Take away DS4 = ECM response?

[GM2theEnd]

I am beginning the retrofit of DB2 IP into 1998 K3500 4x4 4l80E. I have a standalone TCM I believe wil work, but my question is:

If the DS4 is taken away and the live feed is provided for the fuel cutoff solenoid, what would be the ECM's response. I would expect conniptions, but just wondering what to expect. I was going to try to feed in the throttle pos sensor and try it once I get it running. This would be prior to doing the wiring, etc. I think I have a pretty good handle on everything. It would be nice if it would shift with the stock ecm, but wondering if anyone out there could predict the outcome.

What will the ecm do when the DS4 Ip is unhooked?

[daustin]

Email Bobby Martin, he wrote a book on doing it. mini1275@bellsouth.net
Don

[GM2theEnd]

I have contacted Bobbie and his book does not cover the OBDII as far as I can understand. My truck is a 1998 and I'm getting ready to jump in with both feet.

[daustin]

Oh, i thought it did. My bad.
Don

[hfriesen]

This is my first time posting but I have learnt a lot in this forum so its time to give back a little.
I am not a mechanic. I just like a challenge. So this is just my personal experience.
I have a 97 suburban 6.5 diesel with a 4l80e transmission and when my injection pump went on me last winter I decided to do a conversion. The mechanics that I talked to said it couldn't be done but I had read enough on this forum that I knew it was possible. I do not have a standalone transmission controller and when I first fired up the burb after the conversion I was very curious if my tranny would work. I took it for a drive and it shifted through all the gears. The tranny did have issues before the conversion and now after driving it for the summer(about 8000 miles) I am replacing the tranny next week. If you have specific questions about how I did things feel free to contact me and I will help you in any way I can. I know I would have appreciated more advice when I did mine. Just in case you are wondering, it is possible to keep your dual thermastat piping the way it is. You can work around it.
All the best with your project.

[convert2diesel]

This is my first time posting but I have learnt a lot in this forum so its time to give back a little.
I am not a mechanic. I just like a challenge. So this is just my personal experience.
I have a 97 suburban 6.5 diesel with a 4l80e transmission and when my injection pump went on me last winter I decided to do a conversion. The mechanics that I talked to said it couldn't be done but I had read enough on this forum that I knew it was possible. I do not have a standalone transmission controller and when I first fired up the burb after the conversion I was very curious if my tranny would work. I took it for a drive and it shifted through all the gears. The tranny did have issues before the conversion and now after driving it for the summer(about 8000 miles) I am replacing the tranny next week. If you have specific questions about how I did things feel free to contact me and I will help you in any way I can. I know I would have appreciated more advice when I did mine. Just in case you are wondering, it is possible to keep your dual thermastat piping the way it is. You can work around it.
All the best with your project.

Three questions:

1. Does the convertor lock-up and if it does, when. Depending on speed, throttle position should change lock-up depending on load.

2. When the tranny shifts, is it at the same speed regardless of the throttle position (is the tranny running only in default mode) or does the shifting pattern change with load/throttle position.

3. What sensors did you leave on the engine and what did you use (or not) to give the computer TPS info? (maybe this should have been question 1):D.

This is really interesting to me as I am debating keeping the electronic tranny in my next conversion. As the Caddy has a flashable ECM, it would allow me to custom tailor the shift pattern/line pressure/lock-up for the diesel and towing requirements.

Bill

[hfriesen]

Three questions:

1. Does the convertor lock-up and if it does, when. Depending on speed, throttle position should change lock-up depending on load.

The converter locks up normally depending on load. I had it hooked up to a snapon computer yesterday to check what is wrong with my tranny. The computer couldn't diagnose it but we could see the shifting and the lockup were working fine. The problem is that reverse has basicly quit and in forward I have to take it easy so that it doesn't slip. Monday I will get the tranny pressure tested to see if we can diagnose it better.


2. When the tranny shifts, is it at the same speed regardless of the throttle position (is the tranny running only in default mode) or does the shifting pattern change with load/throttle position.

The tranny shifts depending on load. The more I throttle it the higher the rpms when shifting.


3. What sensors did you leave on the engine and what did you use (or not) to give the computer TPS info? (maybe this should have been question 1):D.

I did not use any of the wiring on the motor except the one wire to open the fuel selenoid on ignition. I left the tps in the truck. I took a regular gm throttle and cut off the top rod where the cable hooks in and welded it to the to of the tps so that it pulls the cable and sends a signal to the ecm at the same time. It took some measuring and figuring to get it right since it has to pull the cable in proportion to the travel of the throttle.

This is really interesting to me as I am debating keeping the electronic tranny in my next conversion. As the Caddy has a flashable ECM, it would allow me to custom tailor the shift pattern/line pressure/lock-up for the diesel and towing requirements.

Bill

I found that I could play around with the shift point by turning the sensor on the tps a bit.
It doesn't always shift exactly the same so I am wondering if it wants an input from the injection pump???
I drove the truck with the bad injection pump and it was very rough on the tranny so I don't know what issues the tranny had going into the conversion.
I will install a different tranny next week and then I will have a better idea. If the tranny acts strange I will get a standalone transmission controller.
I think it should be okay because it gets the tps reading and the vehicle speed reading comes from the tranny.
If anybody knows the relationship that the electronic injection pump has with the system I would like to know. I haven't found anyone who has been able to tell me that.

