Guss

I know there are quite a few posts about this sort of issue and I've checked everything mentioned inside those posts, so heres the skinny... My Runner had a miss so the first thing I checked was spark, compression, and fuel. I've got spark and the compression is running between 125 and 150 across all cylinders. The injectors had been rebuilt about a year and a half ago but I pulled them anyways and checked for debris and I found a little but cleaned it out and swapped the#3 and #1 injectors to see if the problem followed the injector swap or remained at the #3 cylinder. I still had the issue on #3.

Next thing I did was to pull the harness apart and check the splices for a wire that might have come loose, but everything was still intact. I soldered the joints to be sure it wasnt the problem and put everything back together and tried the engine again but still had a miss on #3.

My next thought was to check continuity of the wire. I checked continuity across the splices, and also checked it from the yellow wire coming out of the resistor pack to the connector end (by the way, I replaced the harness end with a new one) that hooks to the injector and had good continuity. Put everything back together and as you might have guessed...still #3 was dead!

I'm at a loss because at this point in the other posts someone either found a loose connection in the wiring harness or a bad injector and I've found neither. What am I missing?? Thanks in advance for the help!

Dirt Driver

A couple things come to mind.

1.) 125psi is low and 150psi on the highest makes for a less-than-ideal variation. What compression numbers did you get for each hole? What about #3?
2.) Do you have a noid light? Can you check that the injector on #3 is firing? You can make an LED test light fairly easily if necessary...
3.) Is the spark to #3 consistent? Hang a timing light on that plug wire and see if the flashing is steady. Just because there is spark with the plug in open air doesn't mean there is spark while running.

Guss

Compression on #3 was near 150. I think it was #2 that was on the low end at 125-ish. #1 and #4 were also close to the 150 mark as well. I know thats kind of vague but the only compression tester I have immediate access to is one that you hold in place and not a screw in one (borrowed it from the farmer next door). I dont have a Noid Light and I'm gona get one this weekend. I tried to make one using an 1157 socket and bulb that I had but didnt get and response from the light and didnt really trust it since it wasnt an LED. I will also double check the fire using a timing light. Will get back to you soon... and Thanks a bunch!

Dirt Driver

Incandescent bulbs won't work as a noid light because they don't react fast enough. Noid lights use a strobe-type light instead and LEDs have a latency that is far shorter than any injector's opening time, so they are suitable too. Come to think of it, I may modify my $2 test light with a super bright LED so I can use it as a noid too.

A 430Ω resistor (standard value) will work for current limiting a 30mA LED on a 12v system.

Guss

Ok...was able to borrow a true noid light and I do have signal to that injector and I also checked the fire to the #3 plug with a timing light and it is good too. So I'm guessing I will pull the injectors and have them professionally cleaned...again! Our shop mechanic says theres a good place in Little Rock that can do them probably same day and does nice work so I'm going to give that a try. I also checked the voltage at no.10 & no.20 at the ecm and had 12 volts. I'll report back after the injector bath and service! Thanks for the help!

Dirt Driver

You said you switched the injectors around and the problem stayed on the same cylinder. That rules out the injector...

Guss

I had a friend over when I swapped the injectors and hes thinking I may have got the 2 mixed up when I tried to swap them. Nothing else makes any sense to me.

scope103

Before you pull the injector you could listen to it. Just because it's getting voltage doesn't mean it's opening. You can make your stethoscope out of a piece of rubber tubing; there's an audible click when it opens. (compare to the others)

Alas, just because you can hear it opening doesn't mean it isn't clogged, but do the easy stuff first.

Guss

Ok... I couldn't tell if any of the injectors were clicking so I went ahead and pulled the injector and took it to the shop. They said it was working fine and nothing was wrong with it. They suggested I check the resistance in the wires to the injectors to ensure I'm getting good voltage but Ive done that and they are all in good shape. I've tried changing plugs and wires again and also checked to make sure my valves didn't somehow get tight on me. I'm at a loss...this isnt making any sense at all.

I did notice a little backfiring through the throttle body when I revved the motor, but if I understand that right it should be a fire problem and not a fuel problem. Double checked the firing order too. When I swapped the spark plug from #1 and #3 I did notice that the plug on #1 was an orange color and #3 was a black color as if it were getting fuel but not fire.

Any other suggestions would be appreciated but I'm thinking I may have to wait until I can get some funds to take it to a professional. Again, thanks for the help! If I figure it out I will definitely post a follow up!

Stu Pidasso

Here is a nice and easy diagram of the injector wiring.

Stu Pidasso

If you gently remove the plastic wrap/electrical tape that contains the wires of the wiring harness you will find the splices shown above. Moisture, dirt, vibration, and corrosion do a real number on wiring and electrical components. The thing is the splice may look good and the insulation on the wire may still be there, but the problem could be further down the wire. I am not promising you this is your issue. In the event that it is you can easily splice new leads in the connect your plugs to the new leads. You seem to have some skills with electronics. I am thinking I may do this with my harness now since the motor is out and I can easily get to it. The burnt orange plug sounds like it is running lean in that cylinder to me. It could be that you have been losing the connection to you injector for some time and now it is finished. The injector alway gets voltage when the switch is on. The ECU pulses a ground to the injectors. So you will read voltage at the plug even if the ground is bad. One would think that you should read ground on the negative wire to the injector, but that is not so. You will read resistance I cannot remember how many ohms. This is known as a normally open circuit, the ECU gets signal from the ignitor to let it know when to do the pulse the engine relative to TDC.