Tbi swap build thread

[68c10owner]

Originally Posted by cjracing15

If you use in tank pumps you will have to get a FI tank. The fuel injected tanks have baffels in them to control fuel slosh so the pump will not suck air if the tank is low of gas. Plus you will have to get the sending unit and pump.

I am just going with one tank right now because that is what i have. I will get both tanks working in the futrue.

I have talked with "Dirtylarry" about what he did and it sounds real good.

He swap the one primary tank on his truck with the in tank pump, and then monted a transfer pump so he can just pump gas out of the spare tank when he needs it. It will be cheaper I think than making every thing work like stock. (unless I can find a donor parts truck cheap)

My truck has dual tanks but I only use one so I guess it doesn`t matter. I`ve only used the other tank when I was running low on gas and was worried if I had enough to get to the station.

[DirtyLarry]

This is going to be a nice and informative thread!

With TBI, I think you guys will probably be fine running a frame mounted pump to pull fuel through the dual tank switch valve however you may need to figure out a way to pause the frame mounted pump while you switch tanks otherwise you will stumble the engine momentarily. As far as the pump, just mount the pump as low as you can below the tanks and switch valve and on the engine side of the switch valve.

The problem I had running a frame mounted pump with my 8.1L was twofold. First, 8.1L requires 60 psi fuel pressure but on my marine controlled 8.1L it only requires 43 psi. None the less, the return side ports on the OEM switch valve are little bitty 5/16 ports and restrict the high pressure fuel return flow back to the tank causing the fuel pressure to run around 100 psi at the fuel rail! Once I bypassed the switch valve the fuel pressure ran normal. This would not be an issue for TBI as TBI only runs around 12 psi and what little fuel goes back to the tank is very small compared the later model sequential EFI engines. GM used that exact switch valve on TBI trucks anyway so again, the fuel return through the switch valve won't be a problem.

The second issue I had with the frame mounted pump was mainly off-road where you are crawling along on the trails at 2 MPH for hours on end without any wind blowing over the pump to keep it cool. Once I would stop for a minute to take break or something then try to restart the truck it would only crank as the fuel pump was too hot and cavitated the fuel inside. The pump would scream like crazy when it was warm too! Being my truck sees more off-road than on, I wasn’t going to be able to live with that so I swapped to a ’87 TBI tank, ’87 TBI sending unit with a Corvette fuel pump to feed the 8.1L the pressure it needs.

GM and AC Delco pn for the switch valve 14029228


Here is how I had my frame pump mounted. Protected by the cross-member from road debris and also shielded from the exhaust. This contraption is gone now that I have converted to an in-tank pump and a transfer pump to move fuel from the secondary tank to the primary.

[DirtyLarry]

Originally Posted by joe231

Hey DirtyLarry, what kinda pump do you use for a transfer pump?TIA

Mr. Gasket #12D. Summit Racing pn MRG-12D. It is a low pressure/high volume pump. The pump is actually labled as diesel fuel but it will work as a gasoline transfer pump per Mr. Gasket tech line. I am happy with it so far with only testing it in the garage a few times. Moved 1/4 tank of fuel in less than 4 minutes from the secondary to primary tank. Will be making a run to the mountains in a few weeks so I should have real world results soon.


Mounted on a fabricatedcross member between the frame rails. Operated by Painless Wiring electric fuel pump harness kit PRF-50102 (Summit Racing pn) and a toggle switch.

[DirtyLarry]

Rfmaster,

What you said above about VSS sounds right for 1996 and later OBD II sequential multiport EFI systems but I can’t find anything in any of my older GM STG service manuals for TBI years that state the VSS has anything to do with Deceleration Enleanment or Deceleration Fuel Cut Off. It could be one of the functions that takes place behind the scenes that isn’t really called out in the service manual.

From what I understood, the main sensor to control fuel on OBD I such as TBI is the MAP as it constantly monitors engine load and adjusts fuel pulses accordingly. Once you get into OBD II on sequential multiport things get a lot more complicated and more inline with your description above.

The only function I can find for the VSS in TBI years is to provide a pulse signal to the DRAC for the speedometer, RWAL ABS module, and cruise control module. The VSS isn’t even mentioned anywhere in any of the drivability symptom flowcharts or anything other than inop speedometers, cruise, ABS, etc.

For what it is worth, my 8.1L running multiport EFI on a Delphi MEFI-4 controller (similar to a GMPP RamJet engines and GM Marine engines) doesn’t have any VSS inputs either to run, and run well even with a manual trans. The whole MEFI-4 system is an entirely weird deal anyway.

I know you are an engineer and know this stuff a lot better than any of us but are you sure about the VSS function on TBI?

[skidder111]

So, rf & Dirty Larry, is there any benefit to installing a VSS in my ride? As mentioned above, it is an 89 setup, so there is no DRAC in this setup. I'm still using the mech speedo and have no cruise. THANKS FOR YOUR HELP!

[DirtyLarry]

Skidder,

I would venture to say you are good to go without VSS on a manual transmission. With an automatic, yes, you would need it for the torque converter lockup. Your earlier post mentioned a concern with going into closed loop. Closed loop is achieved by the engine coolant temperature sensor (ECT) and O2 sensor inputs not vehicle speed.

My 8.1L with a manual trans does not have a VSS at all. Even though the 8.1L is multiport EFI, mine is running an OBD I speed density calibration system through a Marine MEFI-4 engine controller with a protocol that is very similar to the old TBI and TPI systems of the late 80’s and early 90’s. As far as fuel delivery, the main difference is my 8.1L fires 8 injectors under a higher fuel pressure in batches where as TBI is firing 2 at a lower fuel pressure. Firing the 8 individual coil packs on the 8.1L is what is unique about the MEFI-4 controllers as they are very versatile in programming what they can control….but that is a whole nuther story.

This is one of the reasons I have chose to go with aftermarket harnesses opposed to reworking a donor vehicle harness. First, a donor vehicle TBI harnesses are getting old (last TBI truck was built 15 years ago!) and the harnesses tend to be very brittle and stiff, end connector break at the touch, etc. Second, a creditable aftermarket harness vendor such as Howell or Street and Performance, etc has already put a lot of research into knowing how to properly wire these things. Most of those companies have gone to the manufactures and purchased the original engineering layout drawings to create stand alone harnesses without all the unnecessary circuitry. For $325 a nice fresh harness is hard to beat vs. pulling your hair out trying to rework an old harness only to still have a 15+ year old harness when you are done.

[chevymotocross]

Originally Posted by cjracing15

Yes sir been in the service feild going on nine years now. Mostly comercial refrigeration, but I do residential on the side.

HVAC guy here too. We do strictly residential heating/cooling... no refrigeration Actually just started out in the trade 3 months ago. Like it lots so far and the pay is good.

[rfmaster]

GM to all from wet So-Cal

This morning I had a bit of free time - here is headlight circuit diagram for CUDA using remote relays to switch headlight circuit. Use BOSCH style relays and 12 (or 10) AWG SXL (SAE J-1128) automotive grade wire to bring current to your headlights. On relay control side you can use smaller gauge wire (16 to 18 AWG) to make harness a bit easier. Unfortunately, many use commonly available THM grade wire which is not suitable for automotive applications due to extreme temperatures. Make sure to use weather pack style inline fuses or fuse links! Absence of fuses can lead to fires!

Ignition circuit and ECM interconnect is to follow... Hmmm we are getting lighting and thunder here - very unusual!

[rfmaster]

Basic ignition and power



//RF

[79blazer]

I did a TBI swap on my Caprice a couple years ago. Donor vehicle was a 88 truck. I was fortunate to have the complete factory service manual, including complete wiring diagram book. I did reorganize wires, so that FI input/output were together, all other wiring separate.

After much research, I found that the ford E2000 Inline fuel pump works good. It is capable of much higher pressures than a stock TBI requires, yet it doesn't flow too much to where a 5/16 return line would cause over pressure. It runs cool, an doesn't draw too much amps. You can use quick connections, or clamp hoses to it. I doubled clamped. I bought two (one for spare) for $30 at a pick-and-pull I think. It was in many Ford vehicles, so it was easy to find. http://www.partsamerica.com/ProductG...rtnumber=E2000 One advantage is you wouldn't have to drop the tank to repair it, should it fail. Buy it used cheap (try to find a newer, cleaner one) or instantly, no shipping necessary.

The sock filter in the tank also acts like a baffle.

Disadvantage to some inline pumps (some times the e2000 too, according to my research) they may be difficult to prime. As in: if you run out of gas, it may be hard to get fuel pressure back. That is because they are better at pumping fuel, than drawing a vacuum.

There's pro's and con's to everything. I am glad I used a old harness, because I learned alot about fuel injection when I did it.

Man reading this thread brings back memories of when I did mine! Mine was a 7747 ECM too. For example a simple brass male/female 90 degree elbow from Homedepot works for the oil pressure sensor.

