Injector stops on warm start

[ArcaineGST]

Problem: Injector 2 stops firing when starting car after driving/warming up to normal operating temperature.

Background: The car will start fine from a cold start, warm up, and continue to drive just fine for as long as I want. When I turn the car off, say to fill up gas, and then restart it, it misfires/sounds like it's only running on 3 cylinders. Sometimes if I restart it immediately after shutting it off, it will restart with no issues. In order to get it back to normal start with everything fine, I have to let it sit for about 2 hours until it cools.

Checks: Happened today when filling up gas, so when I got home I left it running poorly and listened to each injector with mechanic stethoscope. 4, 3, and 1 clicked, but 2 did not. Pulled the spark plug from 2 and it was sparking beautifully (no change in idle). So I pulled the connector plug from the injector and no change. Pulled the injector connectors from the remaining 3 cylinders and all three dropped the RPMs.

Has anyone heard of anything close to this? Or can suggest some additional tests? I want to say faulty injector, but then why would it run just fine for hours from cold to hot on a cold start?

 

[cammons]

Could be just a faulty injector, try swapping the bad injector to a different plug and try listening to it. Like move injector 2 to cylender 3 and 3 to 2. If it still does the same then more likely the injector is bad.

 

[DSM1G90]

Been there and done that with my Laser: No.3 was doing the same-intermittent firing and Code 41 from the ECU.

A DSM user on here had a set for sale with low miles on there .. and got them cheap.

Got my firing issues solved with the full tradeout.

Just make sure that, if you just replace one, that it matches the other three-be it a single jet or a multijet injector.

 

[ArcaineGST]

Thanks guys, I'll pick up some new injectors, and give it a try. Any brand recommendations? Not familiar with yet, but I guess I'm about to be, .

Also, will I need to drain the fuel rail/system before unplugging injectors? Or are they hot swappable?

 

[gofer]

You need to relieve the pressure in the system or else it will spray and there's potentially 43psi in there. The best way to do it is unplug the fuel pump connector on top of the fuel pump hanger (under the back seats) and start your car and let it die, as if it ran out of gas. Once it shuts off you can plug the connector back in, just so you don't forget later, and perform whatever maintenance you need to on the fuel system and there won't be any pressure in the rail.

 

[delta448]

Ohm out the resistor pack and injector first, both cold and warm?

 

[ArcaineGST]

You need to relieve the pressure in the system or else it will spray and there's potentially 43psi in there. The best way to do it is unplug the fuel pump connector on top of the fuel pump hanger (under the back seats) and start your car and let it die, as if it ran out of gas. Once it shuts off you can plug the connector back in, just so you don't forget later, and perform whatever maintenance you need to on the fuel system and there won't be any pressure in the rail.

Excellent, thank you!

Ohm out the resistor pack and injector first, both cold and warm?

I've done the injectors and the connectors previously, and remember all injectors falling within spec, but one connector was lower. I will retest at both cold and warm on injectors and post results.

Where/how do I go about doing the 'resistor pack'? Is that the sealed up long black box sitting over the spark plug coil packs?

 

[gofer]

*cough* SEARCH *cough* how to test it. ---> http://www.dsmtuners.com/forums/maintenance-repairs/382964-injector-resistor-pack-test.html

It's the silver box on the firewall that sits just behind the IM, the connector is circled in the picture.

http://www.dsmtuners.com/forums/151542336-post52.html

 

[ArcaineGST]

*cough* SEARCH *cough* how to test it. ---> http://www.dsmtuners.com/forums/maintenance-repairs/382964-injector-resistor-pack-test.html

It's the silver box on the firewall that sits just behind the IM, the connector is circled in the picture.

http://www.dsmtuners.com/forums/151542336-post52.html

Duh, mybad about not searching that one. I've literally been able to find everything I've ever needed by searching on here. Shouldn't have gotten lazy just because we've started talking about it. Sorry bout that.

