how do you test injectors?

[coltkelz]

how do you test injectors? i have doon some searching and i cant find any methods on testing dsm injectors. i know that with the fuel rail detached from the head and the injectors pointing out i turn the key and the injectors dont spray. i have voltage at the injector plug buy i dont know how to properly check that out . if anyone has methods to testing the injectors please help. thankyou.

 

[snooopy365]

Don't ever try it like you did!
The injectors are just pushed into the rail, as soon as the fuelpump turns on, they are going to fly out of the rail.
As well the gas is flying all over the place, this method is working fine, if your goal is to set your car on fire!

But because you didn't post something about a big fire: You don't have any fuelpressure in the rail, so maybe your fuelpump is dead or not working.

 

[1990AWD]

Agreed with most of above, but the injectors aren't going to be firing unless the engine is cranking anyway.

What makes you think they're not firing? Are your spark plugs wet?

 

[coltkelz]

i pulled the rail off the head and left the injectors hooked up and turned the key as i would to start it and no fuel came out of the injectors. plugs are dry. as for the fp i know its good i just replaced it yesterday and i have fuel at the rail aswell as good pressure.

as for the method i used i read it on this site to do it that way.

 

[boost97gst]

Wait, You pulled the rail out, then cranked it? Then you say no fuel came out yet right after that you say you have pressure at the rail??? Im confused. The injectors would fly out of the rail quit violently and fuel would fn gush out. Listen, i dont think you have pressure at the rail. I dont think your pump is turning on. But, that said, im not familiar with a colt. Im assuming it has a 4g63 so my knowledge would be applicable in that case. The injector pulses are generated by a combo of the CPS and/or CAS. Without signal from those the pump wont even turn on(in dsms anyway).

 

[coltkelz]

the fuel pump comes on and i have pressure. i know it comes on ### i have it sitting right behind me along with the fact that when i pull the return fuel line off i can turn my key and drain my tank. my sensors are all good as i just replaced them all my fuses are good my ecu is good. which none of the info given in repys here adress the question asked so if you dont have info on the question asked please dont post.

 

[Tyeler18]

The injectors won't fly out.

I use this method all the time. If you have good injector o-rings they stay in fine. Did you test the injector with a noid light or a dvom?

 

[coltkelz]

i tried using a volt meter but it didnt work. i read on here somewhere i can use a test light aswell but havent tried yet.

 

[Tyeler18]

How do you know you have voltage at the plug then?

To properly test the HARNESS side of the injector go buy a noid light set from a local autoparts store. There's usually 3-5 different styles. I believe the Bosch style one was what I used, that will tell you if you're getting power to the injector. I find it hard to believe that all 4 are that toast that they won't spray, so more than likely you're not getting power or your not getting a ground to the injector plug.

What's your fuel pressure at the rail?

 

[coltkelz]

the volt meter jumps around when power should be applied saying there is current. if there wasnt the voltmeter wouldnt register anything. and noid lights are 50 bucks so im not buying one. as for pressure im not sure exactly what it is at the rail as i dont hav e a guage for it.

 

[Tyeler18]

the volt meter jumps around when power should be applied saying there is current. if there wasnt the voltmeter wouldnt register anything. and noid lights are 50 bucks so im not buying one. as for pressure im not sure exactly what it is at the rail as i dont hav e a guage for it.

So uh... how do you know you have enough pressure at the rail?

Yes they are $50, but if you want to properly test something you need to get the tools to do it. And they do have a return policy just so you know.

 

[coltkelz]

i clamped the return line shut which makes the pressure ruse since it cant leave the rail and it makes no difference.

 

[Tyeler18]

i clamped the return line shut which makes the pressure ruse since it cant leave the rail and it makes no difference.

So again.... how do you know you have enough pressure at the rail?

 

[coltkelz]

if theres no return theres no way for there to be low pressure it keeps building untill the pressure is released.

 

[Tyeler18]

if theres no return theres no way for there to be low pressure it keeps building untill the pressure is released.

This is assuming your fuel pump is working properly. Funny story. I bought one of my DSM's non running. Wouldn't start. Had compression, spark, and fuel to the rail. I spent 3 weeks testing everything from injectors to ecu, to CAS etc. Pulled the rail off multiple times, clamped the return line multiple times. Still nothing. Injectors were firing via the ECU, but no fuel was spraying out. When I pulled the rail off fuel would POUR out of it while engaging the fuel pump. Needless to say I was stumped. Decided to throw an AFPR on it to check fuel pressure. Low and behold fuel pressure was maxing at a measly 20 psi WITH the return line clamped off. 20 psi looks the same as 40 psi when it comes spraying out the feed line FYI, however, 20 psi isn't enough for the car to start. Turned out the PO installed the fuel pump without the top hat, so all the pressure was bleeding back into the thank (which BTW we have a bleed off valve in the fuel pump, so even with the line clamped it will STILL bleed off). New top hat and she fired right up.

