'76 280Z Question on dist/manifold vacuum, dist timing, fuel pressure, brake booster

[Jennys280Z]

Well my car was running great and almost all at once in between times I drove it, the next time I turned the key it seemed to be back to where it was before -- running poorly as if it wasn't firing on all cylinders. If you guys remember I caught my #1 cylinder not firing and just cleaning the contacts on either end of the #1 spark plug wire, cleaning and gapping the plug and the car ran wonderfully again. For a few more drives at least.

Then it was right back to running terribly again.

But even worse, it was running badly and I verified that all six plugs were firing with my timing light so whatever was affecting it this time wasn't as simple as a dead cylinder.

In case of poor spark, I've replaced all my spark plug wires with the same blue NGK brand, looked over my NGK V-Power plugs again and verified they were all in normal and great condition, looked over the distributor again and verified it was clean and in great shape.

And I ran into this story:

http://mybuildgarage.com/2010/09/1975-datsun-280z-restoration/

If you read just below where it says: "Looks like this issue was a two parter!" it sounds like his car is suffering the same problem mine is. I emailed him last week on youtube but no response so far. It's crazy how he starts describing the problem and not mentioning how he fixed it! He goes right into talking about polishing his wheels and taking the car on long trips, so I know he fixed the problem somehow.

My car at one point was misfiring and popping too, sounding like from the intake, until I added brand new gas, and then the backfiring went away but it still ran horribly. But I wonder now if this had to do with the fact that I let it sit and started it up again (intermittent) than the fact that I changed the gas. It seems like just letting it sit and starting it up again a few days later is all it took to go from great to terrible again. I don't think AFMs break and then magically fix themselves, maybe this is how they go bad though.

So I think this is an ignition problem even though the car doesn't seem to want to rev to high RPMS in neutral or while driving, and there is no power to where it feels like I'm driving a golf cart instead of a Z. I'm too scared to go full throttle to see if there's a difference in that vs. light/medium throttle so maybe one of you guys can come drive my car? j/k

If you guys remember my car has no vacuum switching valve. It was removed and bypassed So before I write another novel, and to continue on from a previous post here months ago, I have found the vacuum line to the distributor was cracked. I got some electric tape and taped it back on for a short term fix but it turns out it's virtually severed in two. So I ordered some new 5mm silicone vacuum hose on Ebay and hopefully it shipped today. I'm wondering since my car was set up for full-time vacuum advance but I wasn't getting hardly any vaccum to the distributor because my hose was cracked, if this could retard my timing sufficiently to make my car run like hell, even at light to moderate throttle? Or without this vacuum present, could this somehow cause an intermittent problem with the distributor firing the spark plugs, particularly with the #1 cylinder...?

Another really stupid question someone will get mad at me for asking, but what is the hose that goes from the rocker cover to the throttle body for exactly? I guess that this just reroutes air caught above the camshaft back to the engine to be recycled and burned. But if this hose is cracked really bad, will this disturb the vacuum in the system even more?

And my brake booster is still kaput. So I disconnected the hose to it at the intake manifold and taped the pipe shut. (Yes I drove with unboosted brakes yaay) I figured if I left it open it would be a huge vacuum leak but since I've taped it shut that should have completely stopped the leak there. BUT...couldn't that magnify or exaggerate the vacuum leaks elsewhere in the system like these cracked/taped hoses I'm talking about? Can I get my brake booster off without disconnecting my master cylinder from the brake lines (and thereby not make a mess, not get air in the lines and add a lot more work?). I have three manuals here and no good step-by-step for removing the brake booster. I would assume I have to drain the master cylinder, separate the brake lines from it, disconnect the brake pedal from the linkage to the master vac, disconnect the master cylinder from the master vac, unbolt the master vac from the firewall via four bolts underneath the dash, and reinstall another one with the reverse of this procedure. Is this correct? Is there anything else I need to know, or any helpful hints that could help me get the job done? Thanks!

Also, using the timing light to check my dist timing is so hard. It flashes so fast, and honestly I can't even see the little notch on my crank pulley at all when it goes by. So I scored some chalk the other day. I'm going to stick my nose in there and try to find that notch and chalk it up, and then put some chalk marks on the timing plate on the front cover around the 13 degree line, and THEN see if I can use my bionic vision to see the chalk lines meet up there even though it's flashing like three times too fast! GRRRRR

It's hard to do this on my own especially when I have no experience or anyone mechanically inclined among friends or family that I won't have to tow my car and spend money on to help me.

