1985 2.8L V6 4x4 PU carb & Q's - Need Help!!! - S-10 Forum
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1985 2.8L V6 4x4 PU carb & Q's - Need Help!!!

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Old 11-04-2003, 03:27 AM   #1
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1985 2.8L V6 4x4 PU carb & Q's - Need Help!!!

Thanks to any out there who can help.

Problems:

- I am burning a lot of gas it seems. I know this model is a hog, but this is pretty abnormal.

- getting a little bogging upon acceleration\initial gas pedal

- high RPMs between shifting (45+ or so sometimes)*this may not be a big problem.

- I had a tranny tech take it for a test run, and he feels the tranny is ok, but he did mention it felt like it was "missing" (misfiring).
I'd like to understand what that means.

- hard starts when cold (takes initial pressing of gas pedal before, then cranking 2-3 times to get started. Starts fine if driven recently though).

- doesn't seem to have a lot of power, up a steep hill for example. I've heard they aren't the most powerful models, but this seems a bit abnormal.

- loud "whine" when in 4L (no noise when in 2w drv, slight whine that seems normal in 4H...but pretty loud in 4L). Chevy serv tech had a listen and said it was normal, but I thought I'd check.

I read many posts here saying the 2.8L v6 (carbureted) is a gas hog, but I want to check everything I can myself to try and get it running best "it" can.
Hope you can help.

The truck sat for 5-6 years, only making dump trips until I picked it up and started restoring it. It was running horribly back then, now it's cruising pretty well - except for some problem areas this post is about.

Things I've done so far:

- Changed oil
- Changed tranny fuild (also trying LubeGard in the tranny)
- new shocks (4)
- new spark plugs (although, I F'd up and forgot to gap them, having that checked now)
- new spark cables
- new air filter
- New PCV valve
- New Flowmaster Cat conv, muffler and pipe
- I have fixed the rough idle with replacing many deteriorated
vacumm lines (seems to idle fine now at 8k rpm or so in drive when warm. Before it was horrid and I had to turn the idle screw up to keep it running).

*** going to have the sparks gapped, radiator flushed, new thermometer put in.

I should say I'm a novice to any in-depth work on vital parts (I can fix up and restore 2 cycle scooters),so I'm very new to anything involved (eg - part names and their locations on the carb). Sorry, I'm learning slowly.

Carb Related

When you guys talk about "overhauling your carb" what exactly does this entail? Can any of you describe this in steps and in laymans terms?
Can you walk a newbie thru anything like this?

How much would you estimate for a tech to do a carb overhaul with what I have?
(Just want to know what $ I'll be looking at if I can't do these things myself).

I want to clean, replace gaskets, and adjust the carb for optimum efficiency but with power. Again, I've read here that this engine\carb really aren't the best but i'd like to get this one running best I can.

Is it really tough\involved to take the top half off the carb to get to the jets? I'd like to clean the jets and passages, so far all I've done is use carb cleaner on the carb top\choke plate\etc. when taking the air filter cover off.

I can adjust the idle, but can you describe where the mixture screws are and, in steps, how to adjust the air mixture for best performance?

Other stuff



Sorry for the MANY questions, if you can help it would be so appreciated.
Old 11-05-2003, 09:23 AM   #2
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your carb

My 85 has only one ajust screw. It was sealed Calif carb. I paid $ 325.00 to get repaired. This was done by a Carb shop. One thing you might do is change the fuel Filter. This is where the carb meets the fuel line. You have to take off the fuel, the filter is inside the carb. Hope this helps.
Old 11-05-2003, 01:06 PM   #3
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The off-the-line bog is usually from a dead/dying accelerator pump. If it's sat for 5-6 years, it's time for and overhaul for sure. If you're not sure what doing a carb overhaul entails - I'd highly recommend taking it off, and handing it to someone who's familiar with them - if you're counting on driving this thing, it's not the best place to start experimenting.

> seems to idle fine now at 8k rpm or so in drive when warm
Wow - I can't even get mine to rev to 8K matted to the floor!
Old 11-06-2003, 05:46 AM   #4
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I forgot to mention I changed the fuel filter this past summer as well. Good point though.
I also just installed a new cap and rotor, belts, with a new oil change from i shop I like. Also had the sparks gapped (and all for a pretty fair minimal charge which was a change).

The accelerator pump...this is the same thing as the fuel pump, correct?
Or is it something else?
I think that's a possible cause at this point, everything else checks out and it drives and idles fine (although gas hoggy) when warm. Would it be a cause of eating so much gas though?

Roughly, how much would a new fuel pump installed run me for an 85 chev s-10 v6 2.8L 4x4?

At this point I'm mainly trying to help better this gas munching problem which could be carb related as well. I mean, there was a period when I picked it up for rescue when i thought it would be useless. Now it's driving damn well.

Not sure I can afford a new carb, but how much have some of you seen rebuilds\adjusting run ya?

