bc.

I really didn't want to start a new thread for an issue that has been beaten around a bit, but I am.

My problem is after I installed a new head gasket I noticed that my vacuum gauge was at about 14mmHg, it used to be at 20mmHg. I am lazy so i adjust the CAS to get it as close to 20 as I can and got to about 18. It never felt as quick as it did before so i decided to take the valve cover off and set the CAS the right way, as per fsm. The vacuum went back to 14mmHg and the car still didn't feel quite right. Compression test yields a low of 145psi and a high of 150psi across all 4.

So i go out and buy the cheapest timing gun I can find and put the motor in timing mode and check where I am firing. Turns out I was WAY past 15 deg, like maybe at 30 or more. This leads me to believe that my timing is off mechanically by a tooth or two so I take off the valve cover again but everything looks fine...




Side Notes:
1) I know the chain marks don't match the cam marks, i believe the chain fell off the crank because they weren't even close to matching up.
2) this is the second time I have replaced my HG, the first time after I put one in it ran perfectly, better then ever actually, idled great and vacuum was at 20mmHg but I never re-torqued the head studs and it blew again.

Before I do something stupid, I wanted to get another opinion on what could be going on.

Thanks,
bc

jr_ss

Pull your fuel pump fuse, spark plugs and CAS plug and crank the motor over until you can get the timing marks to line up with the chain links. Then install your CAS per FSM.

__________________
My SR20VET

cotbu

your first mistake is wanting 20mmhg. just because your pulling a lower vacuum than what most claim, means nothing. And you failed again for advancing the timing to try to achieve that 20mmhg. You could have caused more damage by advancing the timing.

The fix: You appear to be at TDC,(verify compression stroke) then install the cas per fsm, then set the base timing to 15deg, along with a idle adjustment. increasing'/lowering the idle is a safer way to increase vacuum. If your vacuum is low and you're running rich?(vice/versa) Get a tune, and or tuneup.

__________________

LoverTechnologies "Half Broken Things!"

bc.

ok, got the marks on the chain to line up with the marks on the gears. The CAS was already in the right position on the gear but i pulled it and put it back in anyway...

I only wanted 20mmHg because that is what I had before I blew the HG and what I had after I replaced it the first time. And I didn't adjust the timing mechanically, I only adjusted it by turning the CAS, which shouldn't do any mechanical damage (as in no interference with valves / pistons) i didn't know it could do other damage?

I don't think it is running rich, I can't smell anything. I recently pulled off the IACV and cleaned it, my idle is at about 800rpm, but it will drop after a little bit of engine braking to 500rpm but if I poke the gas it will go back up to 800 and stay there.

cotbu

With 30deg of base timing. you would most definitely detonate even with 93oct and probably only 7psi boost, and that equals the other damage.

Set you car into timing mode, set idle +50rpm or even +100rpm more, this could help you out, until you find the vacuum leak you have.

__________________

LoverTechnologies "Half Broken Things!"

bc.

Thanks,

I was thinking about how it could be a vacuum leak, but every time I come straight back to timing because after setting up the timing the right way and going into timing mode, it was firing at 30deg by itself.

I will put it back together and see how she does.

bc.

Ok, I lined the marks on the chain with the marks on the gear and re-stabbed my CAS. It basically right on to begin with but w/e.

The car idles fine and with a slightly higher vacuum then before, like 16mmHg maybe 17. But when go into timing mode (I think? TPS pulled reved above 3k 5 times and idle adjusted to 850rpms) this is what I get:


Did I do something wrong going into timing mode or is my timing just this far off? Is there I sure fire way to tell if I am in timing mode correctly? I am hesitant to adjust the timing to 15 because it is so far away, also, that is how I did it before and it just feels sluggish.

jr_ss

How To Set Crank Angle Sensor (CAS) Timing on the SR20DET Engine

Did you do it like this? I have a feeling you aligned the marks wrong... There's no way for your timing to be that far out if the CAS was stabbed correctly and your timing chain marks lined up with the marks on the cam gears..

