Fuel system question / ongoing problems

[the_dingman]

So it's not been since early December that my 4Runner ran properly... I've gone through lots of troubleshooting, and I thought I had it pegged at the fuel injector that had me with a dead cylinder.

Problem:

I sent my fuel injectors in to RC Engineering, and they came back a few days ago looking brand new (the went in with rust and peeling paint, now they look like brand new metal). I put everything back together, and my engine did start, and runs if I keep the throttle up, but dies on idle. It sounds perfect for a second after starting, then gets rough. RC said one of my injectors was 'dripping'.

Possible problem:

I'm leaking fuel out of the 2nd and 3rd injectors, after removing them, it seems that I pinched the seals, and they need to be replaced.

First question:

Would a 'dripping' injector cause a dead cylinder?

Second question

Can my leaking injectors (leaking between the fuel rail and the injectors) be the current cause of running rough. In other words, can low fuel pressure before the injectors cause the engine to run rough?

Third question:

Is there a way to pressurize the fuel system without the intake plenum installed? I'd like to see if there are any leaks after replacing the seals before putting it back on.

Fourth question

I may still have a dead first cylinder. So far I've replaced my plugs and wires, distributer cap, and had my injectors rebuilt and tested. I've also performed a compression test, with cylinders 2, 3 and 4 testing at 180psi, and 1 (the one that was dead) at 184. I know the spec is for 172... Is it possible that my compression being too high it the problem?

Beyond spark plugs, wires, distributer cap, and fuel injectors, what could be a possible problem? What's the best way to find out if my injector is getting a signal?

 

[Alabama4Runner]

Unfortunately I cannot answer most of your questions. However....first the easy one. Too high compression is not a problem so forget about that (your question 4).

Did they say you had a dripping injector before or after their service? If it was dripping then they should have repaired it. Call them if you need to to verify but I'm guessing that it wasn't returned "dripping".

I can't answer your second or third questions, sorry. The only other thing that I could think of is the start-up injector but if that's the problem then it should go away fairly quickly after the engine warms up.

I'm guessing it's the leaky injectors or something totally different.

 

[K_Labs]

Second question

Can my leaking injectors (leaking between the fuel rail and the injectors) be the current cause of running rough. In other words, can low fuel pressure before the injectors cause the engine to run rough?

Well of course it will cause your engine to run rough. For starters injectors are supposed to turn fuel into a fine mist. Dripping will cause it to burn differently because when your injector is working properly it turned into a vapor almost. Thus causing your engine to run rough. I'm not saying it's the only problem but it's 1 of the problems. If you aren't getting the right air fuel mixture it will burn differently also. Because the downward stroke of your cylinder has not changed you still have the same amount of air now u just need to get your fuel right.

0oh a dead cylinder..... Ouch please God let it be anything but the rings or heads.

 

[drmorbius]

If it sounds perfect at all you no longer have a dead cylinder by definition ("sounds perfect for a second"). Yes dripping injectors would cause it to run rough and flood out at idle. I am not sure, but if you turn on your key without starting it, doesn't your electric fuel pump run then? If it does then that will pressurize your system.

 

[klr toy]

I would start by checking if you have any engine codes. It sounds like it runs ok in open loop and then when it goes into closed loop a few seconds after startup is when you have an issue. In open loop, the ecm uses preset parameters. In closed loop, it relies on the various sensors to provide feedback and then uses that info to make adjustments to how much fuel the injectors deliver. Your compression is not a problem at all. You can eliminate the bottom end. I think you have an electrical problem or possibly a vacuum/egr valve leak. If you pull the plugs and they are all dry, then you should be able to eliminate spark. If any of them are wet, then I would lean toward the ignition system. You can isolate the egr valve by removing it and blocking off the ports or by capping the small vacuum lines coming off your throttle body. If you have no codes then it can get tedious. You will have to start checking all of your sensors with an ohmeter and make sure they are in spec. Any Haynes or Chilton manual will have that info. The first ones I would check are the throttle position sensor, the green and brown coolant sensors at the front of the thermostat housing, and then maybe the mass air flow sensor. Other than that, good luck!!! Confirming this stuff on your own will be much cheaper than sending it to a shop or changing parts.:biggrin2:

