How to test for faulty injector plug?

[DeadsEvolution1]

Ok so I ohmed out an injector plug and the resistance measured out correctly. Now my problem is that cylinder 2 injector isn't working at all. We start my car pulled off an injector plug one at a time on each cylinder. If we pulled cylinder 1,3 or 4's plug the car would die but if we pulled number 2 the car would stay on just like normall. The car is spuddering like crazy so we pretty much know that it's an injector or a plug or what??

Can someone tell me how to test the plug to make sure it works? Or does the coil control that as well?

 

[redyute1]

Pick up a set of noid lights from auto zone,they plug in the injector harness and will flash if there is pulse/or power.But have you done a compression test or test the coil,can be any of those causing the misfire.

 

[talon913]

its sounds like your injector plug my number 2 on my 90 laser wasnt firing either it ran like pure shit.what i did was tap the top of the injector and plug with a screwdriver lightly and it fixed my problem i guess the fuel filter had let something in and clogged up the injector or something but i know that helped me

 

[DeadsEvolution1]

All good info. Now how do I test the coil? Every spark plug is firing, the fuel pump is turning on it's just that one injector that is not working. So my assumption is that that one is failing or clogged or something.

Oh and for the compression test I have not, but the block is a brand new 2.3 stroker motor with a rebuilt head.

 

[talon913]

did you make sure the pins are pushed all the way in on the injector plug and that its making complete contact with the injector?? i had to put a lil bit of rtv for the pin to stay in the plug.if it comes out a slight bit it wont make contact and if you been upluging it then might have pulled the wire out a lil bit.check that to

 

[DeadsEvolution1]

They were pushed down as far as they could go on. I am hoping it's a just a faulty or clogged injector cause I have a new one now but if not I don't know what else to look at? Does the coil control the plugs?

 

[talon913]

actually i think the resistor box up top controls the plugs and if its firing 3 then i think that has to be fine..mine was pushed all the way down but the pin itself inside the plug was push up not making contact.thats what i mean does teh pins in the plug look like the rest??

 

[DeadsEvolution1]

I'll have to take another look at the plug, It's very possible that you are right and would make sense. Also thanks for the info on the resistor box too. I didn't think it would be bad if 3 are firing but still had to ask just in case. I will check tomorrow and give you and update tomorrow

 

[talon913]

ok bro goodluck.. i know exactly how a laser will run on 3 cylinders or any 4g for that matter i drove home thinking i blew the car up and was extremely pissed cause it happend out of no were..but it came out to be that when i hit boost i think something tugged on the wire and pulled it out a lil bit .im glad i didnt sell my car for 300 bucks that day.i even payed a mechanic 20 bucks and all he did was play with the wire and it ran perfect ...

 

[DeadsEvolution1]

Lol ya I wouldn't sell my car now, new stroker in it so I'm addicted . But as soon as i get day light I will be up looking at it Thanks for your help check back tomorrow

 

[steve]

If you look at the schematic you'll see that the injector is power off the MPI relay through one of the resistors in the resistor pack (one for each injector) to the injector. The other side of the injector goes to the ECU where the ECU pulls it low to fire the injector. Not much to it.

The power to the resistors is common to all 4 so the problem has to be past the common point. If you measured the resistance of all the injectors and they all matched you need to make sure you have 12v at the injector with the ignition on and that the ECU is good. I have to double check but I seem to remember that the ECU has a pull up on it's side so you might see 12v on both pins of the connector when your checking.

 

[DeadsEvolution1]

Ok so I put in a new injector with no help to my issue. Has brand new spark plug wires and spark plugs still sounds like it's missing. I made a video, its from my phone so sorry about the quality but it'll have to do

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Tell me what you guys think. It is a 2.3 Stroker BTW

 

[talon913]

thats deffinently your wires to the injectors or like steve said..mine sounded EXACTLY like that..have you tried takin the spark plug out?? i remember the tip on my spark plug was smashed in and that was another reason why it started doin that.

 

[DeadsEvolution1]

Yes I put in a new spark plugs, and wires look up . And I tried a new resistor pack and no help so it's gotta be the ECU now

 

[steve]

Have you measured anything or are you just a parts swapper?

It's possible that the ECU is bad. It's just as likely that it can be fixed but you have to pull the ECU and see what you got to know. If you have any friends with DSM's it's safer to put your ECU in their cars to see if the still misses than it is to put another ECU in your car.

If you have an EPROM ECU is worth seeing if your can be fixed if it's bad.

 

[DeadsEvolution1]

Steve:

I had opened up my ECU and took a look around there where no scorch marks, leaking capacitors or anything. It just Appeared normal. The reason I suggest it's the ECU is cause there is nothing left to check or is there? I could put it in another DSM and try It that's not a bad idea at all Let me know

 

[nestamon99]

Before you go through the problem of swapping out computers, check the compression of the cylinders. If you have spark and the connector is working properly, you probably have a problem with the valves. Take a look! Just my 2 cents

 

[DeadsEvolution1]

The valves were replaced less than 500 miles ago and the block is brand new. I couldn't understand how it wouldn't have good compression and no fuel is getting in cylinder 2

 

[steve]

The valves were replaced less than 500 miles ago and the block is brand new. I couldn't understand how it wouldn't have good compression and no fuel is getting in cylinder 2

I'm always amazed that people think any of this makes a difference. It doesn't take anytime at all for an engine to fail. It could have been working 5 mins ago and you still need to check all these things because they might be the reason why it's not working now. While I don't think this is a problem with the valves, checking compression should always be a part of the diagnostic procedure. And while your doing it you get to check the condition of the spark plugs which can tell you if your burning oil, or getting too much or no fuel, etc.

If the compression is good in all the cylinders, and the plug is good and sparks then you know that the problem is likely in the fuel delivery and formulate a plan to test each part of it to narrow it down.

I was expecting picture of the ECU board. Few people are qualified to just look at it and say it's good. I know that I can't, but I can see many more problems than most people because I've seen a lot and know what to look for.

 

[DeadsEvolution1]

Here is what My ecu looks like and I can't use my real camera just my phone cause I do not know where my charger is. The back of the ecu does not have any scorch marks at all but I did find some black spots around a certain area of the ECU that is concerning....

You must be logged in to view this image or video.

 

[steve]

That's pretty serious damage right there. There should be a capacitor, C106, where your board is burned that is used to filter the incoming 12v from the car. Also in that area is one of the ISC traces.

Here's a MD166260 (91-92 federal turbo MT FWD) that has the parts but before it was repaired a second time. (The first time was a typical cheap cap replacement by a "professional" rebuilder. Looking at the picture I think this one was actually dead from a blown CPU. You can see the dark spot in the middle of the large black chip IC6, that's signs of it cooking. If I have time I'll take a picture of a good ECU for your car.)

So right off the bat your ECU is questionable. It's not a EPROM ECU so you may be better off replacing it than having it fixed.

 

[DeadsEvolution1]

This is the second ECU my car has been through in only a few months. I have an eprom that went bad in the beginning now it did another with almost similiar symptoms. When my e-prom went bad the car would only idle not able to rev up or anything just idle. Now this one fried on the injector side. I am going to send in my E-prom to get fixed now any ideas where I should send it? And I just picked up another regular ECU

 

[steve]

I am going to send in my E-prom to get fixed now any ideas where I should send it?

. Perhaps me. There's a reason why I know all this stuff.

 

[DeadsEvolution1]

PM sent

 

[1fast97gsx]

Why don't you switch injector pins at the ecu and switch the injector connectors accordingly .. that way you would rule out wiring / connectors leaving only the ecu as a possibility if the injectors were already swapped....