Venture cranks well, but doesn't want to start

I have a 2000 Venture, 3.4L motor. It's always been quick to start with just a flick of the key. Suddenly, that has changed. Now it cranks and cranks, then eventually will start. Good thing the battery seems strong! Once on the road, it runs great! Smooth, no missing/popping, lots of power, accelerates well. When idling, it hunts a little. It goes from about 800 RPM to 600 RPM and back up. It's not that noticable, except at night when you see the headlights dim then come back up... then dim then come back up.

Anyway, back to that starting issue. My wife and I have both noticed that giving it a little gas while cranking seems to help. Like the unstable idle, that may be a clue, but I'm not exactly sure what it's telling me. Lastly, the SES light is not on.

I've already replaced the fuel filter and the 7X Crank Sensor. No change in symptoms. So here's my thoughts, let me know what you think:

1.) Throttle position sensor. Maybe "rest" position is intermittant and the computer doesn't know how to handle it. Giving it a little gas puts the TPS into a "readable" area and the car starts and drives perfectly. This would also explain the hunting when idling.

2.) Coil Packs. I've read a lot of complaints about them causing hard starting on these vans. But bad coil packs are also usually associated with intermittantly stalling or really rough idling/running, which I don't seem to have.

3.) Fuel Pump. This is the problem I'm dreading the most, due to cost and the labor to do it (myself). Perhaps the fuel pump is not kicking in right away when attempting to start the car. The unusual thing is, when I put my ear towards the fill tube (with the fuel door open), I don't hear it running. Typically you can hear a "whine". I was hoping to determine whether the pump was pre-charging the system with fuel pressure before the key was placed into the "Start" position, but I can't hear the pump running -- ever. Anyway, I don't think this is the problem; when on the highway, I can floor the pedal and allow the RPM's to go all the way up and it doesn't choke. If the pump was weak enough to cause hunting at idle, you'd think it would starve the motor for fuel at high RPM's.

Any ideas? I know this is a lot to ask, but I don't have access to fancy diagnostic tools nor am I doing too well financially right now. :frown:

I'm gonna go with the fuel pump or its controls. Check all fuses and relay. Ya need to check fuel pressure. The pressure with KOEO, how's it holding pressure with key off and fuel pressure running. I dont have the specs handy but they're easy to find.

Another possibility would be the IAC - Idle Air Control Valve. That may also explain the idle hunting and the "press on the gas" to make it start. Hmmm...

OK, the problem is getting significantly worse. Wife no longer wants to drive it, so we are swapping vehicles until this gets resolved.

*It still cranks endlessly, unless you hit the gas about 1/2-pedal; then it fires up.
*Runs "OK" cold. Idles at about 1,100 RPM, some missing/popping, until it warms up.
*Still runs great at speed (on the road). Accelerates normally, cruises normally. Good power, no missing.
*The problem is when approaching a stop. Engine begins to hunt. Then hunts so bad it'll stall at the stop. Stalls at red lights, stop signs, when attempting to park, etc.

I took out the IAC, cleaned it and re-installed it, but that didn't change anything. But that doesn't necessarily exonerate it either. I'm gonna' R&R it and post back; until then I would still appreciate any other thoughts or ideas you guys have. Thanks!

OK, the problem is getting significantly worse. Wife no longer wants to drive it, so we are swapping vehicles until this gets resolved.

*It still cranks endlessly, unless you hit the gas about 1/2-pedal; then it fires up.
*Runs "OK" cold. Idles at about 1,100 RPM, some missing/popping, until it warms up.
*Still runs great at speed (on the road). Accelerates normally, cruises normally. Good power, no missing.
*The problem is when approaching a stop. Engine begins to hunt. Then hunts so bad it'll stall at the stop. Stalls at red lights, stop signs, when attempting to park, etc.

