timing belt failure leads to odd problem

[rumor76]

Ok, tried to find a solution to this problem and haven't had much luck. This is driving me batty... A couple weeks ago the timing belt went out on my 4G64 (2.4L) spyder. It happened in a parking lot, got there no prob, wouldn't start when I went to leave. After tearing into it, I discovered the b/s belt looked original (130k) and snapped and took the somewhat newer outer belt with it. I replaced both, put it all back together, and the engine gets about two or three cranks into starting and bogs down with no attempt to run. I know my timing marks are on the money (with one exception I'll ask momentarily), and my b/s is oriented properly.

I have spark, I have fuel. when I take the plugs out and crank it over it cranks normally, not sluggish at all. I performed a compression test and got 170/170/185/190. Measured voltage at primary and secondary ignition coils and it was spot on. I tried to start the car without the battery in the system since it had died over the last couple weeks i've been messing with this and no difference.

So here's where I'm at... I'll admit I have not checked the crank or cam position sensors since I can't see any reason for them to go bad at the exact same time as the belts. Even with good compression, I decided to pull the heads to ensure proper operation, the valves and pistons were fairly well carbon coated, so it was pretty easy to see there had been no strike on any of the valves (don't ask me how that happened, I must've cranked it half a dozen times before I accepted the timing belt was gone...), and I made sure they all seated straight with no leaking (pretty obvious from the compression test). I put everything back together and same dang thing, cranks two or three times, then bogs down like it's overcompressing or something. I should point out that all the valves opened and closed properly, so there's no chance they are sticking closed or anything.

I have two questions and a plea for help:

1) could either my cam or crank sensors cause what I'm describing?

2) when I line up all my marks, should I be at TDC on the intake stroke or the power
stroke? I seem to be on the power stroke when I line them up, but I always thought it
was the intake stroke.

I did try to put the camshaft gear 180 deg. off thinking I was supposed to be on the intake stroke, but I have the exact same problem there too, which stands to reason since the crankshaft will have spun 360 deg. and would essentially be in the same position.

So anyway, thanx for reading all this, any help would be much appreciated...

 

[fedj18]

first off I'll start here...when you have the head off and you put it back on and set the number on piston to TDC it can be on either compression or exhaust stroke. The difference comes in when you set the cams in and align the camshaft gears. The cams should be aligned so the valves on cylinder 1 are all closed, and follow the guidelines for the cam marks, (I'm assuming that the timing belt alignment marks are the same or very similar to the 4G63).

Now to adress your slow cranking issue, it may have nothing to do with your timing belt breaking recently. First things to check would be your battery condition, battery cable condition (i.e.: corrosion or loose connections), and possibly drive belt driven accessories suce as power steering, alternator, or a/c binding (this is unlikely). Also if you know how to, perform a voltage drop test across the positive cable while cranking to see if there is excessive resistance in the cable.

Now on another note since your BS it could be hard to say if there was any mechanical damage that may be very minor and would only show it's face if the engine were torn down and checked throughout.

 

[rumor76]

Well, thank you for your reply, I very much appreciate it, but I'm afraid it didn't really help that much. When the piston is at TDC and the car begins to crank over the only place it has to go is down, that puts it at the beginning of the intake or power stroke. As for the battery, there is no reason to suspect the wiring since it was starting just fine before the belts broke, and I am using a running car to jump start mine (I actually used two different cars, no change), and it doesn't help. There's no corrosion anywhere on my cables either.

Since this problem has cropped up I try to start the car without any of my accessories attached to save time breaking down and rebuilding the engine after evrything I try, so I know it is not any of them. The b/s and oil pump sprockets all turn easily, and the crankshaft and camshaft seem to turn with an acceptable amount of force while the plugs are out. When they are in, it is damn difficult to turn the assembly more than a half inch at a time.

 

[fedj18]

Well I gave it a shot. Another thing that came to mind was that possible there becomes an excessive amount of resistance internally in the starter as it heats up trying to start the engine. and yes TDC 1 would be at the top of power stroke, it's often called TDC 1 compression because it is at full compression. As for an acceptable amount of resistance...without the spark plugs in it should turn 100% free without catch. If that is the case thenyou are ok there. Also with the spark plugs in there should be times about every 180 degrees when you come across the compression stroke and you would be compressing the air causing it to be tough to turn. From what you describe it all sounds normal. It coud be possible that if the crank sensor was damaged when the belt broke that it is not getting the proper signal and then not firing at the correct. As for the bogging down though I still don't see a sensor causing that.

 

[rumor76]

Thanks for your replies, they are appreciated... I had a buddy suggest that since I live on a hill, I should put it all back together and push it down the hill and pop the clutch... I did it and sure enough, the darn thing fired right up! I drove it back into the garage and listened to some severe clattering that was coming from my heads and tried to find out why the engine had vibration to it, and I'm wondering if my oil pump didn't go out on me when my inner belt broke and left me with a spun bearing... I've posted another question in the forums here regarding my oil pump location:

http://www.dsmtuners.com/forums/newbie-forum/345678-oil-pump-clarification-2-4l.html[/URL]

If anybody has any insight into this, please help! Thanx!

 

[SrKegler]

Are you sure the rear BS is in sync?

 

[rumor76]

Yeah, I made sure of that... but it's a moot pooint now, I just got it running a half hour ago...

Apparently, after I got it all back together, my battery was still dead, so I took the battery out of the loop and had been jump starting it with my grand cherokee. I guess my cables were too thin to carry the current needed to start it or something, because I put the battery on charge last night and when I went to start it after work today it fired right up, no hesitation or anything, so I'm good to go...

Thank you to everybody who replied with suggestions!!

Randy