truck not starting

[big reaper]

First off. This is not a Chevy it is a dodge ram 5.9l gas engine.

We have been working on this truck for about 2 weeks now and I'm stumped.
It cranks but will not fire. If you hold the throttle wide open it will start and chug for a couple seconds but that's all.
So far we have ran a dry compression test and found 119-125 psi from all cylinders. Wet showed 140-145 psi. Leakdown test showed no more than 3% from any cylinder.
New parts.
Plugs wires cap rotor inn.module. all new sensors throughout engine. New computer. Fuel system has been gone through and everything replaced from the fuel pickup to the fuel rail.

Nothing that has been done has changed anything. It still acts the same as it did when it was dropped off. Ran the codes and nothing came up no cel or anything.

So here I am trying to find out any other ideas. Just want to get this thing running so I can get paid.

 

[rebelgregory]

Timing? What's the Fuel pressure? What's it supposed to be?

 

[big reaper]

It had ~50 psi of fuel pressure when we checked after changing the fuel pump and sending unit. Timing is difficult to tell since it won't start but while cranking it is right near where it should be.

A little more information.
It was running fine then one day going down the road it just started cutting out at 55 then it wouldnt get above 45 and then it just died at a stop light. That's when it got brought to my buddies house by tow truck. The owner asked a mechanic at the dodge dealership who talked him into getting all the parts that have been replaced. He wouldn't listen to us just kept giving me more and more parts to replace on it. Now he is starting to listen and willing to let us actually diagnose things instead of just throw parts at it.

 

[Chief Brody]

If you hold the throttle wide open it will start and chug for a couple seconds but that's all.

I would think that if you are getting fire and fuel and it won't run it has to be timing... I would check and double-check the timing

 

[blazinzuk]

I had an old Geo Metro that did the same thing. It ended up being a bad ground on the computer.

I didn't find it that was the second time in my life I took my car to a mechanic, because I simply could not figure it out.

So I might start looking for ground problems

 

[big reaper]

How do you check to make sure the fuel injectors are firing? I'm pretty sure they are firing but just want to double check since everything else I've checked isn't helping.

Eric thanks for the suggestion. I'll start running grounds to see if any look or even test bad. We have checked every other wire for a break of continuity.

I can not think of anything else we have verified it has fire. And every other part of the ignition and fuel system has been replaced.

 

[rebelgregory]

On a TBI system, you can watch 'em spray. On a direct or multiport unit, you can put a screwdriver or mechanics stethoscope on the injector. You should be able to hear them 'clicking'. If you have fuel pressure, and they're clicking, you've got fuel. Since it's not starting, you can also spin it over and pull a spark plug or two. You should have fuel on the plug if it's not running.

 

[diesel4me]

The crank sensor controls both fuel and spark on dodge engines,make sure its getting a signal to both ,you should be able to hook up a test lamp to an injector to see if it pulses OK,and use a spark plug as a tester to see if you have spark..

My friend has found a few dodge's with baffling troubles like this ,one with a 360 v8 was towed to his shop from another local garage who gave up on it after installing a good used engine,the thing refused to start and they bailed on it rather than tie up their only lift for days--my friend talked to a dealer tech at the dealership he knew well,he told him to make sure all the sensors were plugged into the correct harnesses,and he found two that were swapped,they had the same plugs and color codes--I dont remember which ones though..truck fired right up and ran great !..he never would have found that problem if he hadn't been given a heads up probably..

He's run into that a lot on VW's,they use the same plugs on everything it seems,and they often get crossed up after being removed for engine work...

Another Dakota was towed in ,that would not start if the temp was under 40 degrees reliably...no spark--but if you warmed the computer up with a heat gun for a few minutes,it fired right up and ran good,as long as you didn't shut it off long enough to cool back down,it'd run all day!..

Friend installed a salvage yard computer--it cured it,these trucks had them on the inner fender under the hood,and they corrode and get blasted by heat and moisture there,so I suppose its not uncommon for them to fail that way..

Two weeks after he "fixed" it,it was towed back in,and we soon discovered it had no power getting to the coil..but after poking around under the hood,we saw the test lamp light up,while it was still connected to the coil 12V wire!--and it started up!--ran about 10 minutes,then stalled like the key was shut off,and the lamp went off--we started pulling on the wiring harness and the one going across the front of the engine that was threaded under the water pump must have had the coil wire in it,as long as I held it in a certain position it would get power to the coil and run..

Rather than tear the harness apart,that had more thin wires inside than AT&T's main junction box,we decided to run another hot wire from the fuse box to it that only was hot with the key on...truck hasn't come back to haunt him yet!..