My Desmog Thread (4 Viewers)

[goodol84]

Set it wherever it needs to be to not ping.

Start at stock (7*). If it pings under load at 2000rpm, then start retarding in 4* increments until it quits.

I have retarded it to the point that it runs like crap and the noise is still there. what does pinging sound like? maybe it is just a coincidence that the noise started after my desmog. it is more like a squeel(eeh,eeh,eeh) than a ping or knock. could this be an intake leak or clutch noise?? (I say clutch because it has been acting up and getting harder to get into gear) the noise starts around 1800 RPM moving or not...

 

[GLTHFJ60]

I have retarded it to the point that it runs like crap and the noise is still there. what does pinging sound like? maybe it is just a coincidence that the noise started after my desmog. it is more like a squeel(eeh,eeh,eeh) than a ping or knock. could this be an intake leak or clutch noise?? (I say clutch because it has been acting up and getting harder to get into gear) the noise starts around 1800 RPM moving or not...

Pinging is predetonation, and definitely doesn't sound like a squeal. Could be a belt, an accessory bearing going bad ( alt bearing, smog pump / idler pulley bearing ) or the clutch. Where is the sound coming from?

 

[goodol84]

It is hard for me to tell by myself so i think i need to get a helper. I am almost positive it is not a belt or accessory bearing. It is more towards the center/back of the engine compartment which is why I thought it was predetonation however I have never experienced this and am starting to rule that out. Also wondering if an intake leak would sound like this?? Honestly the truck runs better than it ever has since the desmog. More power, idles smooth, starts right up, just cant stand the damn noise...

 

[GLTHFJ60]

Phew, that's a tough one. How loud is it?

Pinging always sounded to me like someone put a nut in a soda can and shook it around. Really metallic sound.

Definition of pinging / knocking - when a pocket of air+fuel mix ignites outside of the spark, typically right after the spark. Most of the fuel burns with the spark, but some does not ignite until afterwards for one reason or another.

Definition of preignition - when the air+fuel mix ignites before the spark, can be referred to as dieseling, as we sometimes experience in our rigs.

I don't think your sound is pinging, but it's real hard to narrow it down without listening to it. Got someone around your place that can help?

 

[Brock]

last time I heard something like that....in that area....it was the main bearing of my 1973 BMW 2002 tii going bad.

 

[ElliottB]

I am no longer running any BVSV's. Should I cap this port on the carb? Are all of the ports on the carb the same? (i.e. I can use any of them). Currently I will only be using one for dizzy advance and one for the evap valve.

 

[ElliottB]

Also, I seem to be missing the choke opener diaphragm on my rebuilt carb. Is this characteristic of a desmogged carb?

Edit:

Here is a pic of where I don't where to run hoses. I am going by pics I see because the diagrams don't make much sense.

 

[Kief]

re-read this post...& look in a manual

Also, I seem to be missing the choke opener diaphragm on my rebuilt carb. Is this characteristic of a desmogged carb?

Edit:

Here is a pic of where I don't where to run hoses. I am going by pics I see because the diagrams don't make much sense.

I spent a lot of time on this post and some info is not entirely correct so you have to follow through and see which info is correct (thanks Jim C. especially). I have a Haynes manual which clarifies things a lot. The BVSV basically is included to bypass certain features until the motor is up to normal operating temperature. I found out the lower flesh colored one is over $40 bucks if you want to replace it if your old one is bad. All of the ports you circled are in the thread..

 

[ElliottB]

I am not running any BSVS of any kind. It's just difficult to make sense out of that schematic that looks like it was written on a used bar napkin.

 

[ElliottB]

Thoughts on this desmog?

As for the 4 valve cover side of the carb ports:
1) Goes to HAC
2) Goes to Primary advance on carb
3) and 4) are looped together (need to get caps)

The 4 carb ports on the front
1) Goes to HAC
2) Goes to HAC
3) Goes to check valve then onto rear choke diaphragm

The secondary advance on the distributor goes to a tee where a hose is fed into the HAC. The other side of the tee goes through a check valve and into the manifold. The two other ports on the manifold connector are looped.

Thanks for any help!

 

[Trapper50cal]

Its my understanding that dizzy vent line (yellow 2nd pic) needs positive vacuum to remove fuel vapor from inside the dizzy cap...so I have mine attached to manifold vacuum where "gas"filter three prong unit is via the passengerside VCV

 

[FJ40Jim]

The only thing that might be off (hard to see on my screen), is the dissy vac advance. It should come from the lower rear port on the throttle body. See the detail pic in the top corner of the FSM drawing below, labeled 'Advancer Port'.

 

[FJ40Jim]

I am no longer running any BVSV's. Should I cap this port on the carb? Are all of the ports on the carb the same? (i.e. I can use any of them). Currently I will only be using one for dizzy advance and one for the evap valve.

No, they are not all the same.

They are all different, which is why they are located all over the carb, drilled into various internal air or fuel circuits.

 

[FJ40Jim]

Also, I seem to be missing the choke opener diaphragm on my rebuilt carb. Is this characteristic of a desmogged carb?

Yes, non-smog carbs only have a Choke Breaker, not a CB and CO.

 

[ElliottB]

The only thing that might be off (hard to see on my screen), is the dissy vac advance. It should come from the lower rear port on the throttle body. See the detail pic in the top corner of the FSM drawing below, labeled 'Advancer Port'.

Is the "dizzy vac advance" the primary (1*) or secondary (2*) diaphragm on the distributor?

 

[ProwlerDriver]

Is the "dizzy vac advance" the primary (1*) or secondary (2*) diaphragm on the distributor?

Its the bottom one. The one closest to the dizzy cap is the HAC advance.

 

[ElliottB]

That conflicts with what the FSM tells me regarding the HAC. According to the manual the bottom diaphragm (secondary) goes to the HAC.

 

[FJ40Jim]

You've got it right, the green hose is the 1st (main) vac advance. It is labeled in the emissions FSM on p.3-10

 

[ProwlerDriver]

I have my advance for the weber hooked up to the bottom port- Is that right? I thought i remember you telling me the top (main advance) was for the hac and was too much advance for my situation.
Either way it runs great at 10 degrees advance on the initial timing.

 

[FJ40Jim]

Prowler, you &me at sea level altitude can't use the main advance. It is too much timing for a healthy, hi-compression engine, which is why the sub/HAC advance is used instead.

Elliot is up around 7000'MSL, so the engine is getting a much weaker air charge, so the full vacuum advance setup can be used without pinging.