[More Power]

When the new 1994 electronic fuel injection system first arrived, owners of the earlier DB2 equipped trucks who traded for the new trucks were disappointed with the throttle response produced by the new electronics. The DB2 6.5s felt much stronger at 0-50% throttle, where the DS4 trucks felt a lot less powerful. This was due mostly to programming. As a result, GM quickly came out with a new program Eprom for the early DS trucks to improve throttle response. But still, the throttle response of the DS systems never did meet the expectations of the earlier DB2 owners.

What this means to those converting.... Using the electronic APP to control the 4L80 will produce a late shifting transmission unless you ramp up the percent of APP in relation to DB2 throttle application.

Some years ago, there were many DS owners who attempted to switch to mechanical. I know of only one on those who said he was satisfied (i.e. trans shifted the way it originally did) when using the vehicle PCM to control the 4L80 after converting to the DB2. In his case, he created an articulated throttle pedal assembly that recognized the difference in throttle-response sensitivity between the APP and the DB2. Like this:

http://www.thedieselpageforums.com/photopost/data/500/pedersonAPP.jpg

The most successful DS/DB conversions involve using a standalone TCM and abandoning the PCM for trans control. Other than a "Service Engine Soon" light.... it works the way you'd expect. :)

Jim

[DickWells]

Hi: I'm not the guy who created the articulated throttle in Jim's picture, but I did the same thing in a different way, and have been quite happy with the results. I towed across the US and back 3 times without incident. I put on about 40K, towing with the mechanical pump (4911), and the only shifting problems that I had were minor , (in my oppinion). I had to learn to lift my foot between up-shifts, just like you would with a manual. When it acts up, it's a matter of not shifting up out of whatever gear you happen to be in at the time. I get back to proper shifting by throwing it into neutral and shutting it off, then starting right back up. If I couldn't live with that, I'd go with the stand -alone TCM.
The fuel shut off solenoid works just fine with the mechanical pump. The best part of the swap is absolute INSTANT starts, plus, I never got another stutter, or shut-down on the road like I did with the electronics. My record before the swap was about 3K miles! Yes, I had the remote FSD, and a whole bunch of other stuff, still had intermittent ground problems and broken wire contacts, etc. But, the only time the Burb left me stopped on the road, was when my Banks chip came loose in the ECM. Could have fixed it in 2 minutes if I had bothered to shake the box when I checked for bad connections! Paid $135 to the dealer in Mesa, AZ instead!
I have pictures around somewhere of my throttle hook-up, but not sure I can access them, or send them on E-mail, for that matter. I sent hard copies to a guy (in Wi, I think). If he's still active, he might jump in here and help you out. I'm full time RVing in Tx, so I'm a little remote from my Suburban and the old data that I have for it.
Good luck, and keep in touch.
Dick Wells:)

[hfriesen]

Thanks for that post. I found the same thing with shifting, that I had to let off on the throttle a bit to shift but not always. If I was eccelerating fast it would shift great or very slowly if would also shift normally. But it isn't always the same. You have to get a feel for it.
I took my throttle off this morning to take some pictures for you. As you can see I took a grinder to the smooth nut on the throttle so I could take it off to do the welding. I also took a picture under the hood. I used a bracket off of an older 6.2 and modified it to fit. When I installed the pump I mistimed it by one tooth on the timing sprocket so that I had a bit more room for the throttle cable.

[DickWells]

My throttle mechanizm was different in that I used the entire mechanical pedal/lever/base plate unit, mated to the TPS through a roller cam to cam plate shoe which turned the electronic TPS. The roller was turned from a piece of 30/06 rifle barrel! You'd have to be there, I guess. Thing is, I thought the combo of the mechanical return spring up on the IP, plus the coil inside the TPS would be too stiff. Turns out, the thing is very smooth and controled. It's also infinitely adjustable, so that I could fine-tune the interaction between the mechanical and electronic parts.
I never did hook up the cold start fast idle. Never needed it. I did hook up the cold start advance, though. Nice to have just two wires instead of the dozen or so with the elec IP. I put a brass T down at the temp sensor location and put the temp sensor on one end and the cold start advance sensor on the other. Works great.
My bracket for the throttle cable pull at the IP is just a piece of angle iron machined out to miss the T-stat tubing there. That's another reason I didn't hook up the cold start fast idle. Would take a much more ellaborate bracket up there to work around all that plumbing. (See Jim's bracket in the 6.5 DP -- R&R book produced back in 98 or 99)?
There's a bunch of stuff that's been written on the 6.5 electronic to mechanical conversion.
It's not a good thing to do emmissions wise, but it sure does cure a lot of head aches for the owner. BTW, I didn't realize a great deal of increase in power from the big mechanical pump. I got that from the Phazer gears, better intake air, big SpearCo IC, etc.
Keep on keepin on.
Dick Wells:)