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Cold start problems

JMeier
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JMeier

JMeier

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I have a vintage 2001 24 valve 3500 ram with a 5 speed manual trans. When the temps outside get below 40*F the truck is hard to start. The colder it is the worse it gets. However, if the truck has been plugged in over night, it will start fine. The other evening the truck was cold (about 45*F) and had not been plugged in, so I used my wifes hair dryer in the air box to supply hot air (it worked previously), it tried to, but no start and the batteries ran down trying. So I tried to pull start it. As soon as I let off the clutch in 3rd gear it started! I have tried new batteries and my fuel pressure is 15 psi at idle and 10-13 psi at WOT with a FASS DDRP lift pump. I have tested the fuel and air heaters and they check out fine. I had the codes scanned at Autozone and nothing showed up. I have checked for fuel leaks and cannot find any. The battery voltage will drop from 12.67 to 10.56 while cranking warm or cold. The wierd thing is this only happens when its cold. After the truck starts it runs great and will start fine until the engine gets cold again. It can sit for days in warm weather and will start fine. I would keep it plugged in, but that is not feasible in most places I am parked. Does anyone have any suggestions?

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flagmanruss

flagmanruss

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I have an 01.5 but with automatic... the truck has rediculously low miles since I've been sick. Mine was doing the exact same thing. I just replaced the batteries... I stretched them by plugging it in (got an extra season out of it) but in the end, it was the thing to do. The grid heaters draw a lot of juice... I'm assuming you are waiting until the "wait to start" light goes out. That means the grid is hot... I don't know if the grid cuts out when the starter is engaged (maybe someone will tell us) but the starter has to spin it with that load too. The grid heaters continue to run for several minutes... depending on the temp... as you can see in the charge indicator.

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Mopar1973Man

Mopar1973Man

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Ok... Here is the draw on the batteries... WAIT TO START -> Grid heaters 190 Amps... STARTING -> Starter 500-700 Amps POST HEAT -> Grid heater could draw anothe 90-190 Amps for 3-5 minutes after running. Maybe that why I unplugged my grid heaters... LOL My weather is light enough now that I can start up on a cold morning easy without grid heaters (15*F outside is my lowest). So the only load I got is the starting of the truck. So battery recovery time is shorten a lot! ;) My typical cold start lately is about 30*F to 40*F without grid heaters. As for starting there seems to be a problem there... You might think about changing the starter contacts. They get wore out and weak and it takes even more to get it to twist on weak contacts. There really cheap. Fuel Pressure is weak though... 10 PSI is the lower limit... It the stock plumbing that is keeping the pressure low... As for starting problems you might try this too... http://mopar.mopar1973man.com/cummins/general/voltage-drop/voltage-drop.htm

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flagmanruss

flagmanruss

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My appologies... I missed where you said you tried new batteries. I would check the batteries to be sure you didn't get a bad one. I'd check the battery connections... in fact I'd check the B+ leads & grounds especially too. I melted the harness off my C30/ 454 when the BIG ground went bad. I presume you're running the right oil... cold thick oil can really screw things up. That's a long shot unless you just changed the oil. In trouble shooting, it's always well to look at anything which was changed, before the problem started or sometimes attempts to repair cause new problems. (like the batteries, cables) Good advise on the contacts & thanks for the amperage draw specs, Mike.Russ

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JMeier

JMeier

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Starter Contacts were slightly worn. hehe :D Hasnt been cold enough lately to see if it fixed the cold start isuuue, but they needed replaced regaurdless! Thanks Mopar1973Man for the quick reply :thumbsup Saved me some money on the starter. Installed the new contacts and plunger in less than 30 minutes with a kit from Larry B's. :thumbsupIMG_0384.JPG[/attachment:2dbpkrcy]

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JMeier

JMeier

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jlwelding, it is really that simple. 30 minutes. Although, I have worked on Dodge Power Wagons and farm tractors since i was a kid. :thumbsup But this was a new area, and was very straight foward. Most places that sell the contact kit online have some pretty detailed intsructions that were a great help.

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JMeier

JMeier

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Now it gets interesting. We had a little cold spell, (35*F) and the truck would not start. Does the same as it always does. Rolls over, but will not start! So I think about it for a minute and wonder why I can pull start it but not crank with the starter. The only difference is the lift pump wasnt running on the pull start, so I unplug it and try again. The truck started right up! :confused: This morning it was cold again (around 40*F), so I turn the ignition on and let the pump prime, then unplugged it. The truck started right up! :confused: What could be causing this? The truck runs great, has plenty of power, and never stalls or hesitates. Could too much pressure or volume cause hard starts? Why will it only do this when cold?

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Mopar1973Man

Mopar1973Man

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You got a rip in the VP44 diaphram. The pressure is to great at start up so the solution is just like you said you got to disconnect the lift pump form the system during starts now. So for a permanent fix I would wire in a relay to the starter lead so it turns the pump OFF during cranking but as soon as the key is relase the pump comes ON.

The other solution is replace the VP44...

The whole cause of this problem was from low fuel pressure and a diaphram inside the VP44 ripped during this low pressure moment.

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