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Yep craig, it's 12 deg btdc and a manual and we have it set to about 9 right now because of pinging. There is no o2 sensor, vacuum hose does go to the carb-top puter, rev the engine up and the timing hits 20 for about 1/4 second and then goes about 12 deg relatively steady. Strange advance behavior.
The ESA produces unique advance curves that can not be created by conventional mechanical / vacuum advance mechanisms. If you are getting pinging, then the ESA computer must be providing some kind of advance, otherwise it would not ping.I need to run my '87 truck with a little less timing than the specification too. The ESA computer computer provides total timing somewhere in the mid 40's degree range. It's in the factory service manual if you know where to look.
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The Doc man and slant6ram believe there is no mechanical advance in this dist and I cant see one either unless it is under the pickup plate. The rotor doesn't really spring back and forth which either means there is no mech advance or it is rusted solid.
If there is no vacuum pod on the distributor, then there is also no mechanical advance inside.Quote:
re. slant6ram's post, the egr could help the pinging/run-on that was happening before by reducing combustion temps but decarbonizing the combustion chambers could do the same. We hooked it up for good measure for now but I agree that it has nothing to do with the actual problem we are experiencing.
The ignition timing is calibrated to work with the EGR functioning. Disconnect the EGR and pinging is likely.Quote:
I think this engine should have a lot more than 12 to 14 deg total advance. I think this is an excellent starting point.
How do I check if it's in limp mode? can you on-off-on the key 3 times on this chrysler to check? I should prob check not ask but it's down the street and it's raining and I melt in the rain. Prob not important anyway as I wish to replace the ignition.
It's been a while and I'm forgetting how the limp mode works. Limp mode provides a pretty much fixed ignition timing and greatly reduced engine performance. There is not key on-off procedure on these systems. How do I check if it's in limp mode? can you on-off-on the key 3 times on this chrysler to check? I should prob check not ask but it's down the street and it's raining and I melt in the rain. Prob not important anyway as I wish to replace the ignition.
Also be aware that the ESA computer produces different advance curves for a cold engine than for a hot engine. There is a extra temperature sender/sensor in the head that sends a signal to the ESA computer. On the early 80's trucks this is a switch that is either open or closed. On the later trucks it is a thermister (temperature sensitive variable resistor). I do not know what year that changed.
If the temp sender for ESA computer is not hooked up or working, then the computer may not know if engine is cold or hot. With a cold engine, the ESA comptuer provides simulated mechanical advance, and for vacuum advance it provides increased advacne with decreasing manifold vacuum. Yes exactly opposite of a conventional vacuum pod. This greatly enhances cold engine driveability (good reason to keep the ESA computer!!). With a hot engine, it produces advance curves similar to conventional mechanical/vacuum advance distributor.
If your ESA temp sensor is disconnected (or not working) the ESA computer will think the engine is cold all the time and will advance the timing with decreased vacuum such as driving down the road with a hot engine and will cause serious pinging this way. I once saw a '86 S6 truck in the salvage yard where someone had removed the temp sensor for the ESA comptuer ( and left the wires hang) to install an aftermarket temperature gauge in the cab. This would make the ESA computer think the engine was cold all the time.
I used to have a couple good books from OTC (Owatanna Tool Company, they make special tools and also diagnostic tools for all this new fangled electronic stuff). Those books had a lot of good information about how the ESA computer works and what it does with different engine temperature and other variable. After reading those books I went out and played with my truck an was able to verify everything those books said about how the ESA system works. This information is NOT in any Chrysler factory service manual. Unfortunately I lost those books along with most of the rest of my extensive library to an arson fire at a storage facility 2 years ago.
There is a procedure in the factory service manual to check if the ESA comptuer is working. You apply a certain amount of vacuum to the ESA computer and run the engine at a certain RPM and check if the advance is within the specified range. However this depends that the base timing also be set to specification first.
Hope you alll can make some sense of this information. It's difficult for me to convey all the technicalities to you this way. Those OTC books were a great source of ESA system understanding. I think the biggest problem with the ESA computers on a Slant 6 is that no one knows how they work or how to check them and verify that everything is working as intended. Thus everyone is quick to remove them and replace with a conventional distributor ignition.