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General Category => Tech - Help Area => Engine-Driveline-Wheels-Tires => Topic started by: MrC. on October 01, 2018, 11:25:39 PM

Title: TBI
Post by: MrC. on October 01, 2018, 11:25:39 PM
So this weekend was Dually Day,
Started off with a complete rebuild of my TBI, it was dirtier than I thought,
I have a 1994 HD short flat Bed.454. turbo 400 w/ OD

I installed a new key cylinder, which wasn't hard just get the right tools, a steering wheel puller and a plate pusher thingy. I dont know whats its called but I own one now.

I bought the rebuild kit from amazon, very nice kit everything worked perfect except the base gasket, the kit was for the 350 tbi not our 454, keep that in mind. after the rebuild and new fuel filter installed I t'ed in a pressure gauge, I found that you can unscrew the factory "adjuster" in the non adjustable fuel pressure regulator, I craned it downward about 5 revolutions. running at Idle I have 52# of fuel pressure with stock pump, when I floor it no load it drops to 32# then raises back up when I let off, this seems good. I have not installed the new vortec pump that  I bought, I an impress with these numbers unless someone here says otherwise.

I installed a small 2.25 tach, cold she idles at 1100-1200 and warm 850-950, which seems a little high but not to bad.
I found that my knock senor is busted and not hooked up, but I do not seen any code being thrown, so I will address that asap.
I would like to lower the idle, not sure about drilling out the plug and using the torx bit or tweaking the TPI and doing it that way any thoughts?

Over all the day was a huge success, It feels a lot more peppy after the rebuild. ( I used carb cleaner and gasoline) the IRC i left installed and cleaned the underside, you can see the spring and plunger, mine was stuck, i freed it, cleaned it, lubed it now you can move it in and out with your thumb)

I also installed my chain box. this was a 3.5 foot box, but I only have room for a 2.5 foot box, so I chopped it down to fit. Damn I am cheap.

Off to get some tires.
Title: Re: TBI
Post by: ED-NY on October 01, 2018, 11:40:10 PM
You mentioned TPI  but I suspect you were referencing the throttle body.  Instead of trying to explain the this guys video:

Check base timing first....
Title: Re: TBI
Post by: MrC. on October 02, 2018, 09:24:37 PM
I was thinking of doing it this way?

Title: Re: TBI
Post by: ED-NY on October 04, 2018, 04:47:37 PM
Give it a try...if it makes no difference, remove the IAC, clean and compress the pintle and re-install it...then try the first video.

But first check the base timing and adjust the TPS voltage within closed throttle plate range.
Title: Re: TBI
Post by: MrC. on October 05, 2018, 09:14:34 AM
Thanks for the help ED-NY

I have my base timing ( tan wire disconnected ) at 4 degrees BTDC.
I will follow that video and get my base idle as you have suggested.

Q. With my fuel pressure is at 52 psi running at idle, then dropping to 32 psi at full throttle with no load, do you think I should not change my fuel pump to the vortec high pressure pump? I have bought it and a new sock, but was thinking of returning it, since my pressure numbers looked good to me.

Would the high pressure pump be better? could it maintain high pressure while full throttle no load?
its a $60 question, keep and change it, or return it? I can tell a difference after the rebuild/filter/F.P.R. being adjusted.

Also, Amazon has some great prices on 225/70/19.5 tires,  14 ply drive tires.
I am sure they are not as good as goodyear but for me, they should work fine.

Thunderer Drive All-Season Radial Tire-225/70R19.5 127M
by Thunderer
Be the first to review this item 
Price:   $139.00 & FREE Shipping

Title: Re: TBI
Post by: MrC. on February 06, 2019, 10:32:04 AM
So things have been so much better after the tbi rebuild and vortec hi volume fuel pump, it starts better, has way more power, runs smoother. cold fast idle is 1200rpms and warm idle is 1000. in drive with foot on brake is 850rpms.

So now only two issues- fuel mileage this last tank was 5. thats right 5 mpg, it smells rich at idle, no smoke, no loading up, no stumbles, runs great. Could my 50psi fuel pressure be to much for the injectors? could that make it run rich? I have replaced the TPS, I cleaned the IRC. along with the a full rebuild of the TBI. I replaced everything from the fuel pump, sock, filter, rebuilt TBI, replaced TPS, MAP, Temp, O2 sensor. NO codes or lights.

I also replace everything from a new distributor to new plugs on the electric side of things.
what am I missing?

Title: Re: TBI
Post by: someotherguy on February 06, 2019, 01:29:34 PM
I honestly have no idea what amount of pressure the TBI's regulator is capable of dropping, but since the spec on the 94-95 7.4 is 26-32 psi I'd say the Vortec pump is probably too much for it.  Vortec spec being 58-62 psi and you'd figure the pump is capable of more than that if 62 is the high end of the spec...

Title: Re: TBI
Post by: ED-NY on February 07, 2019, 07:01:45 AM
I realize the idle goes up and down..but I would also make sure the truck is going into "closed loop" after warm up. 
Title: Re: TBI
Post by: MrC. on February 07, 2019, 11:40:12 AM
Hi Ed,
How would I verify it is going into closed loop? Without a ODB1 scanner
The website that recommended the high volume pump  was very specific with the part number, and even talked about the 3500HD's had smaller injectors but higher pump pressures from the factory.
I have 52 psi running and under full thortle in park (stomp and let off) not loaded moving.
I can adjust the fuel pressure regulator by backing off the screw and jam nut in the TBI. to decrease the pressure if you think that it is over powering the injectors.

Title: Re: TBI
Post by: ED-NY on February 07, 2019, 05:00:11 PM
Since it's running rich..I would get a scanner on it to make sure it's going into closed loop..that way you can view the data stream to verify that the O2 sensors, engine temp signal etc are performing properly.  You need to locate an OBD scanner to verify... I have an OTC Nemisys that does both OBD1 and OBD2.