Tbi swap build thread

[cjracing15]

C-9 Goes to the small terminal on the starter. ( tells the computer when the starter is engaged)

C-2 You can just disregard this wire.
D-1 Is a system ground. I just ran a main ground for the computer system and grounded it at the back of the head. (Pass. side)

You are right there is not an A-7 wire but there is an A-5 and this is your ses light. It is a ground the the cpu turns on when it needs to. I just used my choke light and put a switched 12 volts to one side and then wired in A-5 to the other side. works great.

A-6 as you said is pk/blk. It ties into sevral places in the harnes to give switched 12 volts where needed.

As for the fuse rating I think stock is 10 amp.

For b-1 I used a inline 20 amp fuse.

as for A-4 it is just a ground from the cpu to turn on the egr relay. so a fuse is not needed.

[FRENCHBLUE72]

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...

[FRENCHBLUE72]

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

[brontotx]

Originally Posted by FRENCHBLUE72

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

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

[FRENCHBLUE72]

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

[FRENCHBLUE72]

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?

[rfmaster]

Originally Posted by FRENCHBLUE72

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?

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

[brontotx]

Originally Posted by rfmaster

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.

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

//RF

Sorry, RF, but I respectfully disagree. Again, I'm no expert (I'm worse - I'm an engineer), 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

[rfmaster]

Originally Posted by brontotx

Sorry, RF, but I respectfully disagree. Again, I'm no expert (I'm worse - I'm an engineer), 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.

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.

Originally Posted by brontotx

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

Missed that one, sorry.

Originally Posted by brontotx

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

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

[cjracing15]

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.

[FRENCHBLUE72]

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)

[brontotx]

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

[FRENCHBLUE72]

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

[brontotx]

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

[cjracing15]

Originally Posted by FRENCHBLUE72

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

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

[FRENCHBLUE72]

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 ???

[rfmaster]

Originally Posted by FRENCHBLUE72

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 ???

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

[glock35ipsc]

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! I take it you are making them?

[FRENCHBLUE72]

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...

[pancake]

Hello again, I have a quick question.

If I use a adapter plate to bolt the TBI to a carb intake:

1) are there rules on whereto mount the sensors that were mounted to the TBI intake.

2) can I use a diffrent coil mounted to the firewall? what kind of coil do I need?

Thanks again.

[cjracing15]

Originally Posted by pancake

Hello again, I have a quick question.

If I use a adapter plate to bolt the TBI to a carb intake:

1) are there rules on whereto mount the sensors that were mounted to the TBI intake.

2) can I use a diffrent coil mounted to the firewall? what kind of coil do I need?

Thanks again.

1) I would put the sensors as close as I could as the factory did it.

2) As for the coil I am not sure. I am sure RF will chime in on it. He rocks on the wiring diagrams.

[rfmaster]

Originally Posted by cjracing15

1) I would put the sensors as close as I could as the factory did it.

2) As for the coil I am not sure. I am sure RF will chime in on it. He rocks on the wiring diagrams.

Thanks CJ

Pancake - you can mount coil on the fire wall (or in its original location). If you do so make sure to run a ground strap (braid) between intake and coil mounting bracket. Low resistance ground return path is required between EST and coil.

I have seen third gen boys mount monster sized coils (lots money) on the firewall. Generally, performance coils can be saver and trouble all rolled into one. The problem stems from current requirement that these coils place on EST module (inside dizzy). To get HV coil to deliver joules of spark energy (at 40 - 50kV) requires more current flowing through the primary (12 volt winding). EST module operates as a switch which turns on & off current flowing through the coils primary windings. More current = more heat. Semiconductor devices do not like heat and fail over time if subjected to operation beyond rated limits. For our trucks, with engines spending most of their lives below 3000 RPMs use of 'monster' coils is not necessary.

One of these days I'll setup experiment in my lab to measure primary coil winding current and publish my results. I have factory coils, but I do not have any 'monsters' for obvious reasons.

As to recommendation on coil - I have never used anything but stock, hence I can not recommend one.

Sensor placement. I prefer to mount my sensors away from heat sources for the aforementioned reasons. I mounted my MAP on the firewall, ESC module is mounted on fender skirt. All my relays are mounted away from engine. GM mounted the same sensors on a bracket bolted to intake manifold.

//RF

[cjracing15]

Ok then your fp is ok then. How did you make it run so that it filled the gas can? Also when you crank the engine over do you here a clicking noise from the injectors?

[FRENCHBLUE72]

No clicking...... I did however find this wire unhooked any ideas on where it should go? It has power when the key is on??? Filled the gas can that im using for the return line while tring to start the truck....

[rfmaster]

FrenchBlue72

Please Refer to figure below



Background Information
Basically, GM implemented a very simple TBI injector circuit. In this implementation ECM acts as a switch pulling Pin B of injector connector to ground completing the circuit energizing injector - fuel is delivered. Ignition switch supply is provided via two circuits 481, 482 (red and white wires) and are always on (as long as ignition key is in run or starting position).

Checks
Requires a functioning DVM - no excuses now, alright???
Injector coil
1) Everything is off, disconnect injector connectors from injectors by gently squeezing release tabs. Set DVM to measure resistance (Ohms), set to lowest range available <300 Ohms. Ignore this if you have a fancy auto ranging DVM. Measure resistance of each injector. Depending on your DVM and test lead resistance you should be able to measure individual coil resistance - about 1.1 to 1.5 Ohms for typical GM injector. If you are reading very high resistance - time to cry. If injectors check out then step 2.

2) Verify ignition voltage supply
With both connectors disconnected make sure that they do not come into contact with anything in the engine compartment. Once secured, turn ignition into run position and measure voltage at Pin A off each connector. With a good battery you should see 11.5 to 12.0Vdc with respect to ground (bat negative terminal). If there is no voltage verify ignition fuse.

3) Re-install injector connectors if step 2 is good.
With ignition on, engine stopped both Pin A & B should measure 11.5 to 12.0 with respect to ground. If Pin B fails to measure same voltage as Pin A then it is possible that connector is making a good contact with injector pins or there is an open injector winding when connector is installed on injector.

4) ECM PWM verification (this requires NOID or un-powered 12 volt test light)
For this test DVM a typical DVM response time is to slow (there are units that can measure frequency or pulses specifically for PWM circuit troubleshooting) and a simple un-powered 12 volt test light will do the trick.
Connect ground lead to engine ground and probe Pins A & B of each injector connector - light should be one for both as long as ignition is on, engine stopped. Get a helper to crank engine while probing Pin B of each connector - the light should be blinking off periodically. This is normal. Otherwise, if it remains solid that may indicate that ECM is not pulling injector circuit 467, 468 to ground. This may be caused by brake in harness, bad injector pull down circuit, etc. Manual shorting of injector control circuit - Pin B is not recommended, but this can only be done once supply voltage pind has been verified (red/white) and only for a short time.

//RF