So again i'll ask, how do you know you have pressure at the rail?

 

[boost97gst]

tyeler: you got WAY better orings than me bro!! Lmao, if i put 43lbs on my pte 1000's, they would and have once on accident, blown right out. I stupidly turned on FP in link while the rail and and injectors were un bolted. What a mess of gas.

 

[Tyeler18]

tyeler: you got WAY better orings than me bro!! Lmao, if i put 43lbs on my pte 1000's, they would and have once on accident, blown right out. I stupidly turned on FP in link while the rail and and injectors were un bolted. What a mess of gas.

Sounds like you need some new o-rings then. I actually do this test on MOST* of the DSM's I've owned any time I swap injectors just to be sure they're spraying, and spraying in a proper pattern.

 

[AWD-TSI]

You could go rent a noid light set if you have a local orielly's around that might help you out with out spending to much money.

 

[sidewaystsi]

This is assuming your fuel pump is working properly. Funny story. I bought one of my DSM's non running. Wouldn't start. Had compression, spark, and fuel to the rail. I spent 3 weeks testing everything from injectors to ecu, to CAS etc. Pulled the rail off multiple times, clamped the return line multiple times. Still nothing. Injectors were firing via the ECU, but no fuel was spraying out. When I pulled the rail off fuel would POUR out of it while engaging the fuel pump. Needless to say I was stumped. Decided to throw an AFPR on it to check fuel pressure. Low and behold fuel pressure was maxing at a measly 20 psi WITH the return line clamped off. 20 psi looks the same as 40 psi when it comes spraying out the feed line FYI, however, 20 psi isn't enough for the car to start. Turned out the PO installed the fuel pump without the top hat, so all the pressure was bleeding back into the thank (which BTW we have a bleed off valve in the fuel pump, so even with the line clamped it will STILL bleed off). New top hat and she fired right up.

So again i'll ask, how do you know you have pressure at the rail?

This is also what i was thinking if the issue is in fact fuel pressure.

 

[coltkelz]

i just replaced the fuel pump and i know it works from the po. and my car started 2 days ago with the same setup. it then stalled and hasnt started since.

 

[boost97gst]

Im with tyeler, check your damn pressure at the rail. Then you can rule that out. You have replaced your filter right?

 

[coltkelz]

ive replaced the pump the filter all sensors wires flugs i did a full overhaul except for bottom end and new cams. but ill look into a pressure gauge.

 

[CrawlinZX14]

Ok, 2 days ago you replaced the pump. Then it stalled and has not started since? Pull your pump back out and make sure something didn't come loose. Next, for idiots trying to test their injectors in the rail like that, I hope you burn your car to the ground being that careless. Take the damn injector out of the rail, get a glass jar and a hand pump. Attach a hose from the hand pump to a pressure gauge and then to the top of the injector without orings in place and clamp it. Get your Fuel presssure up with the hand pump and use a 9v battery to open the injector. It will then spray into the glass jar. Not causing your car to burst into flames cause your dumb, and not shooting injectors everywhere. Hell if you have a spare battery and a stock fuel pump laying around you don't even need a hand pump. Just some fuel line a couple clamps and a battery or trickle charger. You can get a noid tester from. Harbor freight for like 20 bux or rent one from autozone. Why do people have to be so difficult?

I'm willing to bet the oring in his fp didn't seat right and he is bleeding pressure back into the tank. Any takers? Or. The top hat isn't on bleeding pressure back out. Would be funnier to me tho if the pump fell out of the holder, but if he is getting fuel, I doubt that's the case. I am going to bet its in the pump area and not the injectors or harness.

 

[nickk90]

I thought noid lidlghts didnt work on low impedance injectors?

 

[gofer]

Don't ever try it like you did!
The injectors are just pushed into the rail, as soon as the fuelpump turns on, they are going to fly out of the rail.

Please, if you've ever pulled the rail, left the injectors in, cranked the motor, and had an injector(s) fly out, please do it again and video tape it for us all.

To the OP, here's a good place to start. You'll notice that one of the ways I list to check fuel injector operation is to pull the fuel rail, leaving the injectors installed, then have a friend crank the motor while you hold up a 5ga bucket to catch the fuel and watch the injectors.
How To Diagnose A No Start