78 280Z - Finally got it driving - High Idle, will occasionally die (but restart), sound like it has a misfire

[NocturnalEmber]

2 hours ago, Zed Head said:

That's the PCV valve, not the BCDD.  

Yes, the PCV hose from the block to the PV is a specially formed hose.  Yarb referred to it above.  Small one end, big on the other.

When things aren't tuned well the engine will often be non-responsive to tuning efforts.  Kind of a vicious cycle, a rabbit hole.  The missing and break up at higher PRM are probably due to the massive vacccum leak through the PCV valve under the intake manifold and also through the hole in the block.  Air can enter the crankcase through the hole in the side of the block and travel through the engine to the intake manifold.

You can either block the two PCV holes, or get the proper hoses connected.  The EFI system will not work correctly with a partially intact system.

 

.  

 

Looking at EC-2 on the FSM makes the BCDD look like it has a bung on the bottom of it in the initial picture.  That's on me for mistaking it as such. Leave it up to me to do something dumb like that in a community I'm new in.

I did find a picture from ZcarDepot, but I swear the other bung that hose came off of (the larger one) was pointing straight at the ground which is likely why I confused it with the BCDD (because it looks like a bung in the fsm, or I suppose one could confuse the drawing as it having one.)

Then again I could have just been entirely mistaken due to lack of sleep. I'll double check shortly.

The post from Zcardepot:

 

I could be wrong, and like I said I'll look shortly, but I swear that bung did not point out parallel with the car, instead perpendicular to the ground.

Edit, now that I think about it, that pcv valve under the intake manifold did seem further back towards the engine bay, too. But again, this will be cleared up momentarily.

 

Edit: appreciate the continued help @Zed Head (and anyone else giving their time to contribute.)

 

Edited March 4 by NocturnalEmber

[NocturnalEmber]

Well, It appears I had a lapse in memory. 

The receiving end of that bung does indeed point out to the side and not down.

The replacement hose looks to be out of stock. So I'm off to source a brass coupler and a 1" hose to join them together.

Also, I included a picture of just what that hose looked like coming off the car.

 

[NocturnalEmber]

I managed to find a hose that fit, luckily an auto parts store had one in stock from another car that involved some minor trimming to length.

 

However, it is as I feared.  With that hose connected (aka, the pcv valve not sucking in air from atmosphere) the car is back to wanting to die again after running. I had to back the idle screw out about 1 1/2 - 2 turns to keep it idling.

Ive included a video of it below, but its doing the same thing it was doing, but worse; Idling rough, missing, etc. Eventually it died after about half an hour of continuous running (temp gauge got to the lowest point but not far past it, I just added half a gallon of coolant so I assume it was low. Yesterday it would get up to slightly less than or about halfway on the temp gauge.)

Fuel pressure seems to be down now, too. the inline gauge was reading 12PSI when it was struggling to run, giving it gas didn't seem to increase or change it much. A few days ago it was getting around 28 PSI.  I've got an inline fram filter coming off the tank and the gas doesn't look contaminated (though the filter only has fuel present in the bottom portion of it, but it was always like that since I installed it.)

 

EDIT: I decided to try testing the fuel pressure with the engine off. I disconnected the spade connector at the starter, battery has a good 12 volts.

I've done this before, and pressure was fine when I first redid the pump/lines/filters a few months back, but I figured that it was 12PSI just now, why not retest?

Turning the key to start, it took a surprisingly long time to get the pressure to reach 28-29 PSI. I mean holding the key to the start position for 15 seconds about 3-4 times finally got it up there. Fuel pump is loud and clear (and new.)  All the soft lines are new, fuel filter is new, gas looks clear.  I did notice that the vacuum line on the FPR seems rather easy to take off, but nothing seems to be holding it on, either.

Could this be an issue with the FPR itself?  

EDIT EDIT: Being that my car is a 78, it looks like FPR's are basically unobtanium.

 

EF-37 mentions that if the fuel pressure isn't at 36.3 PSI to replace the regulator...and it took forever to just get it up to 29.

 

So it would seem that connecting the PCV line has indeed made the running/idle problems worse. It was misfiring before, but now with that hose connected its worse and likes to die after it has been running for awhile. It will restart with some cranking, but I'm at a bit of a loss as to what my next steps should be.  

 

Edited March 5 by NocturnalEmber

[Patcon]

Fpr is inoperative when the vehicle is off. I think I would start at the tank. You could rig up a temporary source of fuel instead of the tank. If the fuel pressure comes up, there is a problem in the tank

[NocturnalEmber]

31 minutes ago, Patcon said:

Fpr is inoperative when the vehicle is off. I think I would start at the tank. You could rig up a temporary source of fuel instead of the tank. If the fuel pressure comes up, there is a problem in the tank

 

I've looked at the tank and from what I can tell everything coming out of it is clean. I suppose it won't hurt for me to just take the feed line off and put it in a gas can, though.

 

If the fpr isn't operative when the car is off, why does the manual say to test the fpr with the engine off? Genuinely curious, not trying to be sarcastic or anything.

[Yarb]

Remove both the hoses and extend them with barbed fittings available at ace hdw. Otherwise you have to keep filling the tank and you can monitor the fuel coming back.

[Zed Head]

Does pressure drop immediately when the pump is not running?  If pressure drops it might be the FPR.  It could have foreign matter holding it open.

