LUVTruck.com

Hi all, new to the site even though I have owned several Luvs in the past. I am now the owner of a 1980 with the Mikado trim package. This is one of the nicest Luvs I have owned.
Thre is NO frame rot which is so common on these trucks. The bed, rockers and floor pans are super solid. It has a smooth shifting auto trans and working air. I am working on making this truck my daily driver, but it has one problem that is driving me nuts! Upon heavy accelaration the truck bogs down and acts like it wanst to die. If you let off of the accelarator a few seconds, this cures the problem. I have done a COMPLETE tune up, looked for exhaust leaks (none found) and a freind of mine who owns a race shop just rebuilt the carb. He said to him, it sounds like the diaphragm in the vaccum secondary is dry and may have a tear and is not supplying the carb with the extra fuel needed under the heavy demand. This part was not part of the rebiuld kit and I can't find one any where. Is he right?
Should I just buy a webber carb and be done with it? Any and all suggestions will be greatly appreciated! I would really like to get this very nice Luv running the way it should!

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1962 Chevy C-10 Stepside-Rat Rod
1990 Chevy Suburban

The only way to combat violence is with greater violence!
Trying to please everyone is way to hard, but pissing everyone off is a piece of cake!

Maybe, but could also be a fuel restriction somewhere. If you haven't already, replace the fuel filter near the left rear wheel if it has one. Also don't forget the one inside the stock fuel pump. The end turns off with the filter inside.
Does it do this immediatly when you open the throttle, or after a couple seconds of acceleration it just sags back or bogs? The secondary should open at about 3/4 throttle.

I have replaced the fuel filter. It does it the second you open the throttle.

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1962 Chevy C-10 Stepside-Rat Rod
1990 Chevy Suburban

The only way to combat violence is with greater violence!
Trying to please everyone is way to hard, but pissing everyone off is a piece of cake!

It might be the accelerator pump on the carb.

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1975 V8 Luv
1980 Bagged Luv

The carb has been rebuilt including replacing the accelerator pump.

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1962 Chevy C-10 Stepside-Rat Rod
1990 Chevy Suburban

The only way to combat violence is with greater violence!
Trying to please everyone is way to hard, but pissing everyone off is a piece of cake!

what about the clinders over loading with gas and your engine isnt pushnig the burnt gas out quick enough my friend had a ecilpse that did that and it destoryed the 4th clinder becuz of pressure.

I just don't know at this point. like I said its driving me crazy! I have done all I know to do and I have had 2 competent mechanics look at this truck and they can't figure it out. The last one said he thought the carb needed rebuidling, so I had that done, but it still has the same problem. The truck is to nice to give up on! Anyone else with ANY suggestions, please let me know! Thanks!

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1962 Chevy C-10 Stepside-Rat Rod
1990 Chevy Suburban

The only way to combat violence is with greater violence!
Trying to please everyone is way to hard, but pissing everyone off is a piece of cake!

If it bogs after a couple seconds I would suspect fuel related--plugged filters etc. But since it does this instantly I believe it is carb related. The carbs secondary is opened by the linkage when it reaches about 3/4 throttle opening. If the throttle is opened too quick it will cause a bog. The vacuum diaphrams job is to slow this opening to a bit more gradual to prevent this when the secondary is opened suddenly. This allows the fuel to get flowing when the engine is ready to take it.
I think the guy in the first post may be right when he said it may be the diaphram is bad or not working.
A quick check of the diaphram can be made by--with the engine off, look at the position of its linkage and then have a buddy start the engine and see it it moves up or is draw in.

Thanks. I'll give this a try and see what happens. If is the diaphragm in the secondary, does any one know whre I can get one? Like I said, it was not part of the carb rebiuld kit, and I have checked all of local auto parts stores with no luck. Or when funds permit, just go ahead and get a webber carb? I see according to the site the redline 32/36 is the kit to buy. A seller on eBay that is close to me has a kit, but it is a 34/34. I want to make sure I buy the right kit. Does any know what the difference is between the two kits? Thanls for all the advise. This site has already helped me solve or answer questions about my truck! Now, If I can just get it running right.....

