fuel injector resistance reading

grumpyvette

Administrator
Staff member
UNPLUG the harness from the injector,BTW To remove the connector from the injector, push carefully in the middle of the locking clip, with your thumb, This will make the sides, and tips move OUT WARD in their connector slots allowing the tips that hold the injector into the connector to slide out of the way from the injector body, and you can then pull the sides away. WATCH the locking clip - IT can and WILL come off and get lost, if your not careful put your V.O.M. meter on OHMS and put the leads across the two connectors ON THE INJECTOR ,it should read about 11-16 OHMS in most cases, a few are designed to read up to 19 ohms, or as low as 9 ohms , The Ford motorsport injectors in the 24lb-hr flavor test a little lower (14.1-14.3 ohms) than the bosch's @ 22lbs/hr. (15.9-16.3) BUT ALL INJECTORS IN A SET SHOULD READ WITHIN ONE OHM OF EACH OTHER if its out of that range by a wide margin ITS MORE THAN LIKELY DEFECTIVE, checking the OHMS reading as a first step will frequently detect a defective injector, naturally using your trouble codes , a shop manual and a fuel pressure gauge won,t hurt and a shop scope , or engine analyzing software with a read out to your laptop computer helps and can further isolate the problem, at IDLE speeds placing a finger tip on the side of the injector will usually allow you to feel it (CLICKING) adding a couple cans of injector cleaner and about a pint of MARVEL MYSTERY OIL to a full tank of fuel can sometimes free a sticky injector that partly clogged, but don,t do it frequently as its very hard on the CATS and O2 SENSORS if done constantly

acc-74620s_w.jpg

Spray-pattern.jpg

partly clogged injectors tend to reduce power and increase emissions

notice, the injector resistance is usually stated in the description
https://fuelinjectorclinic.com/flow-calculator

https://www.injectorrx.com/injector-size-calculator/

https://www.witchhunter.com/injectorcalc1.php

http://www.raceworks.com.au/calculators/injector-hp-calculator/

http://www.rcfuelinjection.com/Technical

http://www.enginelabs.com/news/calculating-fuel-demands-and-injector-sizing-with-efi-university/
Brand: ACCEL
Product Line: ACCEL Fuel Injectors
Part Type: Fuel Injectors
Part Number: ACC-150826
Injector Advertised Flow Rate (lbs/hr): 26 lbs./hr.
Injector Advertised Flow Rate (cc/min): 269.0cc/min
Injector Impedance: 14.4 ohms
Driver Type: 12 V saturated circuit
Overall Height (in): 2.880 in.
Seat to Seat Height (in): 2.270 in.
Manifold O-Ring Outside Diameter (in): 0.573 in.
Fuel Rail O-Ring Outside Diameter (in): 0.574 in.
Outside Diameter (in): 0.943 in.
Injector Plug Style: Bosch/Amp-style
Wiring Harness Included: No
O-Rings Included: Yes
Quantity:

http://www.megamanual.com/v22manual/minj.htm
finjk1.gif

finjk2.png

finjk5.JPG

finjk3.gif

finjk4.gif


MORE INJECTOR INFO
"Most early EFI systems were batch-fire systems (TPI) where the ECM fired all eight OR BANKS OF FOUR injectors simultaneously. Usually batch-fire systems fire the injectors once per engine revolution. This way, the injectors could be sized small enough to be more easily controlled at idle. Later, sequential EFI systems were refined to fire an injector a few degrees before the intake valve opened. Generally, sequential injection offers more precise fuel control at the price of increased complexity. But on production engines, the benefits are more in the area of emissions and driveability than in performance".


shaw1.png

shaw2.png



Like all electrical devices, injectors have an internal resistance to the flow of electricity. The amount of resistance is measured in Ohms, or impedance. The higher the number, the more the resistance. Injectors are either high impedance or low impedance. It's crucial to get the proper type. While high and low impedance injectors may look identical on the outside and fit the same, if they are the wrong type they can fry your ECU, injector resistor pack, or other expensive parts. High impedance injectors are sometimes called "peak and hold" injectors, while the low impedance injectors are often called "saturated injectors." Make sure you get the right type. If you're not sure what you've got, you can check the resistance of your injector with a DMM (digital multi meter) set to measure Ohms. Saturated injectors have a resistance between 10-18 ohms and peak-hold injectors have a resistance around 2-6 ohms.

your corvette was designed to use the 10-18 ohm rated injectors

viewtopic.php?f=55&t=2055&p=5481#p5481

viewtopic.php?f=55&t=2055

http://www.scottsautorepair.net/viewtopic.php?f=10&t=33

http://www.eficonnection.com/eficonnection/default.aspx

http://garage.grumpysperformance.com/index.php?threads/multi-meters.3110/

viewtopic.php?f=55&t=1241&p=2648#p2648

http://users.erols.com/srweiss/tableifc.htm

http://www.conleyracing.com/article_fuelinjectors.htm

http://www.ecs.fullerton.edu/~sowell/ja ... estRig.pdf

http://www.youtube.com/watch?v=cvlnG5Ki ... re=related

http://www.youtube.com/watch?v=cy_yaAOK ... re=related

http://www.youtube.com/watch?v=_g8PdrT0 ... re=related

http://www.youtube.com/watch?v=NIz5c9ML ... re=related

viewtopic.php?f=70&t=7309&p=24862#p24862

http://www.youtube.com/watch?v=VfynoxL2 ... re=related
 
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grumpyvette

Administrator
Staff member
IF you don,t have (NOID LIGHTS) a set of test leads with clips and an ANALOG volt meter will work as the needle bounces when the electrical pulse hits the leads
you should have BOTH the analog and digital MULTI-meters, each has its uses

http://www.sjdiscounttools.com/ta36330.html

http://www.radioshack.com/product/i...nalog+meter&kw=analog+meter&parentPage=search

http://www.radioshack.com/product/i...ital+meter&kw=digital+meter&parentPage=family

http://www.radioshack.com/product/i...ads&kw=alligator+test+leads&parentPage=search
 

grumpyvette

Administrator
Staff member
I was asked if adding an adjustable fuel pressure regulator helps, on those TPI engines...

naturally the results depend on your application and combo, as an example on the 1985-1996 corvette I useually work on...your engine power is regulated to a large extent by the rate at which you can EFFECTIVELY BURN fuel/air mixture

http://www.msefi.com/index.php

the adjustable fuel pressure regulators can in some combos help noticably IF the injectors used are running at the ragged upper edge of thier flow limits, but in most cases they do very little, WHY?? well the cpu controls the injectors pulse width effectively controlling your air/fuel ratios from feed back from the O2 sensors in the exhaust, at least in theory the injectors are large enought to supply 100% of your engines potential needs running less than 80% pulse width. at the 37psi-42psi the stock regulator provides. BUT if youve made significant changes to the engine combo youll need to EITHER increase the injector size OR cheat by upping the supply pressure to those smaller injectors, obviously adding more pressure with a regulator is limited to the maximum the fuel pump can supply and in most case the stock pump maxs out just under 48psi

play with this

http://users.erols.com/srweiss/calcpchg.htm


youll soon find that useing larger injectors and letting the CPU REDUCE the pulse width is far more effective that trying to boost flow on stock injectors

Matching the Injector to the Engine: generic calculation

Injector Flow Rate (lb/hr) = Engine HP x BSFC
Number of Injectors x 0.8
Injector Flow Rate (lb/hr) = 75 x 0.5 = 11.72 lb/hr
4 x 0.8

