How to troubleshoot your TBI fuel injection system?

Troubleshooting your TBI Fuel Injection System Most of the problems encountered while installing your fuel injection system or after a time of operation are very simple. If your check engine light is on you more than likely have a hard fault meaning something is grounded out, unplugged, operating out of range or has gone bad. See

What are the specs for a TBI crate engine?

4. The cam in the TBI engine is just plain AWFUL. Specs on Stock TBI cam is .050″ tappet lift (intake/exhaust) is 165/175; and maximum lift with 1.5:1 rocker ratio (intake/exhaust) is .382/.402. I got those specs right off the Jegs website selling the new GM replacement TBI crate engines.

What should the air flow be on a 350 TBI?

On the average 350, I like a intake runner in the 165-180cc range and I like my air flow at.500″ lift to be at least the 225cfm that a vortec head flows. Stock TBI head flows around 175cfm.

What kind of Head do I need for a 350 TBI?

Another good reasonably priced set of heads that will work nicely without special intakes on a TBI motor is a set of Summit Racing aluminum heads. Great flow number and stock TBI or aftermarket TBI intakes will bolt right on saving you some money. 50 state legal and better flow numbers than vortec heads.

How does the TBI fuel injection system work?

Your TBI fuel injection system fueling is “triggered” from the ignition system. It is assumed that the coil is operational, a 12 volt ignition 1 (IGN1) source is connected to the positive terminal of the coil for external coil applications or to the positive slot for coil in cap applications. Remove plug wire and check for spark while cranking.

What should the fuel pressure be on a 350 TBI?

From 370-440hp you need to bump the fuel pressure up on the 454 injectors to the 15-18psi to increase their flow rate to 100lb/hr.

How do you install a HEI distributor on a Chevy 350?

Unless the location of TDC is known, the HEI distributor cannot be installed and timed properly. Raise the hood of the vehicle and remove the fuel pump fuse. Use a socket wrench to unscrew the number one spark plug. On the Chevy 350 engine, as you face the engine, this is the right front spark plug.

Why is there no fuel spray from injector?

On the way home it stopped and hasn’t run for weeks now. There is fuel and pressure at the injector but no spray. There is a red wire and blue wire there. The red has 12 volts, the blue is supposed to pulse on cranking. It does not pulse.

What kind of fuel injector does a throttle body have?

The throttle body assembly is equipped with 1 (4-cylinder engines) or 2 (V6 engines) electronic fuel injectors in order to supply fuel to regulate the air/fuel mixture. All fuel injection and ignition functions are regulated by the computer control module, which is sometimes also referred to as the ECM, PCM or VCM.

Why is my fuel injection system plugged in?

The electric fuel pump installed for a fuel injection system will draw considerable more volume of fuel from your tank than your old system did. If there are any contaminants in the tank this many times will plug up or greatly restrict the flow of fuel to the system causing many issues. Step by Step Troubleshooting guide.

Do fuel injectors need periodic cleaning?

Blockage in the fuel injectors might affect vehicle performance. Periodic fuel injector cleaning might be an ideal choice to boost vehicle performance. It also helps to increase the mileage and keep the vehicle running for long. You need not deal with the terms like lower fuel economy in the future with regular cleaning.

How do you clean throttle body injectors?

Spray the injector or injectors with throttle body cleaner, and gently clean the exterior and the tip of the injector with the brush. Do not insert any metal objects into the tip of the injector, as this will enlarge the nozzle tip, permanently damaging the injector.

What is the function of a fuel injector?

The function of a fuel injector is to spray atomized fuel into the combustion chamber of an internal combustion engine. Fuel injection became the primary fuel delivery system in automobiles starting in the mid-1980s.

What do fuel injectors do?

Fuel injectors are parts of modern car engines that deliver fuel to the engine’s combustion chamber, directly or indirectly. These small electro-mechanical devices are typically positioned at a certain angle to make sure the fuel is sprayed towards the engine’s inlet valve or directly into the cylinder.

When to change the TBI pump in a car?

Nice thing about the Actron gauge is the hose is long enough that you can watch it while you drive. If the fuel pressure drops more than 1 psi under 8-10 seconds of full throttle the pump should be changed and dont put the stock TBI pump back in even if your engine is stock.

Why does my GMC TBI not start up?

That could be because either the IAT or ECT is reading too high. Since this has a MAP sensor, I assume it does not have a MAF sensor. You should get an ohms reading from the coolant temp sensor (two wires) and the intake air temp sensor. These specifications are from a 1993 light truck fuel & emissions manual.

Can a TBI be used as a return line?

These fittings are not suitable to use as a return line because they have an orifice in them and restrict the flow of fuel back to the tank. If you have installed your return line to a “vent” line you will need to route the return line in a different fashion. Fuel pressure on a TBI unit should stay constant under all throttle conditions.

Why does my fitech fuel pump not start?

Many times the engine will not start after a longer run and then letting the truck set for a while. It will eventually start after waiting and cranking and waiting and cranking…. not a real dependable situation. Today I had to call the tow truck…again! I drove to the store and came out and would not start.

Can a lack of fuel cause a car to not start?

CASE 1: If the engine started and ran for a few seconds: This means that the reason your pick up (or SUV) is not starting is due to a lack of fuel. Now that you have confirmed that the ‘no start’ problem is due to a lack of fuel, you now need to actually confirm how much pressure the fuel pump is producing with a fuel pressure gauge.

Where to spray starting fluid on GM TBI fuel system?

Spray starting fluid down the bore of the throttle body. When you have sprayed a good squirt of starting fluid, quickly place the air filter assembly’s cover back on. IMPORTANT: Placing the cover back on the air filter assembly is important because it’ll prevent any back-fire, that may occur, from spouting flames out of the throttle body.

What is the TBI code on a 1990 Chevy truck?

Consult a service manual or see below for any check engine light code definitions. You can use a late 80’s or early 90’s GM TBI definition. If you have access to a scan tool use a hook up for a 1990 350 cu. in. 5.7L Chevrolet truck. For some scan tools enter VIN 10th“L” 3rd“C” 8th“K”.

How to fix a 1990 Chevy 5.7L TBI fuel problem?

It ran long enough to drive up on the trailer while under its own power and it also drove off the trailer on its own power (not that same day I brought home) but you did have to keep foot on throttle otherwise it would stall out and not start again until the next day. 1. New Fuel pump 2. New Fuel filter 3. New Fuel pump relay 4.

Can you change the throttle body on a 350 TBI?

Modify the throttle body. This one pretty cheap but does require removing the throttle body. UTIMATE MODS . Stock 42mm TBI units flow around 450cfm which if you look at http://www.carburetion.com/calc.asp a stock 350 even with a cam upgrade to increase the powerband to 5500 rpms isn’t going to use much if any more than that stock throttle body.

Why does my Chevy 350 TBI idle at 800 rpm?

When i drive on the highway it does fine after i get off the highway the idle is at 800 rpm then wants i get in the city that’s when the idle goes up on short distance go and stops. I have changed IAC,TEMP SENSOR, EGR VALVE and SOLENOID, TPS, I have checked hoses for leaks and gaskets.

What kind of diagnostic tool do I need for GM TBI?

The ALDL connector allows for full diagnostics of your unit. A scan tool can be used and set up for a GM TBI application to read the data, or to check for stored codes. Consult a service manual or see below for any check engine light code definitions. You can use a late 80’s or early 90’s GM TBI definition.

Where does the vacuum leak come from on a TBI?

There are instances where the vacuum leak is coming from the adapter plate used to attach the throttle body to the manifold. If this is the case make sure that the seal is positive between the manifold and the adapter plate; also between the adapter plate and the throttle body.

What kind of scan tool do I need for GM TBI?

A scan tool can be used and set up for a GM TBI application to read the data, or to check for stored codes. Consult a service manual or see below for any check engine light code definitions. You can use a late 80’s or early 90’s GM TBI definition. If you have access to a scan tool use a hook up for a 1990 350 cu. in. 5.7L Chevrolet truck.

What causes a fuel injection system to leak?

First and foremost the engine and fuel injection system must be free from vacuum leaks. Vacuum leaks are the leading cause of installation issues with your fuel injection system. Check all sources of potential vacuum leaks including components not related to the fuel injection

Why is there no pulse from the injector?

Used all original electronics and tbi. New wires, plugs, cap, rotor, fuel filter,etc… have spark, have fuel at the back of the tbi. No pulse at all from either injector?

Is there no fuel from injectors to start truck?

No fuel from injectors to start truck. When I try and start my 93 Chevy Cheyenne k3500 no fuel come out of the injectors. If I use starting fluid the truck starts and the injectors work great. Has died a couple times while driving, but mostly runs fine and then won’t start one turned off.

Why does my TRCK not start without starting fluid?

What? well my trck will not start up unless i spray some starting fluid in the tbi, but one its on on it runs great with no problem. i just changed my fuel filter, injector and did a tune up on it what can it be. Click to expand… fuel pump man, these things quit alot… has the truck sat for a while?

What causes a vacuum leak in a fuel injection system?

Vacuum leaks are the leading cause of installation issues with your fuel injection system. Check all sources of potential vacuum leaks including components not related to the fuel injection system. There are instances where the vacuum leak is coming from the adapter plate used to attach the throttle body to the manifold.

What are the symptoms of a bad fuel injector assembly?

Symptoms Of A Bad ‘Spider’ Fuel Injector Assembly. The most common type of failure (related to the ‘Spider’ fuel injector) is usually not the assembly itself going bad, but the fuel pressure regulator going bad. The fuel pressure regulator is infamous for leaking fuel from its vacuum inlet nipple.

Can a bad fuel injector cause a Chevy Silverado to blow?

Less Fuel Mileage – Your Silverado’s engine management computer is constantly adjusting the air/fuel ratio and timing to get optimal combustion. When the fuel injectors aren’t working properly it can’t do that and fuel mileage suffers. Knock/Detonation – Detonation can cause your Silverado’s engine to blow.

How to troubleshoot the’spider’fuel injector assembly?

TIP 1: You’ll need a fuel pressure gauge to troubleshoot the fuel injector assembly on your GM 4.3L, 5.0L or 5.7L pick up (van, mini-van, SUV). TIP 2: You’ll be working around fuel (gasoline), which is extremely flammable. Your safety is your responsibility… so be careful, use common sense and think and act safety all of the time.

What causes a Honda Jazz fuel injector to leak?

Leaking fuel injectors are often caused by a bad a crack in their body. When this occurs they must be replaced. If the injectors are clogged you’ll need to have them cleaned by a professional. When they are dirty but not yet clogged, you may be able to clean them with a good fuel injector cleaner.

What’s the difference between CPI and CSFI fuel injection?

If you don’t know whether you have a CPI or CSFI system, you can find out the difference between them by checking out the info in this subheading: ‘Spider Fuel Injection Basics’ found in this tutorial: How To Test The ‘Spider’ Fuel Injector Assembly (4.3L, 5.0L, 5.7L). Connect your fuel pressure gauge to the Schrader valve.

Can a fuel pump cause a no start condition?

CASE 1: If your fuel pressure gauge read 50 PSI or more as the engine cranked. This means that the fuel pump on your 4.3L, 5.0L, or 5.7L is OK and not the cause of your No Start Condition. The next step is to observe the fuel pressure gauge’s needle (after your helper stopped cranking the engine).

What’s the problem with throttle body fuel injection?

The problem with TBI is that it isn’t very precise: Like the carburetor, it can’t adjust for the needs of individual cylinders.

What should I use to test my fuel pump?

In this fuel pump test, you’ll use starting fluid (or carb clean spray) to see if the fuel pump is not delivering enough or any fuel to the engine. Now, let me tell you that this is not the most accurate way of testing the fuel pump but it doesn’t mean it’s not effective.

Can a carburetor be replaced in a TBI engine?

While it works fine for stock applications, the fact is that General Motors’ Throttle Body Injection (TBI) system is a nightmare for modified engines. Though it is possible to replace the injectors and throttle body, and to reprogram the computer, many find it simpler to “down-grade” to a carburetor setup.

Is there an injector pulse while cranking the engine?

The engine will run if you either spray starting fluid down the throttle body or hook up a remote start switch. If you use the key, there is no injector pulse while cranking. As you let go of the key and return it to the run position, the injectors give one squirt.

What happens if the fuel injector is not working?

Fuel injectors are a vital part of a complex fuel management system. Furthermore, New technology has made fuel injectors more precise than ever in dispensing fuel. If the fuel injectors are not operating properly, then other parts of the engine will be affected as well.

Why is my GMC TBI not running at idle?

It is no fun to get to the plug on these models, let alone screw in a compression tester. The injector pulse is not much and basically there is a straight down spray out of the injectors and no cone pattern when it runs for 2 seconds total or so. Sometimes it will try to run for 7 or eight seconds, rpms going up and down till it stalls out.

How many inches of vacuum stock does a TBI use?

Hook it to all ports on that throttle body. When you get to the map port just move map to a different port on the throttle body. Typical TBI motor will idle with 20-21 inches of vacuum stock. Pretty much any of the cams I recommend or have listed on the website will pull at least 17-18″ of vacuum at idle.

How does the TBI system work on a car?

TBI being a MAP sensor based system will see the leak just like opening the throttle blades and will feed the leak and then you have a high idle. Finding the leak can be tricky as it can be the intake gasket on the bottom side if you are using a Chinese junk carb intake or you weren’t real careful putting the intake on.

How does idle air control work in a GM TBI?

The air gap between the throttle body and the throttle plate is calibrated to allow enough air to pass by it for the engine to run at base idle speed. The IAC (Idle Air Control) valve utilizes the on-board computer to fine tune the idle speed according to engine conditions.

How to reset the baseline idle speed in a GM TBI?

Turn the screw to adjust the idle speed to 650 RPM +/- 50 RPM. Turn off the engine and disconnect the negative battery terminal from the battery using a wrench. Reconnect the IAC valve. Reinstall the air cleaner and remove the paper clip from the ALDL connector. Reconnect the battery terminal after 5 minutes and test drive the vehicle.

How does the GM TBI fuel injection system work?

The GM TBI (Throttle Body Injection) system uses a pair of low pressure fuel injectors mounted above the throttle body opening. Unlike a port fuel injection system, that sprays fuel into the intake manifold runner just above the intake valve, the injectors in this system spray fuel directly into the throttle body above the throttle plate.

What are the symptoms of a bad fuel pump?

Symptoms Of A Bad Fuel Pump. Where To Buy The Fuel Pump And Save. TEST 1: Using Starting Fluid. TEST 2: Fuel Pressure Test With Gauge. Which And Where To Buy A Fuel Pressure Gauge. More GM 4.3L, 5.0L, 5.7L Tutorials. You can find this tutorial in Spanish here: Cómo Verificar La Bomba de Combustible en Los Sistemas TBI (at: autotecnico-online.com ).

What should fuel pressure be on a TBI fuel injection system?

Fuel Pressure is critical to the operation of a fuel injection system. Always check to insure that you have the proper fuel pressure. Fuel pressure should be a constant 10 – 15 PSI on a TBI fuel injection system and is typically around 12 – 13 psi. Higher pressure than 15 psi indicates that there is an issue with the installation.

What should the idle speed be on a GM TBI?

Insert a T-30 size Torx driver into the Idle adjustment screw that is located behind the plug removed earlier. Turn the screw to adjust the idle speed to 650 RPM +/- 50 RPM. Turn off the engine and disconnect the negative battery terminal from the battery using a wrench.

Why is my Check Engine light on after installing fuel injection?

Most of the problems encountered while installing your fuel injection system or after a time of operation are very simple. If your check engine light is on you more than likely have a hard fault meaning something is grounded out, unplugged, operating out of range or has gone bad.

When did TBI chips throttle body injection start?

Welcome to TBI CHIPS throttle body injection services. So Just what is TBI, stands for Throttle Body Injection used by GM in the early 80’s through 1995. The early systems from 1982-1986 are just too old to do much with. 1987-1991 were still SLOW computers with tiny chips limiting what can be done with the system.

What are the symptoms of a bad fuel injector?

Common signs include an odor of fuel in the car, engine performance issues, and the Check Engine Light coming on. 1. Engine misfires and decrease in power, acceleration, and fuel efficiency 2. Fuel odor 3. Check Engine Light comes on Fuel injectors are an engine management component that is found on the vast majority of road going vehicles.

Why does my Chevy truck exhaust smell like gas?

This may be caused by fouled spark plugs, faulty ignition wires or malfunctioning ignition system components. Excessively rich fuel mixture. Proper burning of fuel requires the right proportions of fuel and oxygen. If the vehicle fuel system delivers too much gasoline, there will not be sufficient oxygen in the mix to burn it all.

Why is my Chevy Vortec 4300 V6 leaking fuel?

In the L35 and LF6 engines, the spider injectors are known to leak at the pressure regulator and at the supply and return lines due to a design fault. Outside of leaking fuel onto the exterior of the engine itself, it can cause excess fuel to get sucked into the engine.

Why does my Chevy truck smell like gasoline?

If fuel is taken into the engine but fails to burn, it will give a gasoline odor to the exhaust. Faulty ignition components such as spark plugs, ignition wires, or distributor components may cause ignition failure. One or more cylinders on your Chevy truck might not be firing — meaning that fuel’s going in but not burning.

The engine may still crank when the key is turned, however it will not be able to start due to lack of fuel. This symptom can also be caused by a wide variety of other issues, so having the vehicle properly diagnosed is highly recommended. 3. No noise from the fuel pump

Can a stalling engine be intermittent driveability?

Intermittent driveability problems of any kind are always a challenge to diagnose. When a customer brings you a vehicle and complains of a stalling problem, you may not have much to go on other than their description of what’s happening and when it happens.

What kind of TBI is used for throttle body injection?

2. Throttle Body Injection = TBI The 4.3, 5.0 and 5.7 TBI’s are all the same CFM with 1 11/16th bores. The injectors are different sizes. The 454 is larger with close to 2 inch bores. It is recommended a TBI from about the same size engine to be used in your conversion or larger for high performance built engines. 3. TBI Wiring Harness.

What kind of EFI system do I need for a TBI engine?

TBI Fuel Injection Conversion using a GM TBI EFI system! One of the most popular EFI conversions to older Chevy engines or any engine for that matter is the GM TBI system using the 1227747 ECM.

How to remove Idle Stop cap from a GM TBI?

On a factory TBI unit the idle set screw will be capped from the factory so you cannot mess with it. But you just knew one day you would. Not all caps look like the one pictured but this is the one that is hardest to remove. The easiest way is to first grind the cap flush with the surface of the throttle body.

How much horsepower does a TBI fuel pump support?

First I start with a new Fuel pump, STOCK 75lph TBI fuel pump will only support about 230hp before the fuel pressure drops like a rock.

On the average 350, I like a intake runner in the 165-180cc range and I like my air flow at.500″ lift to be at least the 225cfm that a vortec head flows. Stock TBI head flows around 175cfm.

Why does my TBI die at idle when warm?

With 160K on the TB it was time for a rebuild and good cleaning. The throttle body has been rebuilt with new injectors, fpr, and orings. The idle is not high. It fluctuates and sometimes it cant recover from the drop in rpms and dies.

Can you use the original TBI on a 350?

You can’t use the original TBI. People use this term as like your Stage 3 cam, this has no meaning. For a cam it’s specifications that count when trying to figure compatibility. There are two TBI Swirl Port heads used on the 350 one ends with 191 in the casting number the other 193.

How many miles does a GMC TBI 350 have?

Hey guys. So I have a 95 TBI 350 with about 190K miles on it. This started as a surging while driving at constant rpms. Very noticeable in second gear at about 25 mph. The truck has a NV3500 so the whole truck would surge.

Is there a lift up spring on a TBI?

Spring is known to break on them. take the torq screws out of the top of the TBI and lift up regulator is in the back check spring. ill have to check that out, new idea i havent heard yet.

What kind of injector does a Sonoma 88 S10 use?

Compnine also lists the 92 sonoma with a fuel injector as a ACDelco #217-338. On the 88 s10 the fuel injector is a ACDelco #217-336. Thanks for the help. The Throttle bodies look the same, the injectors may have some internal difference, perhaps the 92 has higher fuel pressure, the 88 only has 9 to 13 lb fuel pressure.

What does throttle body dumping lots of fuel mean?

– CarGurus throttle body dumping lots of fuel. 89 4.3 ltr. model 220 TBI dumping waaayyy to much fuel & flooding engine. Could that be the pressure regulator on top. i have a 91 2.8 tbi that was doing that.

How to troubleshoot a 350 cubic engine backfiring?

First, check that the mixture screw (s) on the carburetor are adjusted properly. Most of the carburetors installed on the 350 use a single air/fuel mixture screw, while some carburetors use two.

Are there any TBI 350s that run rich?

I have a 92 tbi 350 that runs rich. I have replaced the m.a.p. sensor, o2 sensor and the computer does not bring up any codes. I don’t know where to look next.

What causes fuel flow on a TBI 350?

You might try looking at O2 sensor output with a dvom, should cycle from approx. .2 volts d.c. to .8. Look at the fuel flow from the injectors with the engine running, shuld look like a fine cone shaped mist, a bad injector can stick open and flow a heavy stream of fuel. A deffective fuel pressure regulator can cause excessive fuel flow also.

Is the TBI 350 running a heated sensor?

Yes the injectors are good. No I am not running a heated 02 sensor, and I welded a bung for the 02 sensor right where the pipes meet for the collector on block hugger headers. I did a tbi conversion: Heads, manifold, distributor, etc… and got everything from the same vehicle.

What kind of signal does a GM injector pulse have?

Purple/white wire with key on had barely any signal at all. Wires to the injectors have 12v with key on. I have fuel at the rear of the tbi but not sure of the pressure?

Where does the injector pulse come from in a truck?

I guess no one reads….injector pulse comes from ecm..via ignition module..pickup coil.Once ecm senses 400 rpm,s from engine it takes over. But injectors pulse works off of ground from ecm…you have to have the grounds at thermostat and intake or will not pulse injectors.Grounds for all sensors.

Do you need a tachometer for fuel injection?

Use of this section may require a digital voltmeter, test light, fuel pressure gauge, timing light, tachometer and/or a diagnostic scan tool. If you are familiar with vehicles and how they are serviced you should be able to work through this section with no issues.

Used all original electronics and tbi. New wires, plugs, cap, rotor, fuel filter,etc… have spark, have fuel at the back of the tbi. No pulse at all from either injector?

Purple/white wire with key on had barely any signal at all. Wires to the injectors have 12v with key on. I have fuel at the rear of the tbi but not sure of the pressure?

What’s the difference between the 88 and 92 injectors?

The Throttle bodies look the same, the injectors may have some internal difference, perhaps the 92 has higher fuel pressure, the 88 only has 9 to 13 lb fuel pressure. I’m on my way to get the noid light now, its noon here.

What causes PCM to disable fuel injectors?

@jrt2020 , Josh, The anti-theft system (Pass Lock) failure will mimic this, as anti theft tells PCM to disable the fuel injectors.

What causes no power to fuel injectors?

The most important signals that determine the accuracy of a signal coming out of ECU to injectors are crankshaft position sensor and camshaft position sensor, so to test a bad injector, you have to check the voltage on the injector when the ignition key is turned on: NO VOLTAGE? , so what causes no power to fuel injectors?

How is the speed of the injector controlled?

The injector in a basic picture is an electronically controlled valve that is supplied with pressurized fuel from the fuel pump at a certain pressure level injector can be electromagnetically opened and closed at very high speed—this speed controlled by the electronic control unit using.

How to test the fuel pump on GM TBI fuel systems?

One method involves removing the fuel filter and using an adapter, that has a Schrader valve on it, in its place. You then connect your fuel pressure test gauge to this adapter. The other method is to use an adapter between the throttle body assembly and the pressure line.

Why is my GM fuel pump going bad?

In this tutorial I’m going to show you two different methods to verify if the no start condition on your 4.3L, 5.0L, or 5.7L throttle body fuel injection (TBI) GM vehicle is due to a lack of fuel, which usually means that the fuel pump has gone bad. One method involves using just starting fluid and the other involves using a fuel pressure gauge.

What causes no power to fuel injector pulse?

Ans: The engine control unit is the electronic brain that used to control the fuel injector pulse by gathering data from various sensors along the fuel line Question: What causes no power to fuel injectors?

How to troubleshoot your TBI fuel injection system?