I cleaned the electrical contact on my TPS. It was the last contact in the EFI system I didn't clean, sans the fuel injectors themselves which is the only thing I haven't cleaned. I doubt that has anything to do with my problem but here's to being complete.

I checked my manifold vacuum on the same day I found my #1 plug not firing. It was fairly constant at about 13 in Hg +/- 0.5 in. when I want about 17-18 in. here at 4000ft above sea level.

I haven't bought a fuel pressure gauge yet but this is something I've been meaning to do. I am wondering where the best (easiest, while being informative) place to check pressure is? I'm thinking at the rubber hose right above the fuel filter. Should I use a T-connector and let fuel go to the injectors or can I just plug the gauge right into the hose from the fuel filter and stop the flow to the engine? This is an electrical fuel pump so I assume I don't have to start the motor to check the fuel pressure but just turn the ignition on, right? I haven't done this yet because I've been told that fuel doesn't keep an engine from revving, only air can do that. (Not sure this is true).

Sorry for so many issues. Even my issues have issues but you guys have been helpful to me here.

[FastWoman]

Hi Jenny,

It sounds like your car is running lean! I think you've got vacuum leak issues going on. Frankly tape is not an acceptable material for anything other than wrapping wiring, and some people even take issue with that use. It's a fairly simple/cheap matter to round up some new hoses/tubing and to replace all of the rotted vacuum tubing mess you already have. It's avaialble at any auto parts store. The big hose that goes from the valve cover to the throttle body is important, and it's under vacuum. It's part of the PCV system and helps to keep your engine clean. If you have a big split in the thing, you're going to have a huge vacuum leak. That would certainly be sufficient to make your engine run very badly.

There can also be other lean-running issues. Cozye and I have beaten our heads against our respective walls about our '78s, and we're both in a much better place now. However, both of us found that our engines were out of whack even with the sensors all within spec, with new injectors, etc. I concluded it was a semiconductor issue in our engine control units. These units have earlier linear circuitry, as compared to the digital circuitry of a modern ECU. They are prone to drift and degradation. Anyway, you can read about some of our debugging work in the "purs like a kitten" thread.

Hey, girl power!

Edited November 17, 2010 by FastWoman

[cozye]

What Fastwoman said. You have to be absolutely certain that you fix all your vacuum leaks and other issues first though. You will want your distributor advance connected to the throttle body, it wasn't designed for manifold advance source.

After doing more research and searching forums on "resistor water temp sensor" i've found several credible Z mechanics refering to this as a known issue with old ECU's drifting and the fix is to put resistor inline with water temp circuit.

[Jennys280Z]

Hiya guys!!!

Yep there was a big crack in that hose, probably caused from the old-style clamps being tightened and digging into the hose putting a knife-like slice right through it.

So I took off that rocker cover hose, and measured it as a 17mm (probably 16mm) (and approximately 23.5cm or 9.25" long) but the closest thing the auto parts store had was a 5/8" which I thought might be a problem but it wasn't and installed easily. But when I held the old hose up to the window and looked through it I was amazed at what I saw! Have you guys watched those old westerns where a tumbleweed blows down the street right before a gunfight? Well that's what was inside my hose! I thought it might be a natural formation of oil/dust that crystallized like that over the years. But what I extracted was very much man-made. It's a wire ball with hooks on either side. So my question is now, what is this thing, where did it come from, and what should I do with it? It was near the middle of the hose before I pulled it out. Not fastened to anything despite the hooks, but the friction against the inner walls of the hose is more than strong enough that it wasn't bound to move anywhere. Should I install the new hose with this thing in there? Maybe it serves as a kind of stopper to prevent large pieces of dirt or sludge from blowing into the throttle body? *shrugs*

Does anyone get rid of their carbon canister? I don't have emissions tests here anymore even if I was registered to drive but because there's also a venting line coming from the fuel tank I'm leery about bypassing it or removing it. But it'd be nice if I could just run just one vacuum line from the distributor to the throttle body and that's all.

cozye, about what you said about water temp sensors, I actually have noticed that my temperature gauge does not seem to warm up like it should. I remember when my engine was fully warmed up in the past, the needle would sit about half way, maybe a little higher than half-way to about 185-190 degrees. But now even after running the motor for 20 minutes it doesn't even rise a third of the way up, so it reads about 25-30 degrees low. I wondered if this was a faulty thermostat stuck in the open position but now that you brought this up, could this also be related to my problem? I've read some articles online in the past talking about adding that resistor to the circuit too now that you mention it. Thanks!

