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3.4L won't run

Blase

Blase

Well-known member
Joined
Jun 16, 2020
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Ok so I bought a 4runner buggy from a friend of mine. It had been sitting for 2-4 years. Ran GREAT before he let it sit. Was sitting outside with the hood up. Intake was clean nothing got in. I don't see anything in the Exhaust. Nothing that I've seen was open to the elements on the motor. ECM is in the factory spot so it could have seen water. There a security module that was sitting in a puddle of water under the drivers seat.

I put a new battery, dumped all the gas and tried to fire it up. No fuel pump even when I put 12V straight to it so I installed a new fuel pump. Once I did that the fuel pump would come on when cracking but it still wouldn't run. Checked fuel at the rail great clean fuel. Next I pulled a couple of spark plugs and check spark. Spark was great! I know its got air so I thought maybe the injectors are clogged from sitting. To check I got a set of Noid lights to see if the ECM was telling the injectors to fire (suspecting ECM or electrical issues). They are firing so I went ahead and replaced all the injectors.

Still won't start. Doesn't even pop or sound like its trying to run.

Had a buddy come over and tell me I needed to do a compression and leak down test. All 6 cylinders have ZERO compression. Nada Nothing! So we pulled the passenger valve cover to see if the valves where stuck and to look at their position for the leak down test. With all the valves closed we did a leak down on each cylinder on the passenger side. All had leak down past the piston. Also I haven't pulled the front timing belt cover but I did loosen it and pull it back to see if the belts had maybe rotted away. They are there, turning and appear to be in good shape.

Do I have stuck rings from sitting in every hole enough that it won't build enough compression and as such won't run?

is there anything electrical that could cause no compression?

Wiring on this buggy is a mess! Rats chewed some of the wires while it was sitting. For the most part it appears that the engine and body harness wires are fine. Only a very few as of now unused non essential body harness wires are chewed (lights and such). I have a cheapo Auto Zone scanner and it says its reading a code P1600. It will clear the code but it just comes back which tells me its talking to the ECM. I was sure my issue was electrical until we did he compression and leak down test. Now since I have spark and I know the ECM is telling the injectors to fire (plugs are wet wet and you can see fuel on top the pistons when trying to start) I'm not so sure my issue is electrical.

Any thoughts or help is much appreciated!! I'm a garage mechanic. I throw parts at it to try and fix the issue and that's getting $$$. Can this motor be saved?
 

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Blase said:
Do I have stuck rings from sitting in every hole enough that it won't build enough compression and as such won't run?

is there anything electrical that could cause no compression?
Click to expand...

in for tech

I think the answer is Yes, the rings could be frozen against the piston.

I would pull the plugs and put some Marvel Mystery Oil (MMO) in each cylinder and let it soak overnight. Then crank the engine over with the plugs still out to blow out all the MMO.

Put in fresh plugs and crank away...
 
That is my current plan. Will put MMO in tonight and let it soak till after the holiday!

I'm also going to pull the timing cover and make sure it didn't some how jump timing. Its been suggested that maybe dirt dobbers made a nest and when i tried to start it the nest made the belts jump time? I dunno but I'm going to take a look see.
 
Chkn said:
I would suspect timing is more likely than all the rings stuck... but I have been wrong before.
Click to expand...
Famous line "it ran when parked" .....timing belt is easy enough to line up and check if it's a concern.

But seriously, my vote is stuck rings, A vote for lube in the cylinders.
 
Have you tried to get it to run on either or spraying fuel down the intake to make it pop?
 
Sluggy said:
Have you tried to get it to run on either or spraying fuel down the intake to make it pop?
Click to expand...
I have tried that. I had no luck. I've gotten it to pop twice but nothing to serious.

I will say that it seems to be pushing air OUT of the intake v/s sucking air in. That's why we thought stuck valve but with the valve cover off that doesn't seem to be the case.
 
Suck squish bang blow

Very strange with 0 compression on all 6.

Any way you can try a different ECU just to rule it out?

Checked fuses? I would start with the chewed wires, or maybe look for another harness?
 
I will have to buy a new ECU or find one at a pull a part to try another ECU. Which I'm not saying I can't / won't do. But with GOOD spark and fuel the ECU and wires seem less and less like the issue. And I was DEAD set it was an electrical issue when it didn't start right up!
 
obd2 Says P1600. It will clear it but it comes back.
 
I believe the 3.4 is shim over bucket lifters. When the valves wear into the seats, valve lash diminishes to the point that compression is lost and or valves are burnt. Just a thought.
 
She is not running yet. I did figure out that the timing is over 1/4 turn off on the cams. I've got a new timing belt set and water pump. I'm having trouble getting the crank pulley off. I think i've got a good plan to break it lose but i've been sick with the Flu and Covid then the kids got it so I haven't touched it in weeks.

Hoping to get a chance to button it up between Christmas and New years and fire it up. 99.9% sure it was the timing causing it not to start.
 
1/4 turn on the cams??? WTH???

You may be dealing with more than just a timing issue. Valve to piston clearance would be at the top of my concern at the moment meaning potential bent valve.

I don’t think it’s the rings as it’s rotating feely from what I read. The 0 compression on ALL 6 pistons and 1/4 turn off the timing mark is a huge ordeal though that’s 90* off TDC and the symptoms you explain sound about right. That means your valves are 1/4 way open @ TDC of the compression stroke.

