03 Ram 4.7L won't start

[Cat Fuzz]

We just got this truck from the auction knowing it didn't run but not knowing why. Only paid $3k for it. About 70K miles. Quad cab, 4x4, 4.7L engine, Automatic.

When we opened the hood, the intake was missing. Found it in the back seat. The exhaust pipes were disconnected and the fuel return line was disconnected with a test hose attached. The truck briefly and very roughly ran with the pipes disconnected after putting the engine back together and finding that someone had pulled the fuel pump fuse. Fuel pressure is good at 50psi and we know we are getting spark. Found the TPS was bad, replaced it. Has a new ECTS, cam sensor and Bosch Platinum plugs. We'll be replacing the crank sensor tomorrow when it comes in. We have a Snap -on Solus to use also. I ran a boroscope down the pipe and the cat doesn't appear plugged. Compression checks out at at least 140psi per cylinder.

We have no history on this truck and we can't figure out why someone would pull the intake for a no start problem.

Is there some obscure problem that we might have? Could there be an issue with the crank reluctor wheel?

Replacing a few sensors is nothing since we were prepared to replace the engine.

Thanks.

[rockwood84]

have you checked the timing?

[Cat Fuzz]

Coil On Plug. No distributor.

[angus10]

Use the scanner and check for codes if you have not already done so. And maybe you should get a Carfax report, it might tell you something you should know. And maybe someone put something bad in the fuel tank.

[Cat Fuzz]

Found the problem. Pull the VC's and found it had thrown the exhaust rockers. Probably a plugged cat.

Thanks for the input!

[Cat Fuzz]

Clarification: It threw the all the exhaust rocker arms on the right side and only one of them on the left. We re-installed them and it fired right up with the exhaust pipes disconnected. We left them disconnected and trailered it to the exhaust shop to have the cat replaced.

Apparently this is a common problem with the 4.7L engine. Been gathering bits of information about it. There seem to be multiple causes. Ours seems to clearly be a plugged cat causing enough back pressure to hold the exhaust valves closed forcing the rockers to go somewhere else.

[2000izusu]

interesting because on some it is believed to be caused by "lifters" (lack of better word) bleeding down over night. but when that happens it is usually only one rocker that pops out.

now you have to find out what plugged the cats? maybe bad o2 sensors? mike

[Cat Fuzz]

We've already replaced the ECTS, TPS, Crank and cam sensors and MAP sensor. We'll run it on the scanner to make sure everything is cool.

[Cat Fuzz]

Updating for informational purposes:

We drove it for awhile with the new cat and then it started running bad again. We pulled the VC's and found thrown rockers again. Numbers 4,6 and 1 exhaust rockers. We came to the conclusion that its a hydraulic lash adjuster problem. The one on number 2 was collapsed and number 4 would not compress even a tiny bit using channel locks. We ordered up 8 new lash adjusters and replaced all the exhaust lash adjusters on both sides. Found two others collapsed and the rest of them wouldn't compress at all. The new ones had some springyness to them by simply squeezing by hand. So, we'll drive the truck a couple days and see if it happens again.

[2000izusu]

i just heard today from somebody in the asa and he said he had a 4.7 throw a rocker arm once due to carbon build up? does it idle smooth when hot?

what is the update did the lash adjuster fix the problem? mike

[Cat Fuzz]

Originally Posted by 2000izusu

i just heard today from somebody in the asa and he said he had a 4.7 throw a rocker arm once due to carbon build up? does it idle smooth when hot?

what is the update did the lash adjuster fix the problem? mike

The lash adjusters seem to have been the problem. I'm sure that what happened was that the old lash adjusters got gummed up with crud. Some collapsed and some lost their 'springy-ness'. There is a little piston under the ball end that meets the rocker arm. Under the piston is a spring and a ball check valve. It only takes a little bit of crud to make that piston stick. The extra clearance, or lack of clearance or cushioning that the adjusters are supposed to provide is what we think caused the rockers to kick off.

The ball check valve sticking in the open position could also account for others problems and theories of them bleeding down overnight. Either way, it seems that replacing the lash adjusters is the fix for this problem.

These adjusters are a common item being used in a lot of Ford engines as well as Dodge and some foreign engines.


At any rate, we drove the truck quite a bit and now it's sold, with a warranty, and it hasn't come back yet. Been with it's new owner for a couple weeks now. Probably what needs to happen with these 4.7L V-8's and any other engine in a similar valve train configuration is very frequent oil changes or even switching to synthetic to prevent the crud build-up.

[2000izusu]

thanks for the update! i agree the way to prevent this is frequent oil changes, and i am glad it is fixed! the few case i have heard of this happening were on 150k+ mile motors with poor maintenance.
next time i see a ram 4.7L in the push/pull line at auction i will be more serious about buying it! mike

[Cat Fuzz]

Yep. Ended up being a good deal for us. The auction told us it needed the engine replaced. After a few other minor things, we put about $600 into it. I think we sold it for 10K.

Seems like a common theme for modern Chrysler engines. Poor oiling. The 2.7L V-6 in a lot of Intrepids is just a pile. You can bet if we see another one that looks like it may have the same problem, we'll be snapping it up.

[2000izusu]

Originally Posted by Cat Fuzz

Seems like a common theme for modern Chrysler engines. Poor oiling. The 2.7L V-6 in a lot of Intrepids is just a pile.

the 4.7L has no history of poor oiling? your right on the 2.7L, thats why i stay away from 2.7L's manufactured from 1999-2004, but i would buy a 2.7L manufactured 2005,2006,2007,2008,2009 model year (used), reason being is that is when they fixed the oiling problem in the 2.7.