So I took the van in to a shop on Thursday.
The mechanic wasn’t so sure about my pressure test. Apparently there is the pressure when the van is running (which is the test I did). And the pressure when testing without starting the engine (as George_San_Jose1 references, above). The mechanic also claimed there was a better place to test the pressure, underneath and closer to the actual pump. He then said that having tested (somehow, at this point it sounded as if he did the test via his fancy scan tool?) he got values that were correct.
Pursuing the diagnosis further, he found a crack in the exhaust system, by smoking it from up the tailpipe. The technician / mechanic said this leak was causing the computer to be wildly varying the fuel trim to try to make the values right, as seen by the O2 sensor. They also said that one of the new spark plug wires I installed 6 weeks ago was broken at the spark plug end, that it must have broken upon installation (“happens sometimes”), and implying that I had been running all this time on only 5 cylinders (or so I understood; maybe the wire still works to some extent with the charge jumping the broken wire “gap” in order to reach the spark plug?). They spent a lot of time puzzling over the numbers the engine was generating via the scan tool.
Their theory about the P0171 code was that the cracked pipe was causing it, as I said above. But they were also aware of the “crank no-start” problem, which long predated the P0171 code. They tried to get the crank no-start to happen in the shop, but of course it wouldn’t. I suggested that with the hood open in the shop, the engine might be cooling off too quickly for the no-start to happen. So I agreed to drive the van around to warm it up, and leave it sitting for 10 minutes or so with the hood down. Unfortunately, I never made a scientific study of just how many minutes have gone by when the problem occurred in the past. It just seemed to be that it happened somewhere in a 10 to 20 minute window. We tried to replicate this twice, but couldn’t get the problem to happen.
The technician/mechanic said he found a “weird setting” in the van computer that he thought might be something the van “learned” to do in response to the crack in the exhaust, and cleared it; he said he hoped that would account for the no-start, but wasn’t sure.
The shop attempted a cheap fix of the exhaust using epoxy, at the end of the day (the alternative would be quite expensive as it would involve replacing the catalytic converter, they said. Didn’t charge me anything and sent me off to drive the van “at least 15 minutes” to help the epoxy cure. The epoxy smelled awful, and there was smoke from it coming out from under the hood for awhile. Gradually, the smell has gone down. It was quite strong in the air coming out of the heater, strangely (shouldn’t that air be quite isolated from the exhaust system?). There is still, even maybe 50 miles later, fainter odor in the heater air.
The van ran all day Thursday without codes, until at the end of the day (maybe 35 miles after leaving the shop, and maybe the 7th time I shut off the van after having driven it a distance, the same code, P0171, popped up again. And today, the crank no-start problem happened again, also.
The shop didn’t charge me anything for all their diagnosing and the epoxy repair; maybe they felt sorry for me, or maybe they were not too confident of their efforts. Very friendly and very communicative; I really liked the shop for that. The mechanic/technician and soon-to-be-owner told me just to bring it back on Monday if the code returned, the no-start continued, the mileage didn’t improve.
I will do that, since, indeed the code did return, the no-start continued (happened tonight about 8 pm, in the dark with temperature in the forties), and the mileage has not improved.
Too bad. But I feel that they will in good faith try again.
At one point the mechanic/technician wondered whether a leaking injector would explain the no-start problem. He said there was no way to be sure without getting in and looking at the injectors (not so easy in this vehicle as some). But he showed me data on his advanced scan tool that showed all 6 injectors squirting the same amount of fuel while the van was running, which evidence he seemed to think would diminish the likelihood that an injector is leaking. He didn’t rule it out, however.
The mystery continues. I still wonder if the mechanic/technician was right in his assessment that the pump was working fine.
Does anyone have references as to:
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The proper fuel pressure when running, for this 2010 Dodge Grand Caravan 3.8L? Because I saw that with my own eyes several times when I did my test, and it was consistently 36 psi.
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The proper procedure for testing the pressure when not running, and the proper psi numbers to expect (thanks to George_San_Jose1 above… where did you get your information?).
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Does anyone know what the tech was saying about it being better to test the pressure closer to the pump, somewhere underneath, and why he then referred to his scan tool as if it was able to give him the psi without even attaching anything (I really don’t know if he did some physical attachment underneath the vehicle or not, but I want to be able to ask him the right questions when we talk again on Monday).
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No one has commented on my observation (in a prior posting above somewhere) that I ONLY ever get the P0171 code, but NEVER the P0174 code, when you would think that if it were a fuel pressure issue, it would affect both sides of the engine.
as always,
THANKS!
| STZ
November 18 |
Before going the route of replacing the fuel pump, I would replace the fuel filter/regulator. I don’t know about your vehicle, but filter/reg on my Dodge Stratus was on top of the tank and could be replaced without removing the fuel tank and a new one solved my problem of a long crank start.
For me, I drove the car up ramps, supported the tank with a jack (piece of plywood and foam on the saddle), loosed the front bolts as far as they would go while still holding (they are long bolts) and then removed the rear bolts. I slowly lowered the jack and teh tank dropped just far enough (the fill hose hit the frame) so I could replace the part without a full tank removal which was much more involved.
Removing the whole tank would not have been too much more work, but not removing it was much faster.