Duraspark - not the usual questions

[RobbieD]

1984 2.8, C3 auto, 2WD. I'm in the process mapping out the Duraspark conversion, which will include some major rewiring (power distribution box in place of the fusible links), valve stem seals and adjustment, and a thorough cleaning up of the engine bay. I'm keeping the Motorcraft 2150A, with adding the metering block modification.

My question-
What is the best approach to the EGR and Thermactor air systems? They're both controlled now by the ECA (computer), which will obviously go bye-bye with the switch to Duraspark.

Has anybody retained either system, modified to operate without the computer, or is it best to remove both?

I don't plan on leaving any components in place, if they're inoperable.

I've been through all 19 pages in this forum, and didn't see anything which directly addressed keeping these systems, and having them working correctly after a Duraspark conversion.

Any input, is greatly appreciated.

 

[skippy]

Robbie,

I blanked off egr and piped the air pump into pipe running to back of each exhaust manifold,using left over hose from diverting vavle.I also kept the "cat".

I cut all sensor wires back to fenderwell and abandoned the Computer in place.Removed all vacuum lines and resevoir,abandoned all the vacuum relays in place.

Skip

 

[RobbieD]

Hi there Skippy. Thanks for the input; your conversion turned out nice.

I'm keeping the cat, too, and I know that the thermactor air helps it, with a "bump" in the exhaust gas combustion. And I know that the EGR also has some benifits. But I'm just not sure how to keep these guys, operating correctly, without the computer setup it now has.

On mine, the solenoid bank has to go; that's where the new power distribution box is going.

What I'm looking for, is how to rig the EGR and thermactor to operate correctly. I need to look at this closer, but it seems that both systems need to be controlled, to operate or not operate based on the engine's status. I'm thinking, that I can configure something with manifold vaccum.

Again, thanks for the input.

 

[martin]

I believe you could control the egr from a ported vacuum source. Problem is there is not a ported vacuum source on the stock carb. About two or three forum rebuilds ago someone figured out a way to drill and insert a ported vacuum source into one of these carbs but I don't have the information.

 

[RobbieD]

Thank you, Martin. Good point on the ported vacuum, and I do remember the old post you are referring to.

The more that I'm looking at these systems, the more inclined I am to just remove both. Although, I'm still looking at keeping just enough of the thermactor to pump air into the cat, full-time. The concern, is that it'll clog up sooner without the added combustion.

Do appreciate your input; if I'm not mistaken, didn't you come up with the idea for fabricating the manual metering block?

 

[JoshT]

As long as you tune your carb in properly I don't think you would have a problem without either of them. The EGR is going to put exhaust gas back into your cylinders. The fuel and oxygen in this exhaust gas has been used up, and the factory carb set-up adjust the fuel ratio for this nonburnable exhaust gas being in the cylinder. The Air injection system pumps oxygen into the exhaust system after where the EGR takes off. The extremely hot exhaust reacts with this new fresh air in the cylinder and burns what fuel is remaining in the system before it reaches the cat. These systems don't directly affect the cat from my understanding, so you should be fine with out either of them.

Oh and your ECA doesn't control the EGR, but the EGR control the ECA. The control computer under normal operation only detects the position of the EGR valve and adjust fuel tables accordingly. The only time that the ECA controls the EGR is at WOT when it shuts off the EGR.

 

[RobbieD]

Thanks for the response, Josh. Yeah, I'm still reading up on the weird way that Ford laid the EGR in the 2.8. The big Ford book on the 2.8 (#2100-010) implies that the ECA works the solenoids pretty much constantly, so that the EGR only operates in cruise and part throttle; and not in WOT, closed throttle or starting. The stock setup on mine is getting really funky at times, but then it is 25 years old.

Looks to me like there may be a way to ditch the Vent and Control solenoids that the ECA does operate, and leave the rest of the EGR; or, just take the easy route and ditch the whole EGR system and really simplify things.

I'm shooting for doing it over Labor Day, so I've got a little time to pin things down. I take it that you removed, or just bypassed, both of these systems on yours, without any problems?

 

[JoshT]

They are both gone, but... This truck had the DSII, Offy, and Holley 390 Double Pumper by the time I turned 4 and I'm 24 now. Dad bought the truck used from a company the year after it was built, then he started having trouble with the frankenstein computer/carb and it's ignition system. He remembered seeing the Offy intake for the 2.8s I suppose he was eying them for the 2.8 Pinto he had previously. So he went to the local autoparts shop told them he wanted one and the carb. Once he got the stuff he hacked off the factory electronics on either side of the firewall and left nothing but the engine itself in the bay. Set up the DSII system with the new induction setup, and replaced the factory manifolds with a set of long tube headers and true duals. So it was till I got it and replaced the rigged exhaust my cousin put on it when his mother bought the truck, and later put on the 390 vac secondary.

The short version, my truck hasn't had EGR, Smog Pump, or Catalytic Converters in about 20 years. It did fine until I put on the new carb, I just can't get the tuning right now. I might give it another shot, then I'm going to figure out something else. Leaning towards rigging up an FI swap. I might even send that ole double pumper off for a professional rebuild considering that a new one of those runs $600+.

 

[RobbieD]

Man, that truck sure does have a history behind it. You ought to hang on to it, and good luck on getting the carb situation sorted out.

 

[speedysprocket]

As much as you're worrying about the EGR, do you even know if it works? The passages in the heads like to clog up so exhaust doesn't even flow. The only way to clean it is to take the manifold off, and preferably the whole head. The carbon in my old heads was rock solid.
I run the Offy 4 barrel, vacuum secondaty Holley, Mallory dual point, headers with the air tubes and a relatively new cat. I think I have the air pump set to pump into the headers and cat all the time just by giving the 2 valves engine vacum, and I passed emissions like that in CT, plus I get better than stock fuel mileage.

 

[RobbieD]

You do pose a good question. All of the original equipment is intact, just 25 years old and tired (the truck has 156k miles on it, btw). Manually putting a vacuum on the EGR valve itself with the engine idling will stall it; so it appears that the valve is operable, and that the engine has open passages.

Sometimes the truck runs great, at other times it doesn't. Sometimes after I shut the engine off, the solenoids click like crazy for a few seconds. The hard plastic vac lines are brittle, and have been repaired a couple of times.

Bottom line is, it's an old, beat emissions system, which wasn't the best design even when new. I'm not faced with inspections where I live, so at least I have some options. My goal, is to simplify things, and improve driveability and reliability.

At this point, I'm leaning toward just removing the equipment, and storing it in case I need it in the future. I do appreciate your question, and I especially appreciate the info on your setup (it sounds like a nice one that works well).

 

[martin]

Yes I made the manual metering block many years ago, long before I did the hybrid duraspark ignition swap. My air pump fell off around the same time as the m-block came into being and the egr went the same way shortly after when it started sticking open. The truck starts immediately and runs fine other than a minor problem I've been chasing ever since I've had it. Once in a while when the weather conditions are just right it suffers from carb icing. There was a tsb about it but I don't think they ever solved the problem completely. My view is if it's not necessary or beneficial, when it 'falls' off it stays off.

 

[RobbieD]

Thank you, sir. Well, I'm down here in Georgia; I think that hell will likely freeze over before I have to worry about a carb icing problem. I do appreciate your advice!

 

[dangerranger83]

If I were you I would just take off all the emissions crap. As for my 2.8 im putting in, it isnt going to have an EGR valve or any unessesary emission stuff other then a CAT and what ever else it takes to run a TBI set up.