Car trouble

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Bellhead
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Car trouble

#1 Post by Bellhead »

Not sure if this is the right board for this, but here goes..

My father was given a '96 Plymough Grand Voyager 3.3L a few years back. It has about 200k on it. Last summer, it died on the side of the road. No spark, no fuel, no nothing. We used my grandmother's AAA to get it home. The next day, I tried it. Same thing. But the day after it lit right up, on 5 cylinders.

Now, I know it's #6 that's not firing, as I can unplug the injector with no effect. I swapped the plug and injector with #4 with the same results. The odd part is that if I unplug one of the vacuum lines on the manifold, it will run perfectly, with some code for the line I unplugged.

The best answer I've gotten thus far is "get a new car".
Has anyone seen this before, or have a clue what's going on here?
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tony1695
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Re: Car trouble

#2 Post by tony1695 »

I'd recommend researching the exact model of the car. This may be a known issue that people online have figured out how to fix.
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Hayate
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Re: Car trouble

#3 Post by Hayate »

It's probably a good idea to take the car to a professional to have it properly diagnosed. It's hard for anyone to say with any accuracy what is going on without the car in front of them. The internet is good for many things, but often the people writing the stories are not real mechanics.
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Bellhead
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Re: Car trouble

#4 Post by Bellhead »

I will not pay $125 for a professional to diagnose a '96 Plymouth, and I already have tried looking up the exact model online. I have yet to find any possible solutions, or descriptions of similar problems.
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Lordadmiral Drake
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Re: Car trouble

#5 Post by Lordadmiral Drake »

You could try find a workshop manual on the internet, those have step by step diagnosis instructions
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Re: Car trouble

#6 Post by Salemcripple »

I actually made an account just to answer your question lol. But yes I am actually a mechanic, and as already stated it's near impossible to tell exactly what's going on without having the car in front of me. But I can point you in the right direction! I'm 95% sure you're not getting a signal to that injector as you said you swapped them with the same results. But just to be sure you should get yourself whats called a noid light to test it. They can be bought for arround 20 bucks, or rented for evem cheaper. But be sure to get the correct one! Test for a signal at the injector (my guess is you won't have one)

. Next you're going to be testing the wiring . I found this to help http://econtent.autozone.com:24991/znet ... 03c6c1.gif . Make sure you disconnect the negative battery terminal, and testfor continuity through every wire, and every connection in that circuit. Check for cracks, check for loose fitting or corroded connections. Before you go disconnecting the ECU, know that SOME older Plymouths will loose their memory and need to be reprogrammed if they become disconnected. Don't say I didn't warn ya!

If all else tests fine, then your ECU is to blame.

Oh, one other thing I just now thought of! Have you actually tested the spark on that cylinder?

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Bellhead
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Re: Car trouble

#7 Post by Bellhead »

Salemcripple wrote:Check injector signal and spark.
Already done, that was step one. Plenty of spark, and the injector is definitely getting signal. That, and after I unplug it and plug it back in, I can feel it energizing.

That's a good point, though. I could try checking the resistance in the plug wires again, but considering how strong the spark was, I don't think that's it either.

And if it was the ECU, why would a vacuum leak fix the problem?
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Re: Car trouble

#8 Post by Salemcripple »

Hmmmm.. well if your getting spark, getting signal, your ECU is good. It's tough to say why creating a vacuum leak would smooth it out, but it still might be another vacuum leak somewhere throwing off the A/F ratio (even if it is for just for one cylinder) i would start there just to be sure. this site here has some good advice about checking for vacuum leaks http://www.aa1car.com/library/vacleak.htm

You should also test the EGR, here's some info on EGR valves but to really know how to test it, your gonna have to look in a repair manual for your specific application http://www.aa1car.com/library/egr.htm

Fuel pressure can be another problem. Too little fuel pressure can cause a bad spray pattern, and or throw off the A/F ratio. So it should also be checked. A vacuum leak can also cause low fuel pressure as the fuel pressure regulator is vacuum operated.

Have you tried a compression test? Even with no smoke the compression could be low enough to cause misfire.

Other than those, I'd really have to get it connected to a diagnostics scope to see what's happening inside the cylinder while it's running.

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Re: Car trouble

#9 Post by Bellhead »

I may be able to bring it in to school and check it here... They've also got sets of compression gauges and fuel pressure gauges that should work.

I could see compression causing issues, but only on one cylinder would be a little odd.
I might believe it was a fuel pressure issue, if it had a vacuum regulator. Mine doesn't seem to. That, and the cylinder in question is the first one on the rail, and I tried swapping the injector to no avail.

I can try to bring it in in about 3 weeks. It'll be free to then.
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Re: Car trouble

#10 Post by Salemcripple »

You have a fuel pressure regulator, trust me lol. If it's fuel injected it needs a way to vary fuel pressure based on engine RPM. It's at the very end of the fuel rail, and will have a vacuum hose hooked to it. I found this video on replacing a fuel pressure regulator on an older 3.3L so it might be a bit different than yours (just so you know where it is, and what it looks like). Also the way they tested it, won't always work. In the video they found it to be bad because fuel was making g it's way into the vacuum line. It would only do this if the diaphragm inside was ruptured. Yours on the other hand might simply be stuck.

https://youtu.be/3LGZOn0nA-A

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Re: Car trouble

#11 Post by Bellhead »

I'm not saying it doesn't have one, I know it does. I just don't think it's on the fuel rail. I've got a Ram 1500 from the same era, and that one is regulated at the tank. I figured this one was the same, as I did not see a return line at the tank or on the rail. Who knows- maybe it's a vacuum regulator at the tank.

I'll have another chance to look at it today, so maybe tomorrow I'll have a concrete answer, but until Friday, my time for further diag is limited to.. well, about 10 minutes a day, all told. Fun times.

EDIT:
Well, whichever version of the 3.3L that van had, mine is different. I in fact to not have a vacuum regulator on the fuel rail. There may very well be a vacuum regulator at the tank, though I am a little more inclined to believe it is mechanical.

And, coincidentally, the pull-off-a-vacuum-line trick no longer works for some reason. I can take it in in two and a half weeks for Open Shop and compression test it, but that's the best I've got. More to come tomorrow.
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