

 

[cr2k]

Re: Volvo 5.0GL won't rev above 2k RPM

Oh yeah...does your engine have a shift interrupter module. If so your switches could be out of adjustment, or the module could be bad. 2k is about right for this.

But I would try the fuel stuff first.

 

[bruceb58]

Re: Volvo 5.0GL won't rev above 2k RPM

Oh yeah...does your engine have a shift interrupter module. If so your switches could be out of adjustment, or the module could be bad. 2k is about right for this.

But I would try the fuel stuff first.

No shift interrupter on a Volvo.

Definitely need to take off the filters and drain them into a clear glass jar and see what's in there.

Since you have no idea how old the fuel is, I would assume it is old/bad. Yo need to get that out of the equation.

What model is your Volvo? Some Volvo's have protection mode even with carbs. Mine is a 7.4L "LK" with a carb and it has protection mode. I do know that 5.0 and 5.7 "LK" does not but if your is a "BY" model it may.

 

[AZChapBoat]

Re: Volvo 5.0GL won't rev above 2k RPM

Seeing how it ran ok up until I put the fuel treatment in, my gut feeling is it's a fuel issue and not spark plugs/wires (though I am going to check them to see if they need replacing). I have used up all the old fuel in the boat but the damage/clogging to the filters may have been done in the process of burning that fuel. Also could be the fuel pump. I thought I was out of the woods after last weekend when the low rpm's happened the first 15 or 20 minutes and then the boat ran really well the rest of that day, and I ran it at WOT for a good portion to use up that old fuel and get the fuel system treatment working thru the system. According to the literature, the GL (carburettor) engines don't have the protection mode but I'm still learning about this engine. Will have to get the serial no. & model off the engine to be sure. Thanks for the input!

 

[bruceb58]

Re: Volvo 5.0GL won't rev above 2k RPM

There is no fuel treatment that will make bad fuel good again. Some fuel treatments may delay good fuel from getting bad but that is it...no silver bullet I am afraid.

I replace my fuel filters every spring so you need to do that anyway. Drain the fuel filters into a glass jar to see what it may have picked up. That will give you clues to what is in your tank.

 

[Bondo]

Re: Volvo 5.0GL won't rev above 2k RPM

Ayuh,... You've got a Brand New to you boat,...
Do a Full,+ Complete Tune Up,+ Service on it....
Atleast then you'll have a baseline to work from....

Jeeze,... It seems everybody thinks all you do is add Gas,+ GO in a boat......

 

[AZChapBoat]

Re: Volvo 5.0GL won't rev above 2k RPM

Previous owner had a full tune-up & yearly service done on it at the beginning of the year and hardly used it since, but as I'm finding out the outfit that did the work has a lousy reputation and their lease on the marina was not renewed so who knows if they did a good job or not. Filters all look new, but if the gas was bad and the boat sat, they're getting replaced. Previous owner also told me he never used the porta-pottie but when I went to clean that part of the boat I got a little surprise...
I've spent most of the last 3 weekends I've had the boat getting familiar with every part of it, figuring out how everything works and going through it from bow to stern so not the case here of just adding gas & go, but still learning.

 

[Bondo]

Re: Volvo 5.0GL won't rev above 2k RPM

I've spent most of the last 3 weekends I've had the boat getting familiar with every part of it, figuring out how everything works and going through it from bow to stern

Ayuh,... Excellent,.... Welcome Aboard Btw.....

There's No doubt you're fighting a fuel delivery Issue,...
It can be ANYTHING from the tank's Vent,.. to the Carb....
Good Luck,....


Edit; Posts: 22,000
Just alittle bookmark,... Thanks,...

 

[stuartdmc]

Re: Volvo 5.0GL won't rev above 2k RPM

I also have this problem and have been around and around, I went to my Volvo mechanic to get some input and he finally gave-in and told me to check and see if the vapor separation tank was clogged. Mine is located under the High pressure fuel pump; it?s made out of aluminum and will corrode. Row water runs through the tank and cools the fuel releases vapor which allows fuel to be injected at (WOT) HIGH speeds. Well, I ran to the boat and notices that the outer hose connected to the tank was corroded, as I was taking it off it fell off in my hand. The ?? nipple from the tank that the hose connected too had corroded completely off. The hose was so corroded that not a drop of water could get through. I dug deeper and found that the out going lines were dry as can be. So the solution is to unclog the passage way letting water pass through to cool the fuel. Hopefully its not corroded and is ready to fall off like mine was.

Read up on the vapor lock scenario, there?s a flow switch in side the High pressure pump the is related to the fuel flow (WOT).

