No vacuum while cranking

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LeftHandedCat
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Hello, i recently picked up a rescue z32(1991 year) that had a crank but no start condition and was abandoned on the side of the road. I was getting less than 10psi of fuel pressure so i replaced the fuel pump and now that i have fuel pressure it still will crank with no start, spark plugs are sparking properly and are brand new(just replaced them), but i hooked a vacuum gauge up to it and it seems like it's not even pulling half an inch of vacuum while cranking. is this some oddity with these cars i don't know about or is this a serious problem, and where would you suggest i start looking, i've already begun the slow process of replacing the bad vacuum lines btw, but 0 inHg seems low even for a cracked vacuum line or two


itsa300zx
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I'm not sure you can pull a lot of vacuum just cranking the starter, its only about 2-300 rpm with a full battery.

If you have confirmed spark and fuel into the cylinders; last thing is compression. Do a compression test on all the cylinders, if in normal range that means timing is OK and you need to double check spark and fuel. If very low then timing belt may be way off or burnt valves or rings or head gasket. Better yet, a leak down cylinder test will give you more detailed information about the cylinders too.

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DevilZ32
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I'm not really sure how to fix a vacuum problem like this but there are a few things you can check

Engine temperature and oil are good places to start. If your temperature is down by a significant/noticeable amount, you should look into the lifters.

amc49
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Vacuum is an accumulative thing, the engine does not turn fast enough to build any at cranking speed. You SHOULD be getting zero.

LeftHandedCat
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i'm almost positive my honda gets around 1-3 inches of vacuum bouncing when cranking,but if it's normal then that's alright, i simply haven't had time to check nearly anything, and i would check compression before anything but i loaned my compression gauge to a friend i ahven't seen in a while

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NolimitZ32
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Car: 91 AG2 2+0 TTMT swap/E39 BMW 540i6/E53 4.6is Dinan S3
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Are the injectors actually pulsing? Fuel pressure gets you to the rail but not into the combustion chamber. Check the FSM in my signature for the procedure to check the CAS (Cam Angle Sensor) and injectors. The FSM for these cars is very good, you should take a look at the troubleshooting section.

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DCaff300ZX
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1993 CRP TT- Modified
Location: Tacoma, Washington

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NolimitZ32 wrote:
Tue Mar 05, 2019 5:59 am
Are the injectors actually pulsing? Fuel pressure gets you to the rail but not into the combustion chamber. Check the FSM in my signature for the procedure to check the CAS (Cam Angle Sensor) and injectors. The FSM for these cars is very good, you should take a look at the troubleshooting section.
Ditto to this, the FSM has always been a huge help for me along of course with specific help here and elsewhere. The Z32 in my experience is best approached from the FSM unless you know otherwise from experience/preference and the the testing sections are top-notch helping to beat past a lot of confusion and wasted time. This way you also end up with specific questions you can ask here rather than more general questions that may not be easy to answer without guessing.
On top of the suggestions so far, be sure to check for the notorious-to-the-Z32 green corrosion at any connector and clean/replace if necessary.

LeftHandedCat
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Yes, I have limited knowledge about the z32 but i know that the fuel injectors are a constant source of trouble on these guys not to mention the previous owner told me it would start with starting fluid so i knew it was most likely fuel injection related, so the first thing i checked was the fuel pressure and fuel injectors and fuses. Haven't yet had time to take off the rail(i've had a total of 2 hours to work on this car so far because of work and other stuff), but i pulled the ckp off the front and turned it with the ignition on, all 6 injectors are clicking(doesn't mean they're working, but they're clicking). haven't had time to do a proper fuel pressure test either after replacing the pump, i just know it has some pressure now(before it had so little i could easily squeeze the line on the high pressure side).

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NolimitZ32
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So you haven't confirmed that you have fuel pressure you just heard the pump kick on? Have you checked the EGI/EFI related fuses in both fuse boxes? Have you confirmed that your fuel pump relay is actually kicking on or are you going by sound alone?

