1995 Dodge Dakota with the 3.9. Very hard or no start, but will fire up if I pour gas in the throttle body. Good fuel pressure. Seems to point towards the injectors not firing during crank. Any suggestions or ideas?

 

Check your fuel injectors for proper power (Shared) and correct negative from the pcm.

 

Ignition in 'run' position and engine running (primed to get running) at injectors 13.7 vdc. Shut off engine. Turn ignition back on to 'run' position and zero voltage.

This is a ice race truck, so factory fuel pump now located in fuel cell direct wired to battery (with relay). Not utilizing origional pump wiring.

Noticed when trying to restart after running absolutely no fire at all. If disconnect the battery for awhile then try starting again it seems like it will pop on a cylinder or two...sometime starts, sometimes still needs a little fuel added to the throttle body.

I really appreciate the assistance Crazy4X4RT!

 

Check the notorious splice just below the relay box.

 

Per your suggestion I located the troublesome splice which was indeed very corroded. Cut back and resoldered. Still no start.

Had an extra set of hands around so was able to do a little more diagnosis. With ignition in 'start' position had 12+vdc at connector on coil and also voltage at fuel injectors.

Odd...one would think that with fuel and spark it would pop right off, but no. A splash of gas down the throttle body and it fired right up and ran like a champ. Shut down then immediatly tried re-starting...no go.

Additional ideas?

 

Check for codes: https://dodgeforum.com/forum/1st-gen...-96-codes.html (Even if the check engine light is not on, check anyways, because the computer will not always illuminate the bulb if there is a stored code)

When you try to re-start but it won't start --
1) Do you still have power going to the coil? (The spark plugs?)
2) Do you still have power at the fuel injectors?

Another question - you said the wiring for the fuel pump is not stock. How is it wired? What wire does the relay get its switch source (the "turn on" signal) from?
Does, 100% for sure, the fuel pump get power when the ignition switch is in the START position?
I don't care if it get's power in RUN, it must get power in START as well. It can pump pressure up to the (around 50 PSI) in RUN all day long, but if that relay won't stay energized in START, the first time one of those injectors open up, there goes your pressure. And without pressure (in this possible case, no power to the pump in START, therefor no fuel flow at all), you won't be starting up.

Why I think this is probable:
You said if you pour gas down the throttle body, it will start.
So, you pour gas down the throttle body, which provides enough to initially start it. You release the switch back to RUN, and before the engine can die from lack of fuel (using up the gas you poured in) the fuel pump starts up again (because, according to my theory, the fuel pump isn't running in START), thereby, providing the fuel the engine needs.

 

Codes 12-33-55 (A/C removed thus I believe the reason for code 33)

When I try to restart it does still have spark (proven by engine starting when primed thru throttle body) and injectors SEEM to still recieve power. I may be better off digging out an analog VOM to better confirm vs the DMM.

The fuel pump (factory pump mounted in fuel cell) is wired directly to battery using a relay and SPST switch mounted on dash.

So your suggestions leave me with a few thoughts:
1) Verify ACTUAL fuel pressure. I have simply been checking for fuel at rail by pressing the schrader valve. Thinking it runs well when started I assumed pressure is a non issue.
2) I checked battery voltage before (12.5) and during run (13.7) but not under load. Seems unlikely to be a cause considering prime leads to start?
3) Your thought about not getting fuel during crank. Perhaps I shoud run a jumper to starter solinoid and try starting with ignition in 'run' position.
4) Is it possible a bad sensor could be telling the injection system to not feed fuel? No code points me in that direction tho.

 

....but now I am thinking this over in my head. The switch 12v source energizing the RELAY may not have power during crank. VERY possible!

 

Kudos to DodgeRules86! I needed someone to force me into re-looking at the simple stuff. New source for swith power and she pops right off. Thanks again!