Injector Size
14 lb./hr.......up to 225
19 lb./hr.....225-300
24 lb./hr.....300-385
30 lb./hr......385-480
36 lb./hr......480-575
42 lb./hr.......575-670
50 lb./hr ......670-800
Horsepower Range

http://go.mrgasket.com/newproducts/flyers/74098G.pdf
 

grumpyvette

Administrator
Staff member
Re: fuel injector resistance reading and sellecting injectors

my 36 lbs injectors on my 383 SBC are running at the upper edge of their effective range, a lot will depend on how efficiently your exhaust scavenges the cylinders,because if a small part of the intake charge is sucked out the headers during scavenging during the valve overlap that is lost, as far as the engines concerned but it might be a necessary loss to increase the cylinder fill and scavenging.
heres a basic calculator for selecting injector size....NATURALLY KNOWING HOW TO READ SPARK PLUGS AND AN AIR FUEL RATIO METER AND USE OF AN IR TEMP GUN COMES IN VERY HANDY
87fusepannel.jpg


CHECK YOUR FUSES, YOUR SHOP MANUAL SHOULD HAVE A DIAGRAM FOR YOUR YEAR CORVETTE notice, that on this 1985-1987 fuse panel both #8 and #13 are injector fuses

BOTTOM OF THE PAGE, HAS CALCULATORS FOR INJECTORS
btw
On an L98 engine, you can get to the connectors on each of the eight injectors without having to pull any of the intake Disconnect the connector and put a V.O.M.meter across it. As previously posted if it is below 9 ohms it is pretty well not operating fully.

Test with the 'power' off. Unclip one at a time and test it. Reclip and move to the next. Write down each reading. 12-16 OHMs is good.
IF you don,t have (NOID LIGHTS) a set of test leads with clips and an ANALOG volt meter will work as the needle bounces when the electrical pulse hits the leads
you should have BOTH the analog and digital MULTI-meters, each has its uses

http://www.asashop.org/autoinc/dec2000/mech.htm

http://www.toolsource.com/inline-spark- ... 9tckclf4h4

http://www.thepartsbin.com/cartools/dia ... 678-d.html

http://www.radioshack.com/product/i...nalog+meter&kw=analog+meter&parentPage=search

http://www.radioshack.com/product/i...ital+meter&kw=digital+meter&parentPage=family

http://www.radioshack.com/product/i...ads&kw=alligator+test+leads&parentPage=search


HERES WHAT ISKY CAMS SAYS ON A RELATED MATTER

"Intake Restriction and Over Scavenging: "Waste not...Want not!"

It is certainly an over simplification to make the statement "that which is not wasted, should be inducted". However, in the case of restricted intake systems and in particular 2-BBL carb rules, it is not far off the mark. Engines with such restrictions are "choked off" to the point where they will not run much past 6500 RPM (if even that high) without dropping off sharply in power. You might have trouble running very fast yourself if someone had your windpipe choked down to say 50 or 60% of it's normal capacity. Under such conditions, would you volunteer to give blood at the Red Cross? Of course not, but without knowing so, racers often do the equivalent with their engines by running a camshaft better suited for a 4-BBL class! How So?

If you'll recall in last months tech tip: "Longer Exhaust Duration: Is This Really Necessary?" I discussed how, through habit, many racers and cam grinders alike are predisposed to running camshafts with longer exhaust durations, whether they need to or not! Well, in the case of restricted intake applications, if there was ever a situation in which you'd want to avoid the longer exhaust "trap" it's here! Especially the 8, 10, 12 or even longer degree spreads, I often discover people employing.

Use such a cam at you own risk - and don't be surprised to find that your exhaust temperatures are unusually high. Your headers in fact may even glow cherry red. There is a very good reason for this. Raw (unburned) fuel is burning "late" or in the pipe (header/manifold). You may have a good equilibrium of flow going here but there is just one problem. Much of what should be inducted into the cylinder is being scavenged out the exhaust! You see, although back pressure in an exhaust system can be restrictive, the only thing that could be even worse is a reduction of it to the point where you are now, in effect pulling a vacuum. In the case of an intake restriction, very slight back pressure is preferable to avoid "over scavenging".