I've decided to eventually test fuel pressure above the fuel filter where a new hose exists I already put on a year or so ago. It's easier to see what I'm doing above the filter than below it, and the hose below it isn't as horizontal as I thought either. Also, I'm going to test the fuel pressure with the engine running and through a T-connector, per recommendation of one of the local Z mechanics.

I will buy this one; it should pretty much pay for itself after just one use, as it would cost almost as much in labor to get a mechanic to do it for me. I hope this one will work for me:

http://www.amazon.com/Actron-CP7838-Professional-Pressure-Tester/dp/B0009XQUKC/ref=sr_1_1?ie=UTF8&s=automotive&qid=1290148880&sr=8-1

Edited November 19, 2010 by Jennys280Z
clarity!

[Jennys280Z]

Here's a drawing of what I'm talking about. It was sitting in my rocker cover PCV hose. What is this thing?

Edited November 19, 2010 by Jennys280Z

[Zed Head]

I'm going to guess that that is the flame arrester that I've seen arrows point at the location of in the FSM but have never actually seen one. Thanks for the drawing.

[Jennys280Z]

I'm going to guess that that is the flame arrester that I've seen arrows point at the location of in the FSM but have never actually seen one. Thanks for the drawing.

Yup! You're right Zed Head it's a flame arrestor! I was really feeling guilty about putting it back in there before installing it until now.

Here's a link to more information and a photo of what I saw through the hose, though the info. in the responses here is not exactly error-free. But I'll leave it to you guys to parse out the good info. from the bad.

http://www.zcar.com/70-83_tech_discussion_forum/spark_arrestor_where_is_it_whats_it_look_866736.0.html

One thing I read on this link that I didn't know is to only use fuel-injection hose on the intake manifold and not heater hose. I don't think that applies to this hose as it's not connected to the intake manifold. Anyway the hose I used is a heater hose; seems to me like it would be more than sufficient to the task of PCV return but you know me, I dunno...:stupid:

[cozye]

I would leave the evap canister. You don't what fuel vapors in your engine compartment and your gas tank needs to vent. The distributor vacuum advance was designed to run off ported vacuum on the TB and it's no problem to have this T fitted in with the evap canister as designed.

Your water temp gauge should be connected to a separate temp sensor (with one barrel connector). Some years might have used the same sensor with FI, not sure what year yours is but the 77-78 is using a different sensor for the dash gauge. The temp sensor for the FI has a two terminal connector on it just like the injectors. If your problem is intermittent, I'm not sure I would add the resistor just yet until you understand what's going on for certain. Mine and Sarah's problem was not intermittent. If you do have a faulty tstat, it could cause some issues but I wouldn't rely on your dash gauge to prove that.

For the fuel pressure gauge, I would install a more permanent gauge so that you can leave in and drive. This way if it's running good you can see what's going on without stopping the car, and the same if it's running poorly.

A lot of people (including myself) installed this gauge right between the fuel filter and fuel rail:

http://www.summitracing.com/parts/SUM-800160/

you will need this T fitting

http://www.summitracing.com/parts/SUM-G1710/

The fuel line is supposed to be 7mm. However, no fittings are made in 7mm. What I did was use 5/16" fuel hose, which is just a tad larger than 7mm and a tad smaller than the 3/8 fitting. You can get it on and clamp it.

Edited November 19, 2010 by cozye

[Zed Head]

For the fuel pressure gauge, I would install a more permanent gauge so that you can leave in and drive. This way if it's running good you can see what's going on without stopping the car, and the same if it's running poorly.

A lot of people (including myself) installed this gauge right between the fuel filter and fuel rail:

http://www.summitracing.com/parts/SUM-800160/

:alien:

Liquid-filled pressure gauges under the hood are apparently not a good idea, unless you only read them cold.