[cjracing15]

Well I have got a few update pics for ya. I have run all my wires, mounted the computer, I have even tested the fuel pump in the tank and ses light to see if it worked. Well as soon as I hooked the battery back up the fuel pump relay clicked on so first test done. Then I put a hose from the tank into a bucket and hooked the fuel pump wire and a ground wire. Then I hooked up the ses wire ( I am going to use the old choke light for the ses light because I will not need a choke light anymore). Well I took a deep breath with my dad watching the the bucket that I had the hose in and turn the key to the on position. To my delight the ses light came on like it was suppose to and dad said that the pump came on for about 3 sec's and shut off.

So my next project is to run the F.I. fuel lines and install the other tank and see what happens.

Here are a few pics that I took for every-one.

1st. pic Is the computer monted under the dash and the wires run to it.
2nd. pic Is the fuel pump relay mounted on the fire wall.
3rd pic is the fuel pump pump plate that I stole off of the suburban. Had to take off one side of the accs brackets to take the pump off.

The last two are of all the wires run on the engine and, I stuck the breather up there just to see how it would look. After I repaint it I think it will look stock, witch is what I am going for.

I am going to start on the fuel lines Monday and I will update with pics later next week.

Stay tune.

[rfmaster]

Nice progress.
FYI - do not forget to use EFI rated fuel hoses clamps when plumbing your system. Even though TBI system is rated for 13 to 15 PSI operating many pumps are capable of delivering 30+ when deadhead.

So, what's on your XMAS wish list??

//RF

[cjracing15]

Originally Posted by rfmaster

Nice progress.
FYI - do not forget to use EFI rated fuel hoses clamps when plumbing your system. Even though TBI system is rated for 13 to 15 PSI operating many pumps are capable of delivering 30+ when deadhead.

So, what's on your XMAS wish list??

//RF

Thanks, Pick-up EFI hoses today but I am having a hard time finding the clamps for some reason. But the parts store I usually buy my parts from was closed today so I will check with them Friday.(I am sure they will have them) Also picked up a new pump to put in my tank this morning.
Thanks Jamie

[cjracing15]

Originally Posted by rfmaster

Any further updates on your conversion (all done I suppose) ???

//RF

Not done yet I have run into a little problem with it. I have had it running and it ran great but for some reason It has stopped gitting fuel to the injectors and since I have went backed to work I have not had any time to get back and check anything. It has a brand new pump in the tank so I don't know why it has quit but I HOPE to get back to it Sat. If I can stop having to running calls long enuff. I am a hvac thec for a rather large contractor for this area and we have been swamped with calls since I got back. (Globlal Warming my A**.) This is the coldest it has been around here in at least five years.

Anyway I will have an update when I get time to work on it. Thanks for asking. ,Jamie

[rfmaster]

Originally Posted by cjracing15

Not done yet I have run into a little problem with it. I have had it running and it ran great but for some reason It has stopped gitting fuel to the injectors and since I have went backed to work I have not had any time to get back and check anything. It has a brand new pump in the tank so I don't know why it has quit but I HOPE to get back to it Sat. If I can stop having to running calls long enuff. I am a hvac thec for a rather large contractor for this area and we have been swamped with calls since I got back. (Globlal Warming my A**.) This is the coldest it has been around here in at least five years.

Anyway I will have an update when I get time to work on it. Thanks for asking. ,Jamie

You can verify that FP is functioning couple of ways.

1) When you cycle ignition key from off to run ECM goes through a POST routine during which FP relay is energized for about 2-3 seconds (you shouls be able to hear it run) and subsequently turn off. If all other test check out SES goes from solid - blinks off and turns back on solid until engine starts (after cranking). During cranking FP should be energized.

It is rare, but 7747 ECM have been know to loose FP relay circuit driver transistor (2N2907 ) when FP relay is shorted to ground.

2)To verify if FP is functional you can force FP relay into a test operation via bypass, fuel system prime pig tail at the FP relay socket.

[cjracing15]

Originally Posted by rfmaster

You can verify that FP is functioning couple of ways.

1) When you cycle ignition key from off to run ECM goes through a POST routine during which FP relay is energized for about 2-3 seconds (you shouls be able to hear it run) and subsequently turn off. If all other test check out SES goes from solid - blinks off and turns back on solid until engine starts (after cranking). During cranking FP should be energized.

It is rare, but 7747 ECM have been know to loose FP relay circuit driver transistor (2N2907 ) when FP relay is shorted to ground.

2)To verify if FP is functional you can force FP relay into a test operation via bypass, fuel system prime pig tail at the FP relay socket.

Well the Fuel pump is running. I get gas up to the throtle body on the supply line but it just spits gas out the injector. I can pour gas in the tb and it will run untill it runs out of gas???

[rfmaster]

Gas to TB is good. If injectors are not spraying during cranking there are couple of possible problems.

