Need troubleshooting advice for a 95 Caravan that won't start

Maintenance/Repairs
1

I have a 1995 Dodge Caravan with the 2.5L 4-cylinder engine. It currently has 128,417 miles.

Approximately 3 weeks ago, the battery went dead overnight. It was running fine the day before, but the next day it was too weak to start the engine, and I noticed the interior lights were much dimmer than normal. The battery had a manufacture date of 01/2015 so I figured it was just used up.

I got out my spare battery which I had been storing, put it on the trickle charger, and after a couple days, the light changed to green, meaning the battery was full.

I installed the other battery yesterday, and tried to start the van, but it just won’t start. If I crank it for a while, eventually I smell gasoline, but it never starts. The tachometer does not move off of 0 RPM, either. Even when the fuel pump went bad, the tachometer showed a reading while trying to start.

I figured maybe the Hall effect sensor mounted on the distributor went bad, so I tried the Hall effect sensor from my Sundance, and it made no difference. The distributor rotor does turn while cranking.

I tried to retrieve the codes using the “key dance” trick, but only got 12 and 55, which are not helpful. 12 means that the battery was recently disconnected, and 55 means “end of codes”, so nothing useful there.

I checked all the fuses and relays, made sure all electrical connectors are tight, no problem found.

Any ideas?

2

Get a new battery.

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3

I think I told you your spare battery would go bad just sitting around, didn’t I?

Agree with Kurt… get a new battery.

4

It would appear that there’s nothing wrong with the battery.

Tester

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5

You aren’t going to like this.

But the ignition control module is the computer.:grimacing:

Tester

6

It is possible your engine has flooded, Hold the gas pedal to the floor while cranking see if it starts, or pull a plug and see if it smells like gas.

7

If the engine cranks robustly, the battery is ok. For cranks but won’t start the quickest way to a solution is to first determine whether the problem is no spark, or no fuel. It’s almost always one or the other.

Do the obvious stuff first of course. Make sure there’s enough gas in the tank. Nothing leaking under the vehicle. Hoses and connections appear to be the same as they always were, etc etc. Next, decide which you want to test for first. Usually spark is the easiest. Connect up a spare spark plug, figure out a way to ground it to an engine ground away from anything that might explode or catch fire, and watch for a blueish-white spark to appear at the working end while a helper cranks the engine. Report back on the results.

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Update: I tried starting it again today when I got home from work. Today it was warmer outside (71° right now, versus 48° on Sunday). It started on the first try, but misfired horribly for several minutes, then suddenly smoothed out.

I let it idle in my driveway as the engine warmed up. When the temperature gauge reached approximately 33%, the CHECK ENGINE light came on. The tachometer showed approximately 800 RPM, the oil pressure gauge showed approximately 60%, the battery gauge showed approximately 13 volts. I turned it off and did the “key dance” to retrieve the codes, and repeated this several times to make sure I got the codes correctly. The result is 12, 52, 55.

Based on my Internet research, code 52 is an internal fault in the PCM, is that correct? Time to look for a used PCM? 4-cylinder Caravans from this generation are rare, even in junkyards.

Here is one website that shows them “sold out”.

9

Fault 52 is Oxygen sensor stays above center (rich). Probably caused by the misfire. If it is still misfiring clean the spark plugs and erase the fault.

10

It’s interesting that you mention that, because back in August I had a problem where I drove this van to work, and then could not get it started again if my life depended on it. That’s actually what made me buy another car.

Every day for a week, when I got off of work, I tried to start the van, but it never did.
Then finally one day it did start, and was misfiring a lot, but once it warmed up it ran ok. The next day, I replaced the spark plugs, which were all blackened even though they were not old, and then it ran ok until the battery went dead a few weeks ago.

11

If the spark plugs are carbon fouled again the oxygen sensor may be the problem.

12

Any way to test the oxygen sensor, if I remove it, or just buy another one? I already replaced it once, because the engine was burning coolant (cracked head, which I replaced) and I bought the Denso First Time Fit brand.

13

The start-up misfiring symptom could be the engine was flooded. After it runs for a few minutes it clears the flooded condition and then runs smoothly. A leaky fuel injector could cause that. The fluid rail is supposed to remain pressurized when you turn off the engine, and the injectors are supposed to not leak when the engine is off. Also double check the fuel pressure regulator is holding vacuum also. If its diaphragm springs a leak, that can result in a flooded engine. If this happens again remove a spark plug and see if the electrodes are wet w/fuel. If so remove all the spark plugs and let the cylinders air out for a couple days.

14

How do I do that? Remove the vacuum hose while the engine is running? I replaced the fuel injector with new (Standard Motor Products brand) approximately 2 years ago. The fuel pump was also replaced at that time (Denso First Time Fit brand). The fuel pressure regulator has not been changed.

15

If it’s the type that has a vacuum hose connected to it, the way I do it, remember I’m no expert, but with the engine off I first check to see if there’s any gasoline in that vacuum hose. There shouldn’t be. Then I connect up my hand-held vacuum checker gadget (mighty vac, something like that) and verify the fpr’s vacuum holds steady to 20 inches. Everything done w/engine off.

16

I had a professional mechanic look at the Caravan. They had it for a month, and quickly discovered that the problem is that something causes the computer to supply way more fuel than necessary at startup, and while the engine is warming up. Also, at idle it has difficulty providing the correct amount of fuel, which causes a slight misfire and “pulsating” RPMs. However, they could not figure out what the root cause is.

They tested fuel pressure, inspected the throttle body assembly and fuel injector, and observed the diagnostic data on their scan tool. They also checked to make sure nothing is wrong with the engine itself (poor compression, etc). It should be noted that I already replaced the fuel injector twice (first with a GB Remanufacturing one, then with a new one from Standard Motor Parts) and that made no difference. The fuel pump and fuel pressure regulator were also replaced with quality brand-name parts.

The suspicion at this point is a defective PCM. They told me that only a dealer with the factory scan tool can definitively prove that the PCM is bad. Is there anything else to try besides a used PCM?

17

When I’ve had problems with my Chrysler minivans, I have found help at allpar.com. They have a minivan forum. Good luck.

18

It could be the PCM. But it could be a case of GIGO too. Garbage in, garbage out; i.e. if the computer’s inputs are incorrect it will produce an incorrect output. So first make a list of all the sensors used for the algorithm that the PCM uses to determine the amount of fuel to inject.

  • Engine coolant temperature
  • MAF/MAP
  • Ambient air temperature
  • Start mode vs running mode

Of those I’d suspect the coolant temperature and the start/running mode as the most likely causes of incorrect computer inputs. It could be something very simple like a dirty electrical connector or faulty ignition switch. Ask your shop to measure the inputs from those sensors right at the computer’s connector.

19

When I had trouble with an 87 Reliant 2.5, a mechanic diagnosed it as a faulty computer. I was skeptical but I owned an 87 Caravelle 2.2. I checked and the computers had the same numbers on them. I swapped and the problem did not move with the computer. Turned out the problem was carb icing.

My point is, I would check any Mopars with the 2.2 or 2.5 engine not just minivans for identical computer numbers.

20

When you mentioned there is a temperature difference and the mechanic said something is causing the pcm to provide too much fuel, I wonder if you have a defective engine temperature sender. That’s what tells the computer what temp the engine is so that the correct fuel mixture can be provide. The mechanic should have been able to read what temp was being sensed but the sensor when he did the computer diagnostics.