Leogane

Hi,
I have a '95 Maxima, cylinders 3 and 5 are give 150psi, cylinder 2 gives 145psi, the rest are below that mark (125-130). Should that be enough to at least start the engine? Thanks.

Turbobink

iTrader: (2)

Why not just try it and see?

You’ve apparently got an issue needing some level of attention … I’m assuming you’re involved in troubleshooting, attempting to ID the problem.

Leogane

I did with carb cleaner; it didn't start. The problem could also be with certain sensors, that's why I was inquiring about the number of cylinder required.

JvG

Have you checked the codes. Buy a code reader.
Then tell us which codes you have.

JvG

Carb cleaner is not intended for this purposes.
buy Starting Fluid. It IS intended for this purpose.

Starting fluid contains ether. It's highly combustable.
it's intended to start cars with carburetors where it's very cold.

you would need to remove the rubber boot over the throttle body. Then open the throttle, spray in the fluid.
the engine should run for a few seconds if the ignition system is ok. The car won't run because the injection system boot is loose.

Leogane

My car is fuel injected not carburator. I have spark. I'll try starter fluid next. Google said I could use carb cleaner so I thought I'd give it a try. I'm thinking carb cleaner has ether too because it evaporates fairly quickly.

JvG

Have you checked the codes. Buy a code reader.
Then tell us which codes you have.

JvG

of course you have fuel injection.

Starting fluid is highly combustible.
it's intended for starting cars.

JvG

it might not start for many reasons.
The no start reasons are stored in tge ECU.
you need a code reader to access them

please tell us how much experience you have with car repair. Also your age. Beginners are welcome.

Leogane

Yeah, I have a code reader, but I doubt I have codes, the car hasn't run in two years. I just finish putting the engine together and wanted to see if I could get it started. I might have to tear it down again as I have two cylinders at 125 psi and one at 135psi. The highest ones are at 150 psi.

JvG

oh I see. Did you adjust the gap between the camshaft and the valve tappet to specifications.
Incorrect adjustment could be the cause of low cylinder pressure.

Leogane

I know. I painstakingly put them in range, 10-12 milli inch intake 11-15 exhaust. I prob. should say I installed new rings too, and according to what ppl say the psi should increase once the rings break in; correct? I think break-ins require 25-mile drive on high and low speed, change the oil, drive 500 miles and change oil again.

JvG

yes, your compression should increase once broken in.

do read articles regarding break in.
Some advice very gentle break in
Most advise driving the car as normal, but no jack rabbit acceleration.
Some advise jack rabbit starts to seat thr rings.

did you install new camshafts? Look up the instructions to break those in. Some instructions say to to set idle to 2500 rpm or so for a period of time.
that's done before taking the car for a drive.

Congratulations regarding the rebuild.

Turbobink

iTrader: (2)

This is a perfect example as to why more information is better.

Up until now, and based on your ‘other’ compression related thread, we had no idea that you’d recently completed a rebuild.

Based on your compression numbers and based on FSM standards, I was thinking you had a head gasket issue … likely not however.

Low compression numbers subsequent to a full rebuild are managed/addressed differently from those resulting from aged and worn engine parts and components.

… see what I’m getting at?

Leogane

Sorry. I so much hate to take up ppl's time that I may have left out important info.
Here's a scenario: While tightening one of the intake/exhaust sprocket to the camshaft I may have exerted force on in internal component( I thought the wrench I put on the camshaft to keep it from spinning was doing the job, but the camshaft was instead pressing against something internal). Then a friend shuffled my valve followers and I was getting 125psi across the board after installation(143psi min required). When I tried to start up the engine at 125 psi, I heard a noise and one of the cylinders dropped from 125 to 50psi for a while then it mysteriously got back to 125psi. I'm thinking if that valve had gotten bent and was giving 50psi, there is no way it would give 125 psi again on its own; right?
I suspected my valve followers being out of order might be the cause for the 125 low psi, so I release the force on the valves by taking off the camshafts. At first the psi on the #2 cylinder was still 125, I paused and about 30 min later it progressively got to 165psi( I don't know why it was progressive).
After that I was certain if I get those valve clearances w/i range, I'm good to go, but instead I'm getting 125 on cyl.'s 1&4; 145 on cyl. 2; 150 on cyl.'s 3&5; and 135 on cyl. 6.
I was hoping the 3 cylinders above 143 psi would be enough to start the vehicle. I'm getting spark on at least cyl. 5( I haven't tested the others for spark)

JvG

I've has other engines start and run well if compression was well below 125 psi. You should have enough compression to start the engine.

