guypier

I am a pretty good mechanic but I'm stumped on this. My wife was driving the truck on the highway and she heard a klunk from the engine, like that helps me any, but then the car died right on the highway. So I towed it home so I could troubleshoot the problem. I have done a compression test and the psi is: number 1: 145psi number 2: 145psi number 3: 149psi number 4: 149:. So thats good. then I took the valve cover off and checked the valves, springs, and keepers. I checked my timing and valve clearances and the are both perfect. I also made sure I was getting spark. I just changed the spark plugs and wires, new fuel pump, fuel filter, cap and rotor. Made sure the timing chain was still on which is and is tight. So my last thought was the carb because when you give it gas it shoots out fire from the top and when you don't give it fuel it shoot raw gas out. So I had the carb rebuilt and tuned for Colorado altitude and all I had to do was bolt it back on the engine. Tried to start and still shoots flame and raw gas, just cranks and cranks will not fire. What now please help me

supra89t

The thing that catches my eye is that you have the air/fuel mixture shooting back out the carb, with flames sometimes. This tells me you are getting a spark, but that the a/f charge is blowing back out instead of being kept inside the chamber. You've got good compression so I rule out the stuck open/bent valve thing. My guess is that either your ignition timing is way out and is lighting the mixture before the valve closes or the cam timing is way out so that the valve is actually closing late, allowing the mixture to blow back out. OR you have an exhaust valve stuck closed that is holding pressure in the chamber and releasing it when the intake valve opens, shooting fuel/fire back out the carb. Double-check your spark plug wires to make sure they are in the right order and make sure your cap, rotor and wires aren't grounding out anywhere and sending a false spark signal that is causing premature spark and ignition. Maybe the "clunk" was your distributor gear getting munched by the cam gear?

Hope that helps. Make sure you let us know what it is when you find it. Good luck!

guypier

The timing is perfect when it on the compression stroke the rotor is pointing right on number one then I turn 360 degrees and it point right to number four then I went back to the compression stroke and its tight back on number one. And how could the cam timing go out all of a sudden I was not having any problems. About 3000 miles ago I replaced the clutch, throw out bearing, pilot bearing, oil pan gasket, oil pump gasket, head gasket, valve cover casket, exhaust manifold gasket, timing chain cover gasket, fuel pump, fuel filter, fuel lines, spark plugs and wires, valve adjustment and timed the engine. Took about 4 days and they car fired right up no problem, and then just goes out. Any other suggestions.

supra89t

It is not unheard of for timing gear to skip. Something is either broken or timed improperly. Your A/F charge is getting to the combustion chamber, it is just coming back through the carb instead of out the exhaust. I am not doubting your mechanical ability, I just can't think of any other reason a fuel/air mixture would blow back through the carb other than a COMPLETELY plugged exhaust, wacked out ignition timing (or a short or plug wires on wrong place), or wacked out cam timing.

Does any exhaust come out the tailpipe when you crank the truck?
Are all of your spark plug wires on the right spark plugs?
Are all of your plug wires on the right place on the dist?
Are any of your plug wires grounding out or jumping spark with another plug wire?

I am just throwng out ideas. When I get stumped, I always go back and review my assumptions and recheck those little things that I assume that I got right the first time.

guypier

I did not check to see if ant exhaust was coming our when I try to crank it over. Ill recheck the spark plugs and wires but I'm 100% sure they are right because I did not touch them until the truck died. I will recheck the valves as well. Can you tell me what I should be looking for if it was a stuck exhaust valve. And if it was a broken valve, spring or keeper how could I tell. Also do you think I may have broke a piston rod. I don't think I did just because I cant hear any kind of knocking or pinging when I crank the engine. I am also 100% positive the my spark plug/wires are not grounding on each other. One thing I did notice is the cap you screw onto the spark plug where the plug wire clips on they were loose would this be enough to cause the engine not to fire. I figured it would at least run bat run like crap.

supra89t

Meh, a loose cap on the spark plug might cause a little misfire, but not flames shooting out the carb. I doubt the broken rod b/c you checked the compression after the thing quit running, right? If you had a bad rod or piston, you would know it. And if the motor threw a rod on the highway, you would probably have a nice little window in your block.

My though pattern is this: The engine is really just an air pump. If you don't send any fuel to it and just use the starter to crank it over, it should pump air the same as if it was running. Air should go in the carb, out the exhaust pipe. If that is not happening, it seems to me that there is a mechanical reason. Justifying a stuck closed exhaust valve is hard b/c it would have to be broken or severely bent in order to not bind the camshaft. Unless the cam lobe broke off. I have never heard of that happening, though. OR, the rocker arm might have slipped off of the top of the valve so it is not getting opened when the cam lobe comes around.

First make sure the clunk your wife heard was not something bouncing up and completely pinching off the exhaust under the truck.

If you are going to pull the valve cover, use a wrench and turn the crank slowly as you watch each valve articulate through its full cycle. If there is a bind in the sytem, you may be able to feel it while turning the motor manually. Watch to make sure all the valves return to the up position when they are not compressed by the rocker. Try and wiggle the rockers by hand to see if you can get them to slip off of the top of the valve. Look for any marks on any of the metal parts to see if they may have contacted one another where they aren't supposed to touch. Look for gouges, clean spots, dents, dings, etc...

If the thing pumps air as it should when just using the starter, then I would check the ignition equipment next since that would "probably" rule out a mechanical issue.

Does anyone else have any advice? Am I off my rocker?

guypier

You know I may have been an idiot I did not look at the valves I was only looking at the parts that the cam lobes lift I believe they are the lifters I did not even check the valves oops. The valves sit inside the springs right?

supra89t

You got it.

guypier

I can not believe I did that, I bet that is it, I hope. Do you know if any good head shops to redo my head? I would do it but I need that truck running. I have a 91 Toy Pickup as well but it sucks with one car.

supra89t

I don't. You will probably be best off checking with some local shops and make sure that they primarily work on Japanese engines and talk to people who have had work done there (and put some miles on the work). It is sometimes really hard to find a machine shop that understands that you can't just eyeball a jap motor like you can an old small block.

Let me know if that is what the problem was. :cross fingers: