Re: Tbi swap build thread
 

This is a great thread guys I am so glad that it was started however I wish I would have stumbled onto it earlier in my conversion process as I am almost done now... So I am sure I will have questions when I finally get ready to fire this baby up...

Re: Tbi swap build thread
 

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

Re: Tbi swap build thread
 

Can someone tell me really quick what color the wires should be on the starter pink or red?

Re: Tbi swap build thread
 

It is pink on my '82 wiring harness, but may be different for other years.

Re: Tbi swap build thread
 

Looks like I wired it up correct then... sweeeeet

Re: Tbi swap build thread
 

WOW, this thread ROCKS! :metal:

Re: Tbi swap build thread
 

Thanks.

Re: Tbi swap build thread
 

Thanks again

Re: Tbi swap build thread
 

Hi Mark

I went a surge tank setup after reading conversion problems experienced by folks with non EFI tanks. Since our trucks are equipped with long saddle tanks fuel sloshing under low fuel levels can result in fuel sock aeration. When this happen fuel pump may experience instantaneous fuel cavitation resulting in fuel pressure loss and possibly inlet vapor lock. In other words - not good. Jeep guys face this problem all the time, but they have it easy by retrofitting to EFI tanks which incorporate fuel baffles to keep fuel sock covered under extreme angles. Alternatively, a small surge tank with low pressure lift pump is a workable solution. Noted, that this is not cheap nor is it simple to implement. There are couple advantages to surge tank system one being use of low pressure lift pump which can be conveniently mounted which can not be done with high pressure EFI pumps. Typically, low pressure lift pumps are self priming, so that if fuel sock aeration does take place pump re-primes itself while EFI pump keeps on delivering un-interrupted fuel flow to injectors. Low pressure pump fuel delivery can take awhile depending on fuel sloshing which plays into surge tank sizing - mine is about quart.

//RF

Re: Tbi swap build thread
 

Thanks for responding to my inquiry, RF. I don't use my truck off-road and/or operate it at extreme angles, so I don't have concerns about fuel sloshing in the old non-EFI tanks. I usually run each tank down to about an 1/8 full before switching over, but I have to admit to having gone below this level on occasion - I've had no starvation problems at any time with my generally sedate driving.

I mounted my Carter in-line pump on the inside of the frame rail slightly ahead of the transmission cross member. To minimize heat soak from the exhaust and possible vapor lock, I also fabricated an aluminum heat shield that I mounted to the frame rail. When I swapped out the lines trying to resolve the fuel pressure problem, as well as when I had to swap out the first pump that locked up, there were times the fuel in the supply lines gravity drained. Each time, the Carter primed fairly quickly afterward, which I attribute to mounting the pump at a level below the bottom of the tank.

Mark

Re: Tbi swap build thread
 

Ok guys I am having problems getting my set-up to run I have spark and fuel but it will not start with out dumpin gas into the tb I do have power to one side of each injector(should power be on both sides?) Is it possible my fuel pump puts out too much pressure and the tb is by passing it all?

Re: Tbi swap build thread
 

I do have power to one side of the injector while cranking but the other side does not flash?? (for some reason I cannot edit my posts)

Re: Tbi swap build thread
 

With ignition on, you should have 12V+ on both the red and white wires. The injectors do need a solid 12V, so if your battery is weak, they may not fire. The blue and green wires are triggered by the ECM to ground for firing each injector. There are ways to check the injector pulses at the wiring connectors, but require specialized equipment like an oscilloscope or trigger lights.

It is possible the injectors are stuck from having gummed up sitting around -this is what the problem was with mine when I first tried to start it and I was able to get one un-stuck by rapping the injector pod on the side with the handle of a large screwdriver. If you can get one to spray (the truck will run rough on just one injector), a good way to see if they are operational is to use a strobe from a timing gun. I ended up having to buy a new injector for one side.

I doubt that excessive fuel pressure is the problem - I'm pretty sure the bypass regulator is after the point where fuel is pressurized to the injectors. While I'm not sure what harm could be done since I've never tried this, you could try to momentarily connect a ground to the terminal of the injector that doesn't have 12V+ to see if it sprays (to try this, you have to have fuel pressure at the injector). If it sprays, there is either an ECM or wiring problem between teh ECM and the injector, otherwise it is probably the stuck injector I mentioned above.

BTW, I'm no expert on this, I've just been down this road before and I'm trying to give you the benefit of what little I know. Hope this helps and good luck.

Mark

Re: Tbi swap build thread
 

I lightly rapped on the injectors and nothing sooooo I guess I ll wait for a few others to chime in...

Re: Tbi swap build thread
 

While I get the sense that you want to figure this out quickly, these "noid" lights are the cheapest way (available on e-bay for $5-10) to see if all the wires at the injectors are getting the correct signal (i.e., determine if the lack of spray is due to the ECM/wiring or the injectors). Perhaps they are available at your local auto parts store.

BTW, I had to rap on my injectors pretty solidly before the one started spraying.

Good luck,

Mark

Re: Tbi swap build thread
 

Do you here your injectors clicking while you are cranking the motor? If you do they have the right voltage to fire them because that is the clicking noise. If they are clicking that probably means not enuff fuel is getting to the injectors.
I had this same problem and it ended up being a pinched fuel line.

I think the injectors get there signal from the ignition moduel in the distributor. If it is bad you might have spark but the injectors will not fire or vise versa.

keep us posted and good luck,
Jamie

Re: Tbi swap build thread
 

Perform the following check.

