Tbi swap build thread

[brontotx]

I have looked at both the '82 and '87 factory service manuals and have come to conclusion that the cruise control and ECM are simply not connected in this era of trucks. There is the obvious exception of the VSS signal being used for by both the ECM and cruise in post-'87 trucks, which I determined through additional web research to both use the 2000 ppm signal. So, IF I went with the later cruise control (which I have decided not to do - see below), the VSS signal I am getting from my JTR 2PRS should feed both the cruise and ECM, just like they do when the VSS signal comes from the speedometer on post-'87 trucks (and cars).

Basically, my '82 cruise set-up uses a transducer and vacuum modulator mounted on top of the driver's side inner fender to understand and manage the speed when cruise is on. In essence, the transducer is a VSS-like signal, but internal to the cruise control. Since I have all but one of the '82 parts (I'm missing the throttle rod), I have decided to simply try and get this system functioning as the TBI and ECM really don't "know" (or care from what I can determine) if the cruise is engaged. Once I get the throttle rod and have a chance to test and diagnose the '82 cruise system, I'll report back how it works (or not) with the '87 TBI set-up - wish me luck.

RF - you are correct about there being about a dozen variations of the 700R4 TCC lock-up circuit. Since I had purchased an '87 TBI set-up from the e-bay seller in Brenham, TX, and since Houston (where I live) is only about 80 miles from Brenham, I contacted him and purchased the used '87 700R4 from the same donor vehicle (an '87 1/2-ton Suburban) as the TBI was pulled from. The used tranny was in good shape (clear, non-burnt fluid) and has been performing well for some 5,000 miles now. Given the heavier duty nature and use of my C20, I also installed an aftermarket auxiliary transmission cooler and an outboard transmission filter mount/kit that included a temperature gauge, which I use to keep an eye on when towing.

Also, my Carter P5000 pump works great too, although my first one was replaced under warranty by Summit since the first pump occasionally "locked up" and I had to "jump start" it by bypassing the relay using 12V+ direct from the battery to the pump. Given the problems with the first pump, I also purchased a spare since the Carter pump is the only part in my TBI conversion that is not available at my local auto parts store.

I also have a weird problem with the pump running for a few seconds after shutdown. I replaced the fuel pump relay and this problem occurs with both the pre-EBL ECM and the EBL ECM, but the pump still runs on, so my guess is that the ECM signal "decays" instead of shutting off instantly, keeping the relay engaged.

I did not install a surge tank or lift pump and both my tanks are selectable and functioning like yours. While I am happy with my set-up, perhaps you could elaborate to me and others on why you felt these were required?

Again, thanks to all for this great thread.

Mark