You can clamp the return line closed with some vise-grips and test pressure again.  If it shoots up above 36 then it's not the pump or the supply side.  Be careful if you can't see the gauge while you turn the key.  A typical aftermarket pump will hit 90 psi.

Also, the pump should not be loud.  That's a sign that it's working hard to pull fuel in.  Could be a clogged pickup tube in the tank.

Gather more clues. 

[Patcon]

The Fpr is used to modulate fuel pressure using engine vacuum. With the engine off the fpr is basically inoperative. You should get the max pressure of the system, roughly 36,  IIRC

[Yarb]

@Patcon is dead on here. The entire system is antiquated. Funny as I was fighting your battle with my 78 I ran across the same issues. @Dave WM a friend close to me and helped tremendously getting my engine running to spec said “if it’s idling fine and you loosen the oil cap or remove the dipstick and it becomes rough and wants to die, chances are you do not have any vacuum leaks.

[NocturnalEmber]

5 hours ago, Zed Head said:

Does pressure drop immediately when the pump is not running?  If pressure drops it might be the FPR.  It could have foreign matter holding it open.

You can clamp the return line closed with some vise-grips and test pressure again.  If it shoots up above 36 then it's not the pump or the supply side.  Be careful if you can't see the gauge while you turn the key.  A typical aftermarket pump will hit 90 psi.

Also, the pump should not be loud.  That's a sign that it's working hard to pull fuel in.  Could be a clogged pickup tube in the tank.

Gather more clues. 

Will do, I'm about to head out to the garage and do the test. Luckily I have someone that can turn the key to start it while I observe the gauge in the engine bay and clamp down on the return line. Will report back. Pressure didn't drop immediately after the car had been off when I did the priming test last night, but I noticed it had leaked down a few PSI after about an hour or so.

I guess I should probably clarify the pump noise level. In a dead quiet garage, you can hear it running when turned to start (without the starter engaging.)

When the car is running or if there were ambient noise around, likely it would be hard to distinguish unless you knew specifically what to listen for.

 

 

1 hour ago, Patcon said:

The Fpr is used to modulate fuel pressure using engine vacuum. With the engine off the fpr is basically inoperative. You should get the max pressure of the system, roughly 36,  IIRC

 

Yeah, it wouldn't get above 14 PSI running and after disconnecting the starter spade connector and holding the key to start four separate times at about 15 seconds each~ it barely reached 22. This wasn't an issue before, definitely looking into the tank as part of the tests.

 

27 minutes ago, Yarb said:

@Patcon is dead on here. The entire system is antiquated. Funny as I was fighting your battle with my 78 I ran across the same issues. @Dave WM a friend close to me and helped tremendously getting my engine running to spec said “if it’s idling fine and you loosen the oil cap or remove the dipstick and it becomes rough and wants to die, chances are you do not have any vacuum leaks.

Ironically leaving that PCV hose vented made the engine run smoother, the exact opposite of what is supposed to happen. Once I ran the PCV line it now has more pronounced issues.  I'll find the solution, just gotta keep digging.

[NocturnalEmber]

Late night update:

So I started the car and put a vise grip on the return line coming off the fuel rail. - No change in fuel pressure.

I didn't think the car was low on gas considering its only ran for maybe an hour or two combined since I've owned it, but I only put in two gallons to begin with. 

I decided to trust the fuel gauge that was pegged on empty, and put two gallons of gas in it.

 

After I put the gas in, I started the car, and fuel pressure shot up to exactly where it should be (high 20's, low 30's.) I pulled the nipple off the FPR and I want to say it even read around 36 when I did that.

 

Of course the problem during all of this is the engine was still running like in the video above,

 

The fuel pressure also began to slowly fall, eventually settling on 14 or 12 (back where it was since this problem appeared) before the car eventually died on its own.

 

I assume my next step in the process is to look at the tank and pump.  Unless there's something in the tank I wouldn't see, the fram inline filter I have coming off the tank is clean. That doesn't preclude a blockage in the tank though I suppose.  All of the soft lines, pump, and engine bay fuel filter were all installed new a few months ago.

 

I feel it worth mentioning that for some reason, the car seemed to sound like it was running better when that PCV hose was sucking in vacuum from atmosphere. Even when I pulled the vacc line off the FPR (which had suction from the hose, not the FPR itself) the engine seemed to smooth out (though the fuel pressure was still low.) Just weird that vacuum leaks seem to make it want to idle better and not die, but still run rough, and closing up the leaks just makes it run rough and also want to die.

 

Edit: Assuming I end up having to replace the tank if there's some sort of blockage - Do the s30world tanks for the 78Z fit the 2+2? I ask because, well, my car is a 2+2, build date of 12/77 I want to say.  

What are the rubber insulators they are talking about on the website? It says you can re-use the old ones, but I'm just wondering.

 

Edited March 6 by NocturnalEmber

[Patcon]

The rubber insulators are square pads of rubber glued to the top of the tank to prevent it rubbing against the car body.

If you used 2 gallons in just testing then the car is running really rich. Running better with vacuum leaks, which leans the mixture would make sense.

EFI is not my forte. Maybe someone can chime in and tell you what areas need Inspection to see what the PO messed with to make it run with all those leaks. Also the connections at the thermostat housing are important.  If they get reversed it will be really rich. An AFR gauge would still be really useful