Also, how does one know if they're thermostat needs replacing (this S-10 seems to always run cool as per the guage..which is good, but I'm wondering.

thanks again, you guys rock

jd

Last edited by joed; 11-06-2003 at 05:49 AM.
Old 11-06-2003, 11:14 AM   #5
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A fuel pump delivers gas to the carb - the accelerator pump is inside the carb, and covers up the point when you step on the gas and there's minimal air velocity to cause a venturi effect in the barrells by spraying raw fuel into the throat.

Find a rebutable repair shop, and just ask them what they'd charge to rebuild the carb if you take it off & hand it to them.
Old 12-02-2003, 05:04 PM   #6
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sorry for more questions (holiday time and I'm really up in the air about a $350+ carb job at this time - need to stop spending).

Is it tough to take the carb off (85 V6 2.8L 4x4) so i can bring it in to them and save some cash there?
Easy to get back on? Can you describe the bolts to remove exactly?

When you say a dead or dying accel pump inside the carb, are you talking about a part that can be replaced?...or one that can needs to be cleaned\rebuilt?

I have a Haynes service manual I've been using and can't find clear info on which bolts remove the whole carb from the engine.

It really idles and drives great when warm, the "bog" thing is mainly when it's first starting out\cold. Still accel or fuel pump related?...or other?

It does take a 3-5 startings to get running on a cold day though (pump the pedal a bit - then start, takes a few times)
...is this still accel pump related you think?
Is the accel pump related to poorer gas mileage as well?
Or is this fuel pump related?

Everything else has been changed and quoted as working well, so I guess I'm down to carb or fuel pump work at this point if I want to solve this.

thanks so much,
JD
Old 12-02-2003, 06:13 PM   #7
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The accelerator pump works like a water pistol pump, squeeze the trigger and it sprays - same with the accelerator pump. This shot of fuel is needed to overcome the bog. The carbs are not that bad to remove & rebuild, at least for an experianced mechanic. Anyone with some mechanical knowledge should be able to clean one up, a kit is about $15.00 and includes a new accel pump. Compressed air to blow out passages would be the most important tool.

You can do a quick check to see if the vacuum diaphragm is ok on the distributor. I use a new vacuum hose and pull the one off the vacuum pot on the dist. Install the new hose on the diaphragm and suck on it, it should hold vacuum. Before reinstalling the vacuum line, check to make sure it's ported correctly. Do this by starting the engine, no vacuum should in the vacuum advance diaphragm rubber hose. Rev the engine slightly and vacuum should now be in the hose. If not, I'd skip all the massive hose routing and just run a hose from one of the front ports on the carb, actually there are two together on the right side and one by itself on the left side. The one on the drivers side (left) is the ported vacuum line that I used. I removed the smog pump and two miles of detreriorated vacuum hose, now all I have is a ported vacuum hose to the distributor off the carb.

Make sure the choke is fully opening. Check this when the engine is fully warm. In order for the choke to close, like when you get in to start it in the morning, you must depress the gas pedal so the choke blade can close and the high idle cam can position itself. With fuel injection you don't touch the gas pedal but wayyy back in the early days when carburetors were the rage, you had to depress the gas pedal before starting a cold engine. If your having to crank & crank to get fuel back up to the carburetor after it's sat for a few days, this unfortunately is a common problem. The fuel filter is suppose to have an anti-drainback check. They rarely work like they should. The only cure I know is to install an electric fuel pump to quickly fill the carb back up before starting. Install the pump back by the fuel tank so it pushes fuel instead of pulls fuel. Fuel pumps like to push, not pull.

If taking a long drive on the highway, pour some Marvell's Mystery oil in the gas tank. Driving for long periods when running Marvell's through the engine prevent's the spark plugs from fouling is the engine is really caked with baked on crud. The back of the intake valves get a buildup that can also make the engine die as you describe. It's hard to see unless you remove the cylinder heads and take out the valves. Some mechanics call it "coking" whatever you call it, running Marvell's through it will clean it out. I wouldn't recommend doing this in the winter unless it's done on long drives that use up a tank of gas. It can foul spark plugs when there cold.

Ryan

Last edited by Old S-10; 12-02-2003 at 06:29 PM.
Old 12-02-2003, 06:47 PM   #8
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Oh, one other thing that can really hurt fuel miliage is retarded cam timing. Not that kind of retarded. Slow cam timing. This can happen when the cam chain is stretched beyond it's service life. This isn't related to ignition timing, there are two kinds of timing. Valve timing and spark timing. Racer talk is "I retarded the cam 4 degrees to soften up the launch" or " I advanced the cam 6 degrees to get my 60ft times down" You can't advance or retard your stock cam like these guys do but if the chain is saggy, replacing it can certainly bring back performance and pick fuel miliage back up. Worce case, the chain will rubb on the cover and wear a hole in it or the chain will jump a tooth on the sprocket. Sometimes it'll jump back & forth like this for a while, other times the chain will just jump and that's it. You can check a worn cam chain by taking off the distributor cap and turning the crank by hand back & forth. If you can turn the crank a long ways before the rotor moves, that's a bad sign.
Old 12-04-2003, 10:04 AM   #9
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is there an easy carb swap for the 84 2.8 i am experiencing similar problems and would like to go to a betterr carb rather than rebuilding.

thanks
nick
Old 12-05-2003, 07:59 AM   #10
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go with the weber carb, it is a direct bolt on.
Old 12-09-2003, 03:39 PM   #11
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thanks for the responses - it's clear to me that the carb might be out of my league at this point and I might have to either dump the truck and trade up to something else or invest more into the carb rebuild.

