1996 b2500 5.9 hard start cold; easy hot


Tommy2500
06-17-2010, 05:27 PM
My 96 van with 5.9 mpfi, 130,000 mi, very hard to start cold. Just "chugs", won't accept throttle, but eventually goes after it gets warm. Then it starts and runs fine. Replaced tps. Cleaned iac and thr. body. Checked wires/connections/vacuum lines. PCM was replaced 8 mo. ago; old one leaked water into it (long story...). Van has run great for 8 mo. - then one morning - bingo...no start. No ckenglight. No codes by on-off-on-off-on manual check. Any ideas?

alloro
06-17-2010, 08:59 PM
When it's chugging, you'll need to hook-up a fuel pressure gauge and see what it's reading.

Tommy2500
06-17-2010, 09:17 PM
Thanks alloro. Will see if I can borrow a fuel pressure gauge and try it. Note: seems
like the Van is running real rich when cold started. I did just take on 22 gal. of fuel
at a Chevron - Bad load of fuel??? Friend and others on this forum make me think
possible coolant temp. sensor OR IAC. Fuel pressure test is on the agenda first.
Will advise result.

Tommy2500
06-18-2010, 12:14 PM
Did Fuel Pressure test with borrowed Inova Electronics Fuel Injection Pressure Tester. Relieved overnight pressure (there was some), hooked up gauge, key on - instant pressure to 41 psi.I Bled fuel off. Then key on - same psi, key on -start- hard to start,cranked for 4 sec.- stop- crank for 3 sec- weakly started engine, but fuel pressure went up to 48 psi. Held steady-no gauge fluctuation. I never touched throttle. Idle has always seemed low on this vehicle, even when very cold ambient
temp. (20 degr. winter morns.) Engine slowly levelled out to decent idle, but fuel press. never varied. My Haynes manual says 39-41 psi. Can't disconnect press.
regulator or check it- it's in the tank with fuel pump. Is pressure too high? Do I have a faulty pressure regulator? I really don't want to endure a fuel tank removal, especially since I just filled up my 30 gal. tank. Any ideas?

alloro
06-18-2010, 01:37 PM
I know that 48 PSI seems to be on the high side but it's nothing to be concerned over. In fact, I think my fuel PSI is at 46 if I recall correctly.

1. What color is the exhaust, white, blue, black, or no color?

2. Is the crankshaft sensor original? (FYI, a bad crank sensor doesn't throw a code). The crank sensor controls spark timing.

3. Is the pickup coil in the distributor original? The pickup coil controls fuel injector timing.

4. Have you noticed and unexplained loss of antifreeze?

Tommy2500
06-18-2010, 05:04 PM
Thanks for reply, Alloro.
1.no noticable exhaust color - if I had to say one, I'd say barely white (saw this once many months ago)
2.Unknown if crank sensor is OEM; looking at it I'd probably guess it's original
3.Unknown if pickup coil is original; cap has been replaced
4.Coolant level is always in same level in recovery tank; radiator is always full.
Flushed and replaced coolant last summer. No cooling or overheating issues.

I think I see where you're headed in your thinking....Head gasket? Or a timing issue,
either spark or fuel injector? I've noticed in several threads of this forum that a faulty crank sensor can cause many unusual problems with these Vans. And why
oh why, didn't Dodge include an OBD II code for crank sensor? Will check my Haynes for crank sensor tests. What about the pickup coil? Just replace, or what? Thanks again. You are really helping me.

alloro
06-18-2010, 08:30 PM
What about the pickup coil? Just replace, or what?

Although it's a possibility, it's not high on the likely list. In 9 out of 10 cases when the pickup coil goes bad the engine doesn't run.

Tommy2500
06-19-2010, 03:25 PM
Checked resistance of crankshaft pos. sensor as per Haynes. Checked OK. There is some goo from weeping valve cover in the area. But I didn't remove the sensor - the rubber seal seems intact. Can't figure a way to check pickup coil, but took a look inside cap and under cover plate- coil looked OK and it was clean in there. On a whim, I pulled off the IAC 4-prong connector to see if idle fluctuated - no change- then turned on AC - no change. When the engine wants to die when cold, there is a loud hiss from the area of the IAC on the throttle body. Could this condition be due to a faulty IAC? Would that throw a "ck engine code"? The ckengine light doesn't come on when I disconnect the IAC when the engine is running. About at wits end.

alloro
06-20-2010, 12:50 PM
Could this condition be due to a faulty IAC?