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DCaff300ZX
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LeftHandedCat wrote:
Wed Mar 06, 2019 2:19 pm
Yes, I have limited knowledge about the z32 but i know that the fuel injectors are a constant source of trouble on these guys not to mention the previous owner told me it would start with starting fluid so i knew it was most likely fuel injection related, so the first thing i checked was the fuel pressure and fuel injectors and fuses. Haven't yet had time to take off the rail(i've had a total of 2 hours to work on this car so far because of work and other stuff), but i pulled the ckp off the front and turned it with the ignition on, all 6 injectors are clicking(doesn't mean they're working, but they're clicking). haven't had time to do a proper fuel pressure test either after replacing the pump, i just know it has some pressure now(before it had so little i could easily squeeze the line on the high pressure side).
With your limited available time and the definite and constant possibility of wasted time diagnosing the Z32, again it can't be stressed enough how important on these cars it is to go about repairs with a good method and feedback...basically using the fsm for the tests and flow charts to address your specific issues to be able to know what is working for sure, and what is/may not be working. The Z32 has a lot of inter-related issues which without experience with the car (and, even WITH experience) that can make troubleshooting difficult at best, if not nearly impossible without guidance other than wasteful parts swapping.
The Z32 FSM is top-notch and will help you at the very least with finding the problem areas and giving you important tests to determine if a sensor or part is working correctly.

LeftHandedCat
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About time i make a proper post about the whole car now that i have time to seriously start working on it. I have 2 posts about individual issues and kept the info i gave relevant to those, but it seems like they have started to branch off into a general diagnosis and i might as well make a proper thread. I will edit and update this info as i do more diagnostics.

Symptoms:
crank but no start - video: https://www.youtube.com/watch?v=zytTGZH ... e=youtu.be Previous owner says he took it to a shop and they got it to start using starting fluid
Knock sensor code - diagnosed, bad knock sensor or pigtail to knock sensor, put a resistor in the plug temporarily to continue diagnosing vehicle without worrying about ECU failsafe
nearly no fuel pressure - lent my FP gauge to a friend but i could pinch the line with my fingers while someone else primed the pump and it was spurting and barely putting out anything
temp gauge sits at certain level even when vehicle is off - picture: https://imgur.com/a/ZhDc5XP not a priority unless it ends up being relevant to the no start

What has been done:
read FSM EF & EC-77 hard to start or impossible to start under normal conditions
checked all the fuses in the car one by one in all 3 fuse/relay locations - all good
replaced dead battery
replaced VERY worn down spark plugs with new NGK's
replaced a vacuum hose or two that were obviously cracked or not holding
removed knock sensor connector and checked for corrosion - no corrosion
put a spare 1M ohm resistor in the knock sensor connector, cleared codes, then cranked, code 55 but no difference to starting - will replace knock sensor once i can diagnose the no start and get it out of driveway, resistor will at least get rid of the failsafe mode so i can diagnose the car
replaced fuel pump with v6 altima pump that has the same flow rate as stock z32 fuel pump, have some fuel pressure but have not tested how much with a gauge yet, waiting for it back
Reconnected a large hose connected to the intake piping before the passenger side throttle body(picture: https://imgur.com/a/roVsj69) , haven't delved into the vacuum system yet to know where it goes, but an open in the intake piping and a disconnected hose is only going to cause problems
Tried starting with pedal all the way to floor as manual says to do to check air regulator and A.A.C. Valve, no difference even in sound

relevant data:
air filter is some awful aftermarket thing that sits in a horrible place picture: https://imgur.com/a/X8HqV43 so until i can get the stock airbox or a different adapter onto the front of the maf nothing i can do, but seems clean enough shouldn't cause a no start
Crank angle sensor functions(rpm gauge goes up when cranking)
pulled out CAS and spun it with ign on and all 6 injectors click
here is a video of the ScanTech OBD data while cranking with sound https://www.youtube.com/watch?v=zytTGZH ... e=youtu.be
seems like both exhaust bank o2 sensors are sitting at 0.32v but they're too cold for that to be taken as valid data
MAF data seems to be jumping for low to 0.5v(possibly due to wind and me taking off the air filter for that video to check for different numbers and it being windy), goes to around 1v when cranking, no idea if this is normal because the manual only lists 0.8-1.5v at idle as a spec.
TPS is at 0.3v when spec says tps should read 0.4-0.5 volts
fuel pump is getting 12v+ and no resistance to ground
no oil dipstick in engine or car, no clue where it went but looking for a parts car to replace it and check oil levels

things i have not done but will do:
have not done compression test yet - lent a compression tester to a friend recently but will be coming back with compression results on all 6 sensors shortly
have not done fuel pressure test yet - FP gauge is lent out to the same friend, but there is at least fuel pressure now, will come back with FP test results
have not checked all the coil packs, put a tester on plug 1 just to make sure ignition system was working at all, and it is sparking
have not diagnosed or tested any part of the EGR system
drain and replace oil
look up good MAF specs and check MAF
look at all vacuum connections and make sure they are solid as well as ensure all intake piping is connected under the front bumper
adjust TPS, currently sits at 0.3v, FSM says 0.4-0.5v is spec for closed throttle

LeftHandedCat
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Joined: Tue Feb 19, 2019 9:07 pm

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this thread has begun branching far from the original topic and a lot of info i didn't list is becoming relevant, please see the new post i made here https://forums.nicoclub.com/1991-z32-no ... 23395.html as the topic of this thread has already been talked about and resolved

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NolimitZ32
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Car: 91 AG2 2+0 TTMT swap/E39 BMW 540i6/E53 4.6is Dinan S3
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I merged your two threads so people can have all the info in one place, in the future please avoid cross-posting.

