Sorry for the hasty intro. This is my first post, and I am hoping for some guidance because I know I'm in over my head and perhaps even the mechanic as well.

Truck has about 180K miles on it, has run pretty well in the three years I had it. I put a new transmission in it last summer and things were fine.

Over the last month, the fuel gauge started doing weird stuff, like not reading at all, or wobbling back and forth. Additionally, the truck would act like it was going to stall if stopped in heavy traffic...making that little jerking motion that usually signals they're about to die.

This is a truck that has always started on the first crank, and last Monday, it took forever to start, but finally did. I got a mile down the road in the middle of the interstate during rush hour and it died for good. It just spun and spun and never caught.

I had it towed to a shop that came fairly well recommended and the mechanic told me yesterday that he had spark but no fuel, and said the fuel pump was bad, so I bought one, ran it up there, he installed it and called me saying that it now had fuel but no spark. He checked wires, fuses, bypassed relays (for whatever reason), and said the onboard computer would not respond to the diagnostic instrument.

He told me this afternoon he's out of ideas but thinks the computer is fried. He also said something kind of cryptic and I don't know if it's bs, misdiagnosis, etc...he said the cylinders were "hydraulically locked" ie, full of liquid fuel and he had to pull the plugs to release the pressure to even get it to crank at all. He said sometimes the injectors stick wide open and just completely flood out the engine...this sounds completely wrong to me.

At this point, I'm getting desperate...thus far about 500 bucks in and now faced with a new computer that may not even fix the problem. It seems as if we're throwing parts at it in hopes something works.

It's 22 miles away from my home, because it broke close to where I work and when I asked the mechanic if you had to flash the new computers with the VIN, he said he didn't have any way of doing that. Which begs the question how did he know the computer wasn't responding if he doesn't have a diagnostic tool capable of interacting fully with the onboard computer.

I have a couple days to sort this out before the shop reopens Monday and have to either drag the damn thing off or let him continue to work on it.

I work on scientific instruments for a living, so it's not that I'm not mechanically inclined, but this is not my realm and I don't have a good feel for what's good advice or intuition, and what is just "I have no idea what's wrong with your truck."

Thanks.

Oops. Sorry. Put this in the wrong place. It's been that kind of week.

 

What engine and transmission do you have?

I have never heard of or read about a cylinder becoming locked by fuel and I have never heard of injectors flooding the engine with fuel either. Usually when it takes a long time to start like that, it's because the check valve in the fuel pressure regulator is bad. The regulator is part of the fuel pump assembly so you were right to have the pump replaced.

As far as the other things the mechanic said, I think if it were my truck I would get it to the Dodge dealer or an independent mechanic who has access to a Dodge DRB-III scan tool. That would tell for sure if the PCM was bad, but it seems to me if the PCM were bad, even a hand-held scanner would give a code telling you the PCM was bad.

I am no mechanic by any means but this almost sounds to me like there must be some electrical reason there is no spark. Ther can be any number of reasons for no spark, like the distributor or coil being defective, bad plugs or bad plug wires, a bad Crankshaft Position Sensor or even a blown fuse somewhere. When was the last tune up done? And are there any codes now from the PCM?

If this were my truck, I would take it somewhere else for a second opinion at a shop that had the right diagnostic tools to find out what is wrong.

Just my 2 cents. Others here will have better info for you.

Jimmy

 

well my computer died a few months back, got it off ebay for 200 bucks. i think they do returns if it dosent solve your issues. and the install took me about 3 minutes.

 

Sorry for not adding that info earlier. It's a 3.9L V6 with an automatic transmission.

It was tuned up last year. I was getting no engine codes prior to its sudden death last Monday and all he told me is that he can't get the PCM to communicate at all with his device. Whatever that means.

It was running fairly well and getting about 21 mpg up to the time it died, so it's hard to envision too many exotic things wrong w/ the fuel system, etc.

Is it possible to blow the PCM while putting in a fuel pump?

 

They mechanic should have disconnected the battery before installing the fuel pump so no - it shouldn't have hurt the computer.

The fuel lock I've heard of, but not on a dodge - its an fuel injected engine thing - they leak down into the cyls & fill them with gas. When cranking though the pistons will push the raw fuel out the exhaust so this indicates the fuel pump was running while he was not cranking the engine & the injectors were open. Not sure how this is possible.

You can check the computer yourself by turning the key on then off 3 times - the CEL will blink any codes - even if there are no code it will blink the OK - but if you get nothing the computer is gone.

It may have been something the mechanic did - it may not have been. Computers are kind of like light bulbs - sometimes they burn out. If it were my money - I'd say take it to a different shop.

 

Thanks for all the help thus far. Someone said it's about a 3 minute job to put a new one in, it sounds like a "plug and play" thing. Where is the PCM located and are there any special precautions besides unhooking the battery? (Assuming the PCM replacement is already updated with VIN, mileage, etc.)

 

for the 4.7 its on the passanger side by the intake filter. just in hook the battery and then unplug the harness, for a its should be 3 or 4 groups of wires. then there are 3 bolts that you take off. its really plug and play, you just tell the company your vin number and they program it for you.

 

What do you use to get the bolts out? Torx, etc? I envision having to do this myself because the mechanic said he had "done all he could". I have this crazy simplistic idea that when the FedEx guy drops off the new PCM, I drive up there, slap in the new one, the truck cranks right up and I drive home.

 

I have a 2001 Dakota, also with a 3.9. I would think your PCM mounting configuration would be the same. My PCM is held in with 3 Phillips screws, they have 5/16" hex heads on them. It looks like it would be easier if you were to remove the air intake box and snorkel to have better access to the mounting screws. For that you would need a 10 mm deep well socket to remove the air intake box and a pair of large pliers or a big socket to loosen the nut holding the air hat on top of the throttle body. Or you can just loosen the 5/16" bolt that turns the clamp that holds on the snokel tube to the air hat and remove it that way.

I would still have someone else test the PCM with the Dodge scan tool before sinking a lot more money into a new PCM when you (and the mechanic) can't really be 100% sure that it really is bad.

Jimmy

 

I agree. At this point, it's better to have the stealership take a look into it before taking that expensive leap.