Grand Caravan Seems to Flood When Hot, Won't start for 20 minutes

Maintenance/Repairs
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1

My 2010 Grand Caravan 3.8L won’t start when hot, if it has been sitting hot for 10 or 20 minutes. It WILL start if only stopped for a couple minutes… but not if it sits awhile longer… It does not stall, however. Never stopped running once it is running.

It always starts when cold. After hot, it will start again if stopped for a few minutes (less than 5? I haven’t precisely tested, but it will start again easily within a minute or two, or maybe three or four or five or six minutes after stopping). But if it sits for a bit longer, say 10 minutes, or maybe up to 20 or thirty minutes, then it often will not start. It turns over, but just doesn’t catch. Holding the fuel pedal down does not help.

However, having not started, it will then reliably start if I don’t turn it over for another 15 to 20 minutes. After that interval, it will reliably start again.

I wonder if there is an injector leak that only happens when the engine is hot? Or, a similar idea, a fuel regulator leak that only happens when the engine is hot?

Surely someone knows the answer here; it seems like a very clear-cut syndrome that can only have on or two causes…

An identical problem is described in a post from 2010 on this site, but that discussion did not result in any resolution or effective diagnosis.

Thanks in advance for any feedback.

2

A bad crankshaft position sensor can prevent an engine from starting when it’s exposed to engine heat after the engine is shut off.

Tester

3

Very interesting! Thanks. I haven’t got any codes indicating a bad crankshaft position sensor… but maybe that is it?

I had this problem (no start) happen only occasionally 6 to 8 months ago, but now it happens a lot. Recently, as in the last month, I have a P0171 code also. I wanted to get opinions on the no start without mentioning the later P0171 code, though it may be related, of course.

If this problem occurs when the engine is hot, would it cause the engine to shut off while running (which mine does not do)?

4

Read what say’s about a Check Engine light for a bad crank sensor.

Tester

5

Per the list at 1aauto.com you linked to, I haven’t noticed Acceleration Problems, but have noticed:
Rduced Gas Mileage
Engine Misfires
Rough Idling

I have not experienced Stalling, but I have had Difficulty Starting (obviously).

This certainly sounds like one very possible culprit, along with a number of others… I will have to try testing and replacing the Crankshaft Sensor.

6

That experiment – a good one to do in this situation – but the no-help result makes the “flooding” theory unlikely. The crank-sensor idea is definitely plausible. But rather than replacing parts to figure out what the actual cause is, suggest to ask your shop do a proper diagnosis. The first thing to determine is whether the cause of the cranks but doesn’t start is (1) lack of fuel, or (2) no spark. Spark is usually the easier of the two to check.

I expect the shop’s experimentation will show the problem is one of the above two, and once that’s determined the actual cause will be fairly simple to figure out. Sometimes weird problems that are harder to diagnose will cause this. I had a weak spark problem that caused this symptom a year or two ago. Spark was visible during cranking, but slightly orange rather than blue-white. Many years ago, different car, the cause was cylinders severely flooded with gasoline caused by prior fuel system testing. Sol’n was to allow time for gasoline in cylinders to evaporate, took a couple of days.

If shop can’t figure it out b/c it never happens at the shop, ask them to let one of their techs use your car as their daily driver. Eventually it will fail and the tech will be prepared to do some simple testing on the side of the road, parking lot, etc to narrow it down.

7

I’m all for using logic to narrow down the cause. I actually took it to a shop that charged me $180 for diagnosis. They claimed that just replacing the ignition coil pack and the plugs and wires should solve the problem. Said they smoke tested and found no leaks. Did this in only about 45 minutes (should have done more diagnosis in my opinion, since they charged for an hour). Then wanted to charge me $650 for the coil pack, spark plugs, and wires replacement. I refused; and did those myself. Shouldn’t have taken them more than an hour or hour and half, since the coil pack is right on top and couldn’t be easier. Spark plugs took me longer, but it was my first go round. I would think labor for the shop should be about an hour for that, I don’t know. First time I went to that shop and it will be the last.

Anyhow, the coil pack seemed, perhaps, to help, for a short trip or two, but within a day it was clear that the problems, which include running rough, had not gone away. the codes were still occurring. After I then did the plugs and wires, the van runs less rough, but still misfires / stumbles at idle every few seconds, frequently (interestingly, it seems to not happen at every idle; maybe less on a cooler day, not sure, I’ll keep listening/ feeling the stumbles). Before the spark plugs and wires, there was also a P2097 code { P2097 Code: Post Catalyst Fuel Trim System Too Rich Bank 1} that hasn’t appeared since. Not sure what that indicates.

And the no-start-until-another-20-minutes-go-by problem continues unabated. It happened to me twice today.

Trouble is, I have looked up the P0171 code and read any number of web accounts of possible causes, of which about 6 or 8 depending on the site… none of which even mention the crank position sensor, and none of which suggest any way to narrow it down aside from working one’s way through the list. Not too surprising, I suppose, but in the case of parts that cannot be tested, the test is replacing them. For example, the PCV valve is offered as a possible issue. But I don’t know any way to test that valve, and removing it involves destroying it, for this vehicle.

