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Re: 93 Dodge cranks but won't start in freezing temps
RamVan2500 #718591 January 10th 2017 3:31 pm
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Originally Posted by RamVan2500

Find the MIL wire from the PCM and connect a bulb or VM to it and count pulses for codes.


Don't I need to get the MIL to flash somehow to check, otherwise the MIL would just stay lit? I recall having to rotate the key a few times perhaps?

My biggest challenge with this is being able to repeat the conditions causing the issue. Because once the temps are above freezing I have no problems starting the van. When it is balls cold outside, it's also pitch black and that makes problem solving this a pain in the rump.


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Chris (The Ravishing One)
1977 Dodge B200 Shorty V8-360 4.10 rear w/OD A518 tranny
1993 Dodge B250 Hi-Top V8-318
1994 Dodge B250 Lo-Top V8-318 (RIP 1998-2013)
Re: 93 Dodge cranks but won't start in freezing temps
RavshngOne #718595 January 10th 2017 4:27 pm
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Originally Posted by RavshngOne
Originally Posted by RamVan2500

Find the MIL wire from the PCM and connect a bulb or VM to it and count pulses for codes.


Don't I need to get the MIL to flash somehow to check, otherwise the MIL would just stay lit? I recall having to rotate the key a few times perhaps?

My biggest challenge with this is being able to repeat the conditions causing the issue. Because once the temps are above freezing I have no problems starting the van. When it is balls cold outside, it's also pitch black and that makes problem solving this a pain in the rump.


If no codes present it still flashses a end of codes code. Put key into ignition turn switch from off to run three times. Off-run-off-run-off-run. It will flash codes. All you need is a bulb like a test light or even a VOM attached to the wire for the MIL from the PCM.

Only thing off the top of my head that will cause this issue is either fuel pressure too low, should be 43psi, or bad gas, lastly and highly likely is the ECT is faulty. If the ECT is fauty the vehicle will run richer. Too rich it won't start. One way to verify, though inaccurate, is to hold the gas pedal down just a little while starting. This will help lean out the mixture. I had a customer with an 88 Chevy that wouldn't start because of a bad ECT. I usually find the two pins in the ECT corroded more often than a faulty ECT. Too high resistance the colder the ECT reports as it's a Negative Coefficient Thermistor. I'll get back to you with resistance test values incase it escalates to that. Oh the ECM will have history codes so you may not need to replicate the issue. Also the ECM may not detect a faulty ECT only too high or too low a temp reading. Usually a faulty ECT will read -40F. Although I've seen some cause trouble at -27F.

Last edited by RamVan2500; January 10th 2017 4:29 pm.
Re: 93 Dodge cranks but won't start in freezing temps
RavshngOne #718598 January 10th 2017 4:42 pm
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Engine startup is open loop not closed my mistake.
At 32F the ECT that's two wire sensor next to the water outlet neck shall read 29.3-35.9 (kohm).

Re: 93 Dodge cranks but won't start in freezing temps
RavshngOne #718637 January 11th 2017 11:07 am
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I still believe that it is internal to the computer the solder joints go bad and open when cold enough keeping the module from turning on.If you can hook up a check engine light of some sort you could verify this.If the light doesn't come on when the key is on the computer is going bad.For the record I am a professional technician with 33 years experience.


1994 Dodge-Tannenbaum 1976 Chevy-dragonheart 1965 Ford-Screamin Eagle 2
Re: 93 Dodge cranks but won't start in freezing temps
jamvnr61 #718643 January 11th 2017 1:18 pm
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Originally Posted by jamvnr61
I still believe that it is internal to the computer the solder joints go bad and open when cold enough keeping the module from turning on.If you can hook up a check engine light of some sort you could verify this.If the light doesn't come on when the key is on the computer is going bad.For the record I am a professional technician with 33 years experience.

