How to test injector flow rate

The injectors are externally cleaned in a special detergent and are visually inspected. We test the injectors coil for resistance, shorts, and current draw. We wire brush any loose paint and rust from metal injector bodies.

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Plastic injectors skip this step. We remove the filter baskets, o-rings, and pintle caps. This ultrasonic cleaning is performed for a minimum of 30 minutes depending on the condition of the injectors. This cleaning step will be repeated a second time if the fuel injectors fail either the leakdown test or the flow test in the next step. When in closed position, fuel injectors should not leak any fuel. For proper engine performance the injectors in a set should be flowing within 5 percent of each other.

OEM injectors are designed to flow a volume within 2 percent of each other. Injectors are flow tested in two ways:. This duplicates real world conditions such as idling, acceleration, deceleration, low speed, and high speed.

We test fuel injectors at various pulse widths at 3 ms, 6 ms, and 12 ms. Flow testing injectors in both static and dynamic simulations ensures that we will know if your injectors are performing properly under all real world conditions. Injectors with abnormal flow rates or spray patterns are re-cleaned and re-tested. The results of the flow testing are then recorded on an test data evaluation sheet.

Install new filter baskets, o-rings, and pintle caps if the parts are commercially available. Injectors are lubricated to increase shelf life. The injectors are then packed along with the old parts for return.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. It only takes a minute to sign up.

I suspect my fuel pump causing intermittent driveability issues. However I was told that the pressure test by itself is not sufficient for diagnosing fuel pump problems and a volume test must be performed - measuring the volume of the fuel pushed by the pump in a set amount of time by disconnecting the line and directing the flow into some kind of a vessel. I do not understand why a separate volume test is necessary if the pressure shows up fine. Doesn't the fuel pressure depend on the volume of fuel being pushed?

Doesn't low volume equal low pressure? Is this only required when measuring pressure immediately after the pump, rather than at the rail? A fuel pump is designed to provide 3 to 4 times the needed maximum volume of fuel to the engine.

The excess fuel is then returned back to the tank through the pressure regulator and return line. When the fuel pressure is low it is very obvious that something in the fuel system is having a problem.

The importance of fuel injector flow matching - fullBOOST

It could be a bad fuel pressure regulator, plugged fuel filter, bad fuel pump, just to name a few. When the pump can only provide lets say half the maximum volume the pump can still provide the pressure making this condition much harder to diagnose. Further the symptoms of this kind of failure are usually drivability related. What happens is that at idle the engine only uses a small amount of fuel and it runs fine. When the fuel consumption hits the spot where the consumption is greater than what the pump can provide the pressure drops off and some type of drivability issue occurs.

This type of issue can be caught one of two ways. The first is a volume test. The second is by connecting a fuel pressure gauge in such a way that it could be looked at while driving. If under load the fuel pressure drops off then you found your problem. The fuel pumps found in most OEM fuel delivery setups today are driven by an electric motor that is running at a fixed speed.

This effectively fixes the flow rate and discharge pressure provided by the fuel pump. Without going into the nitty-gritty of how fuel regulators operate, the key thing to remember here is that it alters the amount of fuel returned back to the fuel tank to ensure that a fixed pressure drop is maintained across the fuel injectors. This means that the classical relationship between pressure drop and flow rate is not respected.

In fact, fuel rail pressure is almost constant regardless of flow rate. A low fuel pressure measurement at the rail might indicate a clogged fuel filter, some obstruction in the fuel line or a fuel pump that just can't deliver a high enough pressure.

However, the pressure-stabilizing effect of the fuel regulator means that the fuel rail pressure measurement doesn't tell us anything about the adequacy of the fuel flow rate from the perspective of the flow demanded by the fuel injectors.

This is the reason for the flow rate test; you can have good fuel rail pressure but insufficient flow. Consider the fuel rail, kept at pressure p by the regulator.

The fuel pump adds some amount a of fuel into the rail, increasing the pressure in the rail by some amount. Now injectors inject amount b to be burned into the cylinders. If a is larger than b, the regulator flows amount a-b back to tank, keeping the rail still at pressure p.This is the cheap way of getting more fuel into your engine that is required when making more power than the factory fuel injectors can support.