I took out the IAC, cleaned it and re-installed it, but that didn't change anything. But that doesn't necessarily exonerate it either. I'm gonna' R&R it and post back; until then I would still appreciate any other thoughts or ideas you guys have. Thanks!
You should try cleaning out your throttle body. Best way is to remove it and clean both sides of the throttle plate. Put it back on with a new gasket. Use carb cleaner. You can do it without taking off the whole thing, but it's hard to get behind the throttle plate.

If it were a fuel pump problem, you could affect it by not starting your car normally. Instead, turn the key to 'on' and wait a second. Then back to off a moment, then back to on. Do this for several cycles. The idea is to pressurize your fuel line prior to cranking. Since the fuel pump only runs 2 seconds if engine is not turning, you have to make several quick attempts before cranking to get this to have an effect on the fuel pressure. After the fuel rail contains fuel pressure it should start right up IF that were the problem.

I don't think its related to fuel pump. It could be, even could be bad fuel regulation, but only a fuel pressure gauge will tell you for certain.

I think it more likely that the MAP sensor has gone south or you have a vacuum leak. The sensor is used at startup and idle speeds so it will cause the engine to 'hunt' as well. If you can get your hands on an odbii scanner you could read the output of the sensor. The upstream O2 sensor failing will cause the engine to hunt at idle also, but if its that bad it should set a code, and that won't cause hard starts.

One other location to check is the EGR valve which could stick open and cause poor idling also. In general, poor idle, hard start will come back to manifold pressure problems, due to a leak somewhere, or EGR open, or MAP sensor failure, most of which don't set codes. Bad TPS points (as you describe) would set a code.

I am just offering some things to consider, you need to try some checks --like pull the map sensor off the vacuum line and plug that orifice, (I know how awful it is to do this) thus setting the map sensor to non-working to see how that impacts your engine, and doing the cycled startup to check fuel pressure.

FIXED!
The van started and ran OK driving down to work this morning. But coming home was a different story. It started bucking and misfiring. The SES light came on. About halfway home, it began stalling and didn't want to re-start no matter what I did with the gas pedal. When it did run, it sounded like it was only firing on two cylinders. I had to coast to the burm of the road several times with my hazard lights on and wait until it restarted, then floor it and drop it into gear. Vrooom!! Putt, putt, [die]. Then the SES light started flashing while I was driving! Never heard of that before. (I think it was trying to say, "Wake up, idiot! You're car isn't running right!") It was a loooong ride home. The way the motor was hobbling along, misfiring, dropping out then coming back, etc; I seriously thought I lost at least two (of the three) coil packs.

Before taking it somewhere to get it diagnosed (I don't have a pressure gauge for the fuel rail or other diagnostic tools), I decided to take one last close look. I pulled the three plug wires closest to the radiator, one from each coil pack, and had spark. Earlier this week, I had previously looked at the fuel pressure regulator. I inspected the crimp (where the diaphragm halves are joined) and where the fittings are. Seeing no sign of a leak, and remembering that I had replaced that regulator about three years ago, I gave it the benefit of the doubt and moved on. But this time, I didn't; I removed the vacuum line. Not seeing anything unusual, I started to put it back on when a tiny bubble came to the surface of the nipple and popped. That made me curious. So I cranked the engine for a few seconds and looked again. Sure enough, gas was dripping out of the vacuum port. So with the line connected, there was gas getting sucked into who-knows-what!

I just completed R&R of the pressure regulator, and the van is starting and running like new. It starts with a flick of the key and idles very smooth. :)

Thank you everyone who read this thread, and especially to the three who posted their ideas. :thumbsup:

I know this thread is lengthy, but I hope it helps someone else who may be searching for ideas, like I was.

Hey that's great news. You were lucky to get home. I can't tell you how many times I've been stranded on the side of the road by some minor thing like that. Love my vans, but they do keep you busy!

Havent been on this forum in a while, my first instinct while reading your initial post was FPR, glad you found it, those things are pretty notorious on the 60* V6's......