1) Disconnect both injectors from harness. Check the +B (red and green???) injector wire - it should be +12 when ignition key is on and during cranking.

2) If you have +12V on red wire reconnect injectors, get a +12 volt low current test light (or fast DVM). Probe both injector pins (red and green and red and blue - colors are typical, but maybe different) - red should be a steady +12, while the other side should pulse on-off-on during cranking. No pulse indicates that's ECM is not pulling line low. There are couple of possibilities.


//RF

[408cuda]

Hi guys. Found this site after extensively searching the web on TBI swaps and it seems like a great source of info. I am in the process of converting a friends 59 Chevy Apache pickup from a straight 6 to 350 TBI out of an 88 Chevy 2wd pickup. We are using the donor rigs wiring harness. Anyway, I have the mounts fabbed and engine in and and getting close to trying to wire it up. We stripped the harness and all sensors from the donor but the part I am having trouble understanding is what exactly I need to power up for wires from the harness? I plan to add a 6 lug fuse block just for this purpose. I have some wiring diagrams that are helpful, but don't know what wires I NEED hooked to the fuse block, or elsewhere? We are using the 5 speed manual from donor as well and since we are using the stock wiring do I need to do anything to work the VSS? . For a gas tank we were thinking of an 88 Blazer which dimensionally looks doable, and takes the same pump/wiring etc..

Thanks for your time,
Chad

[cjracing15]

I finnally have an update. The truck runs great!! It took longer than I would have liked but it runs better than it ever did with the carb on it. I still need to get a vss from JTR and a chip from Tbi chips because of the cam I have in it. I also need to get a gromlet for the firewall installed for the computer wires. But other than that it is done. I wanted to get a vedio of it running but my camrea is not croperating at all so here are a few pics. Enjoy!

[cjracing15]

A few more.

The engine all together.







The interior put all back together


The choke as a check engine lite.

[cjracing15]

Ok here ya go. These are the only before pics I have.

[cjracing15]

Here are a few pics i forgot I took.

This one is the best I could do. I tried to get a pic of the internal baffel. This is for the pepople that had questions on why shoud you swap out the fuel tanks.


These last two are of the fuel lines that I used and how I flare them so they would have something to calmp to. The other ofcourse is the tank ready to be installed.




My problem ended up being the fuel selector valve. I guess that the 22 year old valve could not handle any extra press. going through it. I had to bypass it and it fired right up.

[pancake]

Hi everyone and thanks for all the great information. I am getting ready to convert my 4x4 rig to TBI and this thread is helping a lot. I have a few questions for you guys. I hope this is ok, I don't want to hijack the thread.

A little about the rig the TBI is going in:
78 blazer with a 350c.i. engine. I pulled the engine from a junk yard with no heads and rebuilt it. The rebuild is pretty much stock except a mid R/V cam and headers. I think the block was fuel injected before, therer is no cut out for a mechanical fuel pump. The heads I put on the block are not off a TBI truck and I know I will have to re-work the two inner intake holes to align with the heads. The tranny is a manual (SM 465) and a NP 205 T/C. This is a trail rig and will only see the road driving from the camp site to the trail head and will be on the trailer the rest of the time. I am thinking of putting a TH400 in this summer with a doubler.

I will be buying a used TBI setup. Should I get a pre 92 or will anyone work? I think Iwill buy a new aftermarket wiring harness from painless or Howell. Do I need to order anything specific for the harness?

Now for the TBI conversion questions:
1) The nuteral safty switch is re-wired so I can start the truck in gear if I need to. Do I just ground the N/S switch? Is it wire B-10? What do I do with the wire if I decide to go to the TH400?

2) After reading about the VSS I will be putting one on the conversion. The VSS conects top the tranny or t-case? Where can I get a cheap one? If I put a TH400 in will I need to change the VSS? The TH400 will have a manual valve body.

3) Where do I put the knock sensor?

4) Where I put the collant temp sensor?

5) I do not have A/C but would like to use the wire from the ECM to bost idel when I need to use the winch. Any sugestions how I would do this? Put in a toggel switch?

6) Which ECM should I look for? Serial #? and will I have to get it re-programed....new PROM?

7) I have a plastic fuel cell in the rig now. I might go to a stock fuel tank with the pump in it in the future. What external pump should I get to ust the fuel cell? Do you have a part number? Do I need a fuel regulator or is this built into the TBI? I do need a return line right?

7) I have also read about a charcoal canister? Do i need one?

Sorry for all the questions but I would like to do this right and you guys seem to know you are talking about. This is the best site I have found for TBI conversion information.

Thank you in advance for the help!!