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Q: Won't start below 40 degrees on 1991 Dodge Grand Caravan

I have had the same problem as several others with my 91 Grand Caravan 3.3 V6 for three years - will not start when below 40 degrees. But this year is the worst with temps hovering below freezing all last week. I have replaced computer on firewall, starter, key switch, ignition distributor, plugs, wires, battery, terminals, (cam shaft sensor, crankshaft sensor by mechanic) and have taken apart and cleaned every connection that is visible, including all grounds. Once it starts in the morning, it starts on first try all day long. Next morning, will not start again. Somtimes first try, sometimes 15 to 20 cranks will start it, somtimes more. I cannot hear the fuel pump either, and the valve on the top of the fuel rack only squirts gas under pressure once while pump should be on then dribbles after that.
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If we are taling a "crank no start" condition, with all the things you have done, have a fuel pressure test and bleed down test performed. This might be on the right track.
I forgot to mention that when it is warm (over 40) it starts first time every time. How can I perform these tests by myself - cannot afford to take it in, but need to keep it running.
I took from your description that your concern was specifically below 40 degrees.

The only way to perform a fuel pressure test is to tap into the port under the hood with a fuel pressure gauge.

My thought is that it seems as if you've spent a ton already on parts that didn't help -- sometimes it's necessary to bite the bullet and have a test done that will give you an answer before spending all that cash on parts. Good luck!
The computer and starter were junkyard, low milage, except for the distributor which was new and the internal sensors, all replaced by a licensed mechanic, and the other parts were new that I installed myself. If I can get it started to take it to my mechanic, as soon as it starts everything is workling well, according to my shop mechanics, being it is too intermittent to diagnose.

If I can tow it to him and he can check it without starting it, and if the test shows that the fuel pressure is low or non-existent, does that mean the fuel pump, which works fine all day everyday after it once starts?
It can be. But thinking now I would probably look at fuel pump relay or engine processor relay under the hood in the power distribution box. Sticking relays can certainly cause intermittent concerns. They can be a real pain to catch. You can tap on them maybe to see if you can get it to work...check for continuity...that sort of thing.
There is no power distribution box under the hood. There are three relays mounted on the right side wall, beside the battery, and four mounted on the left sidewall, behind the jack. Besides the computer on the left firewall, there is some king of computer attached to the air intake on the front, right sidewall. I have only replaced the one on the firewall.
I'm looking at a wiring diagram and see an "auto shutdown relay" that the fuel pump has a wire that goes to. It's a dark green with black tracer wire. This relay probably controls the fuel pump, the ABS pump motor, to name two items.

That said, I'm not entirely sure, and trying to figure out what's wrong 'remotely' like this is always really tough. I can help give you a direction, but ultimately getting help first hand is best. Your concern is consistent with fuel pressure issues or relay issues. But the 40 degree thing is something I cannot logically explain or attach to any known concern. So I have to revert to normal diagnosis and testing.
You are right. It turned out to be one of the three relays on the left sidewall. There is no auto shutdown on this model, and the Dodge dealer parts man could not tell me which relay did what, but I got all seven relays from the auto wrecker and it was one of the three. Now all I have to do is push the key easily and it starts.

For anyone else's informaton, by looking at the various models in the junkyard, there are different configurations of relays for the same model (three, four or five on the left sidewall, two or none on the firewall, and two or four on the right sidewall), but as long as the part numbers on the front of each relay are the same, they are interchangeable between cars.
My mistake. That did not solve the problem. If I jump start it in the morning I only need to crank it abour five times, but without teh jumpstart, it will never start on its own. Replaced battery with a new one, but does not help. Also, after running a few minutes or seconds, engine light comes on, car runs rough, and the computer code now shows 12-26-55. What do I need to do to solve the 26.
The 26 is fuel injector circuit high resistance. I would be looking at fuel injector wiring, or perhaps a faulty injector.
Does that mean removing the intake manifold and the fuel rail to get to each one, and how do I tell if they are bad?
Possibly so, as I believe the code references cylinders 1-2-3, which are in the back. I wouldn't go that far at first though; inspect wiring to make sure all connections are secure, no wires are damaged.
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