A few years back I had a problen with a fuel injection system, which can be a little hard to diagnose. So I set the injectors out to be tested. Well$468 bucks later and still the same problem. One of the injectors they tested cleaned and passed wasn't spraying fuel. It was replaced with a junk yard injector. I wish I had ran across this pdf file it would have made life grand. This is so simple to make.
http://www.ecs.fullerton.edu/~sowell/ja ... estRig.pdf
Bench Testing Fuel Injectors
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raygreenwood
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- Joined: Wed Jan 22, 2003 12:01 am
Its similar to my rig. Its actually quite easy to volume test before an after. You need a digital timer to make sure you are to he second and it can be started and stopped with the same momentary button you use for turning teh injector on and off.
But....to be sure you are actually accurate you need a pretty large supply of pressurized fuel.
Here is the issue. You injectors whil running are never actually open more than a few milliceconds. In a few milliseconds...from each inejctor opening....the actual overall pressure of the fuel supply from the rail does not have the time...nor is enough volume removed...to signiificantly drop the rail pressure. But...several seconds of open time WILL seriuosly drop pressure and skew the flow results. So...you need to have a large enough volume pressurized fuel supply that even wide open for numerous seconds will not change fuel supply pressure.
On cool way to trigger injectors is to use an old D-jet dizzy. Plug the injectors positive into either right or left hand connector in the three pin plug. Ground the negative side of the injector. To the negative on the battery. Put the positive from the battery to the center connector in the three pin plug on the trigger point plate. Install a single pole switch in that line.
I clamped teh dizzy to a plate and hooked it up to a dishwasher motor that I tached out at 1,700 rpm. Be sure to give a shot of oil to the dizzy. Hang the injector in an open topped burette. First turn on the dishwasher motor to get the dizzy spinning at 1,700 rpm....and pop the switch on and time with stop watch.
This does not simulate pulsewidth. However, it is meterable and repeatabale for a before and after test. Ray
But....to be sure you are actually accurate you need a pretty large supply of pressurized fuel.
Here is the issue. You injectors whil running are never actually open more than a few milliceconds. In a few milliseconds...from each inejctor opening....the actual overall pressure of the fuel supply from the rail does not have the time...nor is enough volume removed...to signiificantly drop the rail pressure. But...several seconds of open time WILL seriuosly drop pressure and skew the flow results. So...you need to have a large enough volume pressurized fuel supply that even wide open for numerous seconds will not change fuel supply pressure.
On cool way to trigger injectors is to use an old D-jet dizzy. Plug the injectors positive into either right or left hand connector in the three pin plug. Ground the negative side of the injector. To the negative on the battery. Put the positive from the battery to the center connector in the three pin plug on the trigger point plate. Install a single pole switch in that line.
I clamped teh dizzy to a plate and hooked it up to a dishwasher motor that I tached out at 1,700 rpm. Be sure to give a shot of oil to the dizzy. Hang the injector in an open topped burette. First turn on the dishwasher motor to get the dizzy spinning at 1,700 rpm....and pop the switch on and time with stop watch.
This does not simulate pulsewidth. However, it is meterable and repeatabale for a before and after test. Ray
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Badbugtwo
- Posts: 496
- Joined: Wed Jul 17, 2002 12:01 am
I'm lucky to have access to this setup at the college where I teach...
http://www.badbugracing.com/injectors.htm
http://www.badbugracing.com/injectors.htm
Last edited by Badbugtwo on Sat Jan 22, 2011 9:47 pm, edited 1 time in total.
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panel
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I'm pretty sure Megasquirt has one also.
'65 Bus with a JDM Subaru EJ20 Turbo
Built by Germans powered by Japanese and brought together by Canadians
Built by Germans powered by Japanese and brought together by Canadians
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MarioVelotta
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Re: Bench Testing Fuel Injectors
You didn't get your machine that long ago if I remember correctly SUbuggy?david58 wrote:A few years back
SUbuggy wrote:I have the same ASNU service machine and made an offer to STF members for $100 to service their injectors.......................