 

[klr toy]

Oh, and the easiest way to check if the injector is firing is to hold something such as a long 3/8" extension or a piece of wood or something up against the injector and then hold the other end up to your ear with your hand wrapped around it. This will magnify the sound. If you can hear it clicking, then it is firing. Check all of them like that and compare to make sure they all sound the same. If you don't hear anything on any of them, then you need to start checking the harness between the injectors and the ecm. If you still think it is an injector, unplug them one at a time and see if it runs any different. If you find it runs rougher when you unplug one, then you know that cylinder is firing. If there is no change, then you know that it is not firing.

 

[the_dingman]

Part of the problem testing the injectors is the fact that they are buried underneath the intake plenum, I can't unplug them, or get something to them to listen to them without taking off the plenum, and the engine isn't going to run with it removed.

I know my injectors are good, one was dripping before it was cleaned, after cleaning they were tested and balanced, and are currently as good as new.

I'll have to check sensors and codes, but I have a feeling that my problem is with the fuel leakage at the injectors. My engine ran perfectly until cyl 1 stopped firing (there was no change at idle when I unplugged the spark plug). I guess I need to replace my injector o-rings and see if the problem fixes itself. Unless a new problem popped up in the time it's been sitting in the garage...

I'm also thinking that I may have crossed a vacuum hose or two on the intake plenum, does anyone have a good diagram or high resolution photo of which ones go where? I'm most concerned with the two hoses that run to the power steering pump.

Thanks for all the great help and ideas!

 

[04 sc V8]

Make sure the new o-rings aren't twisted when you install them and lubricate them before installing the injectors. I'm sure after having the injectors redone they're not dripping fuel anymore. A few crossed vacum lines will make it run pretty bad.

 

[K_Labs]

Crossed vaccum lines will make the engine run like a re****ed japanese kid put your motor together. You should definitly look into that and mentioned it sooner. I believe I had a problem with vaccum lines before and there is a link to the power steering hoses else where on this forum. Here you go: http://www.toyota-4runner.org/showthread.php?s=&threadid=33498

I'm thinking it's on page 2 I don't quite remember but it is there.

 

[K_Labs]

Crossed vaccum lines will make the engine run like a re****ed japanese kid put your motor together. You should definitly look into that and mentioned it sooner. I believe I had a problem with vaccum lines before and there is a link to the power steering hoses else where on this forum. Here you go: http://www.toyota-4runner.org/showthread.php?s=&threadid=33498

I'm thinking it's on page 2 I don't quite remember but it is there. yup page 2 2nd post

 

[the_dingman]

I'm fairly sure I got them all right, as most of them are pretty obvious, but there were a few that are so close it's hard to tell.

I'll follow up later today after I replace my injector's o-rings and get them back in.

 

[the_dingman]

update!

So, I think I've fixed the leaks, but I'm still running rough. I decided to pull each spark plug after running, and 2, 3 and 4 were dry and a bit dirty, however #1 came out looking brand new. It seems I'm still not getting fuel into #1...

Now, I had all 4 injectors cleaned and tested, all 4 tested good. I'm fairly sure that it's not even the same injector in the #1 spot... so that leads to... Wiring! Yay!

What's the best way to test if the wires are good all the way to the injector? I would assume that I could jump the pins on the connector to the injector, find the other ends, and test for continuity, but where does the other ends of those wires go?

Am I more likely to have a problem with the ECU than with the wires (I do have a spare)?

So far I know:

-I have spark
-I have fuel supplied to all 4 injectors
-I have good injectors
-My compression is good

I still have a dead #1 cylinder, and it seems no fuel. Where should I look now? :dammit: :wtf: :help: :cursin:

 

[04 sc V8]

The injector wires go all the way to the ECU. You can check them for continuity, I'm sure someone on here must have a wiring diagram for your truck. I have a paper one from a factory service manual. If you can't find one I'll try to scan mine and send it to you.