Help on Lean Burn -Forever interesting.

[Bristol Bill]

Hi
The Bristol ( Fitted with 360a 1978 lean burn) is having its problems at the moment. Whilst on holiday in Normandy the petrol pump split a diaphragm, and the car later decided to shed an exhaust entering a Chateau....
But the main bug is that -when hot - the engine restarts but dies as soon as the box is engaged or when trying to take off. However -If left for a minute - and I mean 60 seconds -it then behaves normally. Where do I start?

I have so far swapped the 'black box' with no change.

I would like a manual that works for engine diagnostics. Is Chilton what I need? and if so which one?
Would appreciate some advice from anyone who appreciates what Chrysler developers designed - Salutations Bill

 

[1978 NYB]

No..... Chilton is not good.

You want Chrysler FSM's which you can get on EBay cheap. You can search for a parts manual too.

1978 Chrysler Dodge Plymouth electrical and chassis service manual 2 manuals | eBay

You can also get a CD or a paper copy from here. And a parts catalog too.

Bishko Automobile Liturature available for 1978, Chrysler, All Categories

 

[73 T&C]

The lean burn system advances the timing (about 10 degrees) during cold start/restart that lasts for the first 60- 90 seconds.

Because you say you changed the computer with no change in symptoms, that is not the problem.

I’m thinking you may have a vacuum leak in the carb or elsewhere leaning out the mix during that time which may be the cause of your current problem.

I would also check the throttle position sensor; first for continuity and then the running voltage getting to it from the computer.

I agree with 1978 NYB that you need the FSM as soon as you can get it.

 

[traintech55]

There are some interesting things about the lean burn system that have many people tearing their hair out.
This sounds like a spark problem. When it won't start check to see it you are getting spark from the coil. Some vehicles have dual pickups in the distributor, others do not. If your vehicle has the two pickups, check the air gap on both. If your car is not equipped with this it still sounds like a spark problem, use a brass feeler gauge as a regular metal one will give you a false reading. Since you changed the control module, this could be ruled out. Keep us posted.

 

[Bristol Bill]

Thanks for the feedback. I await the manuals.
In the meanwhile the leaner than lean burn is interesting so I will check again for leaks. Could a temperature sensor failure cause this?
Appreciate your responses.
Bill

 

[Bristol Bill]

There are some interesting things about the lean burn system that have many people tearing their hair out.
This sounds like a spark problem. When it won't start check to see it you are getting spark from the coil. Some vehicles have dual pickups in the distributor, others do not. If your vehicle has the two pickups, check the air gap on both. If your car is not equipped with this it still sounds like a spark problem, use a brass feeler gauge as a regular metal one will give you a false reading. Since you changed the control module, this could be ruled out. Keep us posted.

The distributor is the single pick-up type so I guess I will also go back and check all leads for resistance.
I am thinking also to check compression and give the carb a run through as a starting point.

 

[traintech55]

Go back to the basics. You need three things for an engine to run at all, fuel, spark, and compression. You have compression in the fact that it will run at all. Check the other two things out.

 

[Davea Lux]

The distributor is the single pick-up type so I guess I will also go back and check all leads for resistance.
I am thinking also to check compression and give the carb a run through as a starting point.

Your run pickup module is probably bad. The early lean burns ('76-early production '77) had two pickup modules in the distributor. This system had a lot of problems transitioning from the start mode to the run mode as the early electronics in the brain box were not up to the task and frequently shorted out. The 'late '77 and '78 lean burn has a single module that performs both the start and run functions. You should also check the the ballast resistor for continuity, a bad ignition switch that has corroded terminals in the run position can also cause the symptoms you are describing. Once you have the FSM, note the circuit voltages that should be present at the coil and module. Given that the car seems to run when cold, most likely the module is heating up and shorting out to kill the engine. You could also have a defective coil that is shorting out after it warms up

Dave

 

[73 T&C]

Thanks for the feedback. I await the manuals.
In the meanwhile the leaner than lean burn is interesting so I will check again for leaks. Could a temperature sensor failure cause this?
Appreciate your responses.
Bill

Temperature sensor only sends signal (ground) when engine is below +/-150 degrees F.