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1600 ITB NA - 18sec
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raygreenwood
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..I can BUY new injectors for pretty close to $468. Ray-
SUbuggy
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4 or 5 months ago.You didn't get your machine that long ago if I remember correctly SUbuggy?
What an EYE OPENER having this thing. forget the cleaning/servicing. The ability to actually see the spray patterns and atomization under different fuel pressures and pulse durations is amazing.
Anyone that thinks they can just look around and throw in any old injector in their custom engine is kidding themselves.
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raygreenwood
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- Joined: Wed Jan 22, 2003 12:01 am
Well said...and one of the minor issues I have been beating people with forever. You can't just take an injector made for an unknown application and run it at whatever pressure you decide your system and your lap top can tune around.
Most injectors are made to run in a very spcific range of pressure with modern vacuum variable fuel pressure regulators.
Not only are the solenoids and springs not able to accurately reseat injector pintles over a certain pressure....@ a given pulsewidth and cycle rate......they also have specific angles ground on the pintle tips to direct spray....added to a specific pintle diameter....plus an engineered amount of pintle lift and seat to pintle clearance.
All of this means that a given injector will give a known and proper spray pattern within a certain operating range of pressure and within a reasonable envelope of cycle rate and pulsewidth. Outside of that it can many times revert to a stream...giving little or no atomization at all....or giving very erratic patterns across a specific range of pulsewidths at a given pressure.
Its worth it to do some experiementing and set up a reasonable rpm rate and max pulsewidth for your system. Then find find an injector whose flow rate fits that profile....and then stay within that injectors manufacturers advertized specific range of pressures. Then get ONE and test it or have it tested to see what its spray pattern is like. Get one from a junkyard if necessary and have it cleaned and tested to see its pattern. Most decent sized cities have at least one place that can do this if you look for them.
Or ..even without a service or a full blown testing rig...you can set up a decent enough system for almost nothing to at least check rpm cycle rate and pressure range issues with a given injector. Ray
Most injectors are made to run in a very spcific range of pressure with modern vacuum variable fuel pressure regulators.
Not only are the solenoids and springs not able to accurately reseat injector pintles over a certain pressure....@ a given pulsewidth and cycle rate......they also have specific angles ground on the pintle tips to direct spray....added to a specific pintle diameter....plus an engineered amount of pintle lift and seat to pintle clearance.
All of this means that a given injector will give a known and proper spray pattern within a certain operating range of pressure and within a reasonable envelope of cycle rate and pulsewidth. Outside of that it can many times revert to a stream...giving little or no atomization at all....or giving very erratic patterns across a specific range of pulsewidths at a given pressure.
Its worth it to do some experiementing and set up a reasonable rpm rate and max pulsewidth for your system. Then find find an injector whose flow rate fits that profile....and then stay within that injectors manufacturers advertized specific range of pressures. Then get ONE and test it or have it tested to see what its spray pattern is like. Get one from a junkyard if necessary and have it cleaned and tested to see its pattern. Most decent sized cities have at least one place that can do this if you look for them.
Or ..even without a service or a full blown testing rig...you can set up a decent enough system for almost nothing to at least check rpm cycle rate and pressure range issues with a given injector. Ray
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manx1641
- Posts: 22
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i'm glad i just read that i tested my injectors at the weekend and although they were all putting out the same amount of fuel i noticed the fuel was coming out in a stream with no spray pattern to speak of, i'm using a fuel pump from an early golf with mechanical injection which i'm told needs more pressure, and injectors from a later model electronic injection golf, i figured i was using too much pressure, i'll be on the look out for a new pump now then i guess,
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raygreenwood
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- Joined: Wed Jan 22, 2003 12:01 am
Before you ditch that pump...and CIS pumps are VERY good pumps, get a gauge and check your pressure. If its way too high, you could start by first installing a "bleed" from the fuel main line to the return line to bring the pressure down.