Yes, Yes I know. You are probably thinking "what's wrong with a little scavenging?". Well, nothing if you can afford it. But with intake restrictions (either small 2-BBL carbs and/or restrictor plates) you must be very careful. You already have reduced intake potential and therefore simply cannot be cavalier about valve overlap and scavenging or you'll be way down on power and have those nice bright cherry red pipes to show for it! Case in Point: One racer who called me was in this exact situation and was running, not surprisingly, a 14 Degree longer exhaust duration. It was Friday afternoon and he needed a cam the next day for the last "points race" of the season and UPS had already picked up at Isky. "Too Bad" I said, "You don't have a set of those low ratio break-in rocker arms because they could really help in this case". " I do have some" he said "but they are only 1.2:1 ratio - is that okay?" I told him to use them (on his exhaust valves only of course) and he finished the race 2nd having come from the back of the pack. Later we made him the right cam so he could avoid this make shift approach.

Unfortunately, the symptoms are not always as obvious as in this case to allow for a speedy diagnosis. Also, it's not only longer exhaust duration that causes the problem. Although it is usually the primary offender, it is often coupled with too close a lobe separation angle of say 104 Degrees. A widening to 106 Degrees or preferably 108 Degrees (some go even wider) is usually prudent.

I am not absolutely dead set against a slightly longer exhaust duration in these cases as a 2-4 Degree longer exhaust lobe is permissible under some circumstances (if your running a completely stock exhaust system including mufflers for example). Each case is different, depending upon the equipment employed. I might even recommend shorter exhaust duration to some; if I feel they have "overdone" their exhaust ports and or exhaust system a bit. What matters is the end result and if you're out of balance on one side simply employ what I call the "Great Law of Compensation" to bring you back to that equilibrium of flow.

So, how can you tell if you may need to make some of these changes in your camshaft? Well, short of trying a lower exhaust rocker arm ratio, you can increase exhaust valve lash .004" - .008" temporarily to see if there is any improvement. You can also try and increase restriction (smaller headers or pipes, or in the case of open headers a longer collector) and simply observe the results. Remember, "One test is worth a thousand expert opinions". Keep this old axiom in your "tool box" and you'll be ahead of the game. How do you think Smokey's shop got to be "The best Damn Garage in Town" anyway? Yes, he had those country smarts, but his experiences in racing and his willingness to test are legendary!"





http://www.rceng.com/technical.aspx

http://www.injector.com/injectorselection.php

http://www.iroczone.com/calcs/injectorsize.htm

http://www.bgsoflex.com/pwcomp.html
 

grumpyvette

Administrator
Staff member
BEFORE YOU GET CRAZY VERIFY YOUR IGNITION FIRING ORDER, AND TIMING, LOOK FOR VACUUM LEAKS,YEAH I KNOW YOUR SURE ITS CORRECT, CHECK IT CAREFULLY AGAIN
MORE THAN ONE GUYS THOUGHT HE HAD BAD INJECTORS AND IT WAS A LOOSE IGNITION WIRE BAD PLUG OR THE WRONG FIRING ORDER, OR A BLOWN FUSE ON THE INJECTORS

also be aware that a leaking injector, or fuel pressure regulator can cause the catalytic converter, to melt internally, blocking the exhaust flow or oxygen sensors to fai
http://www.noidlight.com/

http://www.northerntool.com/shop/tools/ ... _200391521

http://www.noidlight.com/how-to-use-a-noid-light/
THERE ARE SEVERAL DIFFERENT CONFIGS TO MATCH THE INJECTORS your testing
if your injectors have similar connectors to the ones used by most G.M. cars the NOID lights plug in and should work.
injpiggy-ev1_med.jpg

the noid male prongs fit the connector female sockets
noidlite.jpg


http://www.amazon.com/dp/B000OUX9R2?tag ... QTSNSPCDY&

noidkit.jpg


Instructions
Things You'll Need:

* Noid light

1.
Step 1

Disconnect wiring harness connector. You need to undo the connector from the fuel injector. On some car models you may find it difficult to locate the fuel injector's electrical connector.
2.
Step 2

Plug the noid light into the harness connector, that you've temporarily removed from the injector.
3.
Step 3

Disable the ignition. (remove coil wire) After you're sure the ignition won't start, you want to turn over the engine at the starter motor.
4.
Step 4

Check the noid light for flashing. If it flashes rapidly, your fuel injector is receiving a voltage signal. If you see no flash, you have an open in the power feed or ground circuit in the fuel injector, or a blown fuse which could mean that your car's computer or connecting wires are defective, or the fuse needs to be replaced.

