02 Caravan Gremlins
Hey guys. I’ve got an 02 caravan 3.3 with about 220k on the clock. Customer had Vehicle at another shop and they fired plugs, wires, coil pack , crank sensor, computer, fuel pump, injectors and injector harness at this thing with no avail. I believe it has 2 issues. Issue 1 is a long crank once warmed up shut off and let sit for around an hr. First check revealed slight to no fuel pressure with first cycle of the key. If you cycle it 3 or 4 times it will build Pressure and start. I’ve scoped the output feed wire for the FP from the bottom side of the IPM 1 channel on voltage and 1 on amps. When vehicle is acting up low to now fuel pressure I quickly jump to 13 amp spike and 11.83 volts or so, however I get 2 or 3 funny almost injector waveform looking patterns then it goes to zero amps. After several cycles of the key fuel pressure will come up and you can see the commutators with a nice looking signal? I’ve load tested circuit with high beam H11 and the relay seems to be putting out enough current. I am leaning towards a bad fp or possibly a ground issue. I unfortunately didn’t get time to inspect the rear harness and load test it there.
Problem #2. The thing has a random fish bite type misfire driving down the road. It also has a fish bite type stumble on rpm drop at around 1000 rpm. If you power brake to approximately 2k rpm or more on the way back down it’ll have a small stumble. I’ve scoped cam/ crank it looks good while experiencing issue. I’ve also scoped secondary ignition however I only have one secondary lead to clamp on the wires so I can only try one at a time. I’ve attempted to scope primary but kept getting so much interference I could not scope primary and secondary at the same time for whatever reason. I’ve scoped injectors they don’t appear to do anything funny while experiencing symptom. I was thinking possibly something with the 5v circuit? I was planning on scoping that in the morning. Im new to the pico and relatively new to scoping in general but I am very driven to use this tool to help with my diagnostic approach and learn more about it day by day. Has anyone ever ran into this before? I immediately assumed injector harness as I’ve ran into tons of that issue. However it has been changed and I even went to the point of uncovering the harness and very carefully going over every wire all seems good. Any help would be great thanks in advance. I am not on the level most of you gentlemen are with the diagnostics but I’m a hellava lot farther than I was a yr ago.
*This issue has been resolved, see this post for more info:
On the first problem, it most likely is a bad fuel pump. I've been burned twice by installing Delphi pumps in Caravans around that year. Both times, I had to warranty out the pump once, then the 3rd time, they weren't nearby, and had it towed to a dealer, where a factory pump was installed with zero issues. From now on, it's oe pump on all Chryslers, period.
To start off, it sounds like this vehicle has been backed up to the parts store and loaded up, hmmmm,,, Maybe drive it in forward the next time and see if that changes things :)
Can you please post your waveforms for others to see? Telling us how the waveform looks isn't a very good way to get others to analyze your problem. A picture is worth a thousand words.
I didn’t decide get to decide which direction it went into the parts store as it came from another shop with the parts cannon fired at it Lol.
I will get some screen captures tomorrow.
I've had a few Caravans with all those parts installed and they ended up being lean misfires due to intake gasket leaks. A little enrichment around the intake watching the O2 sensors will find them.
If the fuel system is returnless then you certainly need a fuel pump because the pressure should never drop that far. I also doubt you could achieve 13A if you had a bad ground. As for the misfire, where are your fuel trims while it is happening? If they are within +/- 10% then I suspect one of the ignition components, although new, is faulty. "They" may have dropped a spark plug on the ground, then installed it anyway, for all you know. Also the coil pack could be just a crap-brand. I'd at least wanna pull all the plug wires and inspect for carbon tracking.
Geoff, if it was just done, there won't be carbon tracking yet, but if they installed Champion, or Autolite, there's a good chance of cracked porcelain without being dropped. I have ran into it many times in the past, and so I refuse to use Autolite, and only use Champion in Chrysler products, while crossing my fingers, hoping there's no issue. The gap could also be way off. With how many parts have been thrown at this thing, it's obvious someone either doesn't know what they are doing, or they just don't care.
maybe they followed the flowchart..."step5- replace with known good parts and retest" LOL (to Sean)
I am with you on the Autolites. I have had too many issues with new plugs causing issues so I no longer use them as well.
Had a fellow tech go through that. When I got it, relative compression showed me an intermittent sealing issue on two cylinders. Went in-cylinder (lost the captures); cylinder leak-down was enough to get the ok for a valve job. Once the heads we're off the root cause was revealed... worn/pitted cam lobes on the most offending cylinders.
Valve job, cam & lifters....
Thomas papineau that’s the train of thought I’ve had. I feel thats along the lines Of whats going on I didn’t get much time to work on it today and my printer decided to lay down on me and considering the little town we live in i had to drive an hr and a half to get another , by the time I got back I had to try to get a few out for the customers that were in a hurry. I did However throw a vacuum gauge on it while I was waiting for parts and it seemed low to me. What do you guys think. This was around 875 idle.
Jeez, that's low. Possible plugged cat? Jumped time? Relative compression with synch on cylinder one, with cam & crank at the same time on four channels, if available.
I tried to upload the waveforms but it says it doesn't support said file?
I am lost on posting these waveforms. Regardless of what i do it says not an accepted file? Any ideas?
I don't know how yet. I am sure someone will step up and explain.
We currently are only able to accept graphical files such as .png, .jpg, .gif etc.
What program are you using?
pico. I was trying to upload them straight off My computer from wherever picos default storage is.
Those would be the raw files which we're currently working on supporting and should have that feature available soon. In the meantime, you'll need to gather a screenshot (or two) of what it is you'd like to share.
Here is a video that should help you with this process. Let me know if you have any trouble.
Ok guys so problem #1 was a bad fuel pump, actually 3 bad ones in a row. They were precision units from oriellys. The pressure was bleeding off and my assumption was the logic was to run the pump for a very short time when the key was initially cycled, because of the pump bleed off it would not build enough pressure to start, easy enough. Junk aftermarket parts. As for problem #2 the customer decided to deal with it due to the high miles and not wanting to stick anymore money in it. I did however grab a few waveforms. Please keep in mind i am new to scopes and in particular to pico so some of these may look goofy to you guys. I made my own pressure transducer and for some reason there is some interference or a bad sensor im not sure ill get that figured out at a later time. Cranking looked ok but it looked like excessive back pressure while running? I am not real familiar with in cylinder waveforms, although i have been trying to study them online. Anyhow here is what i got.
Please tell me it finally got a factory pump? Like I said, I ran into this twice with Delphi, which used to be an oe supplier.
In cylinder waveforms are something that I need some class time on, because it is so new to me, in fact, my scope gets used once every month, or two, because I worked for so long without one, that I rarely need it for diagnosis.
I still would not be surprised to see a cracked plug too.