4G64b with positive pressure coming out of intake.

[labguy1970]

Hi All,

Relatively new here, but I've been utilizing the site for trouble shooting and ideas for my 1988 US version L300. I've run into a problem after the rebuild that I'm not able to figure out, and am hoping someone will be able to point me in the right direction.

A little back story about my US L300(ie van wagon). I recently rebuilt the 4g64 petrol engine, and thought I did a good job as I've done a few rebuilds in the past. I do have the both service manuals for the year and followed the instructions carefully. The head was done, and the bottom end as well. I installed all the internals, in the correct order and direction. As I said, I thought I did a good job at putting it all back together and back into the van. Not the easiest thing to put back in the van, glad I had another set of hands. Everything looked good, I didn't change much from before the rebuild. I did changed the wires, cap, rotor, fuel filter, plugs, all the timing components. I eliminated the balance shafts, with a balance shaft elimination kit. I also removed the jet valves and filled the holes with specifically designed bolts(found a kit on line for the Mitsubishi engines).
So once in, I thought it would start up with very little fuss. It didn't. It turns over. It has good even pressure in the combustion chambers. There is a good spark at all the plugs. It's getting fuel(I can smell it and see it spray out of the plug holes when the plugs were out). I believe the exhaust system to be clear of obstructions. It is timed properly, or at least as close as I can get without it running. The timing belt looks to be on correctly, at least the marks line up. I've checked lots of things in the hopes that it would be something simple. I just happen to be turning the engine over without the air intake hose attached and noticed that I was getting fuel spray out along with air. It only happens once per revolution, as it feels like there is a bit of vacuum in the revolution. It's hard to tell, due to the speed of rotation. Do I have a stuck valve? Is the EGR valve stuck open? Did the elimination of the jet valves cause this? Or something else?

Any help would be great.

Cheers,
Jason

[thedjjack]

cam 180 degrees out so exhaust is out the intake valves and sucking on the exhaust side?

[labguy1970]

cam 180 degrees out so exhaust is out the intake valves and sucking on the exhaust side?

I thought about this, but I don't believe it's the case. The cam has a key that the cam sprocket goes onto, and it will only go on one way. the cam sprocket has a timing mark that lines up with the timing mark on the head. So I don't believe I could have put the cam in 180 degrees off. If I had put the cam in 180 off, the sprocket would still go on, but then I'd have to turn the cam and cam sprocket 180 degree to have the timing marks line up.

I did have a thought that one of the hydraulic lashes for the valves might be stuck. Would one be able to extend enough to cause the valve to stay open during a rotation or part of the rotation?

[TieMyShoe]

Reset everything back to TDC and check your mechanical timing again.

[labguy1970]

Reset everything back to TDC and check your mechanical timing again.

I'm guessing you mean the alignment of the distributor after the setting the engine to TDC, or am I reading that incorrectly? If I'm reading it right, I've done this a good number of times to date. I'll try it again just to make sure.

Thanks for the suggestions so far.

[Feds]

Look for vacuum leaks. I did a swap on an RX-7 once and didn't block the air injection port in the manifold. Took me a week of screwing around before someone a little more experienced pointed it out to me.

See if it will run on quick start as well. That will tell you everything except your mixture is correct.

[TieMyShoe]

Its a bit hard to gauge what is exactly happening by your description. However if you have A/F mixture floating about in the in the intake something is not timed correctly. If the mixture is being sucked in and out, in and out you have an issue with your intake valves. If it is coughing out the intake you have your firing order out most likely. I'm not sure on the 4G but most 4 bangers fire 1342, make sure the dizzy isn;t 180 out.

[yojimbo]

The cam may not be 180 degrees out, but it could be 180 degrees out with respect to the crankshaft. If I remember my timing correctly. The crankshaft turns twice as fast as the cam, so the crank timing mark and the cam timing mark only line up every other turn of the crank. To time the engine its usually on the timing mark on the crank when piston 1 is at TDC, and then set the cam to that. If you didnt check 1 is at TDC (or whatever the manual says) then it seems to me it could be 180 out. If it was anywhere close, it would be trying to fire. Basically, recheck all the timing and the firing order, did you assume the direction of the dizzy rotation when refitting leads? Theres a lot you can get wrong to make this happen :D

[labguy1970]

I've yet to get to anything in the past couple days, and it looks like things are on hold until early next week. Thank you all for the suggestions on things to try. I'll keep the board posted on what it ends up being, or if I've gone through everything and it's still a no go.

Cheers,
Jason