Would that throw a "ck engine code"?

Yes

No

Tommy2500
06-21-2010, 03:57 PM
:)Went to NAPA, bought new IAC (59$). Put it in and everything works perfectly. Idles great, starts correctly, idle adjusts when ambient temp. is cold or when I turn on the AC. Lesson: IAC is an "output actuator", not an "input sensor". I thought it was a temperature sensitive problem - the engine idles and started fine when hot, not when cold- so I figured a temp. sensor or something was the problem; BUT - no ckeng lite nor no OBDII codes. SO; the computer inputs were OK - computer processing good (ie. responses were appropriate/accurate) - but the "output actuator", the thing that translates the computer responses into mechanical action (IAC in this case) wasn't "actuating" like the computer wanted it to do. IAC was broken/clogged/fatigued spring/bad diaphragm/etc.
I learned something here. THANKS ALLORO! I owe you bigtime.

Edit; 6/23/10 2 days later, same problem is back....this lesson is wrong....I learned very little, except that logic doesn't apply to this Van.

alloro
06-21-2010, 09:22 PM
Whew, glad that's finally fixed. Four days is about my limit to stay up around the clock trying to figure out a solution. :bloated:

Tommy2500
06-22-2010, 12:27 AM
Yeah, Alloro, now we both can get some unworried shuteye.
Now, if it would only quit raining here......

Tommy2500
06-23-2010, 05:57 PM
:confused:OK, so now what's going on? Van ran OK for 2 daze, now I come
out this morning, try to start it, and Bingo! SAME EXACT PROBLEM!!!
Do I just keep throwing $50 bills at the d*#* engine buying all sorts of expensive actuators and sensors? I'm not taking this thing into my local Dodge dealer for him to rip me off (or so say all friends who have done that). Any more ideas, other than a firebomb in the gas tank?

alloro
06-23-2010, 09:34 PM
the engine idles and started fine when hot, not when cold

Sigh! What about the 2-wire CTS, not the 1-wire one for the gauge, I mean the 2-wire one that tells the PCM the engine coolant temperature...have you tested or replaced that?

Tommy2500
06-24-2010, 01:03 AM
Double Sigh... Haven't tested nor replaced 2 wire temp. sensor. It's in
such an awful location...need to remove alternator, AC compressor, Belt,
and all kinds of brackets just to get to the darn thing to test it. I can't
even SEE it, let alone test it. Wouldn't it send me a code if it was bad?
Why would the thing work fine for 2 days, then crap out again? Do I have a bad new part, the IAC I bought 3 days ago?

alloro
06-24-2010, 09:02 PM
Some code readers will display what various sensors are reading while the engine is running. Using such a reader, you could see what it's reading for the coolant temp and compare it to your dash gauge. It's not an exact science but if the two temperature reading were in the ballpark to one another, you could safely assume the CTS was good.

Another method would be to disconnect the plug from the PCM (engine cold) and take an ohm reading on the wires running to the CTS. Plug the PCM back in, run the engine up to temp, then turn it off, disconnect the PCM plug again, and take another ohm reading to compare the results.

Yes it's possible to have a new part go bad. It's happened to me more often than I'd care to count.

Tommy2500
06-28-2010, 02:11 PM
Interesting approaches to checking coolant temp. sensor. I don't have a code reader like you do, and hesitate to mess with PCM. I have found that the problem is intermittant; leads me to believe a bad wire, ground, or connector. And, I'll probably
just go ahead and replace the temp. sensor because I've decided to replace the radiator hoses,thermostat, coolant, coil, plugs and wires, and valve cover gaskets. If
the crank sensor isn't too pricey, it'll get replaced too. Gotta throw a few hundred
bucks and couple days work at these vehicles every couple years, instead of the monthly payment for a new one, eh? Later. Thanks.

Tommy2500
10-07-2010, 03:45 AM
Just a quick note to this thread; the Van finally decided
to throw me a check engine light. OBD code said 117 - temp.
sensor low output. So it WAS the 2-wire temp. sensor (hidden
in the toughest location on the engine!) that was the culprit
all the time. It just took a while for the thing to get bad enough
to show a code. What a pain-in-the-rump to change.....But glad
we persevered. All fixed now; waiting for the next catastrophe....

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