[Chubby Bunny]

While trying to resolve a persistent code 1, the timing belt broke. I was testing O2 sensor voltage at the ECU while someone else was driving, when the car died, going up hill. At first, I thought I had shorted out the ECU so we tried restarting the engine. I could tell by the way it cranked that something wasn't right, and confirmed that the belt had snapped.

Surprising since it's a brand new belt on a newly rebuilt engine. I think there are three possibilities:

1. I did something wrong when installing the belt the first time. However, I was following the service manual and I don't see any signs of wear on the belt.

2. Defective belt. We bought a DNJ kit. I was less than impressed with the quality of some of their parts.

3. Maybe something fell into the timing cover. That very morning, she had an alarm professionally installed on the car and the horn was mounted on the d.s. fender well, less than a foot away from the timing cover. Maybe they dropped a screw down there, or even a tool.

We will replace it with a quality belt and cross our fingers that we didn't bend a valve.

 

[msc]

Wow, that really sucks.

The only possibility I can come up with (other than a junk belt) is if a foreign object got between the belt and a pulley. This would cause a stretch and strain concentration at the point of the foreign object. I would expect it to leave a mark on the belt cogs at the break if this is what happened.

Did you have all the belt covers in place? Many people get away with leaving them off but they do more then just keep your fingers out of the belt.

Unfortunately I’m pretty sure you will have at least one bent valve. You can do a leak down test to confirm before pulling the head.

Mike

 

[jwharnish]

Wow, that really sucks.

The only possibility I can come up with (other than a junk belt) is if a foreign object got between the belt and a pulley. This would cause a stretch and strain concentration at the point of the foreign object. I would expect it to leave a mark on the belt cogs at the break if this is what happened.

Did you have all the belt covers in place? Many people get away with leaving them off but they do more then just keep your fingers out of the belt.

Unfortunately I’m pretty sure you will have at least one bent valve. You can do a leak down test to confirm before pulling the head.

Mike

I imagine you are starting to question why you to get into the CRX at this point. One challenge after another with the 88. Never saw a new belt do that, and agree with Mike that either junk belt or foreign object caused it. Also agree that bent valve is almost 100%. Another way to check which valve is bent is do a valve lash check. The bent valve will have a lot more clearance than the other valves, due to not seating completely.

 

[Chubby Bunny]

I imagine you are starting to question why you to get into the CRX at this point.

I wouldn't mind so much if we had an adequate place to work on it and we didn't depend on the car for transportation. As it is, we're doing all of the work in a covered parking garage, trying not to get caught by security.

But she LOVES the car.

 

[Baker]

2. Defective belt. We bought a DNJ kit. I was less than impressed with the quality of some of their parts..

Just based on that, seems like you were apprehensive to begin with, I would never have gone with a company like that and will fault the quality of the belt.
I would have gotten a Gates belt, they've been in the game for years.

 

[jwharnish]

Just based on that, seems like you were apprehensive to begin with, I would never have gone with a company like that and will fault the quality of the belt.
I would have gotten a Gates belt, they've been in the game for years.

Agree, and not just any Gates belt, but the blue one is what I bought. Not sure, but I think Gates basic black belt is from china. Blue race quality belt is US made.

 

[Chubby Bunny]

Since the cam stopped turning as soon as the belt broke, is it fair to say that whichever valves are currently open are the ones most likely to be damaged?

I will start work on this over the weekend.

 

[jwharnish]

Since the cam stopped turning as soon as the belt broke, is it fair to say that whichever valves are currently open are the ones most likely to be damaged?

I will start work on this over the weekend.

valve lash check will show which valves are bent. bent ones will have larger gap.Depends on how much the valve was open when belt broke. There is some clearance between valve and piston, so that only the valves that were mostly open fully would be affected.

 

[Chubby Bunny]

For somebody that's unlucky with cars, I seem to be getting lucky.

