Hey folks. I have been working on this project and I thought I was nearing the end. My 2003 Mazda 6i (2.3L Auto) had a warped head b/c it was driven while overheating. I took it off and paid to have the head re-worked back into spec. After reinstalling everything I went to start it up and it just sits there and turns over without starting up. The camshafts and timing chain were reinstalled exactly how they came out, so that shouldn't be the problem. The thing is, the car was running before the teardown, just poorly, which makes me think the fuel pump is not the issue. I did notice when it I was trying to start it it would turn over 3-4 times normally, then on the next turn it would "bog" down, turning more slowly, then would go back to normal. Would this make you think starter? I had charged the battery overnight and while it didn't have a full charge, it was turning the engine over just fine. I am missing the o-ring that sits on the fuel injector for the #4 cylinder, so I was wondering if the fuel rail wasn't pressurizing properly, but I am not even smelling fuel out of that cylinder. I am going to pick up this o-ring tonight. But for now, any thoughts??

 

I'd double-check the timing and make sure it isn't 180 degrees out of phase. (Remember these are 4-stroke engines, so the pistons reach TDC twice for a single compression cycle.) If you're off by 180 degrees, it will try to spark at the same time the fuel/air mixture is trying to get into the cylinder rather than during the actual combustion stroke (intake, compression, expansion, exhaust) Spark should come between compression and expansion, not between exhaust and intake.

 

Hmmm ... Makes sense. I'll double check the timing and let you know what I figure out. Thanks!

 

My friend and I marked the placement of the camshafts and made sure not to move the crank, so wouldn't the reinstall be right if we lined everything up correctly?

 

Do you think the bog could be the engine just be hitting a harder compression stroke? I was wondering if it was the starter because once and a while when it "bogs" down I hear a noise, kindof like a grinding noise that is made when a starter starts to go out. The starter before thebeginning of thisproject was fine, but it has been getting a lot of use trying toget thisengine to start.I know this can't actually be anything inside the engine because I was very carefull in re-installing everything. I torqued the caps and head bolts using the proper sequence and torque, installing the timing chain, etc... One idea my friend had wasthe crank pulley.Is there a certain way that is supposed to be aligned, because there are no indicator marks on the pulley or crankshaft to align it. So maybe this is making some kind of noise? Who knows.

On the agenda for tonight: I am going to double check the injectors and fuel pump are workingand also check for spark.

 

Not necessarily.

Your crank would go around twice to the camshafts single revolution...valves only open/close once during the compressions cycle, but the piston moves up/down twice.

Intake open/Exhaust closed- air/fuel are pulled into the engine by piston moving down in cylinder
Intake closed/Exhaust closed- piston raises is cylinder compressing air/fuel mixture,
Intake closed/Exhaust closed - spark occurs igniting mixture, forcing piston back down in cylinder
Intake closed/Exhaust open - piston moves back up cylinder expelling burnt gasses

 

Hmmm ...ok. Any ideas on what could be causing the momentary "bogging" and "grinding" ?

 

Ok ... after I charged the battery I tried starting again to see what was going on. While it still didn't fire, it didn't make the "bogging" and "grinding" noises it was before. My conclusion there is that there wasn't enough juice from the battery for the start to turn the engine over, thus making the grinding noise.

I also pulled the fuel injectors after trying to start the car and I did smell fuel, so that mustnot be the problem.

The bad thing is I think I burned up my starter while figuring all this out!

The only thing I can think of is the timing. Even though I marked both camshafts of their exact position and didn't move the crank, the Mazda tech that I talked to yesterday at the dealership said that even that wouldn't guarentee that the timing was correct. What do you guys think? Do you think it is a timing issue? Does anyone have the procedure to set the timing correctly? Thanks!

 

Top Dead center of the #1 cylinder is where everything needs to get aligned to.

I'd say get the crank to TDC #1 (piston at the top of the cylinder), then remove your valve cover and set the cams to TDC #1...you should be properly timed at that point.

Have you done a compression check on your motor to verify that everything sealed up properly after the rebuild?

What kind of pressure do you have in the fuel line? It should be between 55-65 psi. Looking in the manual it doesn't look like there is an easy way to check that other than hooking in an in-line gauge through your fuel lines at the filter.

I think the start-start-start-bog thing is your cylinder getting flooded with fuel.

Are you getting spark? You can take one of the wires off of the spark plug and let the arc jump to the engine block (or anything else metal) while you are cranking, check all (4) cylinders.

 

My friend who put the timing chain back on said he aligned the marks he made and the chain wenton perfectly, so he still thinks the timing is right.

I have not yet done a compression check yet. Let me ask this: If the engine was running before the rebuild, just poorly due to the warped head, then the block should be ok to go don't you think? Other than the possibility of not sealing everything up perfectly during the rebuild do you think the block is ok?

Dont know on the fuel line pressure. I don't have an inline guage and since the fuel supply has always been ok I will leave this as a last resort to test.

Still need to check spark ... I have been home alone without any extra hands for the past few days so I have to wait for someone to help me on that.

One more question ... what will exactly happen if the timing is just off a little bit? Say like one tooth? Because when I was trying to start it would crank and crank and crank, then act for a fraction of a second like something wanted to happen, but then go back to crank crank crank. If the timing is just barely off should it start and run, only run poorly? Will there be any noises while trying to start? Or will it just sit there and crank without firing?