The no-start issue has happened intermittently over the past year. It m a y have become less during the winter, which would point to the crank sensor possibility, if I am to understand that the sensor can be “bad” in a way that only occurs in hot weather (?), rather than in an engine that is of course, hot most of the time… If the sensor malfunctions when hot, then why can I start the van easily if I have only stopped for a few minutes (the engine all warmed up), but if I stop for something like 10 or 15 minutes (also engine all warmed up), then it wont’ start…

I am not a very experienced car diagnostic person, but I do wonder if a leaking injector that only leaks when the engine is hot, but stops leaking as the engine cools off some, could be the problem… so if one stops for a short while, then the leak isn’t enough to cause a problem, but after 10 or more minutes, enough fuel may have leaked into a cylinder to cause a flooding problem? Does that make any sense to you more experienced mechanics? And then after an even longer period (the 20 minute recovery), the leak has stopped and again there is not enough built up to cause the no-start?

8

It takes time for the hot mass of the engine, etc. to soak into the sensor. When the car is moving there’s enough air circulation to keep the sensor cool enough.

A healthy sensor is reliable hot or cold, moving or idling, engine running or engine stopped, just recently stopped or stopped several minutes ago.

9

Tester

10

Thank you Shanonia; your answer makes a lot of sense! And thank you again, Tester, for all your prior help and for this link, which is very detailed and helpful. I think I should test (? how?) and/or replace the crank position sensor as a first effort. And the page suggests trying a fuel injector cleaner before replacing fuel injectors… does anyone know of a good fuel injector cleaner?

Thank you also to George_San_Jose1 for your suggestions.

I am very very glad I posted here; getting all kinds of learning and good ideas!

11

Crank sensors generally work by one of two methods.

  • It senses a rotating magnet on the crankshaft. This type of crank sensor contains loops of fine wire that produce an electric voltage pulse as the magnet passes by the sensor. The faster the magnet is moving, the better this type works.

  • A semi-conductor hall-effect device senses the same rotating magnet and produces similar voltage pules. Google will explain how a hall-effect device works. Hall effect devices aren’t affected by the velocity of the magnet.

Either type could be be affected by heat. The first one, with the fine wires wrapped around a core , if the core heated and expanded, that movement could break a wire create an open circuit, but could conceivably reconnect as it cooled. An open-circuit is easy for a shop tech to detect using an ohm-meter. Rather than checking that however, the tech would usually check for a visible spark. A faulty crank sensor, the symptom is no-spark.

12

Take a hair dryer/heat gun and heat up the sensor.

If the engine doesn’t start, that’s the problem.

Tester

13

I replaced the Crankshaft Position Sensor yesterday. All symptoms remain. Van r still won’t start after sitting 10 minutes hot, but starts 20 minutes later. Car still throws P0171 Error Code. Van still stumbles at idle, though possibly less than before, oddly enough (we’ll see as I drive it a few days; it seemed to fluctuate daily anyhow, so it may just be a fluctuation). Car still presumably gets poor mileage (haven’t driven enough to be sure).

So what to test / replace next?

I’m thinking run injector cleaner, test fuel pressure (and replace fuel pump if called for), then clean / replace injectors. but as for fuel pump, would a bad fuel pump cause the particular details of no-start?

14

Test the fuel pressure to see how long the residual fuel pressure holds.

http://eva2.homeip.net/eva2/FU01/ch5.5.3.html

Tester

1 Like
15

Your refernence is to the Bentley Manual for VW GTi, Golf, Jetta 1985-1992. Do you think these instructions and diagrams will apply to my 2010 Dodge Grand Caravan. I realize the general concept “test the fuel pressure to see how long the residual fuel pressure holds” m a y apply (are the fuel systems sufficiently similar for this to apply? Do all systems have a fuel “accumulator”? Is the pressure referenced in the Bentley VW manual correct for my van?) I’m not a very experienced mechanic, so I am leery of attempting to transpose these 1980s era instructions to a vehicle two decades later and a completely different make and model; I think I need better instructions to accomplish this (perhaps a handy-dandy Youtube video for my vehilce, for example? I rely heavily on those).

Thanks for your suggestions.

16

The principle is the same.

Hook the fuel pressure gauge up.

Start the engine and measure the running pressure.

Shut the engine off, and watch how fast the residual fuel pressure bleeds off.

Tester

17

It is disappointing to have to keep at it; thanks for the update. We don’t know if it’s lack of fuel or lack of spark, but one way to track down lack of fuel is the pressure test Tester advises.

A quick no-tools way to address lack of fuel is to do the key dance: turn the key to Run for a few seconds, then Off and back to Run. Each time it’s turned to Run, the fuel pump should run for a couple seconds. You may hear it. Each time it runs it brings fuel and fuel pressure up to the engine. After a half dozen or so of this key dance, turn the key all the way to Start. Does it now start?

A good place I have found for help with my Plymouth and Chrysler minivans is the minivan forum at allpar.com - a site dedicated to Chrysler products.

Good luck and please keep us informed.

18

That lets you know if the fuel is draining back into the fuel tank as the vehicle sits.

It doesn’t tell you if the residual fuel pressure is bleeding off too quickly allowing vapor lock.

Tester

19

Wouldn’t it overcome vapor lock [if present] and deliver fuel and fuel pressure to the engine? It does overcome lack of fuel caused by a leaking anti-drainback valve. All this assumes the fuel pump is running as it should, briefly, each time the key goes from Off to Run.

20

Vapor lock occurs when the anti-drain back valve allows the residual fuel pressure to bleed off too quickly, but still leaves a column of fuel in the fuel line and fuel rail(s) where it boils in the fuel rail(s)

Since there’s a column of fuel already in the fuel line/rail(s), running the fuel pump doesn’t allow any gas to reach the boiling gas in the fuel rail(s).

Tester