Engine will crank but not start

Tiny
RONWARP
  • MEMBER
  • 1992 DODGE VAN
  • 130,000 MILES
My Ram Van 250 with a 318 ci engine was idling fine a few weeks ago then began to sputter and died. I thought it had ran out of gas but that's not the case.

I suspected the ECM (been replace 4 times!) So I had sent it out for testing. They found 'leaking caps' and I had them refurbish and test it. Did not fix the problem.

I also replaced the ASD relay. Did not fix the problem.

I checked the coil. Tested within specs. I have 9 volts at the coil when cranking. Have a new battery.

I also checked the voltage at the Throttle position sensor. Has 5 volts when ignition is 'on' so computer is getting a signal apparently.

I had previously had the van die on me once and a fuse link wire melted. Replaced it with a circuit breaker setup that's worked fine over the years. It was not blown and is functioning.

I am at a loss as to why it will not start. I have no spark. Checked the distributor and it seems okay. I understand that the Crank Position Sensor could be an issue. Is there a simple test for this component?

Otherwise I am at a total loss as to why it won't start. It is definitely electrical in nature as I have fuel and the fuel system pressurizes when the key is in the 'on' position.

Thanks for any help you can send my way! RW
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Thursday, September 26th, 2013 AT 11:06 AM

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Tiny
CARADIODOC
  • EXPERT
Forget the Engine Computer. Chrysler had almost no problems with them in that time period. Forget the throttle position sensor as that will not cause a no-start.

You already tested the crankshaft position sensor. Its signal and the signal from the camshaft position sensor in the distributor must show up at the computer, then it turns on the automatic shutdown, (ASD) relay. That's what switches on the battery voltage to the ignition coil. Given that you have voltage to the coil during cranking, but there's no spark, a failed ignition coil is the main suspect.

Even if the ASD relay doesn't turn on during cranking, you'll still appear to have fuel pressure because it will turn on for one second when you turn on the ignition switch. That relay also sends current to the fuel pump or pump relay so the pump will get the pressure up to normal even if it doesn't run during cranking. You have to look for injector pulses too, but in this case, concentrate on the no spark.

Have you checked for diagnostic fault codes? If so, what came up?
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Thursday, September 26th, 2013 AT 11:42 AM
Tiny
RONWARP
  • MEMBER
Hi CardioDoc!

Thanks for getting back to me so fast! And for your explanation of how the CPS works.

The diagnostic codes only give me "1-2" for battery voltage (I bought a new battery). Otherwise, "5-5" which is the end of the analysis. I was a little confused why nothing else would indicate during this.

I did take the coil to the auto parts place and their diagnostic chart showed the expected range of resistance between the input power leads and the coil wire lead. It seemed within specifications. Even with that, could it still be a coil issue? Seems plausible.

Thanks for your help and expertise! :) Ron
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Thursday, September 26th, 2013 AT 12:20 PM
Tiny
CARADIODOC
  • EXPERT
If you replaced the battery, you erased any fault codes when you disconnected it. Code 12 just means the battery was disconnected. That code will self-erase after 50 key starts. Also, the Engine Computer needs to relearn "minimum throttle" before it will know when it has to be in control of idle speed. Until then, you may need to hold the accelerator pedal down 1/4" to get it to start and stay running. You won't get the normal idle flare-up to 1500 rpm for the first few seconds, and it will usually stall at stop signs. Once the engine is running, minimum throttle will be learned when you drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the pedals.

As for the ignition coil, I've never actually tested one. I did have one fail intermittently and I chased it for over a year on my '88 Grand Caravan. It finally failed completely two years ago, THEN I could diagnose it. That was the first time since the van was new that it didn't get me back home.

The problem is the resistance checks you're having done are rarely going to not pass. The wires don't break that often. What usually happens is the spark arcs to the metal case instead of going to the spark plugs. Current takes the path of least resistance, and once that occurs inside the coil, it leaves a carbon track behind, just like can happen inside a distributor cap, and that carbon track is a conductor. Resistors used in electronics are made from the same carbon.

It is also possible for some of the loops of wire in the secondary part of the coil to short together or the varnish insulating those wires can burn off. The range of specs for resistance is so broad that a partially-shorted secondary can read lower resistance than it did when it was new but will still fall within the acceptable range. The voltage it can develop will be reduced, and if it can't develop enough to jump the gap between the rotor and distributor cap terminal AND the spark plug, AND the high-resistance spark plug wire, you'll have a no-start, hard-start, or misfire condition.

The symptoms on my van mimicked a bad accelerator pump in a carburetor, which at first didn't make sense. That's why I never suspected the ignition coil. By the time I got under the hood whenever the engine stalled, I never caught it having no spark until the day it failed completely. That's when it finally presented the same symptom you have now.
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Thursday, September 26th, 2013 AT 10:59 PM
Tiny
RONWARP
  • MEMBER
Thanks CardioDoc! I have decided, based on your feedback, to purchase a new coil despite the fact that it supposedly tested "okay" with regard to the OEM specifications of resistance. It was in range, but I believe you may be correct about this being the real culprit! Talk about frustration.I usually am pretty good with electrical issues, but I hate spending money to replace parts to chase a problem! I did have the EMC serviced, new ASD relays (they come as a pair), and then the new battery. So, I just order online from Advance Auto and I will let you know if this provides the fix. If so, I'll be sure to send you some $$$ for your great help! Have a nice weekend! :) Ron
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Friday, September 27th, 2013 AT 8:48 AM

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