You are removing the pintle cap to increase flow through the injector. The factory uses pintle caps to restrict the flow of injectors and to help flow match injectors.

By removing the pintle caps you are unrestricting the flow through the injector.

how to test injector flow rate

Because of this modification their may be flow variance between injectors. This is due to the fact that before the stock pintle cap was the fuel flow equalizer through the fuel injector from the factory and now after decapping the fuel injector, the only thing that is now making the injectors flow the same is the factory machining tolerances within the injector.

How to Test Fuel Injectors—3 Simple Methods

If you have a spark plug that looks like its noticeably richer or leaner than other cylinders, I recommend modifying another factory stock fuel injector of the same flow rate and part number, having it flow tested, swapping the problem injector out and testing again.

Ok onto how to do this modification. Heres a video for the visual learning people out there:. Now for what cant be seen in the video.

Fuel Injector Flow Testing

In this photo you can see the dark ring inside the black fuel injector O-ring retainer. This is the friction weld that holds the pintle cap onto the injector. This is what needs to be ground off.

how to test injector flow rate

So heres a visual reference of the pintle cap half off the injector. And then heres the pintle cap completely off the fuel injector. The part you see in the middle of the completely decapped fuel injector is the pintle. You just want to grind off the friction weld that holds the pintle cap on and nothing more. So that is how you modify your fuel injectors to flow more fuel, now heres the proof this works.

The injector part number is I modified 8 of them and then sent one out for flow testing to witchhunter. Here are the returned test results:. So from these test results, we can see at Using witchhunter.Once an injector is manufactured, the flow rate can not be altered. By raising fuel pressure, more fuel is forced out the metering orifice per pulse width.

Thus, someone who has performed modifications to their vehicle i. For example, a Ford Mustang 5. What would the flow rate be at 50 psi? Figure 1 shows flow rate changes due to pressure of some popular injector applications. Figure 1. Raising fuel pressure to overcome a major fuel deficiency problem is a band-aid solution and should be avoided. In addition, high pressures can make some injectors to become unstable, or in some cases, completely shut-off. Finally, it must be realized that when the fuel system pressure is increased, fuel pump volume is decreased.

So if you though you richened your fuel system by raising the pressure with an adjustable regulator, but the lean problem persists or becomes worse, then you most likely have a fuel volume problem.

The fuel pump is not pumping a sufficient volume of fuel to feed the system. In general, fuel pressures should not exceed 65 psi except during boost in special applications such as turbocharged or supercharged engines with high boost pressures.

All rights reserved.Dan Ferrell writes about do-it-yourself car maintenance and repair. He has certifications in automation and control technology.

how to test injector flow rate

Photo courtesy of storem on Flickr. Testing fuel injectors sometimes can be easier than you think, whether on a TBI throttle body injection or an EFI electronic fuel injection system. Often, these injectors face common problems you can diagnose visually TBIor with the use of some simple tools. The modern fuel injection system works more efficiently and reliably than the previous carburetor model.

The system has a better control over the air-fuel mixture under any driving conditions. Occasionally, though, buildup from impurities in the fuel, or injector system electrical or mechanical problems may contribute to rough idle, misfires, harmful emissions, poor engine performance, and fuel economy. This guide can help you get those injectors back in shape applying some simple tests you can apply to both TBI and EFI systems. You can visually inspect the fuel spray on TBI system injectors.

Fuel flow spray is readily accessible, making it fast to check for potential problems. A single, solid spray or irregular pattern means the injector needs cleaning, or that an internal part wore out or broke. You can try to fix an irregular fuel spray pattern by adding a quality cleaning fuel system additive to the fuel tank.

Or take your car to the service shop and have them clean the system. To troubleshoot the injector, apply the tests described in the following section Testing EFI Injectors. Photo courtesy of Albertas Agejevas on Flickr. Unlike injectors on throttle body fuel injection TBI systems, those used on an Electronic Fuel Injection EFI configuration don't have their fuel spraying accessible for inspection.

And sometimes the fuel rail assembly, which holds the injectors in place, offer little room to access the injectors without removing the complete assembly.

