2005 Dodge Caravan won't start when warm, starts fine when cold / cool

kent.dahlgren_193836
Sat, 07 Jun 2025 23:47:49 +0000
Maintenance/Repairs

I solved this, and the summary is: it was the fuel pump (3.8 liter).

But the more nuanced answer is that it was a variety of sensors that contributed to a variety of issues, some of which seemed like they were related, and I want to share those because the process was so fascinating, and now the van runs amazingly well (with better fuel mileage).

Troubleshooting this problem was the most interesting part, but first off: I needed to figure out how to start the van when it was warm - nobody likes being stranded.

I found that I could get the van to start if I put water under the intake plenum, which cooled the fuel rail, therefore directing cooled fuel back to the fuel pump, allowing it to start.

The man issue: there is a gasket inside the fuel pump that’s supposed to maintain fuel line pressure, but at about 100k miles, these gaskets can get a little wonky, and by “wonky” I mean: they expand when the fuel is warm, draining fuel pressure.

When the fuel is hot, and the pressure is gone, the fuel rail is supplied little but vapor, resulting in a “cannot start” that feels a lot like vapor lock.

So cooling the fuel rail can help you through the situation, and in my case I used that method for about 18 months as I troubleshot the other issues, because the fuel pump is under the passenger-side rear seat, and I decided it was more fun to procrastinate.

The van is originally came from Alaska, and then it sat in a field in Western Washington for a few years before my son drove it to me via Mexico.

The summers in Central Texas are brutally hot, so I expected there would be some maintenance that reflected the extremes of cold to hot, but in reality none of the issues turned out to be related to that at all; having done auto and truck maintenance in a combat capacity in the military, I’m impressed that the van does as well as it has, given the extremes it has experienced.

I researched all the sensors that might be effected by changes in temperature, and found out that almost all of them are expected to last about 100k miles. That was an ah-ha for me.

I’ve been an engineer in the photocopier business, and am aware that there’s such a thing as a “duty cycle” for “field replaceable units,” which plays into an extended maintenance routine. Well, learning that a lot of stuff is expected to last 100k miles made sense.

I got the van at 70k miles, and started having issues at about 120k, so this started to click in as a common maintenance issue that most people would overlook, resulting in them getting rid of an otherwise decent ride because they thought it was a lemon.

The good news is that the sensors are not expensive and not impossible to replace. Each sensor was about $18-$30, and along the way I replaced the following, all while relying upon my ghetto method of starting the van when it was warm (pouring a couple gallons of water under the intake plenum, on top of the fuel rail).

Along the way I replaced the following:

camshaft position sensor

crankshaft position sensor

idle air control valve

temperature sensor

ignition coil

ignition wires

new spark plugs

new injectors

water pump

I think that’s it, and as mentioned: the van ran progressively better the more I replaced these modules and components, even though I was putting off replacing the fuel pump.

Finally, I decided to replace the fuel pump, and realized I’d purchased the wrong one: my van is the “Stow-n-Go” and that fuel pump is shaped differently than the vans that aren’t the “Stow-n-Go,” which is cool because I just ordered the correct one, which arrived the next day.

Replacing the fuel pump isn’t that hard, really. I was nervous about breaking the fuel lines, but it went fine and didn’t take me that long.

Now I have a van that fires right up, runs better than it did when I received it, and gets better mileage, and all told I didn’t have to put that much money into it.

Hope this helps someone. I found that most forums had this problem and solution presented piecemeal, and that didn’t help me much. I took about 18 months to get to the bottom of it, because I like understanding the whole system. Totally worth it.

4 posts - 3 participants