Our 96 B2500 3.9L V6 van started to act out a few weeks ago. First it refused to start and when it did it the engine run very rough and died when you touched the acceleration.

Replaced the fuel pump assembly, distributor cap, rotor and spark plug wires and now it runs smooth and pulls great but it starts rather hard regardless if the engine is cold or hot.

I've tried to put the key on a few times to help the fuel pump build-up more pressure - it makes no difference. The only thing that helps is to pump the acceleration a few times while cranking the engine.

Any ideas on what's going on & how we can tackle this issue?

 

You could try putting the key in the ignition position, letting it sit there for a few seconds so the fuel system can properly pressurize, and then trying to start it. These vans have features built into the fuel system to ensure they remain pressurized even when shut off. If there's anything wrong in that system, it won't maintain pressure after it's shut off, and may give you hard starting problems.

After running the van, let it sit for a few hours and check the static pressure in the system to see if it is within specifications. The system may depressurize to some degree if it sits there for an extended period, but there are parameters it should operate within.

Even though this sounds more like a fuel issue, it couldn't hurt to look at your ignition coil as well.

 

Thank you CW! I tried to prime the fuel system as you described and it doesn't solve the problem.

Ignition coil is almost new (MSD coil). Is there any other thing I should be aware of?

I remember than when I had an old Mercedes W126 diesel it made a lot of difference if I started the engine with the accelerator pedal down.

I don't know if that will change something in a gas powered Dodge 3.6L V6 since this is a completely different engine. Does anyone know what could cause a hard start on this engine?

 

Check the IAC on throttle body.
Look here:
https://www.rockauto.com/en/catalog/...ac)+valve,6072

 

Check the running & static pressure in the system anyway just to make sure it's not related to the line pressure itself. It only takes a few minutes. Try spraying starting fluid into the air intake when you start it up. If it fires up faster, you have a fuel issue. If it is the same, it's very likely you have an ignition issue. This is a very crude test, but it should give you at least some important information.

Apart from that, I'd check the throttle position sensor, though I'm not sure it will have much of an impact on how quickly the vehicle starts.

 

Thank you @Busted Knuckles and @Celticwarlock !!

IAC Valve is almost new and clean as a whistle - it caused some rough idling previously so we had to change it.

Good idea with the starting fluid/pressure check - I believe we have to go that route even if the fuel pump is new, maybe the mechanic screwed-up the installation of return lines/pump vent or something.

If this proves to be another fuel issue I'm that close of cutting a visiting hole in the van floor for the fuel pump assembly...

 

What brand IAC did you install?

 

That could be due to a bad throttle position sensor (TPS).

 

@Hey You the IAC is Standard Motor Products brand most likely and keeps idle perfectly regardless of cold or hot engine.

@alloro Is there any other sympthoms associated with a bad TPS?

Unfortunately the OBD 2 port is not powered on this van so I cannot check the TPS through the OBD interface. I remember that there was a certain procedure to check the error codes without an interface on GM vehicles. Is there such a procedure for an OBD 2 Dodge van?

 

Key trick might work. Cycle the ignition On-Off-On-Off-On, (not start) quickly, then watch the check engine light, it should blink the codes at you.

Of course, if the PCM thinks the TPS is doing its job, it won't set a code...... you also can't get pending codes, or history codes using this method.

Why is there no power at the diagnostic port?