Help diagnosing a no start / rough start problem.

[wret]

My daughter is having trouble with her 99 GS. So far I have diagnosed it only over the phone, but she has a couple halfway savvy people helping her on the other end. At first it wouldn’t start at all and her friend suspected a timing belt failure. After checking the alignment at TDC, he was able to rule it out. He finally decided the problem was two bad injectors. They replaced them today and it ran seemingly okay for a short period and then digressed to very rough running/stalling. He said that injectors are burning out. Does this sound like an ECU problem? I know turbo 2g’s are notorious for ECU problems but I know too little about 420A’s.

 

[dr1665]

You might check the connection at the ASD and fuel relays on the firewall on the driver's side. At the same time, I'd see about backprobing the CAS and CMP for alternating 5VDC to be sure the ECU is seeing the proper cam and crank signals.

Then again, it could just be really bad plug wires. They're known to cause all kinds of problems. Good luck, sir.

 

[Shadow98]

Another possible problem would be the coil pack. My car would stall whenever I stop at a light and not make much power (almost die) when i'd tryed to go. Check the resistance on it, i'll post what it's supposed to read later. I'm at work right now, or you can look it up. I know it's been brought up before.

 

[DSMcrazy3]

Wret that ECU problem you speak of is mainly focued on 95 and some 96's. It's the 1 plug ECU.

 

[Locke]

One thing that plagues 420a's, much of the main harness runs in a loom next to the EGR pipe, on the driver side of the engine. This often melts the insulation on some wires resulting in various who-the-hell-knows kinda problems, usually bad. Sometimes this does not burn the loom, so it will have to be removed, and the wires within visually inspected individually.

The ASD relay Driggs speaks of is unique to Chrysler motors, so is often overlooked by those unfamiliar with it. If it fails, you will have no fuel or spark. It can get gunked up and act intermittently, though rare. Simplest way to check is to listen for a sharp "click" when it is powered on or off. Less than infinite ohms through the relay for gunk. Poor power (flaky connection) can also cause it to act intermittently.

What has come of the over-the-phone diagnosis? What has been checked or tested, and the results?

 

[wret]

Well, the report is that there is spark in all cylinders but there was a problem with two injectors and they were replaced. I know injector failure is somewhat rare and if two were failing at the same time, it's highly likely that the problem originates elsewhere. No CELs.

 

[Doug99RS]

The power for the injectors is shared on a common wire (ASD circuit) and should be 12volts. The ground is individually provided through a driver in the PCM.

You mentioned two cylinders being dead and while I don't want to steer your mechanic too far from the injectors has he considered a bad coil pack? It has companion cylinders (1&4, 2&3) which could account for two dead cylinders. Then there's also the possibility of a blown head gasket between two side by side cylinders (1,2 or 2,3 or 3,4).

A simple KV Tester like this one:here
Can VERY quickly tell you which cylinder is truly dead and which isn't. Then you can start swapping plugs and wires to different holes to rule out things.

You've got a PM.
Doug

 

[VelocitàPaola]

I'd recommend looking for melted wires near the EGR return tube, like Locke suggested. If at all possible, try to trace the injector wires all the way back to the ECU and ASD relay.

Like Doug said, the injectors have a continuous +12V supply, but the ground is interrupted by the PCM. If the wires melt and short against an engine ground, the injectors will be forced to sink an incredible amount of current, destroying them in no time.