I checked all of the valves at the top end of the clearances and in most cases, the blade didn't go in (I adjusted them mid-range when we rebuilt the engine). When it did go in, there was drag the blade. So I think the valves are ok.

I also was able to video the valves using one of those colonoscopy cameras from Amazon, and the valves looked good from the inside as well. For $27, it's a pretty handy tool.

For only 3,000 miles on the engine, the pistons look pretty sooty, but perhaps that's normal. Below is a video of the piston surfaces. You will see a wet spot on the center of the #1 piston. I'm not sure what this is from because the car has not run for over a week. I will check this again after we replace the belt. If it's a leaky injector, I think I could see it with the scope.

 

[Chubby Bunny]

We pulled the timing cover off and there was no sign of anything that might have torn the belt. It must have been a defective part.

Thanks DNJ!

 

[audacious562]

That or it was to tight or put on wrong

 

[jwharnish]

That or it was to tight or put on wrong

Negative on this. Car ran so timing belt was installed ok. Can't really over tighten the belt, since the spring tensioner controls the tightness.

 

[Chubby Bunny]

New belt is back on and it runs but is throwing code 4 (crank angle). I thought we were maybe off by a tooth like last time, so we adjusted the cam sprocket by one tooth the other direction. Didn't make any difference.

The only other possibility is that timing needs adjustment at the distributor, but it was fine before the belt broke.

 

[msc]

Do yo have the factory service manual or are you working from other documentation?

Reading the FSM it looks like code 4 would be triggered by the ECU not seeing the signal at all. Possibilities are bad sensor in the distributor, bad wiring, or bad ECU.

Unplugging the distributor, spaying the contacts with some contact cleaner, and reconnecting may solve the problem.

Unplug the connector at the ECU and look for 350Ω to 550Ω between B10 and B12. Also measure for possible shorts to ground on either pin.

The timing marks are used differently on D16 vs D15 engines. Read the manual, understand the timing marks, and you will never have to question the timing again.

Mike

 

[Chubby Bunny]

Thanks.

I do have the FSM which shows that to install the belt, UP on the cam sprocket should be on top with the 9 and 3 oclock marks flush with the top of the head. # 1 piston should be at TDC with the single notch aligned with the two sights on the timing cover.

I will check the electronics but since this code was not present when the belt broke, I assumed it meant that the cam was not in time.

 

[msc]

Your trying to use the D15 timing marks on your D16 engine.

For the D16 you need align the mark at 7 o’clock with the pointer on the cylinder head back cover. This mark is very difficult to see with the engine mount in the way. Study the illustration for the Si timing on the same page in the service manual. It’s page 6-26 in the 91 manual.

The ECU doesn’t have any sensors to tell the relationship between the cam and crank. The diagnostic steps in the manual for code 4 all focus on the electronics so I would look there. Think of things that may have been disturbed or moved around a bit with your recent work. The ECU and sensors in the distributor are not likely to spontaneously fail. 30 year old wires and connectors in the engine bay can get flakey and be sensitive to movement.

Mike

 

[Chubby Bunny]

Problem solved. When I unplugged the 12 pin connector, I noticed that one of the two pins was pushed back, to where it was barely visible, and was obviously not making contact. I plugged it back in and pushed the wire in from the backside of the plug. Now there is no code and car is running fine. It must have happened when we pulled the cap off.

 

[Chubby Bunny]

I'm resurrecting this post because it's not quite resolved, like I had thought.

The car idles fine but has low power and backfires under deceleration. I decided to have a shop take a look at it. Their verdict was a bent valve, but they didn't do any checks to verify this. The thought the cam timing and ignition timing looked good.

I decided to do a compression check. The first time, I was able to get all cylinders over 150 psi but I wasn't paying much attention to the revs. Second time, I counted five revs. The 4th and 1st cylinders were at 150 and 2 & 3 were at 120. But in general, the cylinders all seem to build pressure.

I think I will check the timing myself. (I have a feeling that the shop didn't know how to property check timing.)