Turn ignition key into RUN position (do not crank). With a DVM measure voltage (with respect to engine ground) on both injector terminals - you should have voltage (11.5 to about 12Vdc) on both sides of the connector. Repeat for for both connectors.

If only one side has voltage you have injector with open winding (highly unusual) or injector connector that is not properly seated and engaged with injector pins.

Note the color of wires that have voltage.

When you pour a bit of gas into TB do you get engine firing up???

//RF

Re: Tbi swap build thread
 

Sorry, RF, but I respectfully disagree. Again, I'm no expert (I'm worse - I'm an engineer:lol:), but my understanding is that one side of each injector always has the 12V+ and the ground is switched/pulsed to the other terminal/side of the connectors by the ECM. Thus, testing for voltage across both injector connector terminals as you suggested will not show 12V (I just checked my truck and confirmed the lack of 12V across the injector connector terminals when in RUN).

With the key in RUN position, you should be able to measure 12V from the red wire on one connector (or the white wire on the other connector) to an engine or chassis ground, but not to the other connector terminal.

In regard to pouring gas into the TB, he said it would start in post #186.

cjracing: The relationship between the ignition module in the dizzy and the injectors is that the module tells the ECM that the engine is spinning (and at what RPM). The ECM needs to check that the engine is spinning because it is a potentially very dangerous situation if the ECM allows the injectors to fire (i.e.,release fuel into the TB) when the key is in the RUN or START positions and the engine isn't spinning. Since FB72 said his engine would start when he poured gas into the TB, the ignition module is working fine and it is my belief that his problem is (1) an ECM problem, (2) an open in the wiring between the ECM and the injector connector, or (3) a stuck/defective injector.

Since the injectors are basically solenoids, I reiterate my earlier suggestion to apply a ground to the non-12V+ terminal of the connector to see if the injector will fire. With a confirmed 12V+ on one injector terminal and a ground to the engine or chassis on the other, the solenoid/injector should click and allow fuel to flow. If fuel doesn't flow, either (1) the injector is stuck or defective or (2) there is no fuel pressure in the injector pod. If fuel does flow, then the problem is upstream of the injector connector in the ECM or wiring. While I've never tried this test, I don't see why it wouldn't work, nor do I think it risks harming anything.

That is my $0.02 and please understand that I am not trying to offend anyone or debate their advice - I'm simply trying to help.

Mark

Re: Tbi swap build thread
 

That's what I said. Kindly re-read my post (engine is not turning).

Furthermore, measuring voltage drop across 1.1 Ohm injector with a common DVM is fruitless. However, with a dual trace O-scope and A-B function one can measure voltage drop across operating injector. But that's not an issue here. In TBI system (same technique is used in many other injector systems as well) one pin of injector is tied +12 volt bus, while the second pin is being tied to a switching circuit inside ECM. Typically this switch circuit consists of high power Bipolar or FET transistor. In case of 1227747 ECM GM used a high power NPN transistor with collector tied to floating injector pin, while emitter is shunted to ground with 0.1 Ohm resistor. A custom (Delco) injector transistor driver IC is used to current limit current drawn by injector - by monitoring voltage drop across 0.1 Ohm shunt.

Missed that one, sorry.

OK = 2 cents accepted (in this economy)
//RF

Re: Tbi swap build thread
 

The batt in my voltage meter has decided not to play today so I quickly probed the wires and I have at least some power to one side of the injector connection on both sides injectors the other wire does not have any voltage(at least not that the test light shows) with the key in any position or while cranking the engine... Looks like i'm off to town for a battery for the meter.. Again guys thanks so much for the many good points of view..


Also on a side note I have a friend bringing over his scanner for the diagnostic port will this tell me anything ???

Re: Tbi swap build thread
 

I'll put together a basic measurement diagram later tonight - this should help you to troubleshoot. I hate guessing and once you have check list it will make it simpler to troubleshoot further.

Scanner
The ALDL will not tell you why injectors are not firing. On the other hand 7747 ECM will give you sensor data. Injector functionality is not monitored by early ECM - we are talking '80 high tech here (PC-AT, remember those 8086??)

//RF

Re: Tbi swap build thread
 

rfmaster - those diagrams you post up are great, and a bunch of help for someone who hasn't looked at a TBI since the early 90's! :lol: I take it you are making them?

Re: Tbi swap build thread
 

cjracing: The relationship between the ignition module in the dizzy and the injectors is that the module tells the ECM that the engine is spinning (and at what RPM). The ECM needs to check that the engine is spinning because it is a potentially very dangerous situation if the ECM allows the injectors to fire (i.e.,release fuel into the TB) when the key is in the RUN or START positions and the engine isn't spinning. Since FB72 said his engine would start when he poured gas into the TB, the ignition module is working fine and it is my belief that his problem is (1) an ECM problem, (2) an open in the wiring between the ECM and the injector connector, or (3) a stuck/defective injector.

Ok the way I understand how the cranking sequence works is the cpu gets a signal from the starter (C-9 prpl wire that goes to the selinoid on the starter)to turn on the fuel pump while it is cranking. When the engine has oil pressure the oilpress switch is what tells the cpu to run the pump and I understood that the module is what fired the injectors in time with the engine while it is running.
Am I wrong? If I am I would like the right sequence.

By the way FB-72 you have checked to see that you have 12 volts to the pump right? If you have and I missed it I am sorry I am just trying to help ya out.

Re: Tbi swap build thread
 

Yhea Thanks RF for your work on those diagrams they are awsome.

Re: Tbi swap build thread
 

Cj if your talking about the fuel pump no I have not checked but the return line is filling up the 5 gallon can quickly... I have 12 volts dc to both injectors on one side only...