How a valve didn’t meet the piston is a mystery. But apparently it had not, bec

But “it ran great when parked”, If he is a buddy of yours. Ask him when the timing belt was last done. And who did it? If it had been done recently or just before it was “parked” rotate the crank by hand and set # 1 cylinder to TDC.

Remove the tensioner and re-do the timing marks IAW the tech manual. I am almost certain it will fire right up for you.

I wouldn’t spend the money or waste time removing the current timing belt. If it were me I would just reset the timing to see if it will start. If it still doesn’t then yank the heads. And inspect the valves to see if they are bent.

It’s an easy check. Flip the head upside down (valves up) place it on a level surface and pour just enough fuel to cover all 4 valves to see if it will let the fuel leak by. A properly seated valve will not allow any fuel to seep by. If any fuel gets by the valve you have a potentially bent valve or cracked head.


Ohhh and make sure that if you do remove the heads the valve spring caps either stay in their respective spots OR you label them. Accordingly to their respective spots. Very important. Because each cam lobe wears into each spring cap differently.
 
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Djordj said:
1/4 turn on the cams??? WTH???

You may be dealing with more than just a timing issue. Valve to piston clearance would be at the top of my concern at the moment meaning potential bent valve.

I don’t think it’s the rings as it’s rotating feely from what I read. The 0 compression on ALL 6 pistons and 1/4 turn off the timing mark is a huge ordeal though that’s 90* off TDC and the symptoms you explain sound about right. That means your valves are 1/4 way open @ TDC of the compression stroke.

How a valve didn’t meet the piston is a mystery. But apparently it had not, bec

But “it ran great when parked”, If he is a buddy of yours. Ask him when the timing belt was last done. And who did it? If it had been done recently or just before it was “parked” rotate the crank by hand and set # 1 cylinder to TDC.

Remove the tensioner and re-do the timing marks IAW the tech manual. I am almost certain it will fire right up for you.

I wouldn’t spend the money or waste time removing the current timing belt. If it were me I would just reset the timing to see if it will start. If it still doesn’t then yank the heads. And inspect the valves to see if they are bent.

It’s an easy check. Flip the head upside down (valves up) place it on a level surface and pour just enough fuel to cover all 4 valves to see if it will let the fuel leak by. A properly seated valve will not allow any fuel to seep by. If any fuel gets by the valve you have a potentially bent valve or cracked head.


Ohhh and make sure that if you do remove the heads the valve spring caps either stay in their respective spots OR you label them. Accordingly to their respective spots. Very important. Because each cam lobe wears into each spring cap differently.
Click to expand...
Toyota 3.4l is a non-interference motor. So no need to do all that…
 
If the coils are sparkling and you have light pulsing on the injector plugs then I would chase after the zero compression.

Also vote that it would be extremely odd that all 6 holes have zero compression due to stuck rings. Maybe if they all had different amounts but zero is odd.

Sounds like you should be looking at engine integrity like cam timing and valvetrain actuation as suggested.
 
I was able to spend some time over the holidays working on the buggy and its now a runner. Timing was the issue. I guess from siting for a couple years dirt and such caked up the crank drive pulley and when I went to start it jumped timing causing all the issues I listed above.

While it is running its still got a couple issues that I could use some help with. :confused:

1st) I have to run it with the MAF (directly behind the air box) unplugged. If I plug it in it will start and run for MAYBE 5 seconds. Even once its warmed up and running if I plug it in it dies immediately.

2nd) its hard to start. Have to give it just the right amount of fuel. too little it won't stay running. To much it will pop and sputter and die.

3rd) its got a hesitation right off idle and takes a while to rev. (I assume this is because the MAF is unplugged).

I haven't gone back and checked compression now that its timed right. I also haven't checked the codes now that its running. :shaking::homer:
 

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I've had these engines stick valves open after sitting for a while...when I did my swap years ago ended up with zero compression on a couple holes. Yanked one head, knocked the valves out and cleaned the varnish in the guides...everything moved nicely. On the other side I just pulled the springs and seals and worked one at a time with some carb cleaner down the guides and everything freed up.

As was mentioned, this is not an interference engine...valves won't hit pistons.
 
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She’s starting and running great now! Issues was the MAF sensor. Now it starts up easy and runs great with not back firing or popping like before.


As it warms up it idles higher and higher. I’ll take a look at cleaning the IAC as suggested.

Thanks for the help and ideas everyone!
 
I haven't looked at the IAC yet but I certainly have a high idle issue! Cold it idles fine. Once it warms up it basically won't idle down. If I rev it up to 3,500 RPM it will only drop back down to say 3,000. Turn the ignition off, fire it back up and its back to a normal idle until you rev it again.

Does this sound like the IAC or could this be a vacuum leak? I can see a lot of dry and cracked vacuum lines (on the list to get fixed!!!). just wondering which is more likely the issue before I pull the TB to clean the IAC.
 
Id start with the vacuum lines. Easiest to change out. What intake tube are you running? Stock? Does it have all the smaller lines connected to it? There is one large one right before the throttle body that goes to the IAC.
 
Right now while I'm getting it going yes I'm running the stock intake tube. Good to know that's what the large line is for!

I have a cold air kit ordered for it because the intake tube and air box are shot! I'll swap out all the lines and go from there starting with the large one that goes to the IAC!
 
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