72 all wired with tbi couple of questions

[BigrobDog]

truck starts and runs great , but when going down the road and wanting to step hard on the gas truck bogs way down , but if u ease in to it easy it runs fine, here is my couple of questions, i used a wiring harness from 90 suburban,put it all on after wards i had to add 12 volts to the injectors, and to the fuel pump relay. and tie my fuel pump wire in to the relay .then it started right up.but i do not thing it is right, at end of harness for tbi goes in to the fuse box and right now that is not attached to nothing, not exactly sure on how to wire up that tbi,also i dont have the trouble shooting plug are the check engine light hooked up . does that go to end of harness some wear,can some one give me some info on hooking up this tbi harness,

[mjensen]

Is this an aftermarket harness, or a transplant from another vehicle? The only real advice I could offer would be to find the wiring diagram for the harness you are using and trace down what should be connected where.

[b.eddy's72]

My buddy did the swap but he used the entire wiring harness from the donor truck. TBI harnesses have multiple grounds that HAVE to be grounded properly. I would suggest to get a wire diagram for the vehicle the harness is out of and track down each 12 source and ground to make sure they are properly attached to the needed source. If it harness was installed properly you should not have needed to run your own power to the injectors or fuel pump.

[GASoline71]

Also... if you bolted on a stock TBI unit and computer on t an engine with anything other than the stock cam, timing, compression ratio, etc... you will need to have he computer reflashed to the new specs. The TBI is finicky to modifications of other than stock setups.

There are a lot of people on this board that have done the swap. Someone will eventually chime in with more info.

Gary

[ChevyCruizer]

i know you are asking about wiring but...what about fuel.

If you are running a stock tank or another carb tank it will not have a baffel in the tank and if the fuel pick up becomes uncovered (such as hard pedal stomp) it will suck air and usually stall out but could stumble and run ruff. A slow and steady pedal press will not slosh the fuel as much and then you would be able to get up to speed.

Just a thought...

[buckskins4ever]

Hate to ask but I didnt read it anywhere in the post....what are you running for a fuel pump? Fuel injection requires more fuel pressure than carbed.........way more.

[BigrobDog]

Originally Posted by GASoline71

Also... if you bolted on a stock TBI unit and computer on t an engine with anything other than the stock cam, timing, compression ratio, etc... you will need to have he computer reflashed to the new specs. The TBI is finicky to modifications of other than stock setups.

There are a lot of people on this board that have done the swap. Someone will eventually chime in with more info.

Gary

no its all from the same truck all i did was remove the suburban 1990 body and put the 72 over the top .

[BigrobDog]

when i took the harness out i disconnected it at the fire wall. and now i dont understand were those wires should go m in pic 3[ATTACH][/ATTACH]

[BigrobDog]

these are the wires im confused about the one next to the booster is the end of the loom that went in to the fuse box, what do all these wires hook up to, and the other pic is of the alternator wiring from 72 red wire and a blue and white do i hook thoes up or not and then my original, two wires are still in the alternator, what are the to original for that are pluged in and what do the old ones from the 72 do . the other is on the 70 harness to the alternator the big red wire goes to a voltage regulator u can see in pic , so do i need to hook up 72 harness to alternator

[BigrobDog]

sorry here are the pic

[Longhorn 70]

too bad it isn't OBDII there are a cr*pload of bluetooth scan tool interfaces for phones out there. I couldn't find one on OBD.

Do you have the "Check Engine" light anywhere?

Do you have the connector out anywhere you could connect a scan tool up to?

If the answer is yes to both above, you could pull codes with a paper clip. You may be going in "limp home" mode and that will do it.

[BigrobDog]

ya i do but was cut off and not sure were to but it back on.trying to find were it went to at end of harness,

[Longhorn 70]

Great, now I am considering doing this......any progress?

[MARKDTN]

Originally Posted by BigrobDog

ya i do but was cut off and not sure were to but it back on.trying to find were it went to at end of harness,

Did the OP get his truck running again? Looks to me like he needs a shop manual for the 'Burb and trace down all the wires.

[71sixgun]

Did you say that you do not have the wiring connected for the diagnostic port? If so, I would definitely hook it up. Diagnostic port is your best friend for OBD systems. What did the donor vehicle have for emissions, EGR, smog pump, Evap canister, and is all of that in place now? If they aren't and the ECU is still searching for input from them, then its not going to run right; ECU's can be reprogrammed though. TBI's can be finicky, but run nice when they are all correct.

[mrolds88]

OP needs to get the diagnostic port and the check engine light connected. Unit should have a 1227747 computer on it. We just did a swap (87 350 TBI to 80 Chevy 1/2 ton. Went flawlessly. OP said something about a red wire going no where. Might very well be a large part of the problem. Also if there isn't a O2 sensor hooked up, that will be an issue too.

[MARKDTN]

Yes, no reason that one shouldn't run nicely.