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  1. #1

    Default 1985 GMC S-15 mystery challenge......who can figure THIS out?

    Bought a 1985 GMC S-15 pick-up about a year ago, MINT condition, 2.8 liter engine, new carburetor, fresh overhauled engine and tranny, ran like new...Developed a pretty significant oil leak from rear of engine, coming from weep hole at torque converter cover. Removed engine, placed on engine stand, replaced oil pan gasket, rear main seal, intake gaskets, and distributor o-ring. Re-installed engine, adjusted valves due to removal of push-rods, and adjusted per Haynes (1 1/2 turns from "no lash"). Engine will not start with static timing where it should be...Twisted distributor to where engine runs somewhat, but strobe light shows timing mark at 12 o'clock, WAY above scale on balancer....Spark plugs chalk black, re-adjusted valves to 1/4 to 1/8th of a turn from lash, plugs now white, perhaps lean condition, but not sure....Engine temperature normal...Has some kind of aftermarket Edelbrock camshaft installed, but not sure if that makes a difference as far as the engine timing....Right now, if I try to start the engine, the engine floods immediately without even touching the gas pedal...Choke has no effect, as I've tried all positions, very strong gas smell, and gas mileage is HORRIBLE....If I twist distributor to where mark on balancer is strobing anywhere NEAR the little scale, the engine is gravely sick, and barely runs....
    Needless to say, I didn't check the timing BEFORE I pulled the engine to see exactly where it was strobing, which would have been good to know...And oil leak is AS bad or worse than before...I believe this engine has hydraulic lifters, and the valves are NOT clattering. Once the engine starts, It acts like it's running on like 4 cylinders, just really piss poor, for about 3 minutes, then smooths out somewhat, with white smoke from exhaust. Twisting the distributor either way makes it much worse. Once on the road, she runs and accelerates really sweet, but if I have to stop for a turn suddenly, the engine dies, but will start back up (vacuum issue?) Engine idling at around 1000 RPM with idle screw all the way out, all vacuum lines are solid, and spraying of carb area with starting fluid reveals no vacuum leak....Drove the truck to work with a full 17 gallon tank, it drank 1/2 a tank in 130 miles, and used 1 quart of oil....
    I really love this little truck, and don't exactly know what to do at this point...A friend at work has a 2.8 in his garage he said I could have for $50, and putting a 4.3 engine would require another transmission, and conversion to TBI which Im being told is a real PITA.....Truck ran strong before I pulled the engine, and not sure what's going on with the timing...I don't see how the thing can run with the rotor button pointing closer to the #2 cylinder than the #1 at TDC...If you move the distributor 1 tooth EITHER WAY, it makes things MUCH WORSE....It will only run in the position I have the distributor in, and it's strobing around the 12 o'clock position....Now there ARE 2 marks on the harmonic balancer, but if you put the #1 cylinder at TDC, there is a mark that lines up on the scale....Vacuum line going to distributor is good, and working, but makes no difference as far as the timing mark.. Oil coming from same place, somewhere behind the flywheel....Real PITA at this point.....Can pull engine again if necessary....What do you guys think? Baffled in Georgia...

  2. #2

    Default

    When your timing it, are you TDC on exhaust or intake stroke?

  3. #3
    Jr. Engineer
    Join Date
    Oct 2013
    Location
    weedsport, NY
    Posts
    212

    Default

    Exactly! You have an after market cam, so the timings going to be off the mark, so you might have to go to summit racing and get a timing degree wheel, and ask them what cam you have. Give them the part number and they might can look it up! But first you need to take care of the gas problem, which sounds like a major vacuum leak! But check the float level first ,then hook up a vacuum gauge. and get some wd-40, listen while you spray around the base of the carb, all vacuum lines! As far as the oil leak, you might have to go to some dye in the oil so you can see just where its coming from! Check your pvc valve, just for fun!

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