Jamvnr61, as I am thinking now, when I made my custom dash, I kept the circuit board in tact and simply removed the CEL bulb because I couldn't seat my tach in there otherwise. I should just be able to throw a bulb in the usual location and see. Is there any other way to test for a failing computer in above 32 degree temps? I think it's going to be 25-27 in the morning here this weekend. I'm an avid skier and last time I went to Whiteface up in your area it was near 0 most of the time. But, I don't want to take my van to Saranac Lake and then be stuck in the morning! LOL

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Chris (The Ravishing One)
1977 Dodge B200 Shorty V8-360 4.10 rear w/OD A518 tranny
1993 Dodge B250 Hi-Top V8-318
1994 Dodge B250 Lo-Top V8-318 (RIP 1998-2013)
Re: 93 Dodge cranks but won't start in freezing temps
RavshngOne #718645 January 11th 2017 1:59 pm
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It still never hurts to check for codes then check for possibly suspect sensors. If it were an PCM internal failure I doubt it would be the solder joints since the potting compound helps hold the pieces together. Temperature and PCM related sounds like capacitors with too much ESR or another temperature sensitive component. 25F is not too cold. The ECM should function well below 25F.

Re: 93 Dodge cranks but won't start in freezing temps
RavshngOne #718646 January 11th 2017 2:01 pm
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Back in 2005 or so, My ECM was failing in my 89. it appears similar in shape to the 93, but mine has a 14 pin connector inaddition to the 60 pin connector.

When it was failing, ususally it was the second start of the day. The relays would click on and off, the negien would stutter fart burp, occassionally backfire, and I wuold have to tap dance with the throttle just to keep it burping and farting.

Then like a switch was thrown, it would run perfectly.

The burpfart sceanario became more frequent and of longer duration until I replaced the ECM which solved the issue. I had found one wire leading to transmission had chafed and was burnt from grounding out on transmission. I thought that was the cause of the demise. Might have been.

My 14 pin connector was also problematic with techs piercing the insulationat the connector. the wires rotted and broke and my get me home fix was to drill out the failed wire through socket, strip wire, push it through and reseat connector.

This aided in destroying the solder joints on the pins, which I resoldered 2 years ago without a stall/no restart situation since.

Some of the 14 pins were fairly wobbly before resoldering when grabbed by tweezers. They are much larger than the pins on the 60 pin connector though

You said you have a backup ECM. Next no start, swap it in.

Ram4Ever has ben trying to school me on capacitors, and it seems that they are lucky to be able to function properly at all at their advanced age.

I have my original failed ECM, and at some point will try replacing all the capacitors and see if it works again. I was unaware of it in 2005 when my ecm was failing, but I am pretty sure the issue was the ECM was not able to hold the ASD relay closed. Pretty easy to bypass a relay with a jumper. I did so later when the relay itself failed, but the fuel pump would run continuously even with key out of the ignition so I had to keep opening hood and disconnecting jumper after stopping the engine, and returning it to drive, until I bought another common relay.

On some jeep forums there are reports similar to yours/mine about the nostart situation and replaced capacitors being the fix. In their case the capacitor ends had bulged in an obvious failure.

None of the capacitors in my failed ECM have obvious visual failures.

You will see that the jeep ecm looks nearly exactly like yours:

http://www.jeepforum.com/forum/f13/fixing-lazy-pcm-new-caps-writeup-501951/

Re: 93 Dodge cranks but won't start in freezing temps
RavshngOne #718648 January 11th 2017 3:22 pm
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Re: 93 Dodge cranks but won't start in freezing temps
RavshngOne #718650 January 11th 2017 3:43 pm
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Again this exact same thing happened to my 1994 b250 last winter I couldn't figure it out until I noticed that the check engine light wasn't self testing.IT should come on for about 30 seconds when the key is first turned on then go out.When cold mine would not come on If I left the key in the on position for 2 to 10 minutes the relay would start clicking then the light would come on and the van would start.Next cold morning if you can see the light this would be the easiest way to determine if the module has failed.If it has never been replaced that's a 24 year old module including the potting material.One more thing one day after it did start the module got cold enough while driving to leave me stuck on the side of the road.


1994 Dodge-Tannenbaum 1976 Chevy-dragonheart 1965 Ford-Screamin Eagle 2
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