Re: Tbi swap build thread
 

ok i decided on the nv3500. So my question is do i need a drac to make my vss work or can i wire the tailshaft mounted vss right to the ecm?

Re: Tbi swap build thread
 

I did a bit of search on this subject since I have never dealt with NV3500 trany. From what I could find the NV3500 employes a 40 pulse VSS (per shaft revolution), so that you'll have to sue a DRAC or Dakota digital buffer module to arrive to 2000 ppm signal that TBI ECM (aka 1227747) is expecting.

The Dokota Digital converter module is a Swiss army knife equivalent of GM DRAC minus the PITA. This module is pricy, but time and effort may justify the initial cost. Check their website SGI-5 Universal Signal Interface Unit.

//RF

Re: Tbi swap build thread
 

ok, also i have a question about dynamic efi. I have browzed there web site how hard is it to learn how to use.

Re: Tbi swap build thread
 

It is a lot easier than trying to burn own chips. There is a main thread (as well as several smaller threads) on thirdgen.org that deals with EBL user questions. Unless you have a fire breathing monster of a camshaft+engine EBL can handle.

I run EBL on all my conversions - see youtube videos. The key to TBI is selecting camshaft that provides about 14-16 in-Hg at idle and steady idle. After market camshaft with LSA of 112deg and higher with up to 214deg at 0.050 will do the trick. Tighter LSA (<112deg) results in lumpy idle which screws up MAP sensor readings and ECM will over fuel the engine. Long duration camshafts >220 deg also create havoc for O2 sensors at idle. Our trucks need low end torque, and high RPM HP is never really needed in a street truck. What we need is flat torque from 1500 to about 4500 RPM to get the weight going (and keep it going). A good RV cam will do this trick without creating problems for TBI system - for example CS1014R (flat tappet).

//RF

Re: Tbi swap build thread
 

Great thread guys! Looking to TBI my 85 here in the near future....

Re: Tbi swap build thread
 

looking to do a tbi swap to my 86 k30 dump. i got a 89 c2500 that used to be my dd. i plan on pulling the motor, wiring and all relays/sensors from under the hood, and computer soon. is there anything else that i will need from the donar truck. also am i gonna have to replace the 86 wiring under the dash or will i be able just to put power to the computer to run all engine componets.

Re: Tbi swap build thread
 

Im redoing my wiring on the 65 tbi, i would like some pictures of the swap done on 60-66 trucks please.

Re: Tbi swap build thread
 

One of the key components is VSS. Depending on the donor vehicle VSS can be PITA. Do you have donor identified? Also, you do not have to replace any of the under dash wiring - EFI is a standalone system and is adapted to your 86 harness - fuse box.

//RF

Re: Tbi swap build thread
 

A guy a few posts back asked about 700r4/4l60 integration. What's involved? I have an 87 sb, 350tbi/350 and of course I want the od. Any info on what might be involved? Really kinda thinking of getting a 94/95 computer and running tbi/4l60 like I had in my 95. Is this easy? A pipe dream? Anyone done it? I have 2 90 2wd burbs in a yard not far away that are still fairly complete with electronic speed outputs for the 700's. My 87 t350 is a cable. Will the tailshafts swap? Can I just put a later cluster in my truck? Sorry for all the questions, but I've been wondering. Thanks, Chip.

Re: Tbi swap build thread
 

Hey Chip
The 93-95 PCM's are (were for their day) advanced powertrain computers and much more powerful than C3 ECM found in 87-92 C/K's. The PCM can control TBI and 4L60E/80E as well as 700R4. It can also be used with manual gear boxes - all of this requires modifying EPROM. This is a long discussion (PCM mods) and better be done else where. There is a lot of information available - TGO, moates and elsewhere.
Regarding Spedo. This is where it gets a bit tricky since 93-95 used electronic speedometers. The VSS produces 40 pulse per shaft revolution which gets passed to DRAC module. DRAC module has three outputs which feed into anti lock brake system computer, cruise control and PCM.

To swap into 87 I would look into converting 4L60E VSS from electronic to mechanical drive with addition of inline VSS module to drive the PCM (assuming that there is no cruise control). This swap would require removal of reluctor ring pressed onto tail shaft and installation of drive gear to drive driven gear. You'll also need speedometer gear housing. For more info see link below.

http://www.transmissioncenter.net/sp...n_______va.htm

//RF

Re: Tbi swap build thread
 

Oy. So, best to keep fairly close, year to year? Seems a bit of a mess. I'm fine iwth swapping the housings, but the rest is a tad muddy. Thanks for the info, though, answered a lot of questions.

