Carb Question Following Rebuild
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=1299
Printed Date: November-22-2024 at 11:57pm
Topic: Carb Question Following Rebuild
Posted By: Jeff
Subject: Carb Question Following Rebuild
Date Posted: March-07-2005 at 6:00pm
I just rebuilt the Holley 4160 on my 1989 Nautique and I have a question about how it's running. I rebuilt it because it was smoking while idling rough and slow, and didn't want to start.
After finding a bad power valve, and cleaning everything, it starts great and purrs like a kitten. The problem it now has is when I get into the secondary's. When running at around 3,000 and I firewall the throttle, the engine is slow to come up to full power. It eventually gets there, and top end is no less than before. This condition just started after the rebuild.
I've checked that the accelerator pump nozzles are clear and I can see the fuel pumping without the engine running and at idle.
I don't know if there is a vacuum leak in the secondary circuit or if the accelerator pump is being sucked dry at RPM's off idle. How would I check?
Anyone have any ideas, or seen this before?
Thanks,
Jeff
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Replies:
Posted By: AWhite70
Date Posted: March-07-2005 at 10:27pm
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Check the vacuum diaphragm on the secondaries. Maybe it's got a leak that is causing the secondaries too slow.
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Posted By: captan1
Date Posted: March-08-2005 at 1:12pm
That's the first place I would look, it's a funky cork "O" ring that seals the diaphragm and a weak signal that opens them or some sort of bind in the operation.
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http://www.correctcraftfan.com/diaries/details.asp?ID=452&sort=&pagenum=1&yrstart=1978&yrend=1978 - 1978 Ski Nautique
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Posted By: Jeff
Date Posted: March-08-2005 at 5:17pm
I've pulled the vacuum diaphram housing off and looked at the diaphram itself. My first though was to put the old one back in, but the garbage man is long since gone.
The diaphram looks fine, and actuates when I suck on the port with the cork "O" ring. Is it supposed to hold a vacuum, or does it bleed down at a small controlled rate?
The cork "O" was replaced during the rebuild, and looks fine. Vacuum leaks are virtually impossible to see so I'd need to check it in operation.
To check for leaks in the system, I'd need to apply vacuum to the port in the carb barrel that ties to the diaphram. I was also thinking that a port may have become blocked during the rebuild. That's why I think the end to end check is needed. Know of an easy way to do it other than vaccum gun and hose held up against the port?
Do you guys think there is anything on the fuel side of the secondary circuit that would cause this condition? and how to check?
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Posted By: danman
Date Posted: March-16-2005 at 2:40pm
jeff-
I think I did the same thing when I rebuilt mine, I replaced the diaphram that came with
the holley rebuild kit. I later found out that
the rod length was differant from the original
that I took off. I had my old one saved, so
I went and matched my old one up with a new one
at a local parts store that had a big holley
display. I'll bet this is your problem
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Posted By: Jeff
Date Posted: March-16-2005 at 3:43pm
Danman,
I would never have thought of that. Now that my old parts are gone, I may have to experiment a bit. I'll head down to my local speed shop, which has been very helpful in the past, and see what they have for parts.
Do you recall if your original diaphram rod was shorter or longer than the rebuild kit. Any details you might have on you carb list number and the replacement parts would be a big help. If it was too long ago, I understand.
A little update, I've leak checked the entire secondary vacuum system and it's as tight as a drum.
Thanks again, I'll let you what I find.
Jeff
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Posted By: Jeff
Date Posted: August-01-2005 at 5:25pm
Problem solved! I e-mailed Holley and verified that my rebuild kit came with all the correct parts. They also gave me a list of things to check, one of which was the accelerator pump linkage. I don't recall changing the adjustment screw durign the rebuild, but it was way out. Once I set it properly, all is back to normal.
Thanks for the help.
Jeff
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http://www.correctcraftfan.com/diaries/details.asp?ID=398&yrstart=1986&yrend=1990 - 89SN
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