Should i fix the TBI or go to carb? And what's this wire?

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

AuroraGirl

Full Access Member
Joined
Sep 8, 2019
Posts
9,693
Reaction score
6,869
Location
Northern Wisconsin
First Name
Taylor
Truck Year
1978, 1980
Truck Model
K10, K25
Engine Size
400(?), 350
Yes, i did. All are fine
if its on the thermostat housing or next to it, then false
And if its onl the original grounds, almost certainly false. GM was shy with grounding and any corrosion and resistance puts them in the not-enough category. lol
 

Bextreme04

Full Access Member
Joined
May 13, 2019
Posts
4,439
Reaction score
5,581
Location
Oregon
First Name
Eric
Truck Year
1980
Truck Model
K25
Engine Size
350-4bbl
This sounds exactly like poor/corroded connections. Do you have new power and ground cables on it from the battery? Have you been running continuity checks on the wires? Voltage drop checks? Continuity check will tell you if you have a good connection, voltage drop will tell you whether you have ENOUGH of a good connection. If you don't have enough of a good connection, you could be dumping voltage spikes through the system and back feeding through into other systems
 

DoubleDingo

Full Access Member
Joined
Jul 3, 2012
Posts
11,256
Reaction score
17,197
Location
Right where I am
First Name
Bagoomba
Truck Year
1981
Truck Model
81-C20 Silverado Camper Special-TH400-4.10s
Engine Size
Carb'ed Vortec 350
This sounds exactly like poor/corroded connections. Do you have new power and ground cables on it from the battery? Have you been running continuity checks on the wires? Voltage drop checks? Continuity check will tell you if you have a good connection, voltage drop will tell you whether you have ENOUGH of a good connection. If you don't have enough of a good connection, you could be dumping voltage spikes through the system and back feeding through into other systems
Reading this reply says a lot. Not related the OP's issue, but it probably explains why my speedometer on my jeep acts wonky. It's been hit and miss for a couple years now, and new VSS usually works normal for a few weeks at best. Right before T-Day I cleaned a bunch of connections, took it for a test drive and it worked perfectly. The next morning fired it up and the speedometer went to 85 mph while we sat there in the driveway! I will be checking connections now, instead of just cleaning them.
 

AyWoSch Motors

The Parts Guy
Joined
Nov 6, 2020
Posts
4,690
Reaction score
13,692
Location
New Mexico
First Name
Ayden
Truck Year
1986
Truck Model
K1500 Sierra
Engine Size
350ci V8
Before anyone gets upset or says 'that was stupid', id like to say, i have no personal issues with TBI. I respect it. I have many GMT400s that have TBI and they run very well. No complaints.
I also have alot of patience with solving problems. Will usually spend alot of time to do things "the right way".
This truck has used that up.

I thank you to everyone who has attempted to help repair the old system, and i may very well use that info on something else down the road.

today I decided im am no longer going to attempt to fix this nightmare fuel injection, and instead have solved my issue another way....
 

AyWoSch Motors

The Parts Guy
Joined
Nov 6, 2020
Posts
4,690
Reaction score
13,692
Location
New Mexico
First Name
Ayden
Truck Year
1986
Truck Model
K1500 Sierra
Engine Size
350ci V8
I bit the bullet and said "Bye bye TBI, hello carburetor!"
Problem solved. A least that part of it.
You must be registered for see images attach
You must be registered for see images attach
You must be registered for see images attach
 

AyWoSch Motors

The Parts Guy
Joined
Nov 6, 2020
Posts
4,690
Reaction score
13,692
Location
New Mexico
First Name
Ayden
Truck Year
1986
Truck Model
K1500 Sierra
Engine Size
350ci V8
After a good cleaning, and a dry fit of the intake.
Looks like its going to go well.
You must be registered for see images attach
You must be registered for see images attach
 

Redfish

Full Access Member
Joined
Nov 6, 2021
Posts
2,658
Reaction score
14,316
Location
Prairieville, LA
First Name
Andrew
Truck Year
1987
Truck Model
V1500
Engine Size
350/5.7
While I was really hoping you would get this fixed...I know exactly where the original air filter housing, the plastic snorkel and any vacuum hoses associated with the EGR valve need to go.

;)
 

AyWoSch Motors

The Parts Guy
Joined
Nov 6, 2020
Posts
4,690
Reaction score
13,692
Location
New Mexico
First Name
Ayden
Truck Year
1986
Truck Model
K1500 Sierra
Engine Size
350ci V8
While I was really hoping you would get this fixed...I know exactly where the original air filter housing, the plastic snorkel and any vacuum hoses associated with the EGR valve need to go.

;)
You want any of that or just the entire setup, let me know..
 

JoeFox

Junior Member
Joined
Jul 16, 2022
Posts
1
Reaction score
2
Location
Coos Bay, Oregon
First Name
Joe
Truck Year
1987
Truck Model
R30 Silverado Western Hauler
Engine Size
454
When you think you've checked everything, take the computer out and have it checked or just replace it.
I have an '87 r3500, when I got it the fuel system was completely torn apart. I put it back together and it turned out all that was wrong with it was the computer.
 

AyWoSch Motors

The Parts Guy
Joined
Nov 6, 2020
Posts
4,690
Reaction score
13,692
Location
New Mexico
First Name
Ayden
Truck Year
1986
Truck Model
K1500 Sierra
Engine Size
350ci V8
Well the install went well, no issues.
Got everything hooked up and on. Figired up all my fuel lines, vacuum lines, as pcv hookups. Filled the bowl on the carb and stated it up.
It runs!! Ran for about 30-40 seconds, sounded great. Nice and smooth. Happy i went with carb.
No i just have to figure out the electric pump and put it back together.
You must be registered for see images attach
You must be registered for see images attach
You must be registered for see images attach

Here are some homemade wedge washers i made for the bolt pattern angle difference, and how they worked out...
You must be registered for see images attach
You must be registered for see images attach
 

bucket

Super Moderator
Staff member
Super Moderator
Joined
Aug 3, 2010
Posts
30,446
Reaction score
28,356
Location
Usually not in Ohio
First Name
Andy
Truck Year
'77, '78, '79, '84, '88
Truck Model
K5 thru K30
Engine Size
350-454
Well the install went well, no issues.
Got everything hooked up and on. Figired up all my fuel lines, vacuum lines, as pcv hookups. Filled the bowl on the carb and stated it up.
It runs!! Ran for about 30-40 seconds, sounded great. Nice and smooth. Happy i went with carb.
No i just have to figure out the electric pump and put it back together.
You must be registered for see images attach
You must be registered for see images attach
You must be registered for see images attach

Here are some homemade wedge washers i made for the bolt pattern angle difference, and how they worked out...
You must be registered for see images attach
You must be registered for see images attach

Very nice work on the wedge spacers!
 

Hunter79764

Full Access Member
Joined
Sep 1, 2021
Posts
344
Reaction score
531
Location
Grand Prairie, TX
First Name
Shawn
Truck Year
1987
Truck Model
Suburban V20
Engine Size
350
You have a reliable pump and return system with the factory TBI stuff, use it. Put a bypass regulator up front for 4 psi or whatever is needed on your carb, return through the stock return line, and you're set. Worst case when you remove the computer etc, you may need to run a new ignition wire to the fuel pump relay. I can't remember on this setup, but if the fuel pump relay circuit goes through an oil pressure switch, I'd keep it there, good safety margin.
 

AyWoSch Motors

The Parts Guy
Joined
Nov 6, 2020
Posts
4,690
Reaction score
13,692
Location
New Mexico
First Name
Ayden
Truck Year
1986
Truck Model
K1500 Sierra
Engine Size
350ci V8
You have a reliable pump and return system with the factory TBI stuff, use it. Put a bypass regulator up front for 4 psi or whatever is needed on your carb, return through the stock return line, and you're set. Worst case when you remove the computer etc, you may need to run a new ignition wire to the fuel pump relay. I can't remember on this setup, but if the fuel pump relay circuit goes through an oil pressure switch, I'd keep it there, good safety margin.
Pump that was in it crapped the bed.
 

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
5,458
Reaction score
8,717
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
But a good factory intank pump and a holley 12-881 regulator is better than just about any other pump you can buy. I've tried almost all of them. Mr gasket 12s on a burb, life expectancy here to stuck 100 miles from here. Unknown pump 85 c10 DOA. replacement airtex lasted 2 weeks. Facet pump worked longest but still died way before my intank pumps have died. Best thing about the facet was it didn't leave me stuck,I could smack it with a wrench and it would start working again. In fairness to the airtex pump,when I called Airtex they told me Rockauto is not an airtex distributor so if they sold me the pump it was overstock from who knows where. The older pumps won't tolerate the ethanol in the fuel. The airtex I replaced it with is working fine,but I did get crazy creative on the install to make sure it could never start dry.
 
Last edited:

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
5,458
Reaction score
8,717
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
I'm sure the next question is going to be how did I install it. I installed it on a bracket by the tank but lower. pump inlet side I used the biggest metal filter I could find mounted vertically so it acts as a reservoir. Pump outlet I put a hot wheels style loop in the fuel hose so the pump is always full of fuel. Pump is angled outlet side slightly up like 10 degrees. A loop in the fuel hose just like a hot wheel track but only about 6" in diameter.
You must be registered for see images attach
 

Forum statistics

Threads
44,182
Posts
950,986
Members
36,305
Latest member
KennedyGS
Top