Next easiest step Pt. 2

Let’s try this again! This example is a bit more open ended as far as diagnostic direction. Everyone is welcome to comment/speculate, as always, but I’d really like to see the DIYers around here weigh in. Put some of those ScannerDanner videos you’ve watched to use!

2007 Chrysler PT Cruiser gets towed in, won’t start. In the parking lot, I start with codes. Only found one:



Yeah, no help there. For the record, this won’t turn into another Audi S5 engine mount situation . The A/C clutch WON’T cause a no start on this vehicle. :lol:

Onto the scan data. This isn’t always the next step I take during no start diagnosis, but I went this direction because there’s a few PIDs here that we can use to our advantage. I picked the ones I want and give the engine a couple cranks:

www.scanshare.io/share/7uCXauCJuU_bxQ5EOvGx-g



Now you’re at the diagnostic crossroad. Where do you go from here, and why? No wrong answers, just interested to know how you’d attack this. Please be sure to include your reasoning (if any) for your next step, so others might learn from your approach.

I think that I would check for spark at the coil because it is real easy on this car even though it has a cam and crank signal. If it has spark i would go to fuel pressure.

I would add a fuel source or check fuel pressure because you have rpm's, cam and crank (should have enough inputs for spark and injector pulse), and the map sensor seems to indicate some vacuum while cranking (like the cylinders could be sealing). I would also look at the tps for high signal.

Scratch the tps. I just looked again and I looks ok.

One vote for spark, one for fuel. Thanks, guys!

id check timing, looks like its out of sync

nm had to get the glasses on. you weren't cranking it when it went out of sync

I can tell by scan data you have RPM, sync, compression.

I would pull out the #1 spark plug wire and check for spark, mainly because all I have to do is grab a spark tester in the top drawer of my roll cart. if I have spark then it's on the fuel pressure testing.

Ro-longo wrote: I can tell by scan data you have RPM, sync, compression...

Saw that too, pretty cool!

I think the starter is drawing too much power, hence low crank speed = no start...? My car (vw polo 9n 1.9 tdi pd engine) will not start with anything less than a 300rpm crank speed

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Lots of different takes on which direction to go next, though a couple of you picked up on my thought process during this diagnosis.

First, the cam and crank PIDs. When doing spark and injection pulse testing, Paul usually infers that if you have both, then your cam and crank signals are present and good. In this case, I decided to turn that idea around and say that if I have cam and crank signals, then most likely spark and injection pulse are there. Too much of a logic leap? Hasn't burned me yet, but that day may come. :lol:

For reference, here's a Chrysler 300M with a jumped timing belt. This is how the PIDs look during cranking with a problem:



Second, the MAP and TPS PIDs. This goes back to one of Paul's case studies involving an S-10 with a broken timing chain:



We already knew timing was OK from the cam/crank PIDs, but watching the MAP sensor show vacuum during cranking is a good sign for compression. Weak vacuum, or positive pressure pulses during cranking, are a big red flag.

At this point, I pop the hood and go directly to fuel pressure. No Schrader valve, but I was feeling lucky/brave/stupid that day and decide to disconnect the fuel line at the firewall. Another crank, and I don't get a drop of fuel out. Jackpot!

I was very surprised to see this current waveform on the fuel pump circuit:



Not beautiful, but doesn't really scream bad fuel pump to me. :huh: Still, it's enough current to give me confidence in the pump power and ground. A pump assembly later, and we're running again.

Thanks for the replies, everyone!

Excellent write up Tyler!

You Guy's haven't gotten this car started yet? Dose it have spark?????????

Hey Sorry somehow i over looked the fix good going.

jimdandy327 wrote: Hey Sorry somehow i over looked the fix good going.

:lol: No worries, sir. I actually did this job around three years ago. I hope it's still starting, wherever it is! :silly: