EFI - Electronic Fuel Injection » Fuel Injection Diagnostics

Faulty Throttle Sensor | Fuel Injection

wolfems — Sun, 12 Sep 2010 12:48:36 +0000

Faulty Throttle Sensor with Robbie McQueen. Robbie talks about how a faulty throttle position sensor effects engine management and fuel injection systems.

A symptom that I see sometimes, is a misadjusted TPS, which turns out to be a faulty TPS, and it’s creating issues for the engine management system.

What this means is, you can have a worn-out lug (the mechanical part that moves with the throttle plate), or they can be worm out electrically, inside the throttle position switch.

Now, what that can create is, if you are holding the throttle position switch at a given point, and inside electrically, it’s not actually connected, it’s worn out, bent, or just damaged in some way, the engine management system is going “I am at 5% load; no I’m not; yes I am; no I’m not….”.

What this can create, is an acceleration enrichment. So, you’re driving down the street, holding the throttle still, and all of a sudden, you are getting enrichment, then you’re not getting enrichment, then you are getting enrichment, etc. It can create a very poor mixture, very poor fuel economy, and sometimes very poor drivability.

What is can also do, because we have a nice sweeping arc of the throttle position switch, and for if some reason electrically, there are damaged points, as you accelerate, and your acceleration enrichment happens, you’ve got a break in that acceleration enrichment. So, all of a sudden it’s getting enrichment, it isn’t, it is again, so once again, you create a flat spot.

That’s working on the acceleration enrichment side of things.

The throttle position also tells the engine management system where to start to work with the idle speed. And as we have mentioned in other articles, idle speed devices are very important to achieving a great driving experience.

So, if for some reason, your throttle position sensor is not working, your idle speed motor doesn’t know where to be.

Now you’ve got two scenarios.

The first is a car that stalls at lghts, and a car that flat spots as it takes off from the lights.

And that could be due to just a faulty throttle position switch.

For more information, you can contact Robbie McQueen at:

Advanced Engine Management / Wolf Motorsport
22 Melrich RoadBayswater, Melbourne
3153, Victoria, Australia
Ph: (03) 9761 3161

When is 12V Not 12V in an Electronic Fuel Injection System?

wolfems — Fri, 25 Sep 2009 05:30:07 +0000

Hi There.

Now, you may remember in a previous post we talked about some of the basic concepts of capacitors, diodes and resistors?

This post goes through what can happen when something that is not meant to be a resistor – becomes a resistor.

“How is that possible?” I hear you ask.

Well, you may have heard about corrosion buildup between pins in a connector, or between the connector and the wire it is crimped to. This corrosion is resistive. That is, it has resistance.

Now, image that you are controlling a relay with your ECU. The relay is switching when you make the output of the ECU go to ground, but the device that you are controlling (we’ll use the example of a fuel pump) does not start running. If you disconnect the fuel pump from the relay, there is 12V there when the relay is turned on. But, when you connect the fuel pump, the pump doesn’t run, and the voltage at the +ve terminal of the pump is almost 0V.

This is occurring because of resistance that has developed between the relay terminal and the terminal on the wire going to the fuel pump.

So, on the face of it, it did initially appear that the 12V from the relay was there and being supplied to the fuel pump, but the resistance in the connection at the relay meant there was only a very small supply of current. There was not enough current to power the fuel pump.

If you just used an LED test light, you will think there is no problem here. But you’d be wrong. An old style test light may give you some more information, as it may glow dimly due to the resistance in the connection.
Sometimes you need to think outside the box if things don’t seem to be adding up.

As older cars running electronic fuel injection continue to age, these types of problems are going to occur more often and diagnosis is going to become more tricky than before.

Keep an open mind.

Until Next Time..

How Do Resistors, Diodes and Capacitors Work In Relation To Electronic Fuel Injection

wolfems — Thu, 10 Sep 2009 04:42:15 +0000

Hi Everyone.

This is not going to be a big lesson on electronic theory, but I thought a lot of you have been asking about some basic info on resistors, caps and diodes, like “what does a diode do?”

So I thought a quick look at these might help you feel a little more comfortable when dealing with them. So here we go……….

Resistors:

Imagine a bar of copper. It has an extremely low resistance. If you put it across a car battery, there will be sparks, and you may even destroy the battery. It allows a massive amount of current to flow through itself.

Resistors can be used to limit the amount of current flowing through a wire. OR they can be used to reduce the voltage on a wire or from a sensor. Imagine the current flow like it is water and it is running through a tap. As the resistance increases (like turning off the tap), less water (current) is able to flow through the wire.

Like a tap, it doesn’t matter which way around the resistor goes, the water can flow either way.

Capacitors:

Capacitors are sort of like shock absorbers. Imagine all of the bumps in the road is like a noisy waveform on a wire. Without any shock absorbers, your car would be bouncing up and down and rattling all over the place. You can put a little shock absorber on each wheel and the shaking and bouncing reduces a little. Put bigger shock absorbers on each wheel and the ride becomes more smooth.

The same thing happens with adding more capacitance to the signal on the wire. A little capacitor will reduce the voltage bumps a little, and the bigger you go, the more the larger bumps will be dampened.

Some capacitors can be wired either way around, but ones with either a – or a + must be wired a specific way.

Diodes:

You go to the supermarket and you walk through the turnstyle. No problem. But then you realize you forgot your money, and you try to go back. You can’t. The turnstyle only lets you travel one way.

Diodes are the same. They allow current to flow quite freely in one direction, but they stop the current from flowing in the opposite direction.

Diodes have a band at one end. Current flows from the end with no band, to the end with the band.

As I said at the beginning of this post, it is a basic overview, so anyone with more intimate knowledge of electronics, please give me a break on some of the descriptions above. They are only basic descriptions to give anyone with no knowledge on these items a way to understand some of the concepts.

Electronic Fuel Injection Fuel Pressure Regulator Flow Rate

wolfems — Wed, 09 Sep 2009 23:28:43 +0000

Hi Guys.

We have come across this a couple of times lately, so I thought it would be worth while sharing it with you.

If you imagine a huge fuel pump. It pumps a huge volume of fuel. That fuel travels along a fuel line, some of it is used by the fuel injectors, and then it comes to the fuel pressure regulator. The only problem is that the fittings and internal galleries on this fuel pressure regulator are much smaller than the fuel line and fuel rail, and so the regulator cannot regulate the fuel pressure down to where it needs to be.

No matter what you do with the adjustment screw (if it is an adjustable regulator), the pressure remains higher than you want it to be.

This is a case where you have too much fuel flow from the pump for the regulator to handle.

The only course of action is to replace the fuel pressure regulator with one that is designed to cope with the fuel flow of your fuel system.

Funnily enough, it is far more common to have a fuel system that cannot deliver enough fuel, and the pump(s) needs to be upgraded.

This is just something to be aware of, as it is not as common as a lack of fuel flow is, and many people find it hard to understand what is going when they are trying to diagnose this curly issue.

Here a link to some info on fuel pressure and fuel pressure gauges.

PS: Measuring the fuel pressure requires a special fuel EFI pressure gauge. You cannot use a fuel pressure gauge designed for a carburetted engine as EFI fuel pressure is 6 or more times greater.

The Importance Of Clean Fuel Injectors

wolfems — Tue, 08 Sep 2009 11:32:40 +0000

What can dirty injectors do to your engine?

Cause Idle Problems – misfires at idle, lumpy idle, inconsistent idle speed.

Limit Maximum Power – In some cases, dirty injectors can cause the air fuel ratio to vary across your cylinders to the point of limiting the maximum power your engine can produce.

Cause Engine Damage – In very extreme cases, you can have a cylinder lean-out to the point of piston damage. This is a rare and extreme case, but it can happen.

What do you need to know?

New injectors should flow within 0.5% of each other.

Cleaned electronic fuel injectors should flow within 2-3% of each other, MAX. Anything above 3% means you may experience one or more of the symptoms above. They really should be within 1% for any serious performance application.

You must also ensure your set of injectors all have the same spray pattern, as you might have injectors that all flow within 2% of each other, but you may have 1 injector that has a bad spray pattern. Putting this injector into your engine will probably mean you might at least have rough idle.

The bottom line is, that if you want to get the most out of your engine, you must ensure you have a good set of clean injectors.
Look at it this way: If you have 4 tires on your car, and 3 of them are inflated to 36PSI, but one of them is inflated to 29PSI, you could not expect your car to handle nearly as well as when all of the tires are inflated to 36PSI.

Cleaning a set of injectors generally only cost between $100 and $200, so it is very cheap insurance when you consider the amount you may spend on your vehicle to modify it.

PS: If we can point you in the right direction to get your current set of injectors cleaned, or if you are after a set of new injectors, contact us at wolfemail@wolfems.com.au .

Increasing Fuel Pressure in an Electronic Fuel Injection System

wolfems — Mon, 07 Sep 2009 05:54:36 +0000

Hi Guys,

We all know that increasing fuel pressure means you get more fuel per squirt right?

Well that may be true, to a point.

The first problem is, that as we increase the fuel pressure (using an adjustable fuel pressure regulator), the extra amount of fuel coming out of the injector does not necessarily increase proportionally. And this only gets worse as you keep increasing the pressure higher, and higher. The higher you go, the less of an increase in fuel flow you are achieving.

The second problem is that you can end up with the fuel pressure on the back of the injector making it harder for the injector to open. This can cause idle problems. This is especially true with high impedance injectors where there is not a lot of injector opening current to overcome the fuel pressure on the back of the injector.

Thirdly, you can have other problems such as less efficient injector spray, and injectors leaking when the engine is not running, but there is still fuel pressure in the rail.

Now, this all depends on the type of injectors you are using, but the general rules apply.

So, what is the answer?

Make sure you have the correctly sized injectors to cope with the amount of power you are trying to achieve. DON’T just screw the pressure up more and more. If you are getting fuel pressure up to numbers like 55-60 PSI at idle, that may end up being a lot more by the time you are at atmospheric pressure, or even more under high boost pressure levels.

Maybe take some advice from someone in the industry who has experience with a project like yours. It’s far better to ask and get some solid advice, than it is to go the wrong way and end up with a substandard result.

OK, that’s it for now.

Timing Lights for Electronic Fuel Injection Systems

wolfems — Mon, 07 Sep 2009 04:50:35 +0000

Most of us know that you cannot begin to even try to start an engine without a timing light (although many have tried in the past – including myself in my early days). But, without knowing that your ECU is delivering the ignition timing that you think it is delivering, at best you can guess what the real ignition timing is, and at worst you can potentially cause damage to your engine.

We don’t want that.

So the first thing we have to do before we tune an engine – either dyno or track tuning, is to make sure the ignition timing the ECU is displaying corresponds to where the engine is when the spark event occurs. That is: If the ECU says 10 degrees BTDC, the spark event must be 10 degrees BTDC. If it is not, change the ECU configuration so it is correct.

Just quickly though, there is one thing to test. Even though you have the correct ignition timing at idle, what is to say that it is correct at say, 3,000 RPM? With modern ECU’s being so configurable, you must check the ignition timing at 2 RPM points. If the timing is correct at both RPM’s you are good-to-go.

If the timing is not correct at both RPM’s you may have a configuration problem, or a triggering issue.

There are two main types of timing lights. Dial Back, and Fixed.

Fixed Timing Lights just flash when the spark event occurs. They may have a button or a trigger, but they have no smarts to make working out the actual ignition timing easier.

As you will see, this may be an advantage.

Dial Back Timing Light – either with a rotating knob, or buttons. These are the top of the line timing lights. But they do have one problem:- If you have a wasted spark ignition system, either with dual output coils, or individual coils fired twice per engine cycle, a dial back timing light may show you the INCORRECT ignition timing. and worse still, this is not an offset from the real timing, it varies depending on the engine RPM.

This is due to the fact that the timing light is using the speed of the ignition pulses to determine the engine RPM. And it uses that engine speed to work out how long to delay the flash event so it shows on its display or dial, what the ignition timing is. Since it thinks the engine is running twice as fast as it actually is, it cannot determine what the CORRECT ignition timing actually is.

I have seen seasoned mechanics have trouble with this many times over the years. It is more common than you may think.

The basic symptom is that they have set the timing, and it is correct at idle, but when they rev up the engine, the timing changes away from what the ECU is saying it is delivering.

So. Make sure you either use a fixed timing light, or, set the dial back to zero if you are checking the ignition timing of any engine running any type of waste-spark ignition system.

If you’d like some more info on Tools for EFI Diagnostics, you can have a look at http://www.wolfems.com/support/EFIFuelInjectionTools.html . There is info on Timing Lights, Pressure Gauges and Multimeters.

General EFI Fault Finding Mindset

wolfems — Sun, 06 Sep 2009 12:38:56 +0000

Hi and welcome to the first of a series of blog entries talking about all areas of EFI, from the very basics, to more advanced installations and features.

These posts will be uploaded once or twice a week, in bite sized pieces. Most of the posts will only be a few hundred words in length, meaning you can read them in a minute or two. This post may be the longest one, partly due to this introduction, but also because the subject is quite broad and is more specific than most of the posts to follow in the future.

I’m sure you will find value in these lessons, even if you are a seasoned EFI professional, but please keep in mind, we are writing to a wide variety of readers, so some of the information may appear a little rudimentary for some of you.

So… Let’s get to the first post.

This posts subject line is “General Fault Finding Mindset”, and that may sound a little dry to some of you, but what I’m trying to get across is that when you are installing and EFI system (or any automotive electronics for that matter), there are a few simple things you can do to speed up the diagnosis when there appears to be a problem.

I’m just going to quickly go through a couple of things now to illustrate what I mean.

Swap Things Out Or Around: If you have one cylinder down and you are trying to determine why it is down, try swapping another driver of the same type to that cylinder. For example, you might swap the plugs on two injectors and see if the problem follows the plug you have just moved, or if the problem is still at the same cylinder.

Look For Pairs: This is a simple way to narrow down the problem. For example, if the engine is missing on 2 cylinders, you can look and see if there are any systems on the engine where those 2 cylinders have common wiring, or drivers from the ECU or 12V supply. Any time there are pairs of items like, dual outlet coils (wasted spark), or injectors wired in sets of 2 (banked injection), it makes finding the problem so much easier. If the engine is missing on 1 cylinder, it is unlikely that the problem is caused by something that is 1/2 of a pair with something else, like a dual output coil for example.

Go Back To Basics: Check for good quality power and ground connections. Wiring is the most common reason for EFI faults, so this is a great place to look for problems.

We will be going into more detail as we go through these posts, but the first thing to understand is that you can get yourself into a way of thinking that immensely increases your ability to solve the problem in front of you.

So,until next time.

Steve.