As for your issue, it sounds like you're on the right track, 1 thing to note: that "awful aftermarket intake" is actually the go to for these cars, it's a JWT POP Charger or a Z1 copy of the JWT. It's what the majority of the Z32 world runs, in fact in all my years of messing with these cars I have never seen a car without one up close. You can get replacement for around $65 IIRC from pretty much any of the vendors. Check your compression, if that's good, it may be time for you to source a good known working ECU, I have a couple if you want, you can send me a deposit for the value and get it back when you return it or keep it if you need and I'll keep the deposit as payment. Let me know and good luck.

LeftHandedCat
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Sorry, i don't use forums a lot, so i was planning on posting that then deleting this but then realized i can't delete a thread after i posted. and my problem with that intake is that it's a very smashed air filter and it's sticking out the front, especially with no bumper or nose plate on this car it's just begging to become soaked with water and hydrolock my engine, especially in the rain or even when driving behind another car on wet roads.

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NolimitZ32
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Car: 91 AG2 2+0 TTMT swap/E39 BMW 540i6/E53 4.6is Dinan S3
Location: Houston, TX

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No harm no foul.

The filter looks terrible, not arguing that, you should definitely replace it. As for cover, obviously it is designed to be run with a nose panel and bumper. Once you replace the filter you can try a modified version of the "flowerpot mod" as a temporary fix while you work to get the nose panel and bumper on. Search Z32 pop charger flowerpot mod.

LeftHandedCat
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that flower pot mod is an excellent idea, i will definitely keep that in mind! Finally got my compression tester back today and the it seems that simply hoping the engine held compression wasn't enough. passenger side bank wasn't even reaching 60psi in the front 2 cylinders and the driver's side bank was a little low(around 120psi). i've started the process of pulling the plenum off already and what a nightmare that is!(even worse than the miatas i've worked on where it's easier to remove the head with the intake attached than to try and get the intake out).my local parts guy said he can get me the intake mani gasket as well as the head gaskets by monday, but after i pull this plenum off there's a good chance i'm going to find a lot more and it may be worth my time to do at least a top side overhaul with new gaskets and valve seals all around, not to mention every single hose in the engine bay tearing long before they come off their nipple.

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NolimitZ32
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Car: 91 AG2 2+0 TTMT swap/E39 BMW 540i6/E53 4.6is Dinan S3
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Not reaching 60psi sounds like a jumped timing belt with some bent valves. The VG in the Z32 is a beast to work on in the car thats why generally people pull the engine for anything more than an intake manifold regasketing. You can pull the heads with the engine in place (there's even a procedure for it in the FSM), this is a lot easier if its an NA.

LeftHandedCat
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I would have pulled the engine, but i wanted to take it apart piece by piece. This is the first time i've worked on a Z series and i would much rather follow each hose and vacuum line as i pull them off to learn where all of them go and understand the system(not to mention I have a toyota 4AGE already living on my engine stand that i'm helping a mate rebuild). i've got the heads almost completely off in the car(could have finished last night but that idler pulley stud on the intake manifold is just being a b**** to remove) and i didn't realize the head bolts were 10mm allen bolts until i got the valve covers off and i need to get myself a 10mm socket that will fit my torque wrench. I will report back when i get the heads off and can inspect the damage, i suspect the right bank head gasket went and the kid ditched the car because he couldn't afford a repair(due to some other evidence left in the glovebox like overdue statement notices). While i could see valves being bent with that low of compression I doubt it. the timing belt seems very new and had way too much tension to jump a tooth(unless the kid got VERY unlucky), plus it was ditched in a parking lot and there's no way he did a timing belt on this car in a parking lot in the middle of nowhere so it was driven a good distance after the timing belt change. either way, the engine needs some SERIOUS cleaning, not to mention an EGR delete and a PCV reroute and i plan on having both heads resurfaced at my local machine shop before putting new gaskets on. from what i can tell it is actually the original engine with 200k miles on it so i want to do a proper overhaul with all the hoses, gaskets, and seals before i put it through any serious abuse.