Injector Ohms came back: COLD/ (1) 2.5-2.3, (2) 2.8-2.6, (3) 2.5-2.3, (4) 2.4-2.3. HOT/ (1) 2.7-2.5, (2) 2.9-2.8, (3) 2.7, (4) 2.6. Hayne's has the range listed for turbo at 2-3 ohms @ 68-degrees F. Looks like all fall within range. Would number two being a little higher effect it?

 

[gofer]

Those are within spec.

Before you spend any money, swap the #2 inj. to #1 and see if the problem follows. Cammons already suggested this and it really is the next step, you could replace all 4 injectors to find out it was something else and end up with the same problem. I understand you're looking for an excuse to buy new fuel injectors but what good are 550's going to do when your car is only running on 3 of them? Troubleshoot it, fix it, then modify it...

What CAS do you have?

 

[luv2rallye]

Or before putting out for pricey new injectors you could try cleaning them: http://www.dsmtuners.com/forums/newbie-forum/448803-cold-weather-engine-issues-2.html#post153136134

 

[ArcaineGST]

Those are within spec.

Before you spend any money, swap the #2 inj. to #1 and see if the problem follows. Cammons already suggested this and it really is the next step, you could replace all 4 injectors to find out it was something else and end up with the same problem. I understand you're looking for an excuse to buy new fuel injectors but what good are 550's going to do when your car is only running on 3 of them? Troubleshoot it, fix it, then modify it...

What CAS do you have?

Stock CAS as far as I know. Haven't replaced it since I've owned the car. Just tested it during my litany of tests in December when car died due to broken CPS. When backprobing the CAS (Ohms) with key ON: Black = continuity, BLU/RED = 5.04, RED = 11.25. Cranking BLU/RED = .4, 2.8, 3, 1.8.

Resistor pack testing will happen here today after I get out of work. Didn't have time on my way in this morning to unbolt the mess of hoses that guard it. Thanks for the link to the test too . I couldn't find it in my Hayne's manual.

Or before putting out for pricey new injectors you could try cleaning them: http://www.dsmtuners.com/forums/newbie-forum/448803-cold-weather-engine-issues-2.html#post153136134

I'm definitely going to swap and test, and then clean them before I buy new. I try to be as frugal as possible, while doing things correctly. Just putting the question out about new in case it comes to that. But that thread you linked to sounds like similar to what's happening for me (searched for injector and misfire stuff. didn't think that it was the cold weather). Thank you!

 

[gofer]

Hmmm... broken CPS?

Could you elaborate a bit more on this too, like what the problem was and what you did to fix it?

 

[ArcaineGST]

After testing the Resistor Pack I got some interesting results. Well, one interesting result.
MALE CONNECTOR: COLD/ 1-3: 57.0, 4-3: 62.0, 5-3: 61.9, 6-3: 6.9. HOT/ 1-3: 56.9, 4-3: 61.9, 5-3: 61.8, 6-3: O.L (couldn't get a reading). Just retested after 2.5 hour cooldown, and 6-3 bounced from 5.4 to 8.9 to 12.6 and back down. Strange.

FEMALE CONNECTOR: COLD/ 1-3: 6.3, 4-3: 6.2, 5-3: 6.3, 6-3: 6.2. HOT/ 1-3: 6.6-6.4, 4-3: 6.5-6.6, 5-3: 6.6-6.5>6.2-6.3, 6-3: 6.7-6.5>6.3. (> equals a drop due after taking readings 2nd and 3rd times while I was in there).

Hmmm... broken CPS?

Could you elaborate a bit more on this too, like what the problem was and what you did to fix it?

Sure thing: Was at stop light one night, went to take off when green, car died, thought I snubbed it. Tried to restart multiple times with jump pack, truck jump, couldn't get started so towed it. Started run through all sensor tests by searching and following other threads. All checked out within spec, except for the last one, CPS. Tested: Key ON> Black=Conintuity, BLU/RED=5.04, RED=12.12, cranking BLU/RED=5,4.9, 5 (no change).

