720World

Little Trucks, Big World

finally getting back to work on truck. 1984 720 king cab with Z24 auto trans.  Engine will start and run but only responds to first little bit of throttle then nothing, getting fuel mist blowing back through carb.

problem started slowly and progressed over a 2-3 week period when it became unsafe to drive on road

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1/  Head gasket blown between two cylinders. By no means definitive, if you find two adjacent cylinders low this could be the cause.

2/ Valve lash is too tight. Intake most likely.

Is it possible that the CAT is plugged up?

My Cat was partially clogged up,was making noise at exhaust 3 and 4 cylinder,both plugs were toasted,the head gasket was blown between cylinder  3 and 4.But I didn't lose power,took it to Jack,he's the one that installed the Jasper engine.My front pipe needed replacing also,when he took off,he noticed that the cat was clogged,part of the inside came apart and was partially blocking the flow.He recommended not putting another cat on it,we don't have smog test here,he also has a 720 truck.You will need to remove cat and look at both ends cause one end may look good but the other may be clogged,that's how mine was,plus it gave me more power without it and I went from 18 mpg to 20 mpg on my 4x4.

need to replace exhaust system from just before cat to tailpipe

will have to get gage and check cyls was running good then just went downhill over a few days

well checked cat not the problem. engine will rev to 1300 rpms then nothing more. will get gage this weekend and check compression. carb is rebuild from guaranteed carbs??? too much stuff to do around the house not to have it running. it idles fine 

It may be time to upgrade your carb.I put a Weber on mine long long time ago,us in Georgia have no smog test so we can let it all hang out,lol.I am down the road from Columbus,mine is a 85 and your's a 84,somewhat different in somethings.Here's where I got mine from,I have bought a idle cut off solenoid to make it idle right,you need it too,trust me.Also here's a video of my conversion,your's maybe a little different.

Could it be an ignition issue? Put a timing light on it and confirm that you have proper advance when you throttle it up. You must have proper spark advance for the engine to rev up in rpm. I would verify that.
Change fuel filter if you haven't lately.

Definitely one of the biggest problems I have suffered from over the years before replacing the tank all together was fuel filter clogs.    

Our trucks run on such low pressure that any little bit of dirt will kill the flow and you won't have anything for the engine to accelerate with, it will idle properly usually but will not pull.

 When the filter is becoming clogged there is a time when the engine demands more fuel than can get through the filter and the carb runs dry. The car literally runs out of gas and acts like it. This usually happens when climbing a hill, passing or prolonged acceleration. The engine will cut in and out but as soon as you let off the gas, the carb fills and driving becomes normal again. If you fail to replace the filter this threshold lowers and it acts up on less steep hills and even around town. It will idle and you can drive it a block or more because the fuel bowl is full. 

If it will idle but you can't pull away from a stop I doubt it's the filter. A simple check is to look at the sight glass on the front of the carb. If gas is showing, there is enough to drive down the block. 

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