You do this by finding a metal "tee". In the leg of the tee that you are going to route through to the return side...hammer a 1/4" slice of brass or aluminum rod in as a plug (aluminum is preffered). Then get a dremmel or a "pin-vise"...and drill the smallest hole in the plug that you can....like 1/64" or less.
By the way...this is temporary.
What you are doing is making a bleed to see if you can bring the main line injection pressure down to something that is sane...because ifyou can find a way to use that CIS pump...it will last forever.
If this works.....tell me, and I will tell you how to make a small adjustable check valve for under $20. The reason why you will need it...is because the experimental bleed you making will drain your fuel line presure after shut down and give you hard starting.
The object here is that if the pump is making more presure than the pressure regulator can handle...bleed it off before it gets there. Ray
You do this by finding a metal "tee". In the leg of the tee that you are going to route through to the return side...hammer a 1/4" slice of brass or aluminum rod in as a plug (aluminum is preffered). Then get a dremmel or a "pin-vise"...and drill the smallest hole in the plug that you can....like 1/64" or less.
By the way...this is temporary.
What you are doing is making a bleed to see if you can bring the main line injection pressure down to something that is sane...because ifyou can find a way to use that CIS pump...it will last forever.
If this works.....tell me, and I will tell you how to make a small adjustable check valve for under $20. The reason why you will need it...is because the experimental bleed you making will drain your fuel line presure after shut down and give you hard starting.
The object here is that if the pump is making more presure than the pressure regulator can handle...bleed it off before it gets there. Ray
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raygreenwood
- Posts: 11914
- Joined: Wed Jan 22, 2003 12:01 am
Not sure there is such an animal as a "bigger" prssure regulator. Maybe...
The problem is this: Pumps do not make pressure at all. They make volume. Volume against a restriction (the regulator) is what creates pressure.
I can only assume that you have a rising rate regulator...yes/no?
A regulator will be manufactured to produce a range of pressure within a given minimum and maximum volume range. If the volume gets too high, it cannot flow through even a wide open regulator fast enopugh to keep from creating more pressure than the unit is capable of. You either get damage to the regulator, spiky and erractic pressures and/or just plain pressure too high.
You could find a regulator i suppose.....that is set up for teh am range you have...that has a physically larger fuel line system. Like if your reg is based on 5/15" ID internal and external lines...a 3/8" would help.
I would hate to lose the pump you have either. Its one of the best made.
Or...you could run the fuel line to a "Y" right before the regulator and run two identical regulators "t"'d at the vacuum source as well. That way twice the volume...same pressure setting. You c an restrict one or both regulators on the return side with a small pneumatic or hydraulic bleed valve...or even a reducing orifice stuffed in the return line. I have done that before. Ray
The problem is this: Pumps do not make pressure at all. They make volume. Volume against a restriction (the regulator) is what creates pressure.
I can only assume that you have a rising rate regulator...yes/no?
A regulator will be manufactured to produce a range of pressure within a given minimum and maximum volume range. If the volume gets too high, it cannot flow through even a wide open regulator fast enopugh to keep from creating more pressure than the unit is capable of. You either get damage to the regulator, spiky and erractic pressures and/or just plain pressure too high.
You could find a regulator i suppose.....that is set up for teh am range you have...that has a physically larger fuel line system. Like if your reg is based on 5/15" ID internal and external lines...a 3/8" would help.
I would hate to lose the pump you have either. Its one of the best made.
Or...you could run the fuel line to a "Y" right before the regulator and run two identical regulators "t"'d at the vacuum source as well. That way twice the volume...same pressure setting. You c an restrict one or both regulators on the return side with a small pneumatic or hydraulic bleed valve...or even a reducing orifice stuffed in the return line. I have done that before. Ray