So it's hard to check the spraying pattern of each injector without the proper equipment. However, you can use a couple of tests that can reveal whether one or more injectors are working on your EFI system and whether the fault is within the injector itself or the controlling circuit. For this test, you'll listen to each injector to determine whether they are working. As the car computer energizes and de-energizes the injector, the valve inside the injector produces a clicking sound as it opens and closes.

One of the tests you can do on a dead injector is by checking the injector's coil. For this test, you'll need a multimeter and the resistance value for the coil inside the injector. You can look up the injector resistance value in the service manual for your particular vehicle make and model. If necessary, buy an inexpensive, aftermarket repair manual at your local auto parts store or online.

And if you haven't used a multimeter before, check the next video for a quick review on how to operate a multimeter. You can check for power and pulse signal as it comes from the computer on each dead injector using a test light, an inexpensive an efficient tool. If any of the previous tests came out negative, it doesn't necessarily mean you injectors are operating correctly.

You tested for some common problems you can troubleshoot at home, but one or more injectors may have a worn or dirty less common valve, or a weak or broken return spring that's causing the injector to block or leak fuel.

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Some of these problems can be a challenge to diagnose without the right tools. But a repair auto shop with professional equipment can help you pinpoint these type of problems. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Question: What causes inconsistent fuel injector noid readings in different cylinders?The Duramax has proven to be a reliable engine since its introduction back in Generally, most owners and service techs are well aware of the importance of keeping a clean fuel system by running clean, high quality fuel, lubricity additives, and routine fuel filter changes along with all other required maintenance.

When problems do arise from the fuel system, the first method of diagnosis is often a balance rate test. Balance rates are measurements that the engine control module uses to keep the injectors firing smoothly, making a more efficient and quiet running engine.

Injector balance rates are only measured while the truck is in neutral, or in drive with the foot on the brake. Unfortunately, balance rates are not measured when the engine is being fueled beyond idle pressures. No balance rate measurements are taken from the ECM under any other conditions therefore leaving a large spectrum of potential data off the table for analysis.

In addition, the balance rate does not measure:. For the ECM to measure a balance rate, it takes in account the fuel rate from the fuel pump and is used to factor how far off each injector is from the average flow of fuel. Essentially, this is all the balance rate is measuring. Cylinder compression, friction, fuel rail pressure, and the fuel pressure regulator are variables that can greatly manipulate the balance rate test.

Checking balance rates is the best place to start when diagnosing a troublesome fuel system, but it is definitely not the absolute answer.

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With a balance rate test, you are not getting the complete injector analysis. A balance rate shows a small fraction of available diagnostics compared to a common rail injector bench test.

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The only way to eliminate the variables present in the vehicle and identify if an injector is running at factory specifications, is to remove the injector from the engine, clean, flush and test it on a properly programmed test stand. This process allows every component of the injector to be tested under simulated engine conditions.

Our Fuel Injector Ultrasonic Cleaning and Flow Testing Process

It is important that injectors are tested at normal operating temperature, from low idle pressures all the way up to full load pressures as much as 29, psi. These tests measure injector delivery, return flow and response time, as well as leakage and spray pattern.

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Product Search.Last Updated: April 29, References Approved. This article was co-authored by our trained team of editors and researchers who validated it for accuracy and comprehensiveness. There are 13 references cited in this article, which can be found at the bottom of the page. This article has been viewedtimes. Learn more The fuel injectors in your vehicle are designed to spray fuel into the cylinders of your engine where it is combined with air and compressed before being ignited by the spark plug to produce power.

As a result, an issue with one of your fuel injectors can cause your engine to run poorly, or even fail to run at all. There are a number of issues that could cause your fuel injectors to fail. Although some may be beyond the expertise of most home mechanics, you can often diagnose a faulty fuel injector using common hand tools. To test fuel injectors, start by popping your car's hood while the engine is running.

Place a thin metal rod or screwdriver on one of the injectors and lean your ear close to listen for an audible clicking sound, which indicates the fuel injector is functioning. Test each fuel injector in your vehicle the same way. If you find one that isn't clicking, there may be a problem with your injector or the electronic component that controls it.

For tips on checking the trigger circuit, read on! Did this summary help you? Yes No. Please help us continue to provide you with our trusted how-to guides and videos for free by whitelisting wikiHow on your ad blocker.

how to test injector flow rate

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