Re: Tbi swap build thread
 

I have a question regarding the EGR solenoid.My CEL comes on spuratically.
I have checked vacuum at TBI=0 at idle,increases with throttle.
no vacuum at egr side of solenoid with engine on or running with throttle.
I can move the egr valve manually and the idle changes,but doesnt stumble.
Does this sound like i have a BAD solenoid?
Vehicle in question is 1989 Suburban R2500 454 TBI(2wd),automatic.
Thanks!

Re: Tbi swap build thread
 

Follow up questions:

1) CEL comes on sporadically - which DTC codes are set? Get wire jumper across pins A & B of ALDL and count CEL flashes (groups of 3 starting with 12)

2) If you apply vacuum to EGR valve with a vacuum pump you should see the valve move and there should be some change in idle quality. Too much EGR and the engine should stall. On high millage trucks there is a lot carbon and oily crud build up in the EGR passages restricting amount of exhaust gases reaching intake manifold plenum. The best thing to do is to carefully remove EGR valve and take a small brush and carb cleaner and try to remove, clear the offending crud.

Depending on EGR type you have it may hold vacuum or slowly bleed it of. A blown diaphragm will leak instantly - use a hand held vacuum pump to check EGR diaphragm.

Depending on calibration EGR valve is enabled when truck is in motion and certain other parameters are met. To check for EGR vacuum control side operation I use a vacuum hose and T with a vacuum gauge temporarily mounted on the windshield (duct tape can be used). The vacuum take of point is between solenoid and EGR valve. If you see vacuum while driving - solenoid is supplying vacuum to EGR valve. Check EGR diaphragm first. Check supply vacuum hose as well (between TB and solenoid input).

If you do not see vacuum then I would check ECM control circuit. The EGR solenoid connector should have two wires - pink-black and gray. The pink-blk should have +13.8 Vdc when engine is running (IGN is on). The gray wire is a control circuit - ECM will pulse this line on-off to control amount of EGR. Most DVM's averaging is too slow, but higher end DVM's may have a frequency function and can pick up the PWM waveform. Naturally Oscilloscope is the a weapon of choice!

//RF

Re: Tbi swap build thread
 

At the moment I cant remember the codes,but I do remember it saying the EGR system,check for operation of the valve,check the solenoid,check the plug to the solenoid.
The CEL light comes on at very strange times. I have driven half way to Sacramento(200 miles) with it NOT coming on,then I have driven down the street about 5 miles and it comes on.
I do plan on cleaning out the EGR passage,so a new valve may be in order anyway.

Re: Tbi swap build thread
 

Well, lets get some basic information squared away before jumping to any conclusions. Pull codes - they should stay put in ECM memory unless battery was disconnected. We'll go from there on.

//RF

Re: Tbi swap build thread
 

Code 32 comes up. I checked the pink/black wire at the solenoid,on my DVM it reads 12.01. I dont have a vacuum pump (other than my wife!lol),so I have to draw vacuum the old fashioned way. When I do there is NO movement n the egr valve when the vacuum source(me) is hooked to the manifold side of the solenoid with the key "ON" engine "OFF".

Re: Tbi swap build thread
 

I hooked a vac gauge up to the egr port(between solenoid) and drove it in town and freeway. Vac reading never got above 5" and would stay there for about 10-15sec and then drop to 0.

Re: Tbi swap build thread
 

EGR solenoid acts as a proportioning device - metering amount of vacuum that reaches EGR valve diaphragm. The fact that you see about 5" inch of vacuum between EGR control solenoid and EGR indicates that control circuit is functioning, but EGR valve diaphragm bleeds off vacuum very quickly. Not being a betting man I would say that you may have a leaky EGR diaphragm. You can temporarily connect EGR valve directly to a manifold vacuum port and if there is no movement - it is time to replace EGR valve!

In the absence of the handheld vacuum pump I would take it off and take it to a parts store - most of the time they have handheld pump handy.

//RF

Re: Tbi swap build thread
 

Thank you very much.

Re: Tbi swap build thread
 

An - unrelated question! On your '89 454 Burban you do not have an AIR pump, right? Is it CA or Federal certified (do you know). The reason why I am asking there was a post recently with a question when GM stopped using AIR on BBC TBI trucks.

//RF

Re: Tbi swap build thread
 

It's a CA truck w/A.I.R.

Re: Tbi swap build thread
 

Another question, would a leaky diaphragm also be the reason it will hold 5" for 10-15sec. and then drop off to 0,repeating that over and over. Or is that the way the system operates,open then close cycles?

Re: Tbi swap build thread
 

I basically have a 1991 suburban with a 208 transfer case with speedo cable.

I need VSS instead of the mech. speedo cable

From reading and research it sounds like I have 3 options:

signal generator - plugs into transfer case speedo cable (do I need Electronic Ratio Adapter??)
reluctor ring/speed sensor - plugs into tail housing of tranny
reluctor ring/speed sensor - plug into rear diff.

Can someone explain which would be the best option? I'm still confused here.

Thanks for any helps guys/gals

Re: Tbi swap build thread
 

What about the optical VSS speedometer used in the 87-89 square bodies with TBI? Mechanical speedo with an optical sensor on the back that feeds the ECM data after passing through the DRAC.

Re: Tbi swap build thread
 

???

Re: Tbi swap build thread
 

VSS produces AC wave signal - ECM expects a square pulse (digital like signal). DRAC module is a signal conditioner - multiplier, divider if you will. Another alternative to DRAC is a Dakota digital 'swiss army' knife ratio adapter. Pricey, but very flexible. I would expect a mechanical speedometer cable to turn 1000 times per mile travel - this is how conventional mechanical spedometers operate. But these hybrid early 90's systems are something else - need to refer to FSM to find out. Do not know.... Sorry.

//RF

I hope this helps

Re: Tbi swap build thread
 

This was in reference to fuel pressure regulator???? Or ??

Re: Tbi swap build thread
 

Would this be the easiest/best option? I really didn't consider this because I just finished building/restoring the gauge cluster out of the suburban.

thanks

Re: Tbi swap build thread
 

Sorry, I was meaning the EGR valve diaphram. The vac would rise to almost 10" and then fall to zero then back up to almost 10" and fall again...constantly. I keep getting the EGR system CEL code.
I have not driven my 'burb very much lately since I got my '82 diesel. But none the less I would like to get it fixed. Thanks

Re: Tbi swap build thread
 

This is normal operation of the EGR system. However, I suspect that you may have defective EGR control valve - it is being constantly being pulsed by ECM. Over time the vacuum switch (inside EGR control valve) may have developed an intermittent and just stays in a vent position until it gets its 'marbles' again. The duty cycle and frequency of the EGR control voltage pulse determines how much EGR valve opens and allows exhaust to enter into intake manifold plenum.

//RF

Re: Tbi swap build thread
 

THANK YOU! I will get a new one,but I also plan to remove the EGR valve and make sure the passages are clean/clear.
Thanks again rfmaster! You're the man!

Re: Tbi swap build thread
 

I believe it is. All the gauges other than the speedo from your 91 cluster will fit right into an earlier housing so the work you did is not wasted.

The optical VSS mechanical speedo clusters are pretty cheap and easy to come by too plus the wiring will be just like shown on the stock wiring diagrams for the earlier cable speedo TBI trucks, Suburbans & Blazers. No point reinventing the wheel here when stock parts will do the trick.

Re: Tbi swap build thread
 

not just TBI trucks,trucks with cruse control used a 3 wire buffer that outputs the correct signal,the 3 wire is gm#25007227

Re: Tbi swap build thread
 

Wow, this is a long thread! Lots of great information. I installed a 1991 TBI engine in my '56 Chevy last fall and was successful getting everything hooked up correctly. I'm having one issue though. The car stumbles slightly on acceleration. Tonight I performed some tests on the throttle position sensor. Gray wire is reading 5v, ground wire is good, but the blue wire isn't reading correctly. At idle, I'm not getting any voltage on the meter. I have to move the throttle quite a ways before I get volt reading on the meter and then it jumps up to about +1.6 volts. At full throttle I'm getting about 3.5 volts. From what I've read, I should see about 0.4 to 0.9 at idle and about 4.5 volts at full throttle. I bought a new TPS and got the same results. Any ideas why it's acting this way?

Re: Tbi swap build thread
 

Can you rotate / adjust the orientation of the TPS so it starts reading voltage at idle? Mine have slotted mounting holes to allow you to do this. If not you could slot the holes on yours to give it this capability.

Re: Tbi swap build thread
 

I thought about that, but it wouldn't help. If I test the sensor off the TBI and rotate it with a screw driver, it doesn't make much difference. The WOT reading is a little higher, but I still have to rotate it a little to get any voltage reading at all.

Re: Tbi swap build thread
 

That's odd to say the least. You should be getting voltage on Pin B (TPS signal) at all times (while ignition is on). The best explanation I can offer is that TPS sensor has a defect. It is not uncommon for a high mileage TPS to wear-out a certain potion of the potentiometer - aka TPS.

