Hesitation in acceleration

[Dinoz]

Hey guys,

I noticed this past weekend that I have some hesitation under load, such as pulling out a skier. I think it was getting progressively worse. Any ideas how to fix, or what the problem might be? It's an '89 Comp with the PCM 351.

Thanks,

DZ.

[DKJBama92Mariah]

Start simple with replacing the fuel filter. Then i'd check the timing. Pull the dist cap and make sure the mechanical advance is moving freely. Then pull the flame arrestor and look down the throat of the carb while someone pumps the throttle. You should see fuel squirt into the throat from the accelerator pump. My money is on the filter though.

DKJ

[Dinoz]

Thanks DkJ,

Is the fuel filter fairly easy to replace? I haven't worked on these engines at all yet. So I'm a little nervous.

[DKJBama92Mariah]

Its pretty simple. It should be located to the front and left of the engine right before the fuel pump. Its probably the old-style canister type where the filter fits inside a permanent metal bowl. I just replaced mine with a kit that uses a spin on filter that looks like an oil filter; a whole lot easier to change. See this link: http://www.skidim.com/prodinfo.asp?number=SIE18-7852-1

DKJ

[Dinoz]

Thanks again.

One more question, do you think that this would effect my overall top end as well? I'm finding that I'm only able to achieve around 37mph at most, RPM at 3,500rpm. Sounds a little low to me. Any thoughts?

DZ>

[DKJBama92Mariah]

Could very well be the filter. That also be caused by the timing not advancing fully or the power valve in the carb not opening. The power valve opens up only under high load situations like WOT or when pulling up a skier. Essentially it just dumps alot of extra fuel into the engine when you need max power. I'd start with the fuel filter though. Its cheap, easy, and should be changed yearly anyway.

DKJ

[Dinoz]

I'll check that out next time I'm at the boat. Would this effect overall fuel economy as well? Again I noticed that it seems to be a little more thirsty than at the beginning of the season.

DZ>

[DKJBama92Mariah]

A leaky power valve will definitely hurt fuel economy, but the problem you're having would make me think that its not opening at all.

DKJ

[Dinoz]

True. I'm more concerned with the performance at this point anyways. But just as a note, if I have a quater tank of gas in it, I will burn that in a matter of 5 to 6 ski pulls now. Not cheap... Is this valve easy to check?

[DKJBama92Mariah]

WOW. Thats pretty bad.

http://www.chevyhiperformance.com/techarticles/74058/

[Dinoz]

That article is great, I will definately check that out as well. It's interesting to read that with this blown valve, it could run extremely rich as well. I'll let you know how it goes.

DZ>

[DKJBama92Mariah]

One thing about that though. Marine Holleys typically don't have the usual power valve blowout problems. They have a check valve somewhere in there to prevent a backfire from blowing it. BTW, 3,500 at WOT is too low. It should be somewhere around 4,000-4,400. Check out the mechanical advance in the disributor as well and make sure they're not sticking. Its free and easy to check and it could easily be causing the problems you're experiencing.

DKJ

[DKJBama92Mariah]

One other thing. You can download the PDF service manual for your engine at http://www.correctcraftfan.com/reference/ It has a pretty decent section on troubleshooting.

DKJ