View Thread: Electronic Fuel Injection Question


kcg795
My Toyota Van has EFI. I've been looking all over the place to find out why it stumbles when I hit the gas suddenly and why it misses. Well. I put the key in the ignition and put it in the ON position, then grounded a test light to the frame and tested one of the fuel injector wires. BOTH wires have + voltage. I'm like, WTF? Is this the way it's supposed to be? I started the engine to see if the test light would do anything. But the engine didn't give me very much time. It died 3 seconds later. I also tested another fuel injector wire and it's doing the same thing. My last 2 injectors are under the throttle body, so, I can't get to them unless I tear it all apart.

Ok, I got positive voltage going to both contacts when, in theory, one should be positive and one should be negative and should be blinking while the engine is running. But it's not doing that. If this is abnormal, I have a feeling that my computer is fucked. If you think this is the problem, I'll run over to a junk yard and get another computer and put it in.

eric rxb
Are you using a voltmeter or a test light? If you're using a test light then it will just tell you if you're getting continuity, not whether the voltage is positive or negative.

kcg795
I'm using a light. I connect one part of it to the frame, which is GROUND and then the other to the injector connectors. If the light lights up, then the connector I touch it to is Positive. Both contacts on the fuel injector connectors are positive. This seems ODD to me.

eric rxb
From my knowledge of circuts and automotive electonics, that would just mean that they are both in continuity with a ground.

lexus1581
Originally posted by eric rxb
From my knowledge of circuts and automotive electonics, that would just mean that they are both in continuity with a ground.

Thats what im thinking too. The light shows contuinity only i thought not thats its a positive connection.

kcg795
If this helps, the light isn't powered. So, the only way I can test continuity is have a battery hooked up in the connection.

eric rxb
Right, but as long as you have a power source and some sort of ground the light is going to be powered. You'd be alot better off with a volt meter if you have one.

kcg795
And the volt meter is going to point to the Positive Side as well.

eric rxb
What I'm saying is that the test light is only telling you that it's got contact, not that it's positive or negative. A voltmeter will actually tell you the voltage running though it.

Carlos Carrera
i think u should throw ur Van into a Cliff :cheers:

eric rxb
Originally posted by Carlos Carrera
i think u should throw ur Van into a Cliff :cheers:

:pd:

lexus1581
Originally posted by Carlos Carrera
i think u should throw ur Van into a Cliff :cheers:

BWHAHAHAHA thats freaken hilarious! But KC is going to be :surprised and then :cry:.

kcg795
We ALL know that the BODY of a vehicle is NEGATIVE!!!! If either of the contacts on the fuel injector wires were negative also, the light wouldn't light. It's like taking both wires to a light and hooking them to only 1 post on a battery. Now, since the light is lighting up while ONE end is connected to the body, which is GROUND or NEGATIVE, and the other end is connected to a fuel injector wire, that obviously means that the wires on the injectors are POSITIVE! It's simple science.

kcg795
Ah fuck it. It doesn't look like I'm getting professional help anyway.

eric rxb
Ok: I've taken over 7 years of physics classes, 4 years of electronics classes and a year of automotive electronics, so I have some idea what I'm talking about.

If you hook anything that is in line with the battery to a ground you're going to get the test to light up because it's the same as hooking it to the ground end of the battery.

eric rxb
Also, don't be an ungrateful douchebag when someone is trying to help you.

Carlos Carrera
Originally posted by kcg795
We ALL know that the BODY of a vehicle is NEGATIVE!!!! If either of the contacts on the fuel injector wires were negative also, the light wouldn't light. It's like taking both wires to a light and hooking them to only 1 post on a battery. Now, since the light is lighting up while ONE end is connected to the body, which is GROUND or NEGATIVE, and the other end is connected to a fuel injector wire, that obviously means that the wires on the injectors are POSITIVE! It's simple science.

i understand that, BUT it that were real, ur injectors werent ''injected'' fuel. cause u got + +

Carlos Carrera
Originally posted by eric rxb
Also, don't be an ungrateful douchebag when someone is trying to help you.

we love u erik dont be mad :ghey: :cheers:

kcg795
I was offended by the "Throwing it off a cliff" remark. I want to get the problem of the engine fixed. I don't believe in replacing the whole vehicle to solve the problem. Remember that. Anyway, I sent the same question to the message board at www.toyotavans.org to get their opinion. The engine runs. But it runs like a very cold carbureted V8. It's just very rough. It managed to let me hit the throttle without letting it die. But, it's still missing. Well, I'll figure it out someday. It's a rebuilt engine, so it has to be electronic.

kcg795
I did take a short video of the engine while it was running. You might hear some knocking. I had the distributor out and I think the timing is kinda messed up. After I removed the distributor and looked at it and put it back in, it seemed to run a little better, but the timing is off. I tried adjusting it. I think I'm just gonna get a new distributor anyway.

Well, here's the video.

http://kcg795.tripod.com/engine.WMV

Carlos Carrera
Originally posted by kcg795
I was offended by the "Throwing it off a cliff" remark. I want to get the problem of the engine fixed. I don't believe in replacing the whole vehicle to solve the problem. Remember that. Anyway, I sent the same question to the message board at www.toyotavans.org to get their opinion. The engine runs. But it runs like a very cold carbureted V8. It's just very rough. It managed to let me hit the throttle without letting it die. But, it's still missing. Well, I'll figure it out someday. It's a rebuilt engine, so it has to be electronic.

Nha, that was a joke, i was cynical in the afternoon

Are u sure ur injectors arent obstructed? try a inj. cleaner.
If that isnt, maybe its the distributor, or finally u got a damaged ECU.

kcg795
Well, I'll replace my distributor. Just gotta save up some money to do so. (I need a job but can't find one around here) If that don't fix odd behavior of this thing, then I'll probably get an ECU from the junk yard. The 84 and 85 Vans both have 3Y-EC engines. The newer rigs from 86-89 have 4Y-EC engines. So, I'll have to find the parts that are designed for the 3Y-EC. Maybe 4Y-EC parts would work if I need to use them as a last resort. I know damn well there's nothing mechanically wrong with the engine. It was rebuilt a while back. So, it's gotta be electronic somewhere. Damn gremlins.

Carlos Carrera
Damn gremlins
hahaha :cheers:

A-Tech
the test light does not tell you positive or negative, it should light up on either of the contacts.

kcg795
We know damn well the BODY of the vehicle is NEGATIVE!! If I hook ONE end of the light to the BODY which is NEGATIVE, and then touch the other end to another part and the light lights up, then the part that I touch is POSITIVE? Make sense? But, it don't matter now. I guess the fuel injection system seems to know what it's doing and it's not at fault. I have confirmed that the problem is my headgasket.