egr valve question

[TomoHawk]

I fooled with my egr last summer manually by sucking on the vac hose, and as expected, the diaphram movrf up & let fresh air ( formerly exhaust) in. when I quit sucking, the diapgram didn't return! Is that right? As far as I could tell, there was only the one nipple for vacuum, and there was no way for air to get in to let the diaphram back to close the air valve. I was thinking about drilling a very small hole to let air in, but I'm not sure if there's enough vacuum to move the diaphram then.

I think it would really help if somebody had a graphic of the EGR circuit & hoses that makes sense. I think the thermal vac valve works- at least it only lets air go one way.

thx

[280zgod]

yeah i gave up the egr battle a long time ago i just plugged the end of it where the pipe used to go down into the exhaust manifold. so try as it might that egr aint sucking nothing but plug. and my z runs fine btw except now the FI has failed again and it cant start but when it did runh it ran well. ~Jerrod

[TomoHawk]

I believe that properly used, the EGR is part of the fix for an over-rich mixture. As a result, you will get a better mix at WOT and more power.

[sblake01]

That is why my EGR is still hooked up on both cars. It runs, it runs right, it starts up, cold or hot, it doesn't run rich, and it passes smog. My F.I. system doesn't fail, etc., etc., etc. There might be a lesson somewhere in there.

[TomoHawk]

I think the problem with my EGR is that I don't know if the thermocheck valve is working right, so I just assume the EGR is always closed. Isthere a section on EGR in the FSm I would assume that if the thermocheck valve was working right, it would open the EGR when the engine is warm & has enough vacuum ( like at higher RPM) and it would lean out the mixture with increased power & gas mileage. I'm starting to think that the vacuum solenoids are involved here, but I don't know how those get activated.

I hope my FSM has some help on this.

FYI, I reopenedthis topic at this time because it's winter here in Ohio, and you pretty much put the cars away until April & lock yourself indoors with a book(s). i.e., research season.

thx

E.G.R.,....F.S.M..... M.O.U.S.E........

[sblake01]

When you say 'thermocheck valve' are you referring to the 'thermal vaccum valve?' You can check that by starting the car cold, disconnecting the hose from the BPT valve, and holding the end of the hose while revving the engine up to 3500-4000 rpm. This must be done while the engine is cold. There should be no vaccum at that point. If there is vaccum at that point the thermal vaccum valve needs to be replaced. That's a fun little job that requires draining out a little coolant before you remove the valve.

[TomoHawk]

Uh Oh..

I'm thinking now that my hoses are mixed up There was a check valve on one hose off the intake that's the size of quarter, anout 7-8mm thick, and it was hooked up to a dashpot. I'm going to read-up on the BPT valve and related stuff. Do you think the vacuum solenoids are involved, or is that just for the a/c stuff? I evennoticed there was even a vacuum-operated thing for the high-idle (it pulled on the throttle rod.) I totally disconnected & removed that.

thx

[sblake01]

The solenoids are for the A/C at least that is what I determined from looking at the FSM. My Z has aftermarket air so it is different and the 810 has more of a ZX type system. That vaccum operated thing you speak of is the BPT valve. I never really knew what it does but the letters stand for Back Pressure Transducer. You can test that by disconnecting the tube from the from the EGR revving the engine again to 3000-3500 rpm and you should feel vaccum on that end of the hose. The car doesn't have to be cold for this test. If you have that little black/brown vaccum delay valve that goes in the vaccum line between the thermal vaccum valve and the BPT valve then you have a former California car. (The brown side faces the front of the engine)

[TomoHawk]

AFAIK, my car has federal emmissions, but the BPT is the only thing that suggests california. There isn't even a catalytic converter, which the muffler guy pointed out.

I determined that the BPT is some kind of a check valve because you can only suck air from one side. From what you say, I think it might allow air to pass through ( or back) slowly, which would allow the EGR diaphram to return to the normal position, otherwise

the EGR would keep opening until the engine stalls, which is why I took it all off.

thx

[TomoHawk]

Im either gonna plug the coolant lines or jus bypass the thermal vacuum valve.

Have you removed your thermal vacuum valve yet? Do you know what the threads are, so I can get a plug for the hole?

thx

[g72s20]

Some scans from a Nissan service manual for Australian emission control systems for the S30 L26T motor. Probably a few differences but the basics might help?

Jim.

P.s. PDF available 550K per 2pages

[TomoHawk]

I'll print those out and read them. Some of the pictures look interesting and similar to the efi L28 engine.

thx