1990 300zx na Auto 2+2 wont start

[Duke51]

Okay so I am having problems with my 1990 nissan 300zx. I bought it and on the why home it stopped working. so since then i have replaced the camshaft oil seals because they were leaking, i replaced the spark plugs, replaced the battery, and have replaced any bad vacuum tubing i found. I checked the ignition coils they work and the injectors seem to be firing i took the CAS off to test them. So next i went to the ECU and its good as well. When i try to start the car its like its right on the verge of starting but it doesn't the engine cranks but just wont start. Does anyone have any ideas about what it might be? or how to narrow down the problem more? I've been using an online manual and have done most the checks. any ideas? thank you.

[johnshop]

I'm no experts but things that might be worth look at:

Bad fuel pump, or a really dirty fuel filter.

Also check the alternator. My car did something like that once I was driving along and bam it stopped. Turned out it was a bad alternator.

Nothing else I could think of.

[Ziggy1621]

My 2+2 dd that when the CAS went out. You can also test the anti theft and the ptu

[Duke51]

i forgot to mention that we already checked the alternator, that was the first thing we thought it might be, its good. we also replaced the fuel filter, and we think we have narrowed the problem down to the engine is getting to much fuel so we're doing checks. is there anyway to chech if the injectors are stuck open without having to remove them? and is it just possible that i only need to replace my o2 sensors? thank you for the help

[t.mcginley.jr]

There's a test you can do just for the O2 sensors: http://www.nicoclub.com/archives/nissan ... ostic.html

Read down at the end of that article for the how-to. Too much fuel should cause it to run like crap, but you would need alot of fuel to not cause it to start. Sounds like a bad PTU to me. Do you have the old or new style PTU??



(Old style is the one on the left)

[Duke51]

it's the new style. so a bad ptu could be my only problem if its the ptu?

[t.mcginley.jr]

Yes, a bad PTU will cause starting issues. A faulty injector or 2 should still let you start it but it would just run rough.

[Duke51]

okay thank you ill check it out and get back you about what i find

[Duke51]

thank you all for your help, i took the ptu out and if im not mistaken it is bad, i did a check on it and some research so im pretty confident about it.

[nissanfreak12]

If you have a bad PTU, you will not get spark. Yes, it will not start but it will also not act like it will start. If you have the new style, you really don't have too much to worry. Yes they still fail, but not often.

You said you replaced the cam seals? If so, how did the timing belt look? When was the last time it was replaced? Have you ohm tested your injectors? You said you checked the ECU, did you get any codes?

You said a car is getting too much fuel, what does that mean exactly? Why do you say that? Did you test the fuel pressure? Compression?

Honestly, when a car all of a sudden stops running, that usually points toward a timing belt jumping a tooth or two. It throws the engine out of time. When you said it acts like it wants to start, that most of the time means either poor fuel delivery or out of timing. If it had no spark, bad PTU, it would just crank at the same pitch. If you have a friend with a 300zx, take some working parts off of his and test that way, see if that fixes the problem, then give his good parts back.

[Duke51]

the guy i bought it from said the timing belt had been replaced recently, when we took it off to change cam sealstiming marks lined up and belt looked new, but just in case we replaced it anyway made sure all timing marks lined up didnt allow them to move while doing so, we also replaced all the tentioner pulleys. the only cody the ecu is throwing is the det code.

[Duke51]

as for to much fuel, the sparkplugs are getting wet, we told a mechanic about it and he said it sounded like it was getting to much fuel, which could be because the exhast is clogged or some other things it could be but i dont remember those right now. i can get specifics later

[Duke51]

okay so heres somemore info, we found a fuel hose coming off the injectors had a nasty hole in it we replaced and have good fuel pressure but the car still will not start. we have also replaced the ptu because the old one was bad still no start. i would check compression and timing but how am i suppose to do that if i cant get it started? any and all help is welcome im stumped and i really want this car to start again, thank you.