I did this on my car for a while but was using the JEGS ~$18 liquid-filled gauge. Eventually I found out that it is well-established that the liquid-filled gauges are temperature sensitive. In my case, the gauge read low as it got hot. But my fuel pressure regulator was regulating high as it got hot. So the gauge hid the problem, for quite a while. What I thought was a 0.5 to 1 psi variation was actually about 4-5 psi.

Below is a link to an article with more info from Aeromotive, a supplier of aftermarket engine products. I discovered my error after I got one of their FPRs and read this bulletin.

http://aeromotiveinc.com/wp-content/uploads/2010/01/TB-902-Tuning-EFI-with-Fuel-Pressure.pdf

Edit - Forgot to say that I also queried over at Hybridz about liquid-filled gauges and got some very good information from Tony D. To give due acknowledgement.

It's interesting to me that JEGS and Summit will put their brand name on a product for use in an application that "they" (whoever they are) should know will give poor results. They're just distributors.

Side note - Aeromotive is offering a free Aeromotive dry gauge with some of their FPRs, at JEGS.

Edited November 19, 2010 by Zed Head

[FastWoman]

I never saw a pic of the flame arrestor before. Mine didn't come with one. The PO had replaced the hose, and the part was undoubtedly discarded. I just made a new one out of numerous layers of bronze screen material soldered together. I think mine is probably better than the OEM thingie. In case you're interested, the flame arrestor keeps any backfire flames from traveling up the hose, into the valve cover, down the timing chain tunnel, and into the crankcase. The result *could* be an explosion. It's probably not a likely event, or else they would have made a more serious one.

It does sound like your thermostat is stuck open or has become inaccurate. If in doubt, you could always just pull the thing out and check it in a pot of water on the stove. It should open at around 180F. You'll need to blow a buck or two on a new thermostat cover gasket. I think it doesn't hurt to unbolt those things occasionally anyway. The alternative is that they seize up. You'll need to drain a bit of fluid from your radiator before taking the thing loose. There's a drain plug on the bottom lefthand side of the radiator. Clean up the bolts before putting them back in. Also get yourself a metric tap and die set, and clean out the aluminum threads with a tap. (Lubricate with oil. Go forward two or three twists, then back one. Forward two or three, back one. Take the tap all the way out and clean the tap every time resistance builds up, or you could jam the thing in the hole.) Use antisieze lubricant to put the bolt back in.

CAUTION: The long, forward-most bolt on the thermostat housing (that bolts the housing to the cylinder head) goes through to the timing chain area, right underneath the guide. Don't use a tap to clean out that hole, as you could bend the timing chain guide, with horrible consequences. You don't need to take the thermostat housing off of the side of the engine to get to the thermostat, but I mention this just in case. Thankfully someone warned me before I made that mistake.

Jenny, you didn't mention whether your engine runs better with that enormous vacuum leak closed up. I presume yes???

Don't forget to replace all the little vacuum lines. They can have splits and cracks too. I'd replace every mm of vacuum line if I were you. It's cheap, it's easy, and you'll probably find at least 3 or 4 leaks you didn't know about.

[cozye]

:alien:

Liquid-filled pressure gauges under the hood are apparently not a good idea, unless you only read them cold.

My gauge reads the same cold as it does when it's been running for an hour. I could see that if you installed it right above the exhaust manifold, but installed by the fuel filter it doesn't get that hot. The fresh supply of cold fuel should also keep it from getting too hot. They are made for under hood applications and you will see them directly on the fuel rail of race cars (although I'm sure they aren't using an $18 gauge). In your case it sounds more like a crappy gauge than a liquid vs. non liquid issue. I know there are a ton of Z owners with the same gauge mounted in the same spot. Might not be ideal for tuning a fuel pressure regulator, but for just checking if your fuel pressure is in spec they are fine. I've got an external gauge too, it reads the same.

[Jennys280Z]

I never saw a pic of the flame arrestor before. Mine didn't come with one. The PO had replaced the hose, and the part was undoubtedly discarded. I just made a new one out of numerous layers of bronze screen material soldered together. I think mine is probably better than the OEM thingie. In case you're interested, the flame arrestor keeps any backfire flames from traveling up the hose, into the valve cover, down the timing chain tunnel, and into the crankcase. The result *could* be an explosion. It's probably not a likely event, or else they would have made a more serious one.

