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catinwoods
New User
Dec 16, 2014, 8:54 PM
Post #1 of 7
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91 chevyp/u wont start
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I have a 91 Chevy pick up with a 4.3l v6 and 180,000 miles everything is original accept starter and alternator (until yesterday). I drove the truck to work on Saturday and it ran fine. Went to start the truck on Sunday and it started right up and ran for about three seconds and died. I cant get it to do anything since. Cranks over but doesn't even attempt to start. I took the ign coil and ign module to AutoZone to test them. They told me both were bad. Replaced them both but still nothing. I've tried squirting ether and gas in the throttle body still nothing. I haven't put a fuel pressure gauge on it, but you can here the pump run and it seem to be squirting enough fuel in the tbi. I put a spark plug tester at the coil wire and it is getting good spark. I put it down on # 1 wire seem to be a little erratic, don't know if that's normal or not. The one thing I noticed is after I crank it awhile I can pull one the plugs out and it seems to be dry, shouldn't they be wet. I don't know what else to try. Any help would be greatly appreciated
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Dec 16, 2014, 11:03 PM
Post #2 of 7
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Re: 91 chevyp/u wont start
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Welcome - nightshift here
Arrrrg! OK you've done some good testing so far which helps as this is now ruling things out as I see it. You seem to have spark, have primed fuel both ether and with gas (but find plugs dry?) and still nothing but cranking.
If your tests were even close that leaves compression still not known or timing. It only takes fuel, spark, compression and sparked on time to get a reaction so move on to even just a few easier cylinders for compression.
You may have jumped time on the timing chain and find compression all too low to fire. Not very common to me with this engine but it's old enough to question it.
When cranking you would notice engine cranks "funny" if familiar with it when normal feel/sounds when it was working. This if off enough will throw off the show and an engine will not run or even much more than a backfire perhaps. Need to rule that out.
I do wonder why the dry plugs if you had one or more out quickly after trying to start it. Careful how much you crank an engine at a time without letting it cool off as starter new or not can only take so much and when/if you flood an engine bad enough plugs might not fire well or at all and some will not just air dry but will require heat or replacement. Do stick to the original suggested spark plugs by Delco more important in newer than this but still a factor. If you have some of those trick plugs with multiple electrodes or other types of IMO garbage they are in question when all things fail something non OE is suspect. BTW - don't fall for those claims at the display of wild power and MPG crap. Any of those trick sales gimmicks are just that, gimmicks and if any worked they would have used them when it was new.
In short - see what your compression is. I'd like to see over 120 and think spec would be about 150ish wet (meaning with a squirt of oil) PSI but am looking for a universally low reading to rule in or out valve timing for now.
Careful with stating fluid you called ether - same thing really. Highly explosive. Best to put air intake parts back in place before cranking but quickly too as the stuff evaporates quickly too vs raw gas but that can be its own problem if too much and or can't get it in the right spot so not conclusive on its own yet,
T
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catinwoods
New User
Dec 17, 2014, 4:13 AM
Post #3 of 7
(1448 views)
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Re: 91 chevyp/u wont start
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I did check compression but not in all cylinders, just #1. It had 140psi. Engine sounds normal when cranked but does nothing. I did get it to backfire 1 time when i poured some gas down the tbi and held the butterflies open while cranking it. Other than that its deader than a door nail, just cranks.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Dec 17, 2014, 4:58 AM
Post #4 of 7
(1442 views)
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Re: 91 chevyp/u wont start
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OK - this is still worth the read and tests taken for an engine to run..........
> http://autoforums.carjunky.com/...LL_NOT_START_P75655/
140PSI compression is enough for some reaction for compression. That leaves spark and fuel and on time. Valve timing must be close enough by compression but doesn't mean distributor is. Take spark test at the plug wire to plug not just the coil wire and missed that the first time I read that. If rotor can't turn for some reason you might get a spark at coil wire but not on to plugs or somewhat rare distributor isn't spinning properly due to a problem such as is broke off a roll pin (guess on my part) from where it gets driven and is all off time but would still show spark if turning.
Knowns or thought known: You've bypassed anything about fuel with no reaction so the up front problem is not fuel or fuel deliver so far.
You see some spark but not sure if on target?
Compression suggests enough as said to react if fuel and spark are present.
******* I think I'd see if distributor rotor is pointing at a cylinder while it's near TDC or way off and if turning rotor by hand it moves too much as in shaft isn't making a good connection. You should be able to feel TDC by turning engine by crank bolt and feeling pressure at a spark plug hole.
Still looking for proper way to set timing for this 1991 not totally trusting the source of info I just read. It showed this is set and adjusted by turning distributor but don't do that yet as said don't trust info yet. Does distributor cap and rotor look like this?
>  <
Pic may not show?
Does this show a bar for timing marks at the harmonic balancer also?
IDK what tests the parts outlet did to conclude items were testing bad and new ones made no difference? These places are parts outlets to sell parts first and not necessarily testing anything properly or should be expected to make a diagnosis even though it's popular to ask and get suggestions.
It should be reacting so for now suspect if spark found at spark plug wire to plug is there it must be way off and we can dig into that if you do find a problem there,
T
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catinwoods
New User
Dec 17, 2014, 6:32 AM
Post #5 of 7
(1428 views)
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Re: 91 chevyp/u wont start
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Yes my cap and rotor look just like that. I did put a spark tester on the plug wire down by the #1 spark plug it is getting spark down there but looks kind of weird. Light on tester looks rapidly dim and bright every so often like when it should actually be firing. Don't know if that is normal or maybe just my mind trying to assume a problem. Don't know if harmonic balancer has timing mark or not, I will check when I get home tonight. As far as checking timing, my plans were to bring #1 up by lining up crank marks (if present) and taking off valve cover to make sure it is firing position by observing if the valves are closed and then seeing if the rotor is pointing at #1. Is this the correct procedure? If it has jumped a tooth on the timing chain how far would this be off? I took the coil and ign module to AutoZone ,o'riely and advance they all told me they both were bad, but I find it hard to believe that both of these went bad at the exact time that whatever is causing it not to start went bad, guess it is possible.
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Discretesignals
Ultimate Carjunky
/ Moderator
Dec 17, 2014, 8:06 AM
Post #6 of 7
(1421 views)
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Re: 91 chevyp/u wont start
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Those spark testers with the lights are useless. They are fine for seeing if you have any spark, but it doesn't take much EMI to set one off. You need to get an adjustable spark tester. Spark should be able to jump a 3/4 inch gap.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Dec 17, 2014, 8:23 AM
Post #7 of 7
(1417 views)
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Re: 91 chevyp/u wont start
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I'm not thrilled with your results for spark at the plug wire to plug. Info suks and sorry for that. Perhaps another can pull out some definite procedures for timing this thing. It's not always done like some even older ones and for a 1991, S-10, 4.3 it just says look for the sticker under the hood for info and I hope it's still there. It may need a new or reman distributor and you must do this right.
This is the garbage I found out there for the exact vehicle you listed. I know better that it's close to change years for this stuff and my info isn't convincing me. Copied below is what I found and it matters!
*******************************IGNITION TIMING1991 Chevrolet Truck S10 P/U 2WD 4.3L TBI 6cylThe Ignition Timing
Special procedures are required for proper adjustmentsrefer to emissions label (Under hood) or servicemanual
******************************************
Complete with typos in it! Don't touch that until you are sure from this site or wherever but do think this is your problem area now..........
Good luck,
Tom
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