__________________
My SR20VET

bc.

Pretty sure i got it right, here is a picture:


I don't know, the only thing I could think is the gun is off. I am getting the signal from the timing loop in the back of engine on the coil pack harness, btw.

I just got done driving it and it feels loads better then it did before when I set the timing to 20 deg. no backfires when in gear when off the throttle and way more power, blew the charge pipe off the TB.

jr_ss

How about just timing the motor without it being in "timing mode". What are your results then?

__________________
My SR20VET

bc.

Never tried that because I thought it would be constanty adjusting the timing. I will check after work and post what I find.

datsunnazi

Stop using the timing loop. That will give you a misreading almost everytime! Just use a spark plug wire between the coil pack and the spark plug. Then put it in "timing mode". You'll be able to accurately time it then.

bc.

Well shit, didn't know that. Do I need to separate out the spark signal wire or can I just wrap it around the whole harness going to plug 1?

datsunnazi

don't use anything like that. Literally go get an old spark plug wire from a ka and pull the coil pack out of the head on your sr. Insert the wire into the coil pack. Install spark plug wire on spark plug. Place timing light pick up on ka spark plug. Time car.

bc.

Gotcha, thanks for the help.

jr_ss

BC, what he said is bs... I've used that loop and many others have as well to time their motors. I've never had an issue timing my motor with that loop, saying it's faulty when Nissan engineers put it there to utilize and only way to time the motor without doing what he said, is horse pussy.

Don't put your car in the timing loop and test it then. I'm curious to see if it is different. It'll only constantly be adjusting timing if there is a load on the motor. At idle it should be 15 BTDC no matter what.

__________________
My SR20VET

datsunnazi

i never said that anything was faulty. i said that it's easier to time an SR that way due to the fact that timing lights are different and inductive pickups are different. i have read literally dozens of threads about this same issue. getting readings of around 30* when measuring timing. this is the failsafe way to get a proper reading on any timing light that is accurate everytime! done. the engine still has to be put into the "timing mode" to ensure proper base timing when the TPS is plugged back in.

so don't throw your "internet weight" around and act like you know everything!

jr_ss

Easier there killer... Yes, you did say there was an issue with it, unless telling the man itll give him a faulty reading every time isnt saying its faulty, asshole... BC you can test it that way, and would yield the same results as using the loop. The loop is the signal wire from cyl 1 coilpack. If there is an issue with it you have bigger things to look for.

__________________
My SR20VET

datsunnazi

I know what the wire does. but like i explained, if he is getting a misreading from his timing light on the provided loop now, he will always get one (with his timing light). and again, like i explained, there are different types of inductive timing lights that may or may not work with the provided loop. from the info given in the OP, all i can infer is that he has an older type (or cheaper) that does not read the signal wire properly, therefore giving a misreading of around 30*. That is why it is more accurate to measure the signal after the coil (with this timing light).

does that make sense?

i personally have used both methods (the loop and the spark plug wire) depending on which gun i have. I have achieved proper readings with both methods.

bc.

I bought a spark plug wire,


removed the coil pack on #1,


pulled apart the coil pack,


connected the plug wire to the 1st plug,



connected the other end of the wire to the exposed end of the coil pack



and finally clamped the timing light inductor around the spark plug wire and checked the timing.

Don't forget the TPS has to be pulled


And you need to make sure you get it into timing mode, rev it 3-5 times above 3k rpm and rpms should drop to near 800, my harness made 3 clicks as it stepped the rpms down to this level, if you don't here this you might not be in timing mode.

Now, it was at 13 degrees of timing and I have seen both 13 and 15 used as the correct number, is it ok at 13 or should I adjust it to 15?

Thanks for the help

jr_ss

Put it at 15... Glad you figured it out. Props to Datsun for the idea...

__________________
My SR20VET

cotbu

__________________

LoverTechnologies "Half Broken Things!"

datsunnazi

people just like to spew the same old information that everyone else says. this isn't the first time I've been proven to be correct on Zilvia.

Glad you got it figured out!