Your engine isn't starting for some other reason.

I've asked you to spray starting fluid directly into the throttle body., then crank the engine. It should run briefly. If it does run you will know that the spark plugs are doing their thing. Also that you have enough compression.

Leogane

The manual for my engine says 143psi minimum. I was hoping 3/6 cyl.'s above the min. psi would start the engine. I tried the starter fluid twice. The second time I saw a little bit of smoke in the engine compartment. The engine sputtered a little but never started.

JvG

You seem to be fixated on compression.

your compression will rise once the piston rings seat.
it is certainly high enough to start the engine.

the test with starting fluid indicates that the engine has spark. Also enough compression to run. That's specifically why I asked you to test with starting fluid.


Your engine isn't starting for some other reason..
It has compression and spark. It needs fuel.
Now figure out what's going on with its fuel issue.

Leogane

Shouldn't the starter fluid take care of the fuel issue?

JvG

I did a Google search: minimum psi for an engine to run. They say 90 psi. I think it's still lower .
pre WW 2 cars had compression ratios of 5 to 1.
which would be 75 psi or so. Our engines operate at
10 to 1 compression. The minimum 143 psi you quote is a figure to evaluate if a worn high mile engine should be rebuilt. Ir if a car should be purchased.

Again, newly rebuilt engines will have lower compression until the piston rings wear a little bit.
Compession will rise once they do.

Check your fuel system

95maxrider

iTrader: (32)

I agree with JvG, don't get hung up on your compression right now. I drove my car for like 1,500 miles back in the day with one cylinder at like 50 psi. It started just fine, but it couldn't hold idle.

Have you checked your fuel pressure at the rail? Is the gas fresh? Are you getting spark?

Leogane

I'm not hung up on compression, I was just wondering if a car would start w/ half of its cylinders not reaching the minimum required psi. On the other hand, I'm using starter fluid, and you guys are talking about fuel sys. The fuel system has nothing to do w/ it if I'm using starter fluid; right? I have spark, but it seems to be intermittent. One of my coil plug does not fire up, I'll have to change the coil plug and see if that's the problem. I tested a signal wire while cranking, it seems to go over twice the limit of 0.2V at 0.4V(400mV).
At this point, I just wanna know what's causing the observed intermittent spark( I see spark, it goes off for like a second then comes back). By the way I get a yellow spark with a spark tester, and some say it doesn't matter, some say it does. My condenser gets to 7M Ohms quite quickly then it tickles past 9M. Please reply if you can help.

95maxrider

iTrader: (32)

The general consensus seems to be that yes, it should start even if 3 cylinders are a little low on compression.

If your fuel system is working properly, then yes, it will still be at play even if you use starting fluid to get it started. Have you disabled your fuel pump or something?

If you have intermittent spark, you need to start checking sensors to see if they're testing in spec. The crank sensors at the flywheel and at the crank pulley, as well as the cam sensor. The wiring in these cars is getting old, check the wires leading to those sensors carefully for any breaks, especially at the connectors. I suppose a faulty ignition switch could also cause issues like this.

Do you have fresh spark plugs and fuel filter? Did you pump out all of the old gas and put in fresh gas?

Leogane

Yes, I have brand new spark plugs. The spark plugs had light carbon deposit on them while trying to get the car started, but I cleaned them, I don't don't know if the carbon deposits means there was combustion. I changed the crankshaft sensor last, I tested it a couple days ago and is fine. The sensor by the crank pulley I may wanna check, but I thought if I had constant spark though intermittent, my crank/cam sensors must be good. My camshaft sensor is w/i spec. Are you saying even if I bypass the fuel sys and use starter fluid, the fuel sys may still interfere( I don't see how)? Right now my fuel pump is disconnected. Do you know if my ignition condenser could cause the problem?

95maxrider

iTrader: (32)

It would really help us if you spelled some of these things out to begin with! Why is your fuel pump disconnected? As already mentioned, carb cleaner isn't the right product for trying to start an engine, you need starter fluid. 4th gen Maximas don't have an ignition condenser.

JvG

Most of us put the entire car together. Then we attempt to start it. Generally it does....... sort of.
We know what works, and what doesn't entirely by experimenting.

You have taken an entirely different route.
You test each subsystem,

While Never Starting The Car
WITHOUT TELLING US THAT.
Then you check minutia .
Then ask questions if the myriad of minutia
doesn't test perfectly.
YOU ARE WASTING OUR TIME.

We assume that you are following standard procedure.
I mean complete the assembly of the engine project.
Then Just Start The SOB. Please do that.