My tank runs about $306.00 if you have to replace it, hopefully, all you need to do is unclog it a screwdriver then run our boat. But first make sure that the water is circulation and returning back through the system.
Lets me hear back?
Stuart

 

[AZChapBoat]

Re: Volvo 5.0GL won't rev above 2k RPM

Stuart - I assume yours is a fuel-injected engine?

UPDATE - I changed the fuel filter and drained the fuel into a clear container and noticed a small amount of sediment; nothing that seemed like the problem but if it was all at the head of the fuel pump intake I guess it would. Removed the fuel line, cleaned the in-line strainer/filter (nothing in it), drained fuel out of the carb, replaced the spark plugs (they were a mess), did a light cleaning of the carb, put everything back together and went for a ride. Engine did the same thing; wouldn't rev past about 2,500 rpm. After about 10 minutes out, decided to head back to the dock; about 1/2 mile from the dock, the engine increased RPM's to about 3,800 and off we went. Ran at WOT for about 1/2 hour and all was running well; all gauges were normal.

The next day, I remembered that I forgot to clean the air filter, so did that before I started the engine. Started it up, got out of the no-wake zone and put the throttle down and immediately shot up to 4k rpm. Ran great the rest of the day, but on the trip back, noticed it would only run at about 3,700 or 3,800 rpm. Performance didn't seem any less and couldn't tell if the speed was any less because I need to replace my pitot tube assembly (always something to fix), but still going to have the mechanic check everything out. I can handle the more simple stuff but want to have an expert really give it a good inspection. I'm not sure exactly what the problem was, but I don't think I'll have any problem with fuel sitting in the tank too long as I burned at least 1/2 a tank this past weekend and I'm sure much more this holiday weekend.

Thanks for everyone's input. This is a great site and I'm reading up on so many posts to learn as much as I can about this great new hobby!

 

[Bondo]

Re: Volvo 5.0GL won't rev above 2k RPM

replaced the spark plugs (they were a mess),

Ayuh,.... How So,..?? Explain a Mess....

Does your Volvo have exhaust Shutters,..?? Are they still Where they belong,..??
An Exhaust Restriction can cause some Major Issues that mimic Fuel issues....

 

[AZChapBoat]

Re: Volvo 5.0GL won't rev above 2k RPM

They were pretty gummed up; significant carbon build-up on them. They looked old, but have no way of knowing how old. I did find a box of 6 plugs identical to the one's I bought so someone may have been thinking of replacing them... Possible the carb is running too rich; mechanic to check this out.

It has exhaust bellows; engine exhausts thru the drive and I haven't checked as I'm still learniing how that part all works. If they were not where they belong and were causing a restriction I thought that problem would manifest itself by high engine temp, which I'm not having. At idle, you can see the exhaust being expelled from the drive unit but will check on that as I have a dock neighbor who had that problem and nearly smoked his engine!

 

[Bondo]

Re: Volvo 5.0GL won't rev above 2k RPM

They were pretty gummed up; significant carbon build-up on them.

Ayuh,.... Black,..??

Have you read This yet,.?? You should...

 

[AZChapBoat]

Re: Volvo 5.0GL won't rev above 2k RPM

UPDATE - turns out the problem is a dirty carburetor. Won't know how bad until it gets torn apart, but thought it would be good to close this thread with the resolution for anyone's future reference. There was also some crap growing under the distributor cap, which I should have checked when I replaced the spark plugs and that couldn't have helped the situation. Yanked the Holley carb off the engine getting it cleaned & rebuilt. One weekend away from the lake will be worth not having to play mechanic every weekend.

 

[AZChapBoat]

UPDATE -Volvo 5.0GL won't rev above 2k RPM

UPDATE -Volvo 5.0GL won't rev above 2k RPM

7-28-09 UPDATE -
Rebuilding the carb did help, but only led us to the root of the problem. After reinstalling rebuilt carb, boat was sluggish and would only top out at 3,600rpm. Compression test showed 2 cylinders were low (about 110 & can't remember which ones). Mechanic thought it was an exhaust restriction. Pulled off the exhaust manifold & found the gasket was deteriorated and water was getting back into the engine. The month-old spark plugs on these 2 cylinders were rusted. Hoping the cylinders aren't pitted and clean up, otherwise my new hobby may consist of hanging out at the dock for some time.

Granted I don't know what kind of attention this engine got, but should a check on these gaskets be part of an annual maintenance program?

Going to replace the gasket and anything else mechanic finds, clean it all up and see what happens.