So I took off all belts, timing belt covers, and discovered a snapped BS belt, which ran into CPS to crack it in half. So I sucked it up, followed VFAQs and other threads here, replaced Timing belt, pulleys, tensioner, etc., BSE, water pump, crankshaft pulley, and drive belts. Quite the project to solo run, but I got through it and car runs great again. Except for this pre-existing condition, which I thought may have been fixed during all the other stuff, but apparently not. It used to do it very seldom, and then slowly got more prevalent. Now it does it every time.

Sorry for the run-on sentences and bad grammar. Tried to summarize in as little space as possible. So I have all the test numbers for almost every other sensor as well.

 

[gofer]

When testing the resistor pack, which is the male connector...

1-3 is for inj. #1
4-3 is for inj. #2
5-3 is for inj. #3
6-3 is for inj. #4​

So your funky readings on 6-3 were more than likely a poor connection with the DMM meter lead and not a fault with the resistor pack. I say that because you were leaning towards inj. #2 being the culprit.

If you were testing on the female connector those measurements don't really mean anything. Those wires coming off the resistor pack go to the injectors and back through the ECU, so I'm guessing you were measuring resistance across the wire/injector/ECU? There is no SPEC on those resistance checks but the fact that they're all consistent I'd call that good.


I asked about the CPS problems because those can contribute to misfires like this, if it was doing it before the BS belt broke then I wouldn't suspect it.

You can pull the fuel rail (three 12mm bolts) and rest it on top of your IM, placing the tips of them in a 5ga bucket or similar to catch the squirting fuel. Leave the injectors plugged into the rail/harness and have someone crank the car while you're watching the injectors squirt (the best time to try this is when it's acting up).

 

[Beaubo]

My girlfriends Jeep Grand Cherokee had this issue with one of the injectors working fine at cold start-up but not working when warm. I tested them with a volt meter by checking ohms and found that I got absolutely nothing when the injector in question was warm.
I replaced it with a new/refurbished injector from Autozone for $40.00 it is an OEM injector that has been refurbished.
This solved the problem.

 

[delta448]

MALE CONNECTOR: COLD/
1-3: 57.0,
4-3: 62.0,
5-3: 61.9,
6-3: 6.9.

HOT/
1-3: 56.9,
4-3: 61.9,
5-3: 61.8,
6-3: O.L (couldn't get a reading)

When testing the resistor pack, which is the male connector...

1-3 is for inj. #1
4-3 is for inj. #2
5-3 is for inj. #3
6-3 is for inj. #4​

Did you test which injector's harness plug has continuity with the wire you're calling resistor pin #6?

Or even look at which color wires are going to injector #2?

http://www.dsmtuners.com/forums/151528346-post6.html

http://www.dsmtuners.com/forums/151528344-post4.html

I really think you just need a new resistor...

 

[ArcaineGST]

Did you test which injector's harness plug has continuity with the wire you're calling resistor pin #6?

Or even look at which color wires are going to injector #2?

http://www.dsmtuners.com/forums/151528346-post6.html

http://www.dsmtuners.com/forums/151528344-post4.html

I really think you just need a new resistor...

Great suggestion about the wire colors running from plug to connector. Didn't cross my mind. Thank you. I actually did test the injector connectors before I started this thread, but didn't notice anything strange so I didn't record the data (most likely because I'm not exactly sure what i'm looking for. First time with fuel ). I'll do it again cold and hot and record the numbers.

Sorry i haven't replied for a few days, was waiting until I did the others tests first. Did the injector spray test, but haven't swapped them to a different cylinder yet. Drove car home, restarted to make sure it was missing, it was so I pulled the rail with injectors attached and had friend crank while I observed. Took video that I haven't uploaded yet, but all the injectors were all squirting. There didn't appear to be any obstructions with the stream pattern. Now, being that I've never observed this before, it could have looked fine to me when it is actually bad.