I believe that, until engine reaches that temp, the vacuum sensor on the Spark advance unit is nullified (grounded out) as to affect on timing advance.

Check for ground when engine is up to temp and, if grounded when above 150 degrees F, change it.

Hope this helps.

 

[CBODY67]

For general principles, check for voltage loss in the battery cables. From the battery terminal to where it attaches to the engine (negative ground) and other places on the car's body. Should be the same voltage as is at the battery terminals, but ANY voltage drop (even .5 volts) can mean an internal cable problem (under the insulation). Look to make sure that all engine to body grounds are in place and have clean contact areas.

Just some thoughts,
CBODY67

 

[Bristol Bill]

Hi
Spent the day getting to know the carb and electrics for the engine.
I'm liking the Electrical service manual but it does not list my SCC 04106086 so I do not have the throttle/vacuum advance figures.
Can someone take a shot of their manual and send it please?

 

[Bristol Bill]

Full spec for Bristol 412 :
Engine 78 360 7593
Distributor 4091140
Carb TQ 9104s
scc 04106086

10 pin connector
Coolant control idle enrichment valve
Electric choke
Vacuum transducer on scc
Air valve diaphragm
Heated air vacuum via temp sensor in air cleaner

Per manual the base advance is 2deg @850- disconnected and plugged

Salutations
Bill

 

[CBODY67]

The CCIE valve should be on the upper front of the carb. It should have one vac hose hooked to it. That vac hose should go to a "thermal vacuum switch" on the intake manifold. It uses coolant temp to vary vacuum to the CCIE valve, to help with cold drivability on an otherwi9se lean-calibration carb. It's vac source would be manifold vacuum, then vary it with engine temp as it goes to the CCIE valve on the carb,

The OEM electric choke thermostat would be in the typical Chrysler location, on the rh side of the carb. It should have a vertical casting in the manifold it is anchored into, just above the exhaust heat passage in the middle of the manifold. There could well be a single wire going to a heater element on the choke thermostat. In addition to the exhaust heat, the heating element helps reduce choke "on" time with a cold/warm engine temp.

The air cleaner snorkel "damper(s)" will be run by the sensor in the air cleaner base, inside the air filter diameter. The sensor is supposed to keep the air temp in the air cleaner at least 100 degrees F, so the damper(s) will modulate between "ambient" or 100 degress F as needed. Vacuum source is manifold vacuum. This tighter control over temp of air entering the carb allows for a little leaner/less emissions calibration of the carb.

Enjoy!
CBODY67

 

[Clover]

I had a ‘75 Fury wagon with 400 lean burn (burned leaded gas-no cat from the factory). I loved that car but it would leave me stranded at the worst times. The only permanent fix for me was to swap to a points distributor. Always ran great after that! I still have the original distributor I think.

 

[Bristol Bill]

No..... Chilton is not good.

You want Chrysler FSM's which you can get on EBay cheap. You can search for a parts manual too.

1978 Chrysler Dodge Plymouth electrical and chassis service manual 2 manuals | eBay

View attachment 194090

You can also get a CD or a paper copy from here. And a parts catalog too.

Bishko Automobile Liturature available for 1978, Chrysler, All Categories

Hi 1978NYB
The electrical manual I have 1978 has nearly all that I need but frustratingly does not list my particular Spark control module which is a 04106086.Is this in the 77 or 79 edition? Can you help looking the timing data up in one of these?

 

[1978 NYB]

I don't have 77 or 79. Just 78 same as yours.

 

[Davea Lux]

Full spec for Bristol 412 :
Engine 78 360 7593
Distributor 4091140
Carb TQ 9104s
scc 04106086

10 pin connector
Coolant control idle enrichment valve
Electric choke
Vacuum transducer on scc
Air valve diaphragm
Heated air vacuum via temp sensor in air cleaner

Per manual the base advance is 2deg @850- disconnected and plugged

Salutations
Bill

The distributor #4091140 fits mid '77-79 318 and 360 engines with the lean burn system. This is the second generation lean burn with the single pickup module.

Dave

 

[Bristol Bill]

Can someone with a 1979 ESM book look up under the heading 'Specifications' 'Electronic Lean Burn System' and tell me if it lists Spark control computer number 04106086? It will be about page 220.