LeftHandedCat
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alright, got both heads off in the car(which actually wasn't as bad as everyone makes it out to be tbh). Thankfully there isn't a single bent valve on either head(pictures of the low compression head here: https://imgur.com/a/OBdhUrD ). going to take them to my local machine shop monday and spend most of tommorow cleaning the crap out of everything. as well as making egr delete plates from the now removed egr tubes and getting plugs for the egr tube bung and both AIV bungs. also my z32(a 1991 year) doesn't have the PRVR reservoir i have been hearing about in the driver's side fender, only the aiv system(now deleted), is that normal for my year or a TT only thing or am i just completely missing it?

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NolimitZ32
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How did you test the valve seating? Just because the valve doesn't look bent, doesn't mean it's seating properly.

LeftHandedCat
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I turned each cam sprocket while inspecting the valves, haven't done too close of inspection tbh but when i dropped it off at the machine shop i told them to vac test it to check for bent valves. sounds like they will get back to me tommorow morning. Normally i would do a valve job anyway since i already pulled the heads, but i want to get it driving asap so i can start work on our gambler 500 car(colorado gambler 500 is in june so we need to get started soon) so if the valves aren't bent i will leave them be and do the valve job when i do the bottom end rebuild and transmission rebuild(pulling the engine out with the trans when i do the rebuild so might as well throw new rings and bearings on it rather than gamb|ing on a 200k mile engine with a list of previous owners i don't know). planning on pulling the diff off tommorow and doing at least a drain/refill/reseal as well as hot tanking all the valve covers and metal bits i pulled out at my shop while i'm waiting for the cylinder heads to get back from the shop. i also dropped a bolt into the lower timing belt cover so it looks like i can't avoid pulling the crankshaft pulley, so i need to find a steering wheel puller to borrow.

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NolimitZ32
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Easy way to test the valve seating is to flip the head over, lay it down so the mating surface is level and fill the combustion chamber with gasoline, if the valves are shut the gasoline stays, if the valves aren't seated properly the gas leaks into the runners.

LeftHandedCat
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just got word from the machine shop, one or two valves are definitely slightly bent on the low compression head and both of them have worn valve seats(possibly never had a valve job on a 200k mile engine) so it definitely needs a valve job. they're asking 450 for the pair, i can do one in my shop but we can't get them in till mid next week, so it sounds like it's going to be money or time(the usual trade).

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NolimitZ32
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Car: 91 AG2 2+0 TTMT swap/E39 BMW 540i6/E53 4.6is Dinan S3
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These engines, when treated right go over 200k often enough without needing any internal work. I am assuming they are going to refresh the heads completely for $450, not just replace the bent valves right? If so, it sounds pretty fair.

LeftHandedCat
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Yes, it came out to just around 550 dollars everything included. When the machinist told me the valves weren't seating well and some were bent(he said many of the cylinders only held 5-9psi even without bent valves) I decided to go ahead and get a full top end rebuild done while i have it off, so they're replacing the bent valves, grinding the others, resurfacing both heads, and doing a valve job with new stem seals(and of course replacing whatever guides may have broken from the slightly bent valves). should run almost like new after I put it back together.

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NolimitZ32
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Car: 91 AG2 2+0 TTMT swap/E39 BMW 540i6/E53 4.6is Dinan S3
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Nice, how do the bores look? Hate to say it but maybe you should consider doing all the "as long as i'm in there" stuff now, although that kind of decision can get away from you very quickly.

LeftHandedCat
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the bores actually look incredibly good for a 200k mile engine(pictures of pistons and at least part of the bores here https://imgur.com/a/dQj1TWS). I am kind of in a rush to get the z done and out of the garage because i have to get our gambler 500 car started on sunday to have it ready in time, otherwise i would do rings and bearings either way, but i looked at the bores and pistons from top and bottom as well as pushed on them with a wooden dowel to see if there was any movement or play that would indicate knocking but all of it looks to be in very good condition so i'm going to reassemble it without doing anything but cleaning on the bottom end.

EDIT: i should probably mention the pistons and bores have been cleaned since that picture was taken before anyone freaks out. taking the heads off was a very dirty job because this engine looks like it hasn't ever been cleaned and crusty dirt stuff got EVERYWHERE

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NolimitZ32
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Car: 91 AG2 2+0 TTMT swap/E39 BMW 540i6/E53 4.6is Dinan S3
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They do look clean but pretty smooth, i'm sure the car will run fine on the bottom end as is.


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