I also need to fix the gas pedal\accell cable - it's DAMN heavy when driving. Your leg actually hurts from having to press it so hard on a freeway trip.
Very odd, something is wrong.

Anyway I'm having to nearly floor the gas pedal sometimes to keep 65 + freeway speeds (in OverDrive).
I think this also pertains to the carb in some way and is another reason this thing eats so much gas - would you agree?
I do get a little "bog" upon acceleration from stop.

What could be happening? Really clogged jets on top of a defective accel pump - combined with a HEAVY throttle\cable?

Geez, i've just about had it. I'm thinking it might be a trade in on something else soon if this is going to cost so much.

thanks again you guys - you rock,
JD
Old 02-11-2011, 12:21 AM   #12
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Talking Re: 1985 2.8L V6 4x4 PU carb & Q's - Need Help!!!

well i hmee exact same year and engine with same problems word for word you named them, but my dad says that i have a hollie carb and its supposed to have a 2 barrel carter carb on it so let me know your thoughts
Old 02-11-2011, 02:07 PM   #13
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Re: 1985 2.8L V6 4x4 PU carb & Q's - Need Help!!!

OP, you probably have 2 throttle return springs on the throttle linkage, pull one of them off, did the for my brother in laws and he said it was much easier to push, he like it better.

Run a tankfull of good carb cleaner thru it, I deleted all the junk off the last one and I think it helped. Dont ditch the truck yet, some guys have had their carb rebuilt for $125. The guy who said $300 had a California Emmissions POS carb.

If you dont want to put $300 into it and dont want it I am sure someone will give you $300 for it in a heartbeat......

Keep at it man you will get it.....

Good luck.
Old 02-11-2011, 03:46 PM   #14
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Re: 1985 2.8L V6 4x4 PU carb & Q's - Need Help!!!

A "Holley" carb is completely different from the Rochester described in this ancient post. Try a fresh post and I'm sure you will get plenty of responses.
Old 02-11-2011, 04:58 PM   #15
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Re: 1985 2.8L V6 4x4 PU carb & Q's - Need Help!!!

Wow, did you guys not notice (except SH) this is Joed's post from 2003? Beast 118 just revived this thread. I was trying to figure out why he was asking about the carburetor. Joe knows this carburetor better than just about anyone I know.

Your dad is WAY off. The stock carb is a Rochester, not a Holley or a Carter.

Send Joed a message. He's the guy to ask.
Old 02-11-2011, 06:46 PM   #16
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Re: 1985 2.8L V6 4x4 PU carb & Q's - Need Help!!!

Quote: Originally Posted by joed
Anyway I'm having to nearly floor the gas pedal sometimes to keep 65 + freeway speeds (in OverDrive).
I think this also pertains to the carb in some way and is another reason this thing eats so much gas - would you agree?
I do get a little "bog" upon acceleration from stop.

What could be happening? Really clogged jets on top of a defective accel pump - combined with a HEAVY throttle\cable?

Geez, i've just about had it. I'm thinking it might be a trade in on something else soon if this is going to cost so much.

thanks again you guys - you rock,
JD
I had this problem with the engine I've just rebuilt. You may not have a carb problem at all... there is only so much you can do on a carb if your piston rings are going out. This would cause the bad mileage, low power and other issues. I would check your compression and see if your rings are going out on you before dropping time and money on a carb rebuild/replacement. If the compression sucks (below 100 psi, I think) you may want to decide to rebuild, swap engines, or do that trade in. The procedure to check this should be outlined in a good service manual.
Old 02-11-2011, 08:50 PM   #17
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Re: 1985 2.8L V6 4x4 PU carb & Q's - Need Help!!!

WOW, missed that didnt I?
Old 02-17-2011, 06:45 PM   #18
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Re: 1985 2.8L V6 4x4 PU carb & Q's - Need Help!!!

Quote: Originally Posted by playawolf
I had this problem with the engine I've just rebuilt. You may not have a carb problem at all... there is only so much you can do on a carb if your piston rings are going out. This would cause the bad mileage, low power and other issues. I would check your compression and see if your rings are going out on you before dropping time and money on a carb rebuild/replacement. If the compression sucks (below 100 psi, I think) you may want to decide to rebuild, swap engines, or do that trade in. The procedure to check this should be outlined in a good service manual.

LOL!! Just in time.


*btw: it was the carb (rings are good).
Old 02-18-2011, 09:47 AM   #19
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Re: 1985 2.8L V6 4x4 PU carb & Q's - Need Help!!!

Yeah Joe, the first time I read this I was like, "Did he get amnesia? Why would he ask that?" haha!!
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