Vacuum advance, 1970 style.

[Markstrimaran]

Old vacuum picture one,

Picture 2 is the switch, I am trying to regulate the distributor advance.

Any help will be appreciated.

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[tgreese]

The TSM will tell you what each of the hoses are, what the devices are, and how to connect them. What do you mean by 1970 style?

The red switch should be the spark CTO. Typically it switches between manifold and ported vacuum at low and operating temperature, respectively. Do you understand the difference between manifold and ported vacuum?

[tgreese]

So this is the '88? There's a vacuum diagram here - http://oljeep.com/gw/vac/88vacuum.jpg

There is also an HDC CTO - heavy duty cooling - that has three nipples, in addition to the spark CTO.

You can run the distributor advance directly from manifold vacuum, but it won't be emissions compliant. There are only two sources of vacuum - manifold and ported.

[Markstrimaran]

So this is the '88? There's a vacuum diagram here - http://oljeep.com/gw/vac/88vacuum.jpg

There is also an HDC CTO - heavy duty cooling - that has three nipples, in addition to the spark CTO.

You can run the distributor advance directly from manifold vacuum, but it won't be emissions compliant. There are only two sources of vacuum - manifold and ported.

Long story, but the smog pump, power steering had no fan belt, smog pump is seized, the air injection tube RUSTED OFF.

I plugged the manifold tube holes, with fireplace mortar.

Pulled all the rotten vacuum hoses.

I don't know the real difference between ported , and manifold.

One way increases idle by 500 rpms.

Other way makes it really hard to start when at operating temperature. But it idles better when cold.

This jeep used to need gas pumped 5 times, as cranking to start. Then it would usually die once, as shifted into gear. * note very cold snow day in winter, left plugged in to engine heater.

Just need the motor too last a couple more years, to hold off the diesle swap. No emmision here, as it helps the corn grow taller.

It still misses, when the engine is cool, and below 1500 rpm.



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[Markstrimaran]

So this is the '88? There's a vacuum diagram here - http://oljeep.com/gw/vac/88vacuum.jpg

There is also an HDC CTO - heavy duty cooling - that has three nipples, in addition to the spark CTO.

You can run the distributor advance directly from manifold vacuum, but it won't be emissions compliant. There are only two sources of vacuum - manifold and ported.

Long story, but the smog pump, power steering had no fan belt, smog pump is seized, the air injection tube RUSTED OFF.

I plugged the manifold tube holes, with fireplace mortar.

Pulled all the rotten vacuum hoses.

I don't know the real difference between ported , and manifold.

One way increases idle by 500 rpms.

Other way makes it really hard to start when at operating temperature. But it idles better when cold.

This jeep used to need gas pumped 5 times, as cranking to start. Then it would usually die once, as shifted into gear. * note very cold snow day in winter, left plugged in to engine heater.

Just need the motor too last a couple more years, to hold off the diesle swap. No emmision here, as it helps the corn grow taller.

It still misses, when the engine is cool, and below 1500 rpm.



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My carburetor has about 5 ports, and the hex port, next to the elbow. Is were I am getting the vacuum for the distributor.

If I took it up to the 79 state, it stalls when cold.
Lots of variable. The chokes, air filter lines, 4x4, cruise, brake, are still functional.

79-FSJ-360_Vacuum-1.jpg

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[tgreese]

Ported vacuum comes from the carburetor. Its port is blocked by the throttle plate at idle, so it goes to zero at idle. At all other throttle postions, it's the same as manifold vacuum. Manifold vacuum comes from the manifold and is high at idle. All the manifold vacuum ports that screw into the manifold are essentially equivalent. There are also manifold vacuum ports on the carburetor, that are not blocked by the throttle plates at idle. You can tell the difference by a vacuum gauge, or by inference from the vacuum diagram.

[Markstrimaran]

Ported vacuum comes from the carburetor. Its port is blocked by the throttle plate at idle, so it goes to zero at idle. At all other throttle postions, it's the same as manifold vacuum. Manifold vacuum comes from the manifold and is high at idle. All the manifold vacuum ports that screw into the manifold are essentially equivalent. There are also manifold vacuum ports on the carburetor, that are not blocked by the throttle plates at idle. You can tell the difference by a vacuum gauge, or by inference from the vacuum diagram.

That sounds really simple? But the cto valve switches the vacuum based on coolant temperature.

So when cold should full manifold vacuum be applied to the distributor?

Or when the cto is at the hot position?

Thanks, If it only had a OBD 2 PORT, lol


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[tgreese]

1979 Jeep TSM, page 1G-19

The first sentence - On all Jeep vehicles with spark CTO, the vacuum spark advance operates on carburetor ported vacuum after warming up. Warm-up driveability is improved by operating the distributor vacuum spark advance by manifold vacuum while the engine is cold.

This is also covered in the '82 manual, but not so succinctly.

[Markstrimaran]

1979 Jeep TSM, page 1G-19

The first sentence - On all Jeep vehicles with spark CTO, the vacuum spark advance operates on carburetor ported vacuum after warming up. Warm-up driveability is improved by operating the distributor vacuum spark advance by manifold vacuum while the engine is cold.

This is also covered in the '82 manual, but not so succinctly.

Thank you.

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