From your description you have a newer style TPS unit - with a slot (AC-Delco 213-895) vs. vertical level arm (AC-Delco 213-3859). Both types, electrically, should provide continuous voltage output at idle (between 0.3 to 0.9 Vdc) without any change in the throttle position. I would start by replacing TPS with another one.

//RF

Re: Tbi swap build thread
 

I already tried a new TPS and got similar results. I need to check the specs on my multimeter and see what the range is. May not read that low.

Re: Tbi swap build thread
 

Hmmm, if your DVM has a 20 volt range it should be able to read idle voltage. Alternatively, disconnect harness connector from TPS, switch DVM to read resistance and measure resistance between A & B and B & C. I always screw up these values that you should see (going from memory), but at idle A & B (black & blue) should read about 1.3 to 2.0 kOhm and B & C (blue to gray) should read between 6.5 and 7 kOhm and between A & C should be around 6.15 kOhm (verified) with TPS mounted on the TB (throttle shaft is engaged into TPS wiper arm slot.

Getting further into this problem I pulled one of these later model TPS sensor from my storage bin and sure enough if there no tension applied by the throttle shaft on the TPS rotor slot the DVM reads infinite resistance! So I can safely confirm that what you are seeing is no fluke. What needs to happen is that some rotational displacement must be provided by the throttle shaft to move TPS wiper arm coupler from its absolute minimum travel position. Playing with screwdriver and DVM, here at bench, it appears to be a very tiny amount of TPS wiper arm rotation. The two TPS mounting holes provide some slop - I would try turn TPS body about shaft centerline until correct TPS values are observed.

//RF

Re: Tbi swap build thread
 

OK, false alarm. It was the meter. With another meter with a lower range, I'm reading .54v at idle and 4.5 volts at WOT. The voltage increases smoothly as I move the throttle. So, the TPS is working as it should.

On to my next question, which is regarding the EGR valve. I don't think it is functioning. I performed the following tests, which I found on another forum. My results are in red.

Shut the engine off and connect the tester directly to the EGR valve. Pull vacuum (around 15 inches is plenty) and be sure it holds for a minimum of 20 seconds. If it does not build or hold vacuum, the valve could be held open by a chunk of carbon, which you could attempt to clean out – but most likely, the valve is bad and needs to be replaced. With vacuum applied, valve held open for well over 20 seconds.

If the valve passes the hold test - with vacuum still showing as holding on the tester, have a helper start the engine while you watch the gauge. The vacuum should bleed off immediately. Vacuum bled off when engine started.

Determine whether the EGR passages in the intake are clogged by carefully depressing the EGR diaphragm with your fingers. Take care to not burn your fingers or get them caught in the openings under the EGR. When you press the diaphragm, the engine should stumble noticeably, and possibly stall. If there is little or no response, the passages in the intake are likely clogged with carbon. Effective cleaning of these passages requires removal of the intake manifold. This is a recently rebuilt engine, so I know the passages are clear. When manually actuated, the engine did stall.

Check the vacuum source to the EGR solenoid. Connect a vacuum tester (Mityvac) to the line leading from the TBI unit to the front (single port) side of the solenoid. There should be full vacuum at idle, around 20 inches/Hg on a stock engine. If not, remove the line from the TBI and connect the tester directly to the TBI to verify vacuum. If none, the port itself may be clogged. Vacuum read 22 in/hg at idle.

Reconnect the line from the TBI to the solenoid and move the tester to the line exiting the rear of the solenoid. At idle there should be NO vacuum reading (be sure you purged your gauge if necessary so that it reads zero before connecting.) Snapping the throttle should show some activity on the gauge as the solenoid briefly commands the EGR open. DID NOT pass this test. Vacuum gauge needle did not move at all.

With the meter set on ohms, you can test the EGR solenoid coil across the two pins in the socket; any reading less than 20 ohms indicates a bad solenoid winding. Reading was 43 ohms.

With the meter set on DC voltage, or using a test light, check the EGR solenoid harness terminal A (pink/black) to ground. Key on, meter should read 12V or the test light should light up. Do not pierce the wire to test, simply unplug it and touch the test lead to the connector pin. Meter read 12.36v.

So, from these results, it appears that the EGR valve itself is not the problem. However, the solenoid may or not be working correctly or it may not be receiving a signal from the ECM. Any thoughts on this one? Do you know of any other tests I could perform on the solenoid before I go buy a new one?