[Johnathon]

Just curious, because it's not really clear with what you have said thus far, but are you getting spark, fuel pressure? if your getting BOTH, make sure there is nothing blocking the air passages, And take a long extension or screwdriver and place it right on the metal part of the top of each injector, have someone turn the engine over for you, with your ear against the screwdriver/extension. You'll hear the injector click. It's a pretty distinct sound. Do that for each injector, just make sure you place the screwdriver/extension in the same spot on each injector. Removing the cas, and turn it by hand will do the same as turning the engine over. Also the *best* way to check for spark on these engines that i have came across (and I could easily be wrong) is to remove a coil pack at a time , and spark plug, put the plug back in the coil pack and plug the coil pack back up, and turn it over. If ya got pretty blue spark your good. With it just refusing to run i would also unplug every single connector on it, one at a time, CLEAN them , put a lil bit of grease back in them, and plug them back up. That CAS connector is really bad about corroding over. And from what i've seen causes some majorly weird driveabilty issues.

[Johnathon]

Also to note, there is a known defect with the 1990 engine's right side head, the one where the CAS is located at. It's a machining defect, and causes the cam gear and CAS gear to wear flat out, make sure that both of those gears are in good order. Later model engines did not suffer from that problem.

[Duke51]

yes, we are getting spark and fuel pressure. i went through and checked the plugs and they all seem to be good. i have been using an online service manual and all the diagnoses say that if everything is good try a known good ecu i haven't yet been able to do that, but i am planning to soon. as for air passages where is the best place to check? and on the CAS when you talk about corrosion is that at the plug? if so the CAS is good as well.

[Ace2cool]

Yes, all the plugs in this car are ridiculously vulnerable to corrosion for God knows what reason.

[Duke51]

okay so here's some more info. we did a compression test and these are the results (now im not sure if it matters but these are "cold" compression readings and by that i mean because we cannot get the car to start and warm up these are readings we took while trying to start the car.) cylinder #1 pressure climbs to 75psi, when we redid the test after adding oil pressure rose to 130psi. cylinder #3 pressure climbs to 100psi, when oil is added pressure climbs to 110psi. cylinder #5 pressure climbs to 75psi, when oil is added it does not change and climbs to 75psi. cylinder #2 pressure climbs to 130psi, when oil is added it climbs to 140psi. cylinder #4 pressure climbs to 120psi, when oil is added pressure climbs to 150psi. cylinder #6 pressure climbs to 150psi, when oil is added climbs to 175psi. so here's some questions now, are these normal readings because we cannot warm the engine or does that matter? also i know that if it goes up when oil is added it means bad rings or bad head gaskets but i dont remember which and can't seem to find the page i had referenced to, along with that question how do i know if its bad valves? and lastly would that cause the car to not start at all? i am willing to pull the engine and tear it down to replace the parts, but i dont want to do all that get it back together and find out it still wont start. Thank you for all the help it's much appreciated.

[Ace2cool]

There's no compression test specs for when the engine is cold. When the engine is cold, the rings haven't expanded to mate the cylinder walls as they normally do.

[Duke51]

okay well that's what we thought, but the mechanic that we have also been talking to to try and figure out why the car wont start said to do a compression test. so if timing is right and we have spark and fuel pressure what are possible problems that it wont start at all? is it possible we have a bad ecu? everything seems to work fine. I'm pretty sure its not the CAS unit, its not throwing the code and when we took it off to test the injectors by spinning it they fired. is it also possible it's just a bad wiring harness? the current one has some iffy spots so we were looking in to replacing that as well. or just a missed vacuum hose somewhere or egr? thank you for your help.

[Johnathon]

Duke, first off let me apologize for not responding sooner.