It does sound like your thermostat is stuck open or has become inaccurate. If in doubt, you could always just pull the thing out and check it in a pot of water on the stove. It should open at around 180F. You'll need to blow a buck or two on a new thermostat cover gasket. I think it doesn't hurt to unbolt those things occasionally anyway. The alternative is that they seize up. You'll need to drain a bit of fluid from your radiator before taking the thing loose. There's a drain plug on the bottom lefthand side of the radiator. Clean up the bolts before putting them back in. Also get yourself a metric tap and die set, and clean out the aluminum threads with a tap. (Lubricate with oil. Go forward two or three twists, then back one. Forward two or three, back one. Take the tap all the way out and clean the tap every time resistance builds up, or you could jam the thing in the hole.) Use antisieze lubricant to put the bolt back in.

CAUTION: The long, forward-most bolt on the thermostat housing (that bolts the housing to the cylinder head) goes through to the timing chain area, right underneath the guide. Don't use a tap to clean out that hole, as you could bend the timing chain guide, with horrible consequences. You don't need to take the thermostat housing off of the side of the engine to get to the thermostat, but I mention this just in case. Thankfully someone warned me before I made that mistake.

Jenny, you didn't mention whether your engine runs better with that enormous vacuum leak closed up. I presume yes???

Don't forget to replace all the little vacuum lines. They can have splits and cracks too. I'd replace every mm of vacuum line if I were you. It's cheap, it's easy, and you'll probably find at least 3 or 4 leaks you didn't know about.

Hey you! You were right!!!

I didn't want to post again until I had an update. I didn't know how things would be going because I went through 6 auto parts dealers here until I found one with some 3/16" hose in stock! (5 ft of continuous hose at least). I couldn't believe that the first place I drove to was out, so I went home and called five more places before they had some? I mean what is the deal? That's like a lawyer's office with no printer ink!

I couldn't post an update because I didn't have anything connected to the dist or the throttle body and my little 3-way connector was off the car so I finally got it put on yesterday. So those vacuum lines were also shot and I had to replace those too at the same time.

But I wanted to use my timing light and this time actually check the timing for the first time ever! So after lots of squinting and bending and using my little mirror and taking a dozen pictures of the pulley from underneath the car, I couldn't see or feel any timing mark on the pulley. So I blipped the car to turnover for a fraction of a second to move the pulley and then took a dozen more pictures and finally that mark showed up in one of them. After I was able to mark it with chalk, seeing the timing was so easy! I thought it was still going to be difficult but it's amazing how chalk takes it from impossible to a cinch. My FSM says when the motor is warm the timing is retarded and it's unnecessary to check it while advanced unless I'm adjusting the phase difference thingie. My car started on the third "blip" of the key by accident that's how badly it wanted to run I guess! And you were right! It felt a lot better. First I noticed it was idling at a normal speed, then I made sure all my spark plugs were firing, then I noticed my RPM continued to slowly increase the longer the motor idled and I had to keep dialing the idle speed down (maybe as the engine warmed up?) to keep it at 800RPM. Then I shut the motor off since it started accidentally, found that mark, chalked it, and started it again and checked timing. It was sparking right at 10deg BTDC, vacuum advance hose on the dist and no temperature wires disconnected/grounded. Of course my car didn't warm up all the way before I did this (at least the gauge didn't). It was sitting at about 145F and didn't want to go much higher.

But it seemed to be running great! The throttle was responsive, it revved normally, no backfires or stumbles, idled pretty smoothly, started so fast it started on accident, and so a little road test in the next day or two will be the final test that it's running great for sure!

Thank you for the advice on the tap and die. I will get one of those. I have the antiseize compound already that I've used for my spark plugs and alternator so far.

But before I worry about my thermostat I really want to fix my brake booster so the car will be fully driveable again (well actually I am getting my seats reupholstered somewhere soon and took my passenger seat out for now and so my car looks like a race car now! Rooooom! But soon my driver's seat too which is in worse shape on the seat) But it's scary to drive with the brakes so weak and so I really don't want to drive it but for short distances and in the daytime. I looked under my dash at how my brake booster was connected to the brake pedal and it was a little confusing. I saw one bolt there that I could loosen so I guess I can just get to loosening that and see what happens!

Thank you so much for your help again! You helped me a lot in the past too and I should thank you for being so helpful to me. I love this website! I need to spend a lot of time here reading through threads. I've learned more from this website than from my manual already and I haven't even cracked the surface of what's on here yet!