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1962 Chevy C-10 Stepside-Rat Rod
1990 Chevy Suburban

The only way to combat violence is with greater violence!
Trying to please everyone is way to hard, but pissing everyone off is a piece of cake!

Egg, I finally has a chance to try what you suggested in you last post. The rod on the vaccum seconday is drawn out as soon as the engine is started. Does this mean the vaccum seconday is working properly and I made have another problem other than a carb problem?

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1962 Chevy C-10 Stepside-Rat Rod
1990 Chevy Suburban

The only way to combat violence is with greater violence!
Trying to please everyone is way to hard, but pissing everyone off is a piece of cake!

The vacuum, linkage check is not 100% but it appears to work ok. There still may be a problem with a small pinhole in the diaphram alowing it to open a bit too soon. No good way to verify that without replacing it to see if it makes a difference. About the only way to find one is to get one off a used carb somewhere---maybe a salvage yard or from someone on here who has swapped their Hitachi out for a Webber and dosen't want the old one any more.
The other thing may be that there is still something plugged in the secondary fuel circuit. Maybe the jet, the fuel mixing tube, etc. Also make sure the proper rebuild kit gaskets where used for your model carb.
Many gaskets can have different holes punched out or not depending on the carb model.
One other long shot is--ignition problems, weak spark can cause a similar symtom, hesitation. Hopefully the plugs are new and gapped correctly? Standard plugs, nothing fancy like platinum, etc.
Good luck on your fix, we've covered about everything I can think of for now.

If you haven't gone through them yet I'd replace the points. Bad point gap, buildup on the points, etc could cause stumble problems or a higher RPM stumble under load that acts a lot like fuel delivery problems.

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95 Isuzu Trooper Daily Driver
86 Isuzu Trooper reliable backup
77 LUV 2wd stock beltway blaster (resting)
79 4x4 LUV project: 2.6L, 5spd, 31s (eventually)

MEPR: Man, my 4x4 makes all other LUVs look good

Thanks for all the info. The plugs are new and gapped at 30 thousandsths. The points have also been replaced and gapped correctly. I am going to a exhaust shop tommorow and have them check for any exhaust leaks I may not have been able to see. In the mean time does anyone have a vaccum secondary they know is in good working order and wants to sell?
Again this Luv is to nice to give up so I will keep trying to I get it right! If anyone else has any suggestions, keep 'em comming! This site has been very helpful so far, I wish I had found it sooner! Thanks for all the help!

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1962 Chevy C-10 Stepside-Rat Rod
1990 Chevy Suburban

The only way to combat violence is with greater violence!
Trying to please everyone is way to hard, but pissing everyone off is a piece of cake!

Hi, just got back from the exhaust shop and the truck did have an exhaust leak. It was right at the flange where the pipe goes into the manifold. The mechanic tightened those two flange nuts (at no charge!) and it has made an improvement in the way the truck accelerates! There is no longer a stutter when you first start off from a light, and there is improvement under moderate accelaeration, but it still bogs under heavy acceleration. At least it seems I'm headed in the right direction!

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1962 Chevy C-10 Stepside-Rat Rod
1990 Chevy Suburban

The only way to combat violence is with greater violence!
Trying to please everyone is way to hard, but pissing everyone off is a piece of cake!

What year truck is this? Could it be a clogged up cat. or muffler?

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OK, I'm over it. Where's the beer?

1980. No cat. Mechanic checked exhaust flow comming out of the muffler and he said it was fine. I am going to replace the entire system with a pacesetter header, new pipes and a cherry bomb muffler in ther near future. Thanks for your suggestion.

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1962 Chevy C-10 Stepside-Rat Rod
1990 Chevy Suburban

The only way to combat violence is with greater violence!
Trying to please everyone is way to hard, but pissing everyone off is a piece of cake!