Have you got the car running yet? If not, and you seem to have spark and the injectors are firing, Ecu is not throwing codes, fuel pressure is good,then change your spark plugs. Make sure you get the right NGK plugs for the engine, do not use another brand of plug. It stands to reason that if when you turn the cas over your getting spark and the injectors are firing, that the ECU and harness is relatively in good order. Base timing should be 15 degrees BTC. Also check your ignition switch. It could easily be powering the ECU in the run position but not the start position. I assume you have checked all your fuses, and fuseable links. There is some on the drivers side fender well, one fuse there is just for the ECU, as well as some relays , one of those is also for the ecu. Also in front of the battery is a fuseable link box, check all of those , and check the ones on the drivers side interior , right behind the left foot rest. If its not running , hope this helps.

[Duke51]

nope still not running, i've checked the fuseable links in front of the battery and those are all good. as for the kick panel on the driver side i've lookd at it briefly, but i dont have the panel that tells me what the fuses are so i plan on going back an looking at that again. and the other fuse box is in the driver front wheel well? if so i have yet to check that one and will get right on that. as for base timing how can i check that? i also replaced all the spark plugs with the proper ones, that was one of the first things i had done, but still not getting it to start. i will check all fuses and check to see if the ecu is getting power in start, oh one more thing is it possible the anti-theft system has a bad ground? i read some stuff on that, but i couldnt really find anything on how to diagnose if it was bad or what affect it would have on the engine causing it not to start. thank you a lot and ill let you know if anything changes.

[Ace2cool]

You can try disconnecting it. It's above and to the right of the ECU.

[Duke51]

so if i disconnect it and the car starts it's the anti-theft system? just want to double-check on that.

[Ace2cool]

Yup. You got it.

[Ziggy1621]

http://youtu.be/bo5bkaywFqw

[Duke51]

okay thanks and thank you for the video. so here's an update I've checked the the fuse on the kick panel on the drivers side, all the ones that need to be there are there and are good. I removed the anti-theft and tried starting it, it didn't start. I then proceeded to check that the ecu was getting power while trying to start the car, when i turn the key to the on position the red light in the ecu is on, but when i try to start it it goes away and when i return the key to on position the red light comes back on, does that mean its losing power when i try to start the car? I also have yet to check the fuses in the driver side wheel well, I plan on doing that this weekend. thanks for all the help guys

[Raw Z]

Jumping in 4 years later... did you ever find out what was causing the no start? I have the same exact issue and cant figure it out! Sorry if I am hijacking your thread but hoping they are related. And yes I am trying to get a NA running while everyone is doing LS1 swaps. The car was my daily until I bought a new car and let it sit for a few months. Then after charging the battery it ran fine for 2 days until I noticed the CEL light come on and off intermittently. Unfortunately I didn't catch what code it was while it would go on intermittently. Then it started bogging down and eventually shut off. It sounds like it wants to start but then the cranking gets weak so I turn the ignition off since I feel like holding it isn't fruitful. Only code I got now is the detonation sensor. I replaced the fuel pump, fuel filter, spark plugs 2, 3, 4 and 5 since they are the easiest to get to and still same result. Unplugged the MAf and still same result. If coilpacks were bad wouldn't I get codes? I am thinking injectors could have gone bad due to stale gas but want to save the grinding the plenum for last to get to the injectors. Next check is PTU, fuses and CAS... anything else obvious I am missing?

Thanks in advance guys... never believed everyone complaining about working on these cars till I hit 200k miles

[NolimitZ32]

Have you checked for Fuel, spark, and compression at the cylinders?

[Raw Z]

I have fuel coming into the fuel filter, anything past that I don't know how to check as I cant access the the fuel injectors. Is there an easier way? I pulled one of the hoses off the FPR and no fuel came out, when I replaced it 3 years ago I am pretty sure some fuel came out, is there some that's supposed to come out? As far as spark, I have replaced plugs 2, 3, 4 and 5 and tested the coilpacks 2, 3, 4 and 5 since they are easy to get to and they passed the ohm test. As far as compression test, I have never done this but may look into it if I have the courage to working on this some more. I keep losing tools in the engine bay, man this thing is hard to work on!