I disassembled an EGR timer - wanna see inside? - DodgeTalk : Dodge Car Forums, Dodge Truck Forums and Ram Forums
 
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#1 Old 02-19-2007, 04:49 PM
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I disassembled an EGR timer - wanna see inside?

I just paid about $165 for a new one of these EGR modules, (it wasn't a common red or gray one; it was an uncommon brown one...) and it appears to have been one of the last of it's breed, so I figured I'd see what's going on inside.

I've done component level electronic repair for nearly 30 years, on everything from mainframe computers to televisions to robots, so I'm relatively fearless, and with a bit of persistence I got the works unpotted.

Low and behold, all of the parts still have their numbers and color codes intact!
Not even one exotic part; everything is pretty much plain Jane (no offense to any of the lovely ladies who might be reading this!) run of the mill basic electronics.

And there's even component designators... Hmm; if I feel ambitious I might try to trace the schematic and repair the thing so I have a spare!

Anyway, here's a picture of it. Pretty cool eh? I bet the tantalum capacitor is faulty. (Oh, I forgot to mention - part of the potting compound had flowed out of this and bugs & etc. got inside - this module was killing my battery...)
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#2 Old 02-19-2007, 05:50 PM
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Doesn't this seem a bit overkill on the number of components to make a time delay timer? I wonder why they didn't use a couple of 555's + output driver?
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#3 Old 02-19-2007, 08:06 PM
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Probably these heavier components are able to provide more resistance to noise spikes on the power bus. A 555, if available in that temp range back then (1981) would, like you said, still require a power output device like a transistor or mosfet to drive the EGR solenoid, which has slightly less than 40 ohms DC resistance. I haven't tried to draw out the schematic yet, but from the number of small signal transistors, I suspect it's an old cookbook design for a flip-flop. The Engineers at G.E. used to grab proven designs out of books of their past successes all the time when I worked there. Saved them making (as many) mistakes.
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#4 Old 02-20-2007, 03:53 PM
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Hey, I'm glad that it's old school stuff and nothing fancy. It can be duplicated rather easily without knowing how to program an IC that whould have the code locked inside.

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#5 Old 03-17-2007, 03:05 AM
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Being bored (-namely it's too breezy outside to be fun to work on the van...) I did a bit of research on some of the other EGR Delay Timers, and I found that they are becoming much less common! Take note of this if you need one: AC Delco has *completely discontinued* them, (I called to verify this) and Standard Motor Parts only still produces their EGT3. (I called them too!) It looks like KEM has discontinued several of them as well!!

Working on antique vehicles makes me feel old sometimes...

Since I have two timers on hand I decided to see what their delay times were. My various manuals claimed the idea with the EGR Delay Timer & CTS system is to prevent the EGR system from operating until the air charge (air fuel mixutre) temperature reaches 60 degrees, and to delay an additional 60 seconds after the air charge temperature does exceed 60 degrees. (In cold weather they figure on the air cleaner's Heated Inlet Air System to eventually stabilize the air charge temperature at around 100 degrees once the engine's exhaust manifold has warmed up sufficiently.)

I set up a bench power supply and wiring to simulate the CTS and EGR solenoid, and found that my Mopar 4111181 is a 90 second timer. This is equivalent to a Mopar 4111481, and the SMP EGT3 and KEM 173-603. These are the Red or Gray colored units.

My Mopar 4111180 is a 60 second delay unit. It is orange colored. These appear to no longer be in aftermarket production. The good news is that the connector and wiring is identical to the 90 second units, so a 90 second delay timer could be used as a drop-in replacement - giving you a slight additional delay before the EGR kicks in.

I don't have one of the 4111179 timers (black colored) to test, so I don't know it's delay time yet. If I find one I'll post the results.

As a further public service, I'll add the only diagram I've *ever* found for the correct and complete Emission wiring of my van - a 1981 Dodge Ram B250 Custom Sportsman 6400 GVW maxi van with 318 & 2bbl carb. It also applies to the 4 bbl version, and the 360 4bbl. The Haynes and Chiltons diagrams aren't even close, and even adjacent year Dodge service manuals don't have this exact diagram.

Oh, BTW - I found it is necessary to test these EGR Delay Timers with a load which approximates the EGR solenoid resistance. I used a 30 ohm resistor. Without the load they won't toggle their output.
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#6 Old 03-18-2007, 09:32 AM
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Geez...you really were bored.

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#7 Old 05-09-2007, 02:34 PM
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Another rainy day here... I finally got my hands on a black 411179, and I found it's delay time is 35 seconds.

These EGR delay timer's purpose is to keep the EGR valve from opening for a period of time after starting the engine, to give the engine a little time to warm up so it won't stall as easily.

So, if passing emissions are an issue for you, I'd think the 35 second delay 411179 is your baby. If the engine is hard to keep running immediately after starting, probably the 60 second 411180, or the 90 second 411181 or 411481 is the ticket.

BTW, these are practically obsolete *now*!

After much runaround and several canceled orders I finally got one from KEM, (which interestingly had the Chrysler insignia on it...) and the invoice stated "Available until stock exhausted". Take that as notice that if you need a new one this is probably your very last chance. In short order they will all be boneyard only parts.
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#8 Old 05-09-2007, 10:38 PM
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So did you ever figure out which component(s) were bad? Sounds like a guy with sufficient electronics savy (like you ) should be able to repair one of these timers.

Do you know if these were used in a large variety of Mopar vehicles during that era, or were these specific to vans only?

Thanks for posting your findings. I love to learn something new.

Pete

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#9 Old 05-10-2007, 12:33 AM
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Hi,

I've been too busy with what good weather that I've been fortunate to have to tear into the tracing of the schematic and any repair yet. For instance I spent a good chunk of last week out with my son raiding the local boneyards for parts for my project van. Whenever things slow down a bit I'll probably tear into the timers again. I have some other electronics I need to get back into too - guitar & bass amps, tape recorders, antique radios, a telescope drive, another 3-pickup guitar... can't forget rewiring my garage & mounting the quick change gearbox on my lathe... uh, that's a lot of stuff isn't it?

I've seen these timers in Dodge vans, pickups, and Ramchargers, as well as cars like the Omni & Aries, which all used EGR systems, up to the entry of the Electronic Spark Control computer on the scene. Since many of our most treasured vintage vans are from the pre-computer era, I wanted to get this information out so that no fellow Vanners would be surprised by yet another non-available part situation, or baffled by what to do if they need a substitute for these poorly documented parts.

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