5.
step 5

disconnect the noid lights and reconnect the injectors to the harness once the noid lights flash and reconnect the ignition wire

6.
step 6
verify you've got consistent fuel pressure of at least 37psi-42psi (depends on year, verify with shop manual)at the fuel rails and drain some fuel to verify theres 100% fuel and no water in the fuel rails



GOOD RELATED TESTING INFO, IF YOUVE GOT SIMILAR ISSUES

http://www.thirdgen.org/service-engine- ... rror-codes

http://www.iroczone.com/2009/10/1982-19 ... -firebird/

viewtopic.php?f=55&t=606

viewtopic.php?f=55&t=1241

viewtopic.php?f=80&t=728

viewtopic.php?f=70&t=9450&p=34592&hilit=sensors#p34592

viewtopic.php?f=32&t=596
I think youll find reading thru these threads / and sub linked info rather helpful


http://forum.grumpysperformance.com/viewtopic.php?f=70&t=7309&p=24861&hilit=start+sequence#p24861

http://forum.grumpysperformance.com/viewtopic.php?f=32&t=10385&p=42943&hilit=start+sequence#p42943

http://members.shaw.ca/corvette86/FuelSystemDiagnosis.pdfhtt

http://forum.grumpysperformance.com/viewtopic.php?f=80&t=728&p=43477&hilit=sensors+camaro#p43477



http://forum.grumpysperformance.com/viewtopic.php?f=32&t=1401&p=39419&hilit=sensors+camaro#p39419

viewtopic.php?f=55&t=1378

viewtopic.php?f=32&t=168

viewtopic.php?f=32&t=1401
 

grumpyvette

Administrator
Staff member
watch the videos


http://www.youtube.com/watch?v=_g8PdrT0 ... re=related

http://www.youtube.com/watch?v=ValTYJUf ... re=related

checking and cleaning fuel injectors yourself

http://www.chevron.com/products/prodser ... s/tcp.aspx

http://www.gumout.com/default.asp

Ive had good results adding a can of either one of these, on particularly dirty or suspect injectors Ive added a can of both but one on one fill-up and the other product on the next full tank of fuel.

http://www.ladyada.net/learn/multimeter/

http://www.multimeterwarehouse.com/usingamultimeter.htm

http://www.wikihow.com/Use-a-Multimeter

http://mechatronics.mech.northwestern.e ... meter.html

viewtopic.php?f=80&t=728&p=9217#p9217

http://garage.grumpysperformance.co...-auto-elecrtrical-connectors.3105/#post-68805

http://www.acmehowto.com/howto/homemain ... teruse.php

viewtopic.php?f=70&t=3901&p=10343&hilit=multi+meter#p10343

http://www.harborfreight.com/ac-dc-digi ... 37772.html

image_493.jpg


http://www.summitracing.com/parts/ESI-501/
esi-501_w.jpg


don,t forget a assortment of test leads

http://www.testpath.com/Categories/Test ... g-3246.htm

http://www.bipom.com/documents/e_z_hook/XJXJLLeads.pdf

http://www.picoauto.com/automotive-test-leads.html





having a wide assortment of different multi meter test leads available is a huge benefit while testing
the clip test leads that test thru a wires insulation without much damage are a big help


693Pred.jpg

bedtest1.jpg

bedtest2.jpg

bedtest3.jpg


basic fuel injector test
(pull your trouble codes and check battery voltage ,alternator output and ignition spark first)

