OT Vortec 4.3 Locking Up - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 04-29-2008, 09:27 PM Thread Starter
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OT Vortec 4.3 Locking Up

I've been building a '94 s10 blazer with the vortec 4.3 in it and when I bought it it wouldn't start. The starter would turn the motor a little bit and then lock up. You could pull the starter and re-install it and it would turn a little more. Some times it would turn enough to top but wouldn't fire. Originally I thought it was a bad starter or bad flex plate.

When I was discovering things I drained the oil and there was maybe 10 quarts of a gas/ oil mixture. I'm thinking maybe it was hydrolocked with oil/ gas.


I pulled the auto and swapped in a manual. I got it to start this winter when the trans was off and just the fly wheel was bolted to the back of the motor. The fuel pump stays on after the motor is turned off.

I went to start it today. It's doing the crank a little and lock up trick again and the oil smells of gas. The fuel pump stays on after the key is off and it's done cranking.

What's a good plan of attack to figure out if the motor is junk, if it's a starter issue, or a fuel pressure issue? I'm not sure if it's getting too much fuel pressure and hydro locking with gas or if something else is broken. I'm just about done messing with the 4.3 and ready to pull the tbi 350/sm465/241 out of my 3/4 ton and drop it in the blazer.
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post #2 of (permalink) Old 04-30-2008, 01:11 AM
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Gas in Fuel? NOT GOOD. Does it mean the motor is toast, not in the least.

First thing...pull the plugs...then turn it over with the fuel pump relay pulled. If it turns over fine....then it's a good chance the problem was hydrolock.

The fuel pump on my 5.7L TBI runs for a few seconds after I shut off my engine....not sure exactly why....but it does...so, maybe it is doing what it should.

Put the plugs back in...crank it...if it starts....good thing.
Stop the engine....wait for the fuel pump to stop...
Pull the plugs again...see if one or more have more fuel than they should...you might also try cranking it with the plug wires pulled to stop it from starting.

It's possible you have one injector that is dumping fuel into the cyl....it should be pretty obvious which one it is.

Please let us know what you find out.

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post #3 of (permalink) Old 04-30-2008, 07:41 AM Thread Starter
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Yeah, i've done the pull the plugs thing in the past and it didn't help but i'll try again. This motor is the 1st generation vortech so I think it's a little different then 1 injector a cylinder later models.

It's a pretty violent lock up and clunk when it locks up so it has me a little worried. I've messed with this motor and am running out of time before i move, the small block swap might be the direction I head.
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post #4 of (permalink) Old 04-30-2008, 08:40 AM
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When it locks up have you tried pulling the plugs and turning it over with a wrench on the crank? With the plugs out I can't think of anything that would lock it up other than a broken crank or a problem with the starter, starter ring or starter drive. Can it be just a simple ignition timing problem?

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post #5 of (permalink) Old 04-30-2008, 09:05 AM Thread Starter
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When I went to restart it after it was sitting the truck was out of gas and I think trying to start it with no fuel burned up the pump. When the pump was bad it would crank just fine.

I did a couple more checks.

I pulled the distributor to coil wire and tried turning when it was locked up, if it was timing wouldn't this help trouble shoot it.

Then I pulled the plugs 3 were dry, 2 were moist but not bad with gas, and 1 cylinder poured out a lot of gas, probably could have filled up a beer can.

Right now i'm working on digging up info on the fuel system. I'm worried it was hydro locked and may have bent a rod.
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post #6 of (permalink) Old 04-30-2008, 09:10 AM Thread Starter
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http://www.autozone.com/az/cds/en_us...rInfoPages.htm

Autozone is actually good for something. That explains the fuel system I have in plain english.

Hopefully it isn't the whole injection unit. I think what i'm going to do is crank it over again empty and put some oil down the cylinders while I crank it. Then I'm going to put 5 plugs back in and pull the wire for the 1 cylinder that filled with gas and see if it will run. I'm thinking the popet valve is suck open in that cylinder.
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post #7 of (permalink) Old 04-30-2008, 09:30 AM
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Quote:
When the injector is energized by the control module, an armature lifts allowing pressurized fuel to travel down the 6 fuel tubes to the poppet valves. In the poppet valves, fuel pressure (working against the extension spring force) will cause the nozzle ball to open from its seat and fuel will flow from the nozzle. It takes approximately 51 psi (350 kPa) to force fuel from the poppet nozzle. Once the module de-energizes the injector, the armature will close, allowing fuel pressure in the tubes to drop and the spring force will close off fuel flow.
Seems like you have one poppet valve that isn't closing, and maybe two that aren't closing completely.

Quote:
The non-repairable CMFI assembly or injection unit consists of a fuel meter body, gasket seal, fuel pressure regulator, fuel injector and six poppet nozzles with fuel tubes. The assembly is housed in the lower intake manifold. Should a failure occur in the CMFI assembly, the entire component must be replaced as a unit.
You may have to replace the whole thing, but first I'd look around for procedures to clean the poppet valves. Maybe you can spray them with carb cleaner from the under side or something. Or put a 2100 on it.

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post #8 of (permalink) Old 04-30-2008, 09:46 AM Thread Starter
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I do have a good 2100 in the basment but i'd have to mess with intakes...

So it's a 1 or 2 cylinder now. With the bad cylinder plug out it runs on 1 or 2 cylinders. I missed with plug wires and they are right. Time to rip apart the intake and clean poppets. I don't even want to know how much a new injection assembly is
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post #9 of (permalink) Old 04-30-2008, 10:23 AM
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I can't imagine going from FI to carb....yuk.....yea, it might get you running but your going to loose performance and MPG.

Try cleaning it first...

If that does not work...I'm sure you can find a used one from a junk yard.

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post #10 of (permalink) Old 04-30-2008, 11:59 AM Thread Starter
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Quote:
Originally Posted by JeepDawg View Post
I can't imagine going from FI to carb....yuk.....yea, it might get you running but your going to loose performance and MPG.
I had the same feeling till I ran a mc2100, awsome simple carb. I'm sticking with fulie but the mc2100 is the only carb i'd run.

I poped off the upper intake and found the plastic pressure fuel line that connects the pressure line to the injector under the intake cracked. There were pools of fuel over the #3 and 5 poppets. The #3 cylinder is the one that was really full of fuel and i'm guessing the engine was clicking on the #5 cylider because fuel was slipping past the poppet.

When I fired the engine this winter is was probably 0*-20* out and when the engine it warmed up it started only clicking on 1 or 2 cylinders. I'm thinking the line was cold enough to seal in the winter.

So $110 in parts later we'll see if it works after I eat lunch.
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