If the misfire still happens on 2 after the injector swap I'm guessing that most definitely suggests the resistor?

 

[ArcaineGST]

Ok, so tested the plug injector connectors again. Results are as follows:
COLD: (1) 34.6, (2) 41.6, (3) 41.6, (4) 41.6. HOT: (1) 36.8, (2) 45.0, (3) 45.0, (4) 41.6. RUNNING: All O.L (no readings).

I tested the female plug for the resistor pack shown on this page a second time: http://www.dsmtuners.com/forums/151542336-post52.html. Got the same results when hot on 6-3: O.L (no reading).

I did discover that my EGR control solenoid plug was all gummed up or melted or something. Check out the pics. Would this possibly cause this issue? And can I clean that out and it be fine, or replace the plug and/or solenoid?

 

[DSM1G90]

Not so much gummed up, but that goo is placed in the connections to prevent outside moisture from corroding larger metal to metal connections, esp under the hood.

 

[luv2rallye]

Problem: Injector 2 stops firing when starting car after driving/warming up to normal operating temperature.

Or can suggest some additional tests? I want to say faulty injector, but then why would it run just fine for hours from cold to hot on a cold start?

I realize it appears you have a problem with injector 2 firing and with your tests i agree, it sure points to it (bad/clogged injector or perhaps intermittant ECU injector driver). But consider you may also have another problem. Your description of warmed up, turning off a couple minutes, and then starting again produces the problem, is the classic description of vapor lock. You may want to check this out: http://www.dsmtuners.com/forums/newbie-forum/217349-vapor-lock-hot-start.html#post1821514. Also: http://www.dsm.org/how-tos/JFM/HotStart.html. I agree the injector 2 still is a problem that needs a remedy but I thought you may want to check this link out in case there's 2 problems (if one is covering up the other).

 

[ArcaineGST]

I realize it appears you have a problem with injector 2 firing and with your tests i agree, it sure points to it (bad/clogged injector or perhaps intermittant ECU injector driver). But consider you may also have another problem. Your description of warmed up, turning off a couple minutes, and then starting again produces the problem, is the classic description of vapor lock. You may want to check this out: http://www.dsmtuners.com/forums/newbie-forum/217349-vapor-lock-hot-start.html#post1821514. Also: Hot Start Problem Fixes. I agree the injector 2 still is a problem that needs a remedy but I thought you may want to check this link out in case there's 2 problems (if one is covering up the other).

I actually came across that thread earlier as well and tried what Jim mentions, removing the vac hose from the FPR and then restarting. Didn't change my situation. I'll retest again tonight though. I didn't however, disconnect the FPR solenoid to see if that is the culprit instead of the regulator itself. Removing the line to that instead of the rail would allow me to test that correct? Or just unplugging it perhaps?

Not so much gummed up, but that goo is placed in the connections to prevent outside moisture from corroding larger metal to metal connections, esp under the hood.

Ahh, so that's normal then. Thank you!

 

[ArcaineGST]

So for an update. Been busy with life, but I swapped injector 1 & 2, and the issue transferred to cylinder 1. So thanks to everyone for the help and troubleshooting. I'll be searching for cleaning tips that work above and beyond using fuel injector cleaners from AutoZone, because I've been using those around a couple times a year. If I need to replace the injectors themselves, it looks like FIC 750s are only 289 from STM. Not intending on going anything larger than an evo3 16g if I do finish upgrading the system.

Will post resolved after injector clean/swap if issue goes away. Thanks everyone!

 

[ArcaineGST]

Wanted to come back and update with the resolved tag, but can't find a way to do so yet. So for now: RESOLVED.

Ended up replacing injectors with stock replacements and so far no issues in over 1500 miles. Thanks for everyone's help with this.