(BTW it rarely hurts to drain old fuel thats over 4 months old and replace the cars fuel filter, then add two different brands of fuel injection cleaner and 6 oz of marvel mystery oil to as full tank of fresh high test gas to the car if its been sitting un-used for very long before you start testing for fuel injection related issues


now Ill assume your battery reads over 12 volts and the starter works, and easily spins the engine
the first step
find the fuel rail shrader valve and remove the cap and connect the fuel pressure gauge
if you turn on the ignition key to get the dash and accessories to light up but don,t start the engine,the fuel pump,
should briefly run to pressurize the fuel rail to about 38psi-42 psi,
this should stay at this pressure level for at least 5 minutes minimum, if it drops slowly your fuel rail is leaking fuel.
now the fuel pressure regulator may be defective or leaking, or in very rare cases the fuel pump may be defective ,
but the most likely cause is a fuel injector(s) stuck in the open position.
next pull the injector harness,
electrical_connectors.jpg

off a single injector at a time, press the wire bar to release the clip, retention, then pull it up and off, the noid light plugs into the harness,
use the spare injector pig tail
injectord3.jpg
injectorpt1.jpg

on the now disconnected injector ,connect the multi meter on ohms setting and it should read 11-13 ohms injector on each injector tested.
if it reads under 9 ohms or over 20 ohms its a defective injector
now use a couple 3 ft long test leads connect one too one of the pig tail test leads
https://www.walmart.com/ip/Uxcell-2...-Clips-Test-Jumper-Wire-1-5m-2-Color/45588242

testlkj.jpg

and to 12 volts, connect the other pig tail lead too a different test lead and watch the fuel pressure gauge,with the key out of the ignition , you should have 38-42 psi of fuel rail pressure, watch carefully while you tap the second test lead to ground (the plenum or alternator case works) the fuel pressure should drop as you tap the ground pig tail lead, this verifies the injector function at least partially, if you don,t see the pressure drop the injectors not allowing fuel flow through it and should be replaced.
after you complete each injector test , turn the ignition key on, to re-pressurize the fuel trail and reconnect the harness to the previously tested injector,
repeat the noid light and pig-tail function fuel pressure test on each of the other injectors individually.
Fusebox2.jpg

youll need a fuel pressure gauge and multi meter

image_6238.jpg

CP7838.jpg


it helps if you have a spare fuel injector pig-tail for testing
injectord3.jpg


having a NOID light injector harness tester wont hurt either
https://www.harborfreight.com/11-piece-noid-light-and-iac-tester-set-97959.html
205107_700x700.jpg

tpishrader.jpg


on the TPI and LT1 efi and many other EFI intakes,
theres a shrader valve,
that can be easily accessed to check fuel rail pressure,
dealing in facts you verify is always preferable.

fuelcirc1.png

shaw2.png


GM part number for the complete fuel rail o-ring kit is 17111696

fprpicq.jpg

if your TPI FUEL PRESSURE REGULATOR DIAPHRAGM LEAKS youll find it difficult or impossible to be starting your car

heres a link to the correct o-rings they are light blue
NAPA sells them at times
all the o-rings on the fuel rails and injectors need to be dipped in thin oil so they insert and slide into place with less friction, this tends to greatly reduce the chance of the o-rings ripping, and yes you need the correct o-rings that fit correctly to begin with if you expect the rings to seal correctly
http://tpiparts.net/inc/sdetail/10950/300
Injector_O_Rings_ezr2.JPG




17113544 - Injector Seals
17111696 - O-Ring Kit
22514722 - Fuel Inlet O-Ring
22516256 - Fuel Inlet O-Ring
tpifp3.jpg

http://garage.grumpysperformance.co...dding-a-fuel-pressure-gauge.15264/#post-88472


http://garage.grumpysperformance.co...njection-at-start-up-problem.7309/#post-24862

http://garage.grumpysperformance.co...oven-facts-if-your-in-doubt.13051/#post-84695

http://garage.grumpysperformance.com/index.php?threads/tpi-fuel-pressure-issue.10385/#post-42943

http://garage.grumpysperformance.co...-system-trouble-shooting-flow-chart